Composite positive electrode active material, positive electrode and lithium battery using the same, and method for manufacturing the same

Abstract

A core containing a lithium transition metal oxide, and a first shell and a second shell disposed outside the surface of the core, wherein the first shell has the chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, where if a is 1, 2, or 3, b is an integer) or the chemical formula X a (OH) b (0 < a ≤ 3, 0 < b ≤ 4, where if a is 1, 2, or 3, b is an integer), and contains one or more first metal compounds represented by the formula, and the second shell has the chemical formula Y c O d (0

Description

Technical Field

[0001] The present invention relates to a composite cathode active material, a cathode employing the same, a lithium battery, and a method for manufacturing the same.

Background Art

[0002] In order to meet the miniaturization and high performance of various devices, in addition to the miniaturization and weight reduction of lithium batteries, increasing the energy density has become important. That is, high-capacity lithium batteries have become important.

[0003] In order to embody a lithium battery that meets the above applications, cathode active materials having a high capacity have been studied.

[0004] Conventional nickel-based cathode active materials had a reduced life characteristic and low thermal stability due to side reactions.

[0005] Therefore, a method capable of preventing the deterioration of battery performance while including a nickel-based cathode active material is required.

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect is to provide a novel composite cathode active material capable of suppressing side reactions of the composite cathode active material and preventing deterioration of battery performance.

[0007] Another aspect is to provide a cathode including the composite cathode active material.

[0008] Still another aspect is to provide a lithium battery employing the cathode.

[0009] Still another aspect is to provide a method for manufacturing the composite cathode active material.

Means for Solving the Problems

[0010] According to one aspect, A core containing a lithium transition metal oxide, a first shell and a second shell disposed on the outer side of the surface of the core, and the first shell contains one or more first metal compounds represented by the chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2 or 3, then b is an integer) or the chemical formula X a (OH) b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2 or 3, then b is an integer), the second shell contains one or more second metal compounds represented by the chemical formula Y c O d (0 < c ≤ 3, 0 < d < 4, if c is 1, 2 or 3, then d is not an integer); and graphene, wherein the second metal oxide is disposed within a graphene matrix, and X and Y are each independently one or more metals selected from Groups 2 to 13, 15 and 16 of the Periodic Table of the Elements, and a composite cathode active material is provided.

[0011] By another aspect, a cathode containing the composite cathode active material is provided.

[0012] By yet another aspect, a lithium battery containing the cathode is provided.

[0013] By yet another aspect, providing a lithium transition metal oxide; providing one or more first metal compounds represented by the chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2 or 3, then b is an integer) or the chemical formula X a (OH) b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2 or 3, then b is an integer); and providing one or more second metal compounds represented by the chemical formula Y c O d ​One or more second metal compounds represented by (0 < c ≤ 3, 0 < d < 4, and if c is 1, 2, or 3, d is not an integer); and providing a composite comprising graphene, wherein the second metal compound is disposed within a graphene matrix. Mechanically milling the lithium transition metal oxide, the first metal compound, and the composite. Provided is a method for manufacturing a composite cathode active material, wherein X or Y is, independently of each other, one or more metals selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements.

Advantages of the Invention

[0014] According to one aspect, since the composite cathode active material includes a first shell containing a first metal compound and a second shell containing a second metal compound and graphene, the low-temperature and high-temperature cycle characteristics and the fast charging characteristics of the lithium battery are improved, and side reactions between the composite cathode active material and the electrolyte are suppressed.

Brief Description of the Drawings

[0015]

Figure 1

Modes for Carrying Out the Invention

[0016] The present inventive concept described below can be subject to various transformations and can have various embodiments. Specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, they are not intended to limit the present inventive concept to specific embodiments, but should be understood to include all transformations, equivalents, or alternatives included in the technical scope of the present inventive concept.

[0017] The terms used below are merely for the purpose of describing specific embodiments and are not intended to limit the inventive concept. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereinafter, terms such as "comprising" or "having" indicate the presence of features, numbers, steps, operations, components, parts, elements, materials, or combinations thereof described in the specification, and it should not be construed as precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, elements, materials, or combinations thereof. The " / " used below is interpreted as "and" or "or" depending on the context.

[0018] In the drawings, in order to clearly represent a plurality of layers and regions, the thickness is shown enlarged or reduced. The same reference numerals are given to similar parts throughout the specification. Throughout the specification, when a part such as a layer, film, region, plate, etc. is "on" or "above" another part, it includes not only the case where it is directly above the other part but also the case where there are other parts in between.

[0019] In this specification, the "particle size" of particles indicates the average diameter when the particles are spherical, and the average major axis length when the particles are non-spherical. The particle size of particles can be measured using a particle size analyzer (PSA). The "particle size" of particles is, for example, the average particle size. The average particle size is, for example, the median diameter (D50). The median diameter D50 is, for example, calculated from the side of particles having a small particle size in the particle size distribution measured by the laser diffraction method and is the particle size corresponding to 50% cumulative volume. For example, D10 is calculated from the side of particles having a small particle size in the particle size distribution measured by the laser diffraction method and is the particle size corresponding to 10% cumulative volume. For example, D90 is calculated from the side of particles having a small particle size in the particle size distribution measured by the laser diffraction method and is the particle size corresponding to 90% cumulative volume.

[0020] Hereinafter, the composite cathode active material according to an exemplary embodiment, the cathode and the lithium battery including the same, and a method for manufacturing the same will be described in more detail.

[0021] It includes a first shell and a second shell disposed outside the surface of the core, and the first shell has a chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, and if a is 1, 2, or 3, b is an integer) or a chemical formula X a (OH) b (0 < a ≤ 3, 0 < b ≤ 4, and if a is 1, 2, or 3, b is an integer), and includes one or more first metal compounds represented by the formula, and the second shell has a chemical formula Y c O d (0 < c ≤ 3, 0 < d < 4, and if c is 1, 2, or 3, d is not an integer), and includes graphene, and the second metal oxide is disposed in the graphene matrix, and the X and the Y are each independently one or more metals selected from Groups 2 to 13, 15, and 16 of the periodic table of the elements.

[0022] Hereinafter, the theoretical basis for the excellent effects provided by the composite cathode active material according to an embodiment will be described, which is for the purpose of assisting the understanding of the inventive concept and is not intended to limit the inventive concept in any way.

[0023] The composite positive electrode active material includes a first shell and a second shell disposed on the outer side of the surface of a core containing a lithium transition metal oxide. The first shell contains a first metal compound, and the second shell contains a second metal compound and graphene. When the conventional composite positive electrode active material is charged and discharged at a high voltage, due to the side reaction between the conventional composite positive electrode active material and the electrolyte, a CEI (cathode electrolyte interphase) is rapidly formed on the surface of the composite positive electrode active material, resulting in a rapid increase in the interfacial resistance between the composite positive electrode active material and the electrolyte. Therefore, the internal resistance of the lithium battery containing the conventional composite positive electrode active material increases, and the electrochemical charge and discharge performance of the lithium battery rapidly deteriorates. In contrast, the above-mentioned composite positive electrode active material in which the first shell containing the first metal compound and the second shell containing the second metal compound and graphene are disposed on the outer side of the surface of the core effectively blocks the contact between the core and the electrolyte, thereby preventing side reactions caused by the contact between the core and the electrolyte. In addition, since cation mixing due to side reactions between the transition metal cations of the composite positive electrode active material and the electrolyte is suppressed, the formation of a resistance layer on the surface of the composite positive electrode active material is suppressed. Furthermore, the elution of transition metal ions from the surface of the composite positive electrode active material into the electrolyte is also suppressed. As a result, the performance degradation of the lithium battery containing the composite positive electrode active material is suppressed.

[0024] More specifically, the first metal compound contained in the first shell stabilizes the transition metal contained in the core and suppresses the elution of the transition metal. Further, the graphene contained in the second shell prevents the release of oxygen contained in the core. Therefore, the double-shell structure including the first shell and the second shell suppresses the elution of transition metal and oxygen from the core. Further, since the graphene contained in the second shell has high electronic conductivity, the interfacial resistance between the composite cathode active material and the electrolyte decreases. Therefore, the high-rate charging characteristics of the lithium battery including the composite cathode active material are improved. Further, since the first metal compound and the second metal compound have voltage resistance, deterioration of the lithium transition metal oxide contained in the core can be prevented when charging and discharging at a high voltage. As a result, the high-temperature and / or high-voltage cycle characteristics of the lithium battery including the composite cathode active material are improved.

[0025] The first shell and the second shell disposed on the outer side of the surface of the core may be sequentially disposed on the outer side of the surface of the core, for example. The first metal compound contained in the first shell further stabilizes the transition metal contained in the core as it is closer to the core, and the graphene contained in the second shell can effectively reduce the interfacial resistance between the composite cathode active material and the electrolyte as it is closer to the electrolyte. As a result, by sequentially arranging the first shell and the second shell on the outer side of the surface of the core, the cycle characteristics and high-rate charging characteristics of the lithium battery including the composite cathode active material can be further improved.

[0026] The first shell and the second shell disposed on the outer side of the surface of the core may be, for example, such that the first shell is directly disposed on the outer side of the surface of the core, and the second shell is directly disposed on the outer side of the surface of the first shell. Since the first shell is further adjacent to the core, the stabilizing effect of the transition metal by the first metal compound contained in the first shell can be further improved. Further, since the second shell is directly disposed on the outer side of the surface of the first shell, a double-layer structure of the first shell and the second shell can be formed. Due to the double-layer structure, the effect of preventing the elution of the transition metal and oxygen from the core can be further improved. Furthermore, by disposing the second shell on the outer side of the surface of the first shell, the interfacial resistance between the composite positive electrode active material and the electrolytic solution can be further reduced. As a result, by directly disposing the first shell on the outer side of the surface of the core and directly disposing the second shell on the outer side of the surface of the first shell, the cycle characteristics of the lithium battery can be further improved.

[0027] The thickness of the first shell contained in the composite positive electrode active material is, for example, about 1 nm to 2 μm, about 10 nm to 20 μm, about 50 nm to 20 μm, about 100 nm to 20 μm, about 200 nm to 20 μm, about 500 nm to 20 μm, about 1 μm to 20 μm, about 2 μm to 20 μm, about 5 μm to 20 μm, about 1 nm to 10 μm, about 1 nm to 5 μm, about 1 nm to 1 μm, about 1 nm to 500 nm, about 1 nm to 200 nm, about 1 nm to 100 nm, or about 1 nm to 50 nm. By the first shell having a thickness within this range, the effect of preventing the elution of the transition metal of the core can be further improved. As a result, the cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved.

[0028] The thickness of the second shell included in the composite positive electrode active material is, for example, about 1 nm to 2 μm, about 10 nm to 20 μm, about 50 nm to 20 μm, about 100 nm to 20 μm, about 200 nm to 20 μm, about 500 nm to 20 μm, about 1 μm to 20 μm, about 2 μm to 20 μm, about 5 μm to 20 μm, about 1 nm to 10 μm, about 1 nm to 5 μm, about 1 nm to 1 μm, about 1 nm to 500 nm, about 1 nm to 200 nm, about 1 nm to 100 nm, or about 1 nm to 50 nm. By having the thickness within the said range, the effect of preventing the transition metal elution of the core is further improved, and the cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved. Also, the side reaction between the composite positive electrode active material and the electrolytic solution is suppressed, and the increase rate of the internal resistance of the lithium battery can be further decreased.

[0029] The metal included in the first metal compound is, for example, also one or more selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. By the first metal compound including the said metal, the first shell can be uniformly arranged on the outer side of the surface of the said core. Also, the stability of the transition metal included in the core can be further improved. As a result, the elution of the transition metal from the composite positive electrode active material can be more effectively prevented. The first metal compound is also an oxide, hydroxide, etc. of the aforementioned metal.

[0030] The metal included in the first metal compound is, for example, also Al. The first metal compound may include, for example, at least one selected from the group consisting of Al2O3 and Al(OH)3. The first metal compound can also include, for example, both of Al2O3 and Al(OH)3. By the first shell including the said first metal compound, the stability of the transition metal (for example, cobalt (Co)) included in the said core can be further improved. As a result, the elution of the transition metal from the composite positive electrode active material can be more effectively prevented.

[0031] In the composite positive electrode active material, for example, the first metal compound contained in the first shell and the transition metal of the lithium transition metal oxide contained in the core can be chemically bonded through a chemical bond. By chemically bonding the first metal compound contained in the first shell and the lithium transition metal oxide contained in the core through a chemical bond, the core and the shell are combined. Therefore, it is distinguished from a simple physical mixture of the first metal compound and the lithium transition metal oxide. Further, the stability of the transition metal contained in the core is improved, and the elution of the transition metal can be effectively suppressed.

[0032] The average particle size of the first metal compound contained in the first shell is, for example, about 10 nm to 20 μm, about 50 nm to 20 μm, about 100 nm to 20 μm, about 150 nm to 20 μm, about 1 nm to 10 μm, about 1 nm to 1 μm, about 1 nm to 500 nm, about 1 nm to 400 nm, about 1 nm to 300 nm, or also about 1 nm to 200 nm. By having the first metal compound with an average particle size in this range, the first metal compound can be uniformly arranged on the outer side of the surface of the core to form the first shell. Therefore, the elution of the transition metal can be more effectively suppressed by the first shell uniformly arranged on the outer side of the surface of the core. As a result, the cycle characteristics of the lithium battery containing the composite positive electrode active material can be further improved.

[0033] The average particle size of the first metal compound is measured, for example, using a measuring device of a laser diffraction method or a dynamic light scattering method. The average particle size is measured, for example, using a laser scattering particle size distribution meter (for example, LA-920 manufactured by Horiba, Ltd.), and is the value of the median diameter (D50) when accumulated 50% from the primary particle side in volume conversion.

[0034] The metal contained in the second metal compound is, for example, also one or more selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The second metal compound is, for example, Al2O z (0 < z < 3), NbO x (0 < x < 2.5), MgO x (0 < x < 1), Sc2Oz (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) is also one or more selected therefrom. By disposing the second metal compound within the graphene matrix, the uniformity of the second shell disposed on the core and the first shell is improved, and the breakdown voltage resistance of the composite cathode active material is further improved. For example, the second shell includes Al2O as the second metal compound x (0 < x < 3).

[0035] The second shell has the chemical formula Y c O eIt may further contain one or more third metal compounds represented by (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer). The Y is one or more metals selected from Groups 2 to 13, 15, and 16 of the periodic table of the elements. For example, the third metal compound contains the same metal as the second metal compound, and e / c, which is the ratio of e of the third metal compound to c of the third metal compound, has a value further greater than d / c, which is the ratio of d to c of the second metal oxide. For example, e / c > d / c. The third metal compound is selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The second metal compound is a reduction product of the third metal compound. By reducing part or all of the third metal compound, the second metal compound is obtained. Therefore, the second metal compound has a lower oxygen content and a higher oxidation number of the metal compared to the third metal compound. For example, the second shell is the second metal compound Al2O x It contains (0 < x < 3) and Al2O3 which is a third metal compound.

[0036] In the composite positive electrode active material, for example, graphene contained in the second shell and the metal of the first metal compound contained in the first shell can be chemically bonded through a chemical bond. The carbon atom (C) of graphene contained in the second shell and the metal (Me) of the first metal compound contained in the first shell are chemically bonded through, for example, a C-O-Me bond (for example, a C-O-Co bond) via an oxygen atom. By chemically bonding graphene contained in the second shell and the first metal compound contained in the first shell through a chemical bond, the first shell and the second shell are complexed. Also, as described above, by chemically bonding the first metal compound contained in the first shell and the transition metal contained in the core through a chemical bond, the core and the first shell are complexed. As a result, the core, the first shell, and the second shell are complexed. Therefore, it is distinguished from a simple physical mixture of the first metal compound, the second metal compound, graphene, and the lithium transition metal oxide.

[0037] Further, the second metal compound included in the second shell is also chemically bonded to graphene through a chemical bond. Here, the chemical bond is, for example, a covalent bond or an ionic bond. The covalent bond is, for example, a bond including at least one of an ester group, an ether group, a carbonyl group, an amide group, a carbonate anhydride group, and an acid anhydride group. The ionic bond is, for example, a bond including a carboxylic acid ion, an ammonium ion, an acyl cation group, etc.

[0038] In the composite cathode active material, for example, a fourth metal doped on the core may be further included. For example, after the fourth metal is doped on the surface of the lithium transition metal oxide included in the core, the first shell and the second shell may be disposed on the outside of the surface of the core. The fourth metal is also, for example, one or more metals selected from Al, Zr, W, and Co.

[0039] The second shell included in the composite cathode active material includes, for example, one or more selected from a composite including a second metal compound and graphene, and a milling result of the composite, and the second metal compound may be disposed in the graphene matrix. The second shell is, for example, manufactured from a composite including a second metal compound and graphene. The composite may further include a third metal compound in addition to the second metal compound. The composite may also include, for example, two or more kinds of second metal compounds. The composite may also include, for example, two or more kinds of second metal compounds and two or more kinds of third metal compounds.

[0040] The average particle size of one or more selected from the second metal compound and the third metal compound included in the composite is about 1 nm to 1 μm, about 1 nm to 500 nm, about 1 nm to 200 nm, about 1 nm to 100 nm, about 1 nm to 70 nm, about 1 nm to 50 nm, about 1 nm to 30 nm, about 3 nm to 1 μm, about 5 nm to 1 μm, about 10 nm to 1 μm, about 15 nm to 1 μm, about 20 nm to 1 μm, about 25 nm to 1 μm, or about 30 nm to 1 μm. By the second metal compound and / or the third metal compound having a particle size in the nano range, it can be more uniformly distributed within the graphene matrix of the composite. Therefore, such a composite can be uniformly coated on the outside of the surface of the core and the first shell without aggregation to form a second shell. Also, by the second metal compound and / or the third metal compound having a particle size in the range, it can be more uniformly arranged on the outside of the surface of the core and the first shell. Therefore, the second metal compound and / or the third metal compound are uniformly arranged on the outside of the surface of the core and the first shell, so that the withstand voltage characteristics can be more effectively exhibited.

[0041] The average particle size of the second metal compound and the third metal compound is also measured by the same method as the average particle size of the first metal compound described above.

[0042] The uniformity deviation of one or more selected from the second metal compound and the third metal compound included in the composite is 3% or less, 2% or less, or 1% or less. The uniformity is also determined, for example, by XPS. Therefore, within the composite, one or more selected from the second metal compound and the third metal compound can be uniformly distributed with a deviation of 3% or less, 2% or less, or 1% or less.

[0043] The graphene included in the composite may have, for example, a branched structure, and the second metal compound may be distributed within the branched structure of the graphene. The graphene included in the composite may have, for example, a branched structure, and the second metal compound and the third metal compound may be distributed within the branched structure of the graphene. The branched structure of the graphene includes, for example, a plurality of graphene particles in contact with each other. By having a branched structure, the graphene can provide various conductive paths.

[0044] The graphene included in the composite may have, for example, a spherical structure, and the second metal compound may be distributed within the spherical structure. The graphene included in the composite may have, for example, a spherical structure, and the second metal compound and the third metal compound may be distributed within the spherical structure. The size of the spherical structure of the graphene is also 50 nm to 300 nm. There may also be a plurality of graphenes having a spherical structure. By having a spherical structure, the composite can have a firm structure.

[0045] The graphene included in the composite may have, for example, a spiral structure in which a plurality of spherical structures are connected, and the second metal compound may be distributed within the spherical structure of the spiral structure. The graphene included in the composite may have, for example, a spiral structure in which a plurality of spherical structures are connected, and one or more selected metal compounds from among the second metal compound and the third metal compound may be distributed within the spherical structure of the spiral structure. The size of the spiral structure of the graphene is also 500 nm to 100 μm. By having a spiral structure, the composite can have a firm structure.

[0046] The graphene included in the composite may have, for example, a cluster structure in which a plurality of spherical structures are aggregated, and the second metal compound may be distributed within the spherical structure of the cluster structure. The graphene included in the composite may have, for example, a cluster structure in which a plurality of spherical structures are aggregated, and the second metal compound and the third metal compound may be distributed within the spherical structure of the cluster structure. The size of the cluster structure of the graphene is also from 0.5 mm to 10 cm. Due to the graphene having a cluster structure, the composite can have a firm structure.

[0047] The composite may be, for example, a faceted-ball structure, and the second metal compound may be distributed inside or on the surface of the structure. The composite may be, for example, a faceted-ball structure, and the second metal compound and the third metal compound may be distributed inside or on the surface of the structure. Due to the composite being the polyhedral ball structure, the composite can be easily coated on the irregular surface unevenness of the core.

[0048] The composite may be, for example, a planar structure, and the second metal compound may be distributed inside or on the surface of the structure. The composite may be, for example, a planar structure, and one or more selected from the second metal compound and the third metal compound may be distributed inside or on the surface of the structure. Due to the composite being the two-dimensional planar structure, the composite can be easily coated on the irregular surface unevenness of the core.

[0049] The graphene included in the composite extends to a distance of about 10 nm or less from the second metal compound and also includes at least 1 to 20 graphene layers. For example, by laminating a plurality of graphene layers, graphene having a total thickness of about 12 nm or less can be disposed on the second metal compound. For example, the total thickness of the graphene is also from about 0.6 to 12 nm.

[0050] The sum of the weight of the first metal compound, the weight of the second metal compound, and the weight of the graphene is about 0.001 wt% to 1 wt%, about 0.005 wt% to 1 wt%, about 0.001 wt% to 1 wt%, about 0.01 wt% to 1 wt%, about 0.02 wt% to 1 wt%, about 0.05 wt% to 1 wt%, about 0.1 wt% to 1 wt%, about 0.001 wt% to 0.5 wt%, about 0.001 wt% to 0.2 wt%, about 0.001 wt% to 0.15 wt%, or about 0.001 wt% to 0.1 wt% with respect to the weight of the core. By including the composite in this range in the composite cathode active material, the cycle characteristics of the lithium battery including the composite cathode active material are further improved.

[0051] The core included in the composite cathode active material includes, for example, a lithium transition metal oxide represented by the following Chemical Formula 1: [Chemical Formula 1] Li a1 Co x1 M y1 O 2-b1 A b1 In the Chemical Formula 1, 1.0 ≦ a1 ≦ 1.2, 0 ≦ b1 ≦ 0.2, 0.9 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 0.1, and x1 + y1 = 1, M is one or more selected from the group consisting of 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), and boron (B), and A is F, S, Cl, Br, or a combination thereof.

[0052] The core included in the composite cathode active material includes, for example, a lithium transition metal oxide represented by the following Chemical Formula 2: [Chemical Formula 2] LiCoO2 The cathode according to other embodiments includes the aforementioned composite cathode active material. By including the aforementioned composite cathode active material in the cathode, improved cycle characteristics and thermal stability are provided.

[0053] The positive electrode is manufactured, for example, by the following exemplary methods, but is not necessarily limited to such methods and is adjusted according to the required conditions.

[0054] First, the aforementioned composite positive electrode active material, conductive material, binder, and solvent are mixed to prepare a positive electrode active material composition. The prepared positive electrode active material composition is directly coated and dried on an aluminum current collector to manufacture a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, after casting the positive electrode active material composition on a separate support, the film obtained by peeling it from the support is laminated on the aluminum current collector to manufacture a positive electrode plate having a positive electrode active material layer formed thereon.

[0055] As the conductive material, carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, ketjen black, carbon fiber; carbon nanotube; metal powders such as copper, nickel, aluminum, silver, or metal fibers or metal tubes; conductive polymers such as polyphenylene derivatives are used, but are not limited thereto, and any material that can be used as a conductive material in the relevant technical field can be used.

[0056] As the binder, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the aforementioned polymers, styrene-butadiene rubber-based polymers, etc. are used, and as the solvent, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not limited thereto, and any material that can be used in the relevant technical field can be used.

[0057] It is also possible to further add a plasticizer or a pore former to the positive electrode active material composition to form pores inside the electrode plate.

[0058] The contents of the composite cathode active material, conductive material, binder, and solvent used for the cathode are at levels commonly used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the conductive material, binder, and solvent can be omitted.

[0059] In addition, the cathode can further contain other general cathode active materials in addition to the aforementioned composite cathode active material.

[0060] As general cathode active materials, any lithium-containing metal oxides can be used without limitation as long as they are commonly used in the technical field. For example, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof with lithium can be used. Specific examples thereof include Li a1 A 1-b1 B b1 D2 (in the above formula, 0.90 ≦ a1 ≦ 1 and 0 ≦ b1 ≦ 0.5); Li a1 E 1-b1 B b1 O 2-c1 D c1 (in the above formula, 0.90 ≦ a1 ≦ 1, 0 ≦ b1 ≦ 0.5, and 0 ≦ c1 ≦ 0.05); LiE 2-b1 B b1 O 4-c1 D c1 (in the above formula, 0 ≦ b1 ≦ 0.5 and 0 ≦ c1 ≦ 0.05); Li a1 Ni 1-b1-c1 Co b1 B c1 D α (in the above formula, 0.90 ≦ a1 ≦ 1, 0 ≦ b1 ≦ 0.5, 0 ≦ c1 ≦ 0.05, and 0 < α ≦ 2); Li a1 Ni 1-b1-c1 Co b1 B c1 O 2-α F α (in the above formula, 0.90 ≦ a1 ≦ 1, 0 ≦ b1 ≦ 0.5, 0 ≦ c1 ≦ 0.05, and 0 < α < 2); Li a1 Ni 1-b1-c1 Co b1 B c1 O 2-αF2 (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.5, 0 ≤ c1 ≤ 0.05 and 0 < α < 2); Li a1 Ni 1-b1-c1 Mn b1 B c1 D α (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.5, 0 ≤ c1 ≤ 0.05 and 0 < α ≤ 2); Li a1 Ni 1-b1-c1 Mn b1 B c1 O 2-α F α (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.5, 0 ≤ c1 ≤ 0.05 and 0 < α < 2); Li a1 Ni 1-b1-c1 Mn b1 B c1 O 2-α F2 (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.5, 0 ≤ c1 ≤ 0.05 and 0 < α < 2); Li a1 Ni b1 E c1 G d1 O2 (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.9, 0 ≤ c1 ≤ 0.5 and 0.001 ≤ d1 ≤ 0.1); Li a1 Ni b1 Co c1 Mn d1 G e1 O2 (wherein, 0.90 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.9, 0 ≤ c1 ≤ 0.5, 0 ≤ d1 ≤ 0.5 and 0.001 ≤ e1 ≤ 0.1); Li a1 NiG b1 O2 (wherein, 0.90 ≤ a1 ≤ 1 and 0.001 ≤ b1 ≤ 0.1); Li a1 CoG b1 O2 (wherein, 0.90 ≤ a1 ≤ 1 and 0.001 ≤ b1 ≤ 0.1); Li a1 MnG b1 O2 (wherein, 0.90 ≤ a1 ≤ 1 and 0.001 ≤ b1 ≤ 0.1); Li a1 Mn2G b1O4 (in the above formula, 0.90 ≦ a1 ≦ 1 and 0.001 ≦ b1 ≦ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f1) J2(PO4)3 (0 ≦ f1 ≦ 2); Li (3-f1) A compound represented by any one of the chemical formulas of Fe2(PO4)3 (0 ≦ f1 ≦ 2); LiFePO4 can be used.

[0061] In the chemical formula representing the aforementioned compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, 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.

[0062] It is also possible to use a compound with a coating layer added to the surface of the aforementioned compound, and it is also possible to use a mixture of the aforementioned compound and a compound with a coating layer added. The coating layer added to the surface of the aforementioned compound includes, for example, a coating element compound such as an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compound forming such a coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method is, for example, a spray coating method, a dipping method, etc. Since the specific coating method is understood by those skilled in the art, detailed description is omitted.

[0063] Furthermore, a lithium battery according to another embodiment employs a positive electrode including the aforementioned composite positive electrode active material.

[0064] By employing a positive electrode including the aforementioned composite positive electrode active material in a lithium battery, improved cycle characteristics, fast charging characteristics, and thermal stability are provided. Also, during charge and discharge, the formation of a CEI (Cathode Electrolyte Interphase) layer between the positive electrode and the electrolyte suppresses the current situation where the internal resistance of the lithium battery increases.

[0065] A lithium battery is manufactured, for example, by the following exemplary methods, but is not necessarily limited to such methods and is adjusted according to the required conditions.

[0066] First, a positive electrode is manufactured by the aforementioned method for manufacturing a positive electrode.

[0067] Next, the negative electrode is manufactured as follows. The negative electrode is manufactured in substantially the same manner as the positive electrode, except that a negative electrode active material is used instead of the composite positive electrode active material, for example. Also, in the negative electrode active material composition, the conductive material, binder, and solvent can be substantially the same as those of the positive electrode.

[0068] For example, a negative electrode active material composition is manufactured by mixing a negative electrode active material, a conductive material, a binder, and a solvent, and it is directly coated on a copper current collector to manufacture a negative electrode plate. Alternatively, the manufactured negative electrode active material composition is cast on a separate support, and the negative electrode active material film peeled from the support is laminated on a copper current collector to manufacture a negative electrode plate.

[0069] Any negative electrode active material can be used as long as it is used as a negative electrode active material of a lithium battery in the relevant technical field. For example, it contains one or more selected from the group consisting of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material.

[0070] The metal alloyable with lithium is, for example, Si, Sn, Al, Ge, Pb, Bi, Sb, a Si-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combined element thereof, and is not Si), a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combined element thereof, and is not Sn), etc. The element Y is, 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.

[0071] The transition metal oxide is, for example, lithium titanate, vanadium oxide, lithium vanadate, etc.

[0072] Non-transition metal oxides include, for example, SnO2, SiO x (0 < x < 2), etc.

[0073] Carbon-based materials are, for example, crystalline carbon, amorphous carbon, or a mixture thereof. Crystalline carbon is, for example, graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite. Amorphous carbon is, for example, soft carbon (low-temperature fired carbon), hard carbon, mesophase pitch carbide, fired coke, etc.

[0074] The contents of the negative electrode active material, conductive material, binder, and solvent are at levels commonly used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the conductive material, binder, and solvent can be omitted.

[0075] Next, a separator inserted between the positive electrode and the negative electrode is prepared.

[0076] Any separator can be used as long as it is commonly used in lithium batteries. For example, a separator with low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention ability is used. The separator is, for example, selected from glass fiber, polyester, Teflon (registered trademark), polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and is in the form of a non-woven fabric or a woven fabric. For lithium-ion batteries, a wound separator such as polyethylene or polypropylene is used, and for lithium-ion polymer batteries, a separator with excellent organic electrolyte impregnation ability is used.

[0077] The separator is manufactured by the following exemplary methods, but is not necessarily limited to such methods and is adjusted according to the required conditions.

[0078] First, a polymer resin, a filler, and a solvent are mixed to prepare a separator composition. The separator composition is directly coated and dried on top of the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support is laminated on top of the electrode to form a separator.

[0079] The polymer used in the production of the separator is not particularly limited, and any polymer that can be used as a binder for the electrode plate can be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a mixture thereof is used.

[0080] Next, an electrolyte is prepared.

[0081] The electrolyte is, for example, an organic electrolyte solution. The organic electrolyte solution is produced, for example, by dissolving a lithium salt in an organic solvent.

[0082] Any organic solvent can be used as long as it is used as an organic solvent in the technical field. The organic solvent is, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof.

[0083] Any lithium salt can be used as long as it is used as a lithium salt in the relevant technical field. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

[0084] Alternatively, the electrolyte is a solid electrolyte. Examples of solid electrolytes include, but are not limited to, boron oxides, lithium oxynitrides, etc. Any solid electrolyte can be used as long as it is used as a solid electrolyte in the relevant technical field. The solid electrolyte is formed on the negative electrode by a method such as sputtering, or a separate solid electrolyte sheet is laminated on the negative electrode.

[0085] As shown in FIG. 1, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 are wound or folded and housed in a battery case 5. An organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case 5 is cylindrical, but is not necessarily limited to such a form and can be, for example, rectangular or thin-film shaped.

[0086] The pouch-type lithium battery includes one or more battery structures. A separator is disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structures are laminated as a bicell structure, they are impregnated with an organic electrolyte, housed and sealed in a pouch to complete the pouch-type lithium battery. A plurality of battery structures are laminated to form a battery pack, and such a battery pack is used in all devices that require high capacity and high output. For example, it is used in notebook computers, smartphones, electric vehicles, etc.

[0087] Lithium batteries are excellent in terms of life characteristics and high-rate characteristics, and are therefore used, for example, in electric vehicles (EVs). For example, they are used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). They are also used in fields where a large amount of power storage is required. For example, they are used in electric bicycles, power tools, etc.

[0088] A method for manufacturing a composite cathode active material according to still another embodiment includes providing a lithium transition metal oxide, and a chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2, or 3, then b is an integer) or a chemical formula X a (OH) b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2, or 3, then b is an integer), providing one or more first metal compounds represented by the formula; a chemical formula Y c O d (0 < c ≤ 3, 0 < d < 4, if c is 1, 2, or 3, then d is not an integer), providing one or more second metal compounds represented by the formula; and graphene, and providing a composite in which the second metal compound is disposed within a graphene matrix, and mechanically milling the lithium transition metal oxide, the first metal compound, and the composite, wherein X or Y is, independently of each other, one or more metals selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements.

[0089] A lithium transition metal oxide is provided. The lithium transition metal oxide is, for example, a compound represented by the aforementioned Chemical Formulas 1 and 2.

[0090] Chemical formula X a O b (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2, or 3, then b is an integer) or a chemical formula X a (OH) bProviding at least one first metal compound represented by (0 < a ≤ 3, 0 < b ≤ 4, and if a is 1, 2, or 3, b is an integer), the method includes mixing the first metal compound with the lithium transition metal oxide.

[0091] The first metal compound may include, for example, one or more metals selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se as described above. The first metal compound may include, for example, Al. The first metal compound may include, for example, at least one selected from the group consisting of Al2O3 and Al(OH)3. The first metal compound may also include both Al2O3 and Al(OH)3, for example.

[0092] Chemical formula Y c O d Providing a composite including at least one second metal compound represented by (0 < c ≤ 3, 0 < d < 4, and if c is 1, 2, or 3, d is not an integer) and graphene, with the second metal compound disposed within the graphene matrix, for example, includes supplying a reaction gas composed of a carbon source gas to a structure including a third metal compound and performing a heat treatment.

[0093] The step of providing the composite includes, for example, supplying a reaction gas composed of a carbon source gas to at least one third metal compound represented by (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer) and performing a heat treatment, where Y is one or more metals selected from Groups 2 to 13, 15, and 16 of the periodic table of elements. c O e The carbon source gas is at least one mixed gas selected from the group consisting of a compound represented by Chemical Formula 3 below, a compound represented by Chemical Formula 4 below, and an oxygen-containing gas represented by Chemical Formula 5 below:

[0094] [Chemical formula 3] C n H (2n+2-a2 )[OH] a2 ​In the formula (3), n is from 1 to 20, and a2 is 0 or 1; [Chemical formula 4] C n H 2n In the formula (4), n is from 2 to 6; [Chemical formula 5] C x2 H y2 O z2 In the formula (5), x2 is 0 or an integer from 1 to 20, y2 is 0 or an integer from 1 to 20, and z2 is 1 or 2.

[0095] The compound represented by formula (3) and the compound represented by formula (4) are one or more selected from the group consisting of methane, ethylene, propylene, methanol, ethanol, and propanol. The oxygen-containing gas represented by formula (5) includes, for example, carbon dioxide (CO2), carbon monoxide (CO), water vapor (H2O), or a mixture thereof.

[0096] Y c O e After the step of supplying a reaction gas composed of a carbon source gas to a third metal compound represented by (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer) and performing heat treatment, a cooling step using one or more inert gases selected from the group consisting of nitrogen, helium, and argon can be further performed. The cooling step refers to the step of adjusting to room temperature (20 to 25 °C). The carbon source gas may contain one or more inert gases selected from the group consisting of nitrogen, helium, and argon.

[0097] In the method for producing the composite, the process of growing graphene by gas-phase reaction is carried out under various conditions.

[0098] According to the first condition, for example, Y c O eFirst, methane is supplied to a reactor in which a third metal compound represented by (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer) is disposed, and the temperature is raised to a heat treatment temperature T. The temperature raising time to the heat treatment temperature T is from 10 minutes to 4 hours, and the heat treatment temperature T is in the range of 700°C to 1100°C. Heat treatment is carried out for a reaction time at the heat treatment temperature T. The reaction time is, for example, from 4 hours to 8 hours. The heat-treated product is cooled to room temperature to produce a composite. The time taken for the cooling process from the heat treatment temperature T to room temperature is, for example, from 1 hour to 5 hours.

[0099] According to the second condition, for example, Y c O e First, hydrogen is supplied to a reactor in which a third metal compound represented by (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer) is disposed, and the temperature is raised to a heat treatment temperature T. The temperature raising time to the heat treatment temperature T is from 10 minutes to 4 hours, and the heat treatment temperature T is in the range of 700°C to 1100°C. After heat treatment for a certain reaction time at the heat treatment temperature T, methane gas is supplied, and heat treatment is carried out for the remaining reaction time. The reaction time is, for example, from 4 hours to 8 hours. The heat-treated product is cooled to room temperature to produce a composite. Nitrogen is supplied during the cooling process. The time taken for the cooling process from the heat treatment temperature T to room temperature is, for example, from 1 hour to 5 hours.

[0100] In the process of producing a composite, when the carbon source gas contains water vapor, a composite having very excellent conductivity can be obtained. The content of water vapor in the gas mixture is not limited and is, for example, from 0.01% by volume to 10% by volume based on 100% by volume of the total carbon source gas. The carbon source gas is, for example, methane; a gas mixture containing methane and an inert gas; or a gas mixture containing methane and an oxygen-containing gas.

[0101] The carbon source gas is, for example, methane; a gas mixture of methane and carbon dioxide; or a gas mixture of methane, carbon dioxide and steam. In the gas mixture of methane and carbon dioxide, the molar ratio of methane to carbon dioxide is about 1:0.20 to 1:0.50, about 1:0.25 to 1:0.45, or about 1:0.30 to 1:0.40. In the gas mixture of methane, carbon dioxide and steam, the molar ratio of methane, carbon dioxide and steam is about 1:0.20 to 0.50:0.01 to 1.45, about 1:0.25 to 0.45:0.10 to 1.35, or about 1:0.30 to 0.40:0.50 to 1.0.

[0102] The carbon source gas is, for example, carbon monoxide or carbon dioxide. The carbon source gas is, for example, a gas mixture of methane and nitrogen. In the gas mixture of methane and nitrogen, the molar ratio of methane to nitrogen is about 1:0.20 to 1:0.50, about 1:0.25 to 1:0.45, or about 1:0.30 to 1:0.40. The carbon source gas does not contain an inert gas such as nitrogen.

[0103] The heat treatment pressure can be selected in consideration of the heat treatment temperature, the composition of the gas mixture, and the amount of the desired carbon coating, etc. The heat treatment pressure can be controlled by adjusting the amount of the inflowing gas mixture and the amount of the outflowing gas mixture. The heat treatment pressure is, for example, 0.5 atm or more, 1 atm or more, 2 atm or more, 3 atm or more, 4 atm or more, or 5 atm or more.

[0104] The heat treatment time is not particularly limited and can be appropriately adjusted according to the heat treatment temperature, the pressure during heat treatment, the composition of the gas mixture, and the amount of the desired carbon coating. For example, the reaction time at the heat treatment temperature is, for example, from 10 minutes to 100 hours, from 30 minutes to 90 hours, or from 50 minutes to 40 hours. For example, as the heat treatment time increases, the amount of graphene (carbon) deposited increases, whereby the electrical properties of the composite can be improved. However, such a tendency is not necessarily directly proportional to time. For example, after a predetermined time has elapsed, no further graphene deposition occurs or the deposition rate decreases.

[0105] Through the gas-phase reaction of the aforementioned carbon source gas, even at a relatively low temperature, Y c O e (0 < c ≤ 3, 0 < e ≤ 4, if c is 1, 2 or 3, e is an integer), and the reduction product thereof, Y c O d (0 < c ≤ 3, 0 < d < 4, if c is 1, 2 or 3, d is not an integer), a composite is obtained by providing a uniform graphene coating on one or more selected from the second metal compounds represented by

[0106] The composite has, for example, a graphene matrix having one or more structures selected from a spherical structure, a helical structure in which a plurality of spherical structures are connected, a cluster structure in which a plurality of spherical structures are aggregated, and a sponge structure (spone structure), and Y c O d (0 < c ≤ 3, 0 < d < 4, if c is 1, 2 or 3, d is not an integer), and one or more selected from the third metal compounds represented by Y c O e (0 < c ≤ 3, 0 < e ≤ 4, if c is 1, 2 or 3, e is an integer) disposed within the graphene matrix.

[0107] Next, the lithium transition metal oxide, the first metal compound, and the composite are mixed and mechanically milled. When milling, a Nobir mixer or the like can be used. The rotation speed of the mixer during milling is, for example, 1,000 rpm to 2,500 rpm. If the milling speed is less than 1,000 rpm, the shear force applied to the lithium transition metal oxide, the first metal compound, and the composite is weak, so it is difficult for the lithium transition metal oxide, the first metal compound, and the composite to form chemical bonds. If the milling speed is excessively high, the complexation proceeds excessively in a short time, so it is difficult for the first metal compound to be uniformly coated on the lithium transition metal oxide to form a uniform and continuous first shell, and it is difficult for the composite to be uniformly coated on the first metal compound to form a uniform and continuous second shell. The milling time is, for example, 5 minutes to 100 minutes, 5 minutes to 60 minutes, or 5 minutes to 30 minutes. If the milling time is excessively short, it is difficult for the first metal compound to be uniformly coated on the lithium transition metal oxide to form a uniform and continuous first shell, and it is difficult for the composite to be uniformly coated on the first metal compound to form a uniform and continuous second shell. If the milling time becomes excessively long, the production efficiency will decrease.

[0108] As described above, the total weight of the first metal compound, the second metal compound, and the graphene is also about 0.001 to 1% by weight with respect to the weight of the core.

[0109] As described above, the average particle size of the first metal compound is also 1 nm to 200 μm. The average particle size (D50) of the composite used for the mechanical milling of the lithium transition metal oxide and the composite is, for example, 1 μm to 20 μm, 3 μm to 15 μm, or 5 μm to 10 μm.

[0110] The exemplary embodiments are further described in detail through the following examples and comparative examples. However, the examples are for illustrating the technical idea, and the scope of the technical idea is not limited only to these.

[0111] (Production of Composite) Al 2 O 3 @Gr composite After positioning Al2O3 particles (average particle size: about 20 nm) in the reactor, CH4 was supplied into the reactor at about 300 sccm and 1 atm for about 30 minutes, and the internal temperature of the reactor was raised to 1000 °C.

[0112] Then, it was held at the said temperature for 7 hours to perform heat treatment. Then, the internal temperature of the reactor was adjusted to normal temperature (20 to 25 °C), and a composite in which Al2O3 particles and Al2O z (0 < z < 3) particles were embedded in graphene was obtained.

[0113] The graphene content contained in the composite was 30.9 wt%.

[0114] Gr (graphene) Graphene was obtained by manufacturing in the same manner as in Production Example 1, except that the Al2O3 particles were not positioned in the reactor in Production Example 1.

[0115] (Production of composite cathode active material) Production Example 1: LCO 100 g (core) / Al(OH) 3 0.05 g (first shell) / Al 2 O 3 @Gr composite 0.05 g (second shell) LiCoO2 (hereinafter referred to as LCO) with a specific surface area of 0.21 m 2 / g, Al(OH)3 with an average particle size of 200 nm, and the said Al2O3@Gr composite were mixed using a hand mixer for 5 minutes to obtain a composite cathode active material in which a composite coating layer of a first shell and a second shell was formed on the LCO surface.

[0116] The weight ratio of LCO, Al(OH)3 and the Al2O3@Gr composite was 100:0.05:0.05.

[0117] Production Example 2: LCO 100 g (core) / Al(OH) 3 0.05 g, Al 2 O 3 0.03 g (first shell) / Al 2 O 3 @Gr composite 0.02 g (second shell) In Production Example 1, except that the weight ratio of LCO (specific surface area: 0.21 m 2 / g), Al(OH)3 (average particle size: 200 nm), Al2O3 (average particle size: 20 nm), and the Al2O3@Gr composite was changed to 100:0.05:0.03:0.02, a composite cathode active material was produced in the same manner as in Production Example 1.

[0118] Production Example 3: LCO 100 g (core) / Al(OH) 3 0.05 g, Al 2 O 3 0.07 g (first shell) / Al 2 O 3 @Gr composite 0.03 g (second shell) In Production Example 1, except that the weight ratio of LCO (specific surface area: 2.21 m 2 / g), Al(OH)3 (average particle size: 200 nm), Al2O3 (average particle size: 20 nm), and the Al2O3@Gr composite was changed to 100:0.05:0.07:0.03, a composite cathode active material was produced in the same manner as in Production Example 1.

[0119] Production Example 4: LCO 100 g (core) / Al(OH) 3 0.07 g, Al 2 O 3 0.07 g (first shell) / Al 2 O 3 @Gr composite 0.06 g (second shell) In Production Example 1, except that the weight ratio of LCO (specific surface area: 2.21 m 2 / g), Al(OH)3 (average particle size: 200 nm), Al2O3 (average particle size: 20 nm), and the Al2O3@Gr composite was changed to 100:0.07:0.07:0.06, a composite cathode active material was produced in the same manner as in Production Example 1.

[0120] Comparative Production Example 1: bare LCO LCO was used as the cathode active material as it was.

[0121] Comparative Production Example 2: LCO 100 g (core) / Al(OH) 3 0.05 g (first shell) / Gr 0.05 g (second shell) A composite cathode active material was produced in the same manner as in Production Example 1, except that Gr (graphene) was used instead of the Al2O3@Gr composite.

[0122] Comparative Production Example 3: LCO 100 g (core) / Al(OH) 3 0.05 g, Al 2 O 3 0.03 g (first shell) / Gr 0.02 g (second shell) A composite cathode active material was produced in the same manner as in Production Example 2, except that Gr (graphene) was used instead of the Al2O3@Gr composite.

[0123] Comparative Production Example 4: LCO 100 g (core) / Al(OH) 3 0.1 g (shell) A composite cathode active material was produced in the same manner as in Production Example 1, except that LCO and Al(OH)3 were used with a weight ratio of 100:0.1 and the Al2O3@Gr composite was not used.

[0124] Comparative Production Example 5: LCO 100 g (core) / Al(OH) 3 0.05 g (shell) A composite cathode active material was produced in the same manner as in Production Example 1, except that LCO and Al(OH)3 were used with a weight ratio of 100:0.05 and the Al2O3@Gr composite was not used.

[0125] Comparative Production Example 6: LCO 100 g (core) / Al 2 O 3 @Gr composite 0.1 g (shell) A composite cathode active material was produced in the same manner as in Production Example 1, except that LCO and the Al2O3@Gr composite were used with a weight ratio of 100:0.1 and Al(OH)3 was not used.

[0126] Comparative Production Example 7: LCO 100 g (core) / Al 2 O 3 @Gr composite 0.05 g (shell) A composite cathode active material was produced in the same manner as in Production Example 1, except that LCO and the Al2O3@Gr composite were used with a weight ratio of 100:0.05 and Al(OH)3 was not used.

[0127] (Manufacture of Lithium Battery (Half Cell)) Example 1 (Manufacture of Positive Electrode) A mixture of the composite positive electrode active material produced in Production Example 1, a carbon conductive material (Denka Black), and polyvinylidene fluoride (PVdF) mixed at a weight ratio of 96:2:2 was mixed in an agate mortar together with N-methylpyrrolidone (NMP) to produce a slurry.

[0128] The above slurry was loaded onto an aluminum current collector with a thickness of 15 μm at 8.5 mg / cm 2 by bar coating, dried at room temperature, then dried again under vacuum at 120 °C, rolled and punched to produce a positive electrode plate with a thickness of 21 μm and an electrode density of 4.1 g / cc.

[0129] (Manufacture of Coin Cells) Using the positive electrode plate manufactured above, with lithium metal as the counter electrode, a PTFE separator, and a solution in which 1.3 M LiPF6 is dissolved in EC (ethylene carbonate) + EP (ethyl propionate) + PP (propyl propionate) (volume ratio 25:30:45) as the electrolyte, coin cells were manufactured respectively.

[0130] Examples 2 to 4 and Comparative Examples 1 to 7 Coin cells were manufactured in the same manner as in Example 1, except that the composite positive electrode active materials prepared in Production Examples 2 to 4 and Comparative Production Examples 1 to 7 were used respectively instead of the composite positive electrode active material of Production Example 1 in Example 1.

[0131] Evaluation Example 1: Charge and Discharge Characteristics Evaluation at Room Temperature The lithium batteries produced in Examples 1 to 4 and Comparative Examples 1 to 7 were charged at a constant current of 0.1 C rate at 25 °C until the voltage reached 4.55 V (vs. Li), and then cut off at a current of 0.05 C rate while maintaining 4.55 V in the constant voltage mode. Then, it was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) during discharge (formation cycle).

[0132] The lithium battery that had undergone a formation cycle was charged at a constant current of 0.2C rate at 25°C until the voltage reached 4.55V (vs. Li), and then was cut off at a current of 0.05C rate while maintaining 4.55V in the constant voltage mode. Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (1 st cycle). At this time, the voltage drop V generated while flowing a current at 1C for 1 second at SOC 10 (when the total charge capacity of the battery is set to 100%, it is the state charged to 10% of the charge capacity, which means the state of being discharged by 90% during discharge) was measured, and the DC internal resistance (DC-IR) was calculated.

[0133] 1 st The lithium battery that had undergone a formation cycle was charged at a constant current of 1C rate at 25°C until the voltage reached 4.55V (vs. Li), and then was cut off at a current of 0.05C rate while maintaining 4.55V in the constant voltage mode. Then, it was discharged at a constant current of 1C rate until the voltage reached 3.0V (vs. Li) during discharge (2 nd cycles), and such cycles were repeated under the same conditions up to 60 th cycles (repeated 60 times).

[0134] At this time, the voltage drop V generated while flowing a current at 1C for 1 second at SOC 10 (when the total charge capacity of the battery is set to 100%, it is the state charged to 10% of the charge capacity, which means the state of being discharged by 90% during discharge) of the lithium battery that had undergone 60 th cycles was measured, and the DC internal resistance (DC-IR) was calculated.

[0135] During all charge / discharge cycles, a 10-minute stop time was provided after one charge / discharge cycle.

[0136] Among the results of the normal temperature charge and discharge experiments, the discharge capacity (0.2C, mAh / g), initial efficiency (0.2C, %), DC-IR (Ω, SOC 10), and DC-IR increase rate (%, after 60 cycles) are shown in Table 1 below. 60 th The DC-IR increase rate at 60 cycles is defined by the following Equation 1.

[0137] [Equation 1] DC-IR increase rate [%] = [((50 th cycle DC-IR) - (1 st cycle DC-IR)) / 1 st cycle DC-IR] × 100

[0138] Evaluation Example 2: Charge and Discharge Characteristics Evaluation at High Temperature and High Voltage The lithium batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 7 were charged at a constant current at a current of 0.1C rate at 45°C until the voltage reached 4.58 V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.58 V in the constant voltage mode. Then, it was discharged at a constant current of 0.1C rate until the voltage reached 3.0 V (vs. Li) during discharge (formation cycle).

[0139] The lithium battery that had undergone the formation cycle was charged at a constant current at a current of 0.2C rate at 45°C until the voltage reached 4.58 V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.58 V in the constant voltage mode. Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0 V (vs. Li) during discharge (1 st cycle).

[0140] 1 st The lithium battery that had undergone 1 cycle was charged at a constant current at a current of 1C rate at 45°C until the voltage reached 4.58 V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.58 V in the constant voltage mode. Then, it was discharged at a constant current of 1C rate until the voltage reached 3.0 V (vs. Li) during discharge (2 nd cycles), and such cycles were repeated 60 thThe cycle was repeated under the same conditions up to 60 cycles.

[0141] In all charge-discharge cycles, a 10-minute pause time was provided after one charge / discharge cycle.

[0142] A part of the high-temperature charge-discharge experiment results is shown in Table 1 below. 60 th The capacity retention rate at 60 cycles is defined by the following Formula 2.

[0143] [Formula 2] Capacity retention rate [%] = [50 th Discharge capacity at 60 cycles / 1 st Discharge capacity at 1 cycle] × 100

[0144]

Table 1

[0145] As shown in Table 1, the lithium batteries of Examples 1 to 4 had lower DC-IR, improved high-temperature life characteristics, and a decreased DC-IR increase rate compared to the lithium batteries of Comparative Examples 1 to 7.

Explanation of Symbols

[0146] 1 Lithium battery 2 Negative electrode 3 Positive electrode 4 Separator 5 Battery case 6 Cap assembly

Claims

1. a core containing a lithium transition metal oxide; and a first shell and a second shell disposed on the outside of the surface of the core, The first shell contains one or more first metal compounds represented by chemical formula X ａ O ｂ where (0 < a ≤ 3, 0 < b ≤ 4, and if a is 1, 2, or 3, b is an integer), or chemical formula X ａ (OH) ｂ where (0 < a ≤ 3, 0 < b ≤ 4, and if a is 1, 2, or 3, b is an integer). The second shell is a reduction product of one or more third metal compounds represented by the chemical formula YcOe (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer), and the chemical formula Y ｃ O ｄ one or more second metal compounds represented by (0 < c ≤ 3, 0 < d < 4, and if c is 1, 2, or 3, d is not an integer); and includes graphene, the second metal compound is disposed within the graphene matrix, and the X and the Y are each independently one or more metals selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements, a composite cathode active material, wherein the first shell and the second shell are sequentially disposed on the outside of the surface of the core.

2. The composite cathode active material according to claim 1, wherein the first shell is directly disposed on the outside of the surface of the core, and the second shell is directly disposed on the outside of the surface of the first shell.

3. The composite cathode active material according to claim 1, wherein the thickness of the first shell is from 1 nm to 2 μm.

4. The composite cathode active material according to claim 1, wherein the thickness of the second shell is from 1 nm to 2 μm.

5. The composite cathode active material according to claim 1, wherein the metal contained in the first metal compound is one or more metals selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se.

6. The composite cathode active material according to claim 1, wherein the metal contained in the first metal compound is Al.

7. The first metal compound is Al ２ O ３ and at least one selected from the group consisting of Al(OH) ３ The composite cathode active material according to claim 1, comprising at least one selected from the group consisting of

8. The composite cathode active material according to claim 1, wherein the average particle diameter of the first metal compound is from 10 nm to 2 μm.

9. The composite cathode active material according to claim 1, wherein the metal contained in the second metal compound is one or more metals selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se.

10. The second metal compound is Al ２ O ｚ (0 < z < 3), NbO ｘ (0 < x < 2.5), MgO ｘ (0 < x < 1), Sc ２ O ｚ (0 < z < 3), TiO ｙ (0 < y < 2), ZrO ｙ (0 < y < 2), V ２ O ｚ (0 < z < 3), WO ｙ (0 < y < 2), MnO ｙ (0 < y < 2), Fe ２ O ｚ (0 < z < 3), Co ３ O ｗ (0 < w < 4), PdO ｘ (0 < x < 1), CuO ｘ (0 < x < 1), AgO ｘ (0 < x < 1), ZnO ｘ (0 < x < 1), Sb ２ O ｚ (0 < z < 3) and SeO ｙ (0 < y < 2), and is one or more selected therefrom. The composite positive electrode active material according to claim 1.

11. The composite cathode active material according to claim 1, wherein the second shell contains one or more selected from a composite of the second metal compound and graphene and a milling product of the composite.

12. The graphene has a branched structure, and the second metal compound is distributed within the branched structure. The composite cathode active material according to claim 11, wherein the branched structure includes a plurality of graphene particles in contact with each other.

13. The graphene has one or more structures selected from a spherical structure, a helical structure in which the spherical structures are connected, and a cluster structure in which the spherical structures are aggregated. The second metal compound is distributed within the spherical structure, the size of the spherical structure is 50 nm to 300 nm, the size of the spiral structure is 500 nm to 100 μm, and the size of the cluster structure is 0.5 mm to 10 cm. The composite is a wrinkled polyhedral ball structure or a planar structure, and the second metal compound is distributed inside or on the surface of the structure. The graphene extends a distance of 10 nm or less from the second metal compound, includes at least 1 to 20 graphene layers, and the total thickness of the graphene is 0.6 to 12 nm. The composite cathode active material according to claim 11.

14. The sum of the weight of the first metal compound, the weight of the second metal compound, and the weight of the graphene is 0.001 to 1% by weight based on the weight of the core. The composite cathode active material according to claim 1.

15. The lithium transition metal oxide is represented by the following Chemical Formula 1 or Chemical Formula 2. The composite cathode active material according to claim 1: [Chemical Formula 1] Li ａ１ Co ｘ１ M ｙ１ O ２－ｂ１ A ｂ１ In the Chemical Formula 1, 1.0 ≦ a1 ≦ 1.2, 0 ≦ b1 ≦ 0.2, 0.9 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 0.1, and x1 + y1 = 1. M is one or more selected from the group consisting of 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), and boron (B). A is F, S, Cl, Br, or a combination thereof. [Chemical Formula 2] LiCoO ２ .

16. A cathode comprising the composite cathode active material according to any one of claims 1 to 15.

17. A lithium battery comprising the cathode according to claim 16.

18. Providing a lithium transition metal oxide; Chemical formula X ａ O ｂ (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2, or 3, then b is an integer) or chemical formula X ａ (OH) ｂ (0 < a ≤ 3, 0 < b ≤ 4, if a is 1, 2, or 3, then b is an integer), and providing one or more first metal compounds represented thereby Reduction products of one or more third metal compounds represented by the chemical formula YcOe (0 < c ≤ 3, 0 < e ≤ 4, and if c is 1, 2, or 3, e is an integer), the chemical formula Y ｃ O ｄ One or more second metal compounds represented by (0 < c ≤ 3, 0 < d < 4, and if c is 1, 2, or 3, d is not an integer); and graphene, and providing a composite in which the second metal compound is disposed within a graphene matrix Mechanically milling the lithium transition metal oxide, the first metal compound, and the composite. The method for manufacturing a composite cathode active material, wherein the first metal compound and the composite are sequentially arranged on the outer surface of the lithium transition metal oxide. X or Y is, independently of each other, one or more metals selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements. A method for manufacturing a composite cathode active material, wherein the first metal compound and the composite are sequentially arranged on the outer surface of the lithium transition metal oxide.

19. The average particle size of the first metal compound is 1 nm to 2 μm. The first metal compound is Al ２ O ３ and at least one selected from the group consisting of Al(OH) ３ The method for producing a composite positive electrode active material according to claim 18, comprising at least one selected from the group consisting of

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