Lithium transition metal oxide, a cathode additive for a lithium secondary battery, and a lithium secondary battery containing the same

Abstract

The present invention relates to a lithium transition metal oxide, a positive electrode additive for a lithium secondary battery, and a lithium secondary battery including the same. According to the present invention, there is provided a lithium transition metal oxide that can minimize side reactions with an electrolyte and suppress gas generation during charging and discharging of a lithium secondary battery.

Description

Technical Field

[0001] Cross - reference to related applications This application claims the benefit of priority based on Korean Patent Application Nos. 10 - 2021 - 0009337 filed on January 22, 2021, 10 - 2021 - 0106774 filed on August 12, 2021, 10 - 2021 - 0106775 filed on August 12, 2021, and 10 - 2021 - 0106776 filed on August 12, 2021, and all of the contents disclosed in the corresponding Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a lithium transition metal oxide, a positive electrode additive for a lithium secondary battery, and a lithium secondary battery including the same.

Background Art

[0003] With the multi - functionality of electronic devices and the increase in power consumption, many attempts have been made to increase the capacity of lithium secondary batteries and improve their charge - discharge efficiency.

[0004] As an example, a technique has been proposed in which a positive electrode active material with 80% or more Ni is applied as a positive electrode material to the positive electrode of a lithium secondary battery, and a metal or metal - based negative electrode active material such as SiO, Si, or SiC is applied together with a carbon - based negative electrode active material such as natural graphite or artificial graphite to the negative electrode.

[0005] Metal and metal oxide - based negative electrode active materials enable a higher capacity expression than carbon - based negative electrode active materials. However, since the volume change during charge - discharge of metal and metal oxide - based negative electrode active materials is much larger than that of graphite, it is difficult to increase the content of metal and metal oxide in the negative electrode to 15% or more. Also, when adding metal and metal oxide to the negative electrode, an irreversible reaction occurs during the initial charge - discharge, and the loss of lithium is larger than when applying a carbon - based negative electrode active material. Therefore, when applying a metal and metal oxide - based negative electrode active material, the amount of lithium lost increases as the capacity of the battery increases, and the reduction in the initial capacity also increases.

[0006] Therefore, various schemes have been studied to increase the capacity of lithium secondary batteries and reduce irreversible capacity. One of them is prelithiation, which is the concept of replenishing lithium consumed in the formation of the SEI layer (solid electrolyte interphase layer) in the initial state within the battery.

[0007] Various methods have been proposed for prelithiation within the battery.

[0008] As an example, it is a method of electrochemically lithiating the negative electrode in advance before driving the battery. However, the lithiated negative electrode is very unstable in the air, and it is difficult to scale up the electrochemical lithiation method.

[0009] As another example, it is a method of coating the negative electrode with lithium metal or lithium silicide (LixSi) powder. However, since the powder has high reactivity and reduced atmospheric stability, there is a problem that it is difficult to establish suitable solvents and process conditions during coating on the negative electrode.

[0010] As a method of prelithiation at the positive electrode, there is a method of further coating more positive electrode material by an amount equivalent to the amount of lithium consumed at the negative electrode. However, due to the low capacity of the positive electrode material itself, the amount of the added positive electrode material increases, and the energy density and capacity per weight of the final battery decrease by the amount of the increased positive electrode material.

[0011] Therefore, a material suitable for prelithiation of the battery at the positive electrode must have the irreversible characteristic that at least twice as much lithium is desorbed as the existing positive electrode material during the first charge and does not react with lithium during subsequent discharges. Additives that satisfy such conditions are called sacrificial positive electrode materials.

[0012] In the case of a commercial battery, after injecting an electrolyte into a case containing a stacked positive electrode, a separator, and a negative electrode, a formation process of first performing a charge / discharge operation is carried out. In this process, an SEI layer formation reaction occurs on the negative electrode, and gas is generated by the decomposition of the electrolyte. In the formation process, the sacrificial anode material decomposes by giving up lithium and reacts with the electrolyte, and gases such as N2, O2, and CO2 generated in the process are recovered by a gas pocket removal process.

[0013] As the sacrificial anode material, over-lithiated positive electrode materials of metal oxides rich in lithium are often used. As the over-lithiated positive electrode materials, Li6CoO4, Li5FeO4, and Li6MnO4 having an anti-fluorite structure are well known. Their theoretical capacities are 977 mAh / g for Li6CoO4, 867 mAh / g for Li5FeO4, and 1001 mAh / g for Li6MnO4, and they have sufficient capacity to be used as a sacrificial anode material. Among them, Li6CoO4 has the best electrical conductivity and good electrochemical characteristics for use as a sacrificial anode material.

[0014] Li6CoO4 is gradually desorbed and decomposed in the formation process, and the crystal phase collapses, and inevitably O2 gas is generated in this process. Ideally, no additional gas should be generated during the charge / discharge cycle after the formation process for Li6CoO4. If gas is continuously generated during charge / discharge, the pressure inside the battery increases, the distance between the electrodes becomes longer, and the battery capacity and energy density may decrease. In extreme cases, there is a possibility that the battery cannot withstand the pressure and an explosion accident may occur.

[0015] Therefore, there is a need to develop a technology that can inactivate or stabilize the final crystal phase of Li6CoO4 so that no additional gas is generated during the charge / discharge cycle.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0017] The present invention provides a lithium transition metal oxide that can suppress side reactions with an electrolyte and mitigate gas generation at the positive electrode of a lithium secondary battery.

[0018] The present invention provides a method for manufacturing the lithium transition metal oxide.

[0019] The present invention provides a positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide.

[0020] The present invention provides a positive electrode for a lithium secondary battery containing the transition metal oxide.

[0021] The present invention provides a positive electrode for a lithium secondary battery containing the positive electrode additive for a lithium secondary battery.

[0022] And the present invention provides a lithium secondary battery containing the positive electrode for the secondary battery.

Means for Solving the Problems

[0023] According to an embodiment of the invention, a lithium cobalt oxide containing a different element, wherein the different element includes one or more selected from the group consisting of a Group 4 transition metal; and a Group 2 element, a Group 13 element, a Group 14 element, a Group 5 transition metal, and a Group 6 transition metal, The cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm and the ratio of the maximum particle size (D max ) to the minimum particle size (D min ) of 10.0 to 60.0 (D max / D min ) as determined by laser diffraction scattering particle size distribution measurement, a lithium transition metal oxide is provided.

[0024] According to another embodiment of the invention, a first step of solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element oxide; and a second step of firing the mixture obtained in the first step under an inert atmosphere and at a temperature of 550°C to 750°C to obtain the lithium transition metal oxide is provided, which is a method for producing the lithium transition metal oxide.

[0025] According to still another embodiment of the invention, a positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide is provided.

[0026] According to still another embodiment of the invention, a positive electrode for a lithium secondary battery containing a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide is provided.

[0027] According to still another embodiment of the invention, a positive electrode for a lithium secondary battery containing a positive electrode active material, a binder, a conductive material, and the positive electrode additive for a lithium secondary battery is provided.

[0028] According to still another embodiment of the invention, a lithium secondary battery containing the positive electrode for a lithium secondary battery; a negative electrode; a separator; and an electrolyte is provided.

[0029] Hereinafter, the lithium transition metal oxide, the method for producing the lithium transition metal oxide, the positive electrode additive for the lithium secondary battery, the positive electrode for the lithium secondary battery, and the lithium secondary battery according to the embodiments of the invention will be described in more detail.

[0030] The terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. The inventor himself / herself should interpret them in accordance with the meaning and concept that conform to the technical idea of the invention in accordance with the principle that he / she can appropriately define the concept of the terms in order to explain the invention in the best way.

[0031] Unless otherwise specifically defined in this specification, all technical terms and scientific terms have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. The terms used in the description of the present invention are for the purpose of effectively describing specific examples only and are not intended to limit the present invention.

[0032] As used in this specification, the singular form also includes the plural form unless the context clearly indicates the contrary meaning. The meaning of "comprising" as used in this specification does not exclude the presence or addition of other specific characteristics, regions, integers, steps, operations, elements, and / or components while embodying a specific characteristic, region, integer, step, operation, element, and / or component.

[0033] Since the present invention can be modified in various ways and can have various forms, specific examples are illustrated and described in detail below. However, this is not for the purpose of limiting the present invention to a specific disclosed form, and it should be understood to include all modifications, equivalents, or alternatives included in the above-mentioned idea and technical scope.

[0034] In this specification, when the positional relationship between two parts is described, for example, "on ~", "above ~", "below ~", "next to ~", etc., one or more other parts can be located between the two parts unless the expressions "immediately" or "directly" are used.

[0035] In this specification, when temporal relationships such as "after ~", "subsequent to ~", "next ~", "before ~", etc. are described, it can include cases that are not continuous unless the expressions "immediately" or "directly" are used.

[0036] The term "at least one" in this specification should be understood to include all combinations that can be presented from one or more related items.

[0037] The term "positive electrode additive" as used in this specification means a substance having an irreversible property in which lithium is desorbed at least twice or more than the existing positive electrode material during the initial charging of the battery and does not react with lithium during subsequent discharging. The said positive electrode additive can also be referred to as sacrificial positive electrode materials. Since the said positive electrode additive compensates for lithium loss, as a result, the lost capacity of the battery is restored, the capacity of the battery increases, and by suppressing gas generation, it is possible to prevent the battery from exploding and improve the life characteristics and safety of the battery.

[0038] The "stabilization of the crystal phase" of the term used in this specification means suppressing the oxidizing property of amorphous CoO2 that occurs after the initial charging of a lithium secondary battery containing a lithium cobalt oxide-based positive electrode additive into which a foreign element has been introduced. By suppressing the oxidizing property of the said amorphous CoO2, it is possible to prevent the side reaction between CoO2 and the electrolyte and suppress the generation of gas.

[0039] I. Lithium transition metal oxide According to an embodiment of the invention, A lithium cobalt oxide containing a foreign element, The foreign element includes a fourth-period transition metal; and includes one or more selected from the group consisting of a group 2 element, a group 13 element, a group 14 element, a fifth-period transition metal, and a sixth-period transition metal, The cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm and the maximum particle size (D of 10.0 to 60.0) by laser diffraction scattering particle size distribution measurement max) and the minimum particle size (D min ) and the ratio of (D max / D min ), there is provided a lithium transition metal oxide.

[0040] As a result of continuous research by the present inventors, it has been confirmed that a lithium transition metal oxide satisfying the composition and particle size distribution as described above can minimize side reactions with the electrolyte and suppress gas generation at the positive electrode during charge and discharge of a lithium secondary battery, while enabling excellent battery performance. This is presumably due to the introduction of heterogeneous elements having the above composition into the lithium transition metal oxide to maintain a more stabilized crystal phase and minimize the decrease in the initial charge capacity. Thereby, the lithium transition metal oxide enables improvement in the safety and life characteristics of the lithium secondary battery.

[0041] The lithium transition metal oxide can stabilize the crystal phase as compared with a lithium cobalt oxide such as Li6CoO4 by containing two or more heterogeneous elements satisfying the above composition. The stabilization of the crystal phase in the present invention means suppressing the oxidizing property of amorphous CoO2 formed after the initial charge of a lithium secondary battery containing the lithium cobalt oxide.

[0042] In this connection, when the crystal phase of the electrode is confirmed by X-ray diffraction (XRD) after completely charging a lithium secondary battery containing Li6CoO4, there is a tendency that there is no amorphous pattern. In the formation process, Li6CoO4 is initially oxidized from Co 2+ cations to Co 4+ cations, and thereafter gas is generated by the oxidation of O 2- anions. When charging is completed, it becomes a composition of CoO2 (Co 4+ ), but since the composition does not show crystallinity, no pattern is observed.

[0043] In the case of Co 4+ cations, when left as it is or during discharge (reduction reaction), Co 2+ cations or Co3+ Since it has a high oxidizing property that tends to be reduced to cations, it oxidizes the surrounding electrolyte and causes side reactions. Due to the side reactions, electrolytes such as carbonates are decomposed and gases such as CO2, CO, and H2 are generated. When subsequent charge-discharge cycles are performed, Co reduced during charging 2+ cations and Co 3+ cations become Co 4+ is oxidized to cations and Co is reduced again during discharge 4+ cations become Co 2+ cations and Co 3+ is reduced to cations, and gases are continuously generated due to the side reactions.

[0044] To suppress such side reactions, it is necessary to suppress the oxidizing property that is the tendency of Co 4+ cations to be reduced. For example, a method of introducing a different element to stabilize the oxidation number of Co 4+ cations can be mentioned.

[0045] In the lithium transition metal oxide, by introducing a different element that can have a fixed oxidation number during charge and discharge of the battery, it is possible to expect the effect of reducing the average oxidation number of Co 4+ cations. Thereby, the oxidizing property of Co 4+ cations can be suppressed, and the generation of gases due to the side reactions can be suppressed.

[0046] However, as the introduction amount of the different element that can have a fixed oxidation number during charge and discharge of the battery increases, the initial charge capacity relatively decreases, and the electrical conductivity may show a decreasing tendency. Therefore, a 4th period transition metal is introduced as the main element of the different element, and by introducing a sub element that can complement the electrochemical properties of the main element together, the stabilizing effect of the crystal phase can be expressed, and excellent battery performance can be ensured.

[0047] The lithium transition metal oxide has a composition in which two or more different elements are introduced by alloying or doping into Li6CoO4.

[0048] Here, the "alloy" means one in which the hetero element is introduced at 10 mol% or more based on the total metal elements excluding lithium among the lithium transition metal oxides. And the "doping" means one in which the hetero element is introduced at less than 10 mol% based on the total metal elements excluding lithium among the lithium transition metal oxides.

[0049] The lithium transition metal compound contains a Group 4 transition metal as a main element among the hetero elements.

[0050] And the lithium transition metal compound contains one or more elements selected from the group consisting of a Group 2 element, a Group 13 element, a Group 14 element, a Group 5 transition metal, and a Group 6 transition metal as sub elements among the hetero elements.

[0051] Specifically, the Group 4 transition metal contains one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0052] And the Group 2 element contains one or more selected from the group consisting of Mg, Ca, Sr, and Ba; the Group 13 element contains one or more selected from the group consisting of Al, Ga, and In; the Group 14 element contains one or more selected from the group consisting of Si, Ge, and Sn; the Group 5 transition metal contains one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; the Group 6 transition metal contains one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

[0053] Preferably, from the aspects of the ease of alloying or doping with lithium cobalt oxide and the stabilization of the crystal phase, it may contain Zn, which is a Group 4 transition metal, as the main element among the hetero elements; and may contain one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W as sub elements.

[0054] Zn, Al, Mg, Ti, Zr, Nb, and W are often substituted at the Co sites within the anti-fluorite lattice structure of the Li6CoO4 crystal phase and have the property that their oxidation numbers remain unchanged. For example, Zn exists in the Li6ZnO4 crystal phase, and an alloy with Li6CoO4 is also easily formed. Since its oxidation number also does not change from 2+, after the initial charge, Co 4+ The oxidizing property of the cation can be effectively suppressed.

[0055] The heteroelements are selected considering whether they can exist within the anti-fluorite lattice structure of the lithium cobalt oxide and whether they have a fixed oxidation number during charge and discharge of the battery.

[0056] As an example, among the fourth-period transition metals, Zn exists in the Li6ZnO4 crystal phase, and an alloy with Li6CoO4 is also easily formed. Since its oxidation number also does not change from 2+, after the initial charge, Co 4+ The oxidizing property of the cation can be effectively suppressed.

[0057] As another example, in the cases of Li5FeO4 and Li6MnO4 that do not satisfy the above composition, an anti-fluorite lattice structure can be formed. However, Mn has multiple oxidation numbers of 2+, 3+, 4+, and 7+, and Fe has multiple oxidation numbers of 2+ and 3+. As a result, when CoO, MnO, Fe2O3, etc., which are raw materials of the lithium cobalt oxide, are mixed and then calcined, Mn or Fe is oxidized and Co 2+ The cation is reduced and Co that is not in the single-crystal-phase anti-fluorite lattice structure 0 , that is, Co metal can be generated. Even if a single-crystal-phase alloyed Li6CoO4 is generated, in the case of Mn or Fe, since the oxidation number easily changes within the operating voltage, after the initial charge, Co 4+ It is difficult to suppress the oxidizing property of the cation.

[0058] Based on all the metal elements excluding lithium from the lithium transition metal oxide, the heteroelements can be contained in an amount of 5 mol% to 80 mol%.

[0059] In order to enable the manifestation of the stabilizing effect of the crystal phase, the content of the hetero element is preferably 5 mol% or more based on the total metal elements excluding lithium. However, when an excessive amount of hetero element is introduced, the electric conductivity of the lithium transition metal oxide decreases, the resistance of the electrode increases, and the performance of the battery deteriorates. Therefore, the content of the hetero element is preferably 80 mol% or less based on the total metal elements excluding lithium.

[0060] Specifically, the content of the hetero element can be 5 mol% or more, or 10 mol% or more, or 15 mol% or more based on the total metal elements excluding lithium; and 80 mol% or less, or 70 mol% or less, or 60 mol% or less.

[0061] Preferably, the content of the hetero element can be 10 mol% to 80 mol%, or 10 mol% to 70 mol%, or 15 mol% to 70 mol%, or 15 mol% to 60 mol% based on the total metal elements excluding lithium.

[0062] Furthermore, within the range of the content of the hetero element, the content ratio of the main element (the fourth-period transition metal) and the sub element (one or more elements selected from the group consisting of the group 2 element, the group 13 element, the group 14 element, the fifth-period transition metal, and the sixth-period transition metal) is determined.

[0063] As an example, the fourth-period transition metal among the hetero elements can be contained in an amount of 10 mol% to 70 mol% based on the total metal elements excluding lithium from the lithium transition metal oxide.

[0064] In order to enable the manifestation of the stabilizing effect of the crystal phase, the content of the Group 4 transition metal in the lithium transition metal oxide is preferably 10 mol% or more based on the total metal elements excluding lithium. However, when an excessive amount of foreign elements is introduced, the electric conductivity of the lithium transition metal oxide decreases, the resistance of the electrode increases, and the performance of the battery deteriorates. Therefore, the content of the Group 4 transition metal in the lithium transition metal oxide is preferably 70 mol% or less based on the total metal elements excluding lithium.

[0065] Specifically, the content of the Group 4 transition metal in the lithium transition metal oxide can be 10 mol% or more, or 15 mol% or more, or 20 mol% or more based on the total metal elements excluding lithium; and 70 mol% or less, or 50 mol% or less, or 30 mol% or less.

[0066] Preferably, the content of the Group 4 transition metal in the lithium transition metal oxide can be 10 mol% to 70 mol%, or 15 mol% to 70 mol%, or 15 mol% to 50 mol%, or 20 mol% to 50 mol%, or 20 mol% to 30 mol% based on the total metal elements excluding lithium.

[0067] The stabilizing effect of the crystal phase of the lithium transition metal oxide is expected to be proportional to the content of the foreign elements. However, as the introduction amount of foreign elements such as Zn, which is electrochemically inactive, increases, the initial charge capacity relatively decreases, and the electric conductivity tends to decrease.

[0068] Therefore, the content of the sub-elements among the foreign elements is preferably 1 mol% or more based on the total metal elements excluding lithium.

[0069] However, when an excessive amount of foreign elements is introduced, the electrical conductivity of the lithium transition metal oxide decreases, the resistance of the electrode increases, and the performance of the battery deteriorates. Therefore, the content of the sub-element in the lithium transition metal oxide is preferably 20 mol% or less based on the total metal elements excluding lithium.

[0070] Specifically, the content of the sub-element in the lithium transition metal oxide can be 1 mol% or more, or 2 mol% or more, or 3 mol% or more based on the total metal elements excluding lithium; and can be 20 mol% or less, or 17 mol% or less, or 15 mol% or less.

[0071] Preferably, the content of the sub-element in the lithium transition metal oxide can be 1 mol% to 20 mol%, or 2 mol% to 20 mol%, or 2 mol% to 17 mol%, or 3 mol% to 17 mol%, or 3 mol% to 15 mol% based on the total metal elements excluding lithium.

[0072] The lithium transition metal oxide is represented by the following Chemical Formula 1: [Chemical Formula 1] Li6Co 1-x-y Zn x M y O4 In the Chemical Formula 1, M is a Group 2 element, a Group 13 element, a Group 14 element, a transition metal of the 5th period, or a transition metal of the 6th period, x is 0.1 to 0.7, y is 0.01 to 0.2.

[0073] Preferably, in the Chemical Formula 1, M can be one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

[0074] In the Chemical Formula 1, x is 0.1 to 0.7 and y is 0.01 to 0.2. Specifically, the x can be 0.1 or more, or 0.15 or more, or 0.2 or more; and 0.7 or less, or 0.5 or less, or 0.3 or less. Preferably, the x can be 0.1 - 0.7, or 0.15 - 0.7, or 0.15 - 0.5, or 0.2 - 0.5, or 0.2 - 0.3.

[0075] The y can be 0.01 or more, or 0.02 or more, or 0.03 or more; and 0.2 or less, or 0.17 or less, or 0.15 or less. Preferably, the y can be 0.01 - 0.2, or 0.02 - 0.2, or 0.02 - 0.17, or 0.03 - 0.17, or 0.03 - 0.15.

[0076] And in Chemical Formula 1, the x + y value is preferably 0.05 or more, or 0.10 or more, or 0.15 or more, or 0.20 or more; and 0.80 or less, or 0.70 or less, or 0.60 or less, or 0.50 or less.

[0077] That is, for the expression of the crystal phase stabilization effect of the lithium transition metal oxide, in Chemical Formula 1, the x + y value is preferably 0.05 or more, or 0.10 or more, or 0.15 or more, or 0.20 or more. However, when the x + y value is excessively large, the electrical conductivity of the lithium transition metal oxide may decrease and the performance of the battery may deteriorate. Therefore, in Chemical Formula 1, the x + y value is preferably 0.80 or less, or 0.70 or less, or 0.60 or less, or 0.50 or less.

[0078] Specifically, in Chemical Formula 1, the x + y value can be 0.05 - 0.80, or 0.10 - 0.80, or 0.15 - 0.80, or 0.15 - 0.70, or 0.15 - 0.60, or 0.20 - 0.60, or 0.20 - 0.50.

[0079] Preferably, the lithium transition metal oxide is Li6Co 0.77 Zn 0.2Al 0.03 O4, Li6Co 0.76 Zn 0.2 Al 0.04 O4, Li6Co 0.75 Zn 0.2 Al 0.05 O4, Li6Co 0.7 Zn 0.25 Al 0.05 O4, Li6Co 0.65 Zn 0.25 Al 0.1 O4, Li6Co 0.67 Zn 0.3 Al 0.03 O4, Li6Co 0.66 Zn 0.3 Al 0.04 O4, Li6Co 0.65 Zn 0.3 Al 0.05 O4, Li6Co 0.6 Zn 0.3 Al 0.1 O4, Li6Co 0.77 Zn 0.2 Mg 0.03 O4, Li6Co 0.76 Zn 0.2 Mg 0.04 O4, Li6Co 0.75 Zn 0.2 Mg 0.05 O4, Li6Co 0.7 Zn 0.25 Mg 0.05 O4, Li6Co 0.67 Zn 0.3 Mg 0.03 O4, Li6Co 0.66 Zn 0.3 Mg 0.04 O4, Li6Co 0.65 Zn 0.3 Mg 0.05 O4, Li6Co 0.77 Zn 0.2 Ti 0.03 O4, Li6Co 0.76 Zn 0.2 Ti 0.04 O4, Li6Co 0.75 Zn 0.2 Ti 0.05 O4, Li6Co 0.72 Zn 0.25 Ti 0.03 O4, Li6Co0.67 Zn 0.3 Ti 0.03 O4, Li6Co 0.66 Zn 0.3 Ti 0.04 O4, Li6Co 0.65 Zn 0.3 Ti 0.05 O4, Li6Co 0.77 Zn 0.2 Zr 0.03 O4, Li6Co 0.76 Zn 0.2 Zr 0.04 O4, Li6Co 0.75 Zn 0.2 Zr 0.05 O4, Li6Co 0.72 Zn 0.25 Zr 0.03 O4, Li6Co 0.67 Zn 0.3 Zr 0.03 O4, Li6Co 0.66 Zn 0.3 Zr 0.04 O4, Li6Co 0.65 Zn 0.3 Zr 0.05 O4, Li6Co 0.77 Zn 0.2 Nb 0.03 O4, Li6Co 0.76 Zn 0.2 Nb 0.04 O4, Li6Co 0.75 Zn 0.2 Nb 0.05 O4, Li6Co 0.67 Zn 0.3 Nb 0.03 O4, Li6Co 0.66 Zn 0.3 Nb 0.04 O4, Li6Co 0.65 Zn 0.3 Nb 0.05 O4, Li6Co 0.77 Zn 0.2 W 0.03 O4, Li6Co 0.76 Zn 0.2 W 0.04 O4, Li6Co 0.75 Zn 0.2 W 0.05 O4, Li6Co 0.67 Zn 0.3 W0.03 O4, Li6Co 0.66 Zn 0.3 W 0.04 O4, and Li6Co 0.65 Zn 0.3 W 0.05 It may contain one or more compounds selected from the group consisting of O4.

[0080] On the other hand, the lithium transition metal oxide has a cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm and a maximum particle size (D max ) and a minimum particle size (D min ) ratio (D max / D min ) measured by laser diffraction scattering particle size distribution measurement.

[0081] And the lithium transition metal oxide has a cumulative 5% particle size (D5) of 3.0 μm to 10.0 μm and a cumulative 95% particle size (D95) of 20.0 μm to 45.0 μm measured by laser diffraction scattering particle size distribution measurement.

[0082] The laser diffraction scattering particle size distribution measurement is a method of obtaining the particle size distribution from the diffraction image obtained by dispersing the lithium transition metal oxide in a dispersion medium, irradiating laser light thereon, and condensing the scattered light (forward scattered light) generated at this time. The laser diffraction scattering particle size distribution measurement is relatively simple, rapid, and can obtain the particle size distribution with excellent measurement accuracy.

[0083] Here, the cumulative 50% particle size (D50) means the particle size up to 50% cumulative based on mass from the smaller side of the particle size measured using a laser diffraction scattering particle size distribution measuring device.

[0084] The lithium transition metal oxide has a cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm.

[0085] To prevent the side reaction with the electrolyte from intensifying due to an overly large specific surface area, it is preferable that the D50 value is 10.0 μm or more. However, when the particle size is overly large, it is difficult to uniformly coat the positive electrode material containing the lithium transition metal oxide on the current collector, and damage to the current collector may be induced during the rolling process after drying. Therefore, it is preferable that the D50 value is 25.0 μm or less.

[0086] Specifically, the lithium transition metal oxide can have a D50 value of 10.0 μm or more, or 10.5 μm or more, or 11.0 μm or more, or 11.5 μm or more; and 25.0 μm or less, or 24.0 μm or less, or 23.0 μm or less, or 22.0 μm or less.

[0087] Preferably, the lithium transition metal oxide can have a D50 value of 10.5 μm to 25.0 μm, or 10.5 μm to 24.0 μm, or 11.0 μm to 24.0 μm, or 11.0 μm to 23.0 μm, or 11.5 μm to 23.0 μm, or 11.5 μm to 22.0 μm.

[0088] And the lithium transition metal oxide has a ratio (D max ) of the maximum particle size (D min ) to the minimum particle size (D max / D min ).

[0089] The smaller the D max / D min value, the more preferable. However, in order to minimize the loss amount of the lithium transition metal oxide and maximize the yield during the particle grinding and classification process, it is preferable that the D max / D min value is 10.0 or more.

[0090] On the one hand, when the difference between the maximum particle size and the minimum particle size is excessively large, the volume of particles with a small particle size may be excessively expressed, and as a result, the side reaction with the electrolyte becomes intense. And the particles with a large particle size have a smaller specific surface area and a relatively lower volume compared to the small particles. Therefore, the average characteristics of the lithium transition metal oxide particles cannot be crystallized, and it is difficult to apply this to a battery, which is not preferable in terms of reproducibility. Therefore, the D max / D min value is preferably 60.0 or less.

[0091] Specifically, the lithium transition metal oxide is 10.0 or more, or 11.0 or more, or 12.0 or more, or 13.0 or more, or 14.0 or more, or 15.0 or more; and 60.0 or less, or 59.0 or less, or 58.0 or less, or 57.0 or less of the D max / D min value can be had.

[0092] Preferably, the lithium transition metal oxide is 11.0 to 60.0, or 11.0 to 59.0, or 12.0 to 59.0, or 12.0 to 58.0, or 13.0 to 58.0, or 13.0 to 57.0, or 14.0 to 57.0, or 15.0 to 57.0 of the D max / D min value can be had.

[0093] The lithium transition metal oxide has a maximum particle size (D max ) of 30.0 μm to 90.0 μm and a minimum particle size (D min ) of 1.0 μm to 5.0 μm.

[0094] Specifically, the lithium transition metal oxide is 30.0 μm or more, or 32.0 μm or more, or 34.0 μm or more, or 36.0 μm or more, or 38.0 μm or more; and 90.0 μm or less, or 89.5 μm or less, or 89.0 μm or less, or 88.5 μm or less, or 88.0 μm or less of the D maxIt can have a value. Preferably, the lithium transition metal oxide has a D value of 32.0 μm to 90.0 μm, or 32.0 μm to 89.5 μm, or 34.0 μm to 89.5 μm, or 34.0 μm to 89.0 μm, or 36.0 μm to 89.0 μm, or 36.0 μm to 88.5 μm, or 38.0 μm to 88.5 μm, or 38.0 μm to 88.0 μm. max It can have a value.

[0095] And the lithium transition metal oxide can have a D value of 1.0 μm or more, or 1.1 μm or more, or 1.2 μm or more; and 5.0 μm or less, or 4.5 μm or less, or 4.0 μm or less, or 3.5 μm or less, or 3.0 μm or less. min It can have a value. Preferably, the lithium transition metal oxide has a D value of 1.0 μm to 4.5 μm, or 1.1 μm to 4.5 μm, or 1.1 μm to 4.0 μm, or 1.1 μm to 3.5 μm, or 1.2 μm to 3.5 μm, or 1.2 μm to 3.0 μm. min It can have a value.

[0096] Furthermore, the lithium transition metal oxide has a cumulative 5% particle size (D5) of 3.0 μm to 10.0 μm and a cumulative 95% particle size (D95) of 20.0 μm to 45.0 μm.

[0097] Specifically, the lithium transition metal oxide can have a D5 value of 3.0 μm or more, or 3.5 μm or more, or 4.0 μm or more, or 4.5 μm or more, or 5.0 μm or more; and 10.0 μm or less, or 9.9 μm or less, or 9.8 μm or less. Preferably, the lithium transition metal oxide can have a D5 value of 3.5 μm to 10.0 μm, or 4.0 μm to 10.0 μm, or 4.0 μm to 9.9 μm, or 4.5 μm to 9.9 μm, or 4.5 μm to 9.8 μm, or 5.0 μm to 9.8 μm.

[0098] And the lithium transition metal oxide can have a D95 value of 20.0 μm or more, or 20.5 μm or more, or 21.0 μm or more; and 45.0 μm or less, or 44.0 μm or less, or 43.0 μm or less. Preferably, the lithium transition metal oxide can have a D95 value of 20.5 μm to 45.0 μm, or 20.5 μm to 44.0 μm, or 21.0 μm to 44.0 μm, or 21.0 μm to 43.0 μm.

[0099] As a non-limiting example, the lithium transition metal oxide can have a D value of 30.0 μm to 70.0 μm and a D max value of 10.0 to 30.0. max / D min value. The lithium transition metal oxide satisfying the D max value and the D max / D min value can be a compound in which M is a Group 13 element, preferably Al, in Chemical Formula 1.

[0100] The lithium transition metal oxide has the property of irreversibly raising lithium during charge and discharge of a lithium secondary battery. In particular, the lithium transition metal oxide suppresses side reactions with the electrolyte, enabling improvement in the safety and life characteristics of the lithium secondary battery.

[0101] II. Method for Producing Lithium Transition Metal Oxide According to another embodiment of the invention, a first step of solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element oxide; and a second step of firing the mixture obtained in the first step under an inert atmosphere and at a temperature of 550°C to 750°C to obtain the lithium transition metal oxide is provided, including a method for producing the lithium transition metal oxide.

[0102] In the first step, a raw material mixture containing a lithium oxide, a cobalt oxide, and a heterogeneous element oxide is prepared.

[0103] As the lithium oxide, an oxide containing lithium such as Li2O can be used without particular limitation.

[0104] Further, as the cobalt oxide, an oxide containing cobalt such as CoO can be used without particular limitation.

[0105] Matters regarding the hetero element are replaced with the content described in the item of "I. Lithium transition metal oxide".

[0106] As the hetero element oxide, a Group 4 transition metal oxide; and an oxide of one or more elements selected from the group consisting of a Group 2 element, a Group 13 element, a Group 14 element, a Group 5 transition metal, and a Group 6 transition metal can be used. As non-limiting examples, as the hetero element oxide, an oxide containing the hetero element such as ZnO, Mg, Al2O3, TiO2, ZrO2, Nb2O5, and WO3 can be used without particular limitation.

[0107] The raw material mixture is prepared by solid-phase mixing the lithium oxide, the cobalt oxide, and the hetero element oxide so as to conform to the stoichiometric ratio described in "I. Lithium transition metal oxide".

[0108] In the second step, the lithium transition metal oxide is obtained by firing the raw material mixture obtained in the first step under an inert atmosphere and at a temperature of 550°C to 750°C.

[0109] The second step is carried out under an inert atmosphere formed using an inert gas such as Ar, N2, Ne, and He.

[0110] In the second step, it is preferable to heat the mixture obtained in the first step under an inert atmosphere at a heating rate of 1.4°C / min to 2.0°C / min so as to reach the firing temperature. When the heating rate is excessively slow, crystal seeds are formed slowly, crystal growth continues, and the particles become excessively large. Therefore, the heating rate is preferably 1.4 °C / min or more. However, when the heating rate is excessively fast, a large amount of crystal seeds are generated at a very high speed, the growth time of the particles is relatively insufficient, the crystallinity becomes relatively low, and the particle size also becomes relatively small. Therefore, the heating rate is preferably 2.0 °C / min or less.

[0111] Specifically, the heating rate may be 1.40 °C / min or more, or 1.45 °C / min or more, or 1.50 °C / min or more; and 2.00 °C / min or less, or 1.95 °C / min or less, or 1.90 °C / min or less. Preferably, the heating rate may be 1.40 °C / min to 2.00 °C / min, or 1.45 °C / min to 2.00 °C / min, or 1.45 °C / min to 1.95 °C / min, or 1.50 °C / min to 1.95 °C / min, or 1.50 °C / min to 1.90 °C / min.

[0112] The firing is performed at a temperature of 550 °C to 750 °C.

[0113] In order to generate crystal seeds at an appropriate rate, the firing temperature is preferably 550 °C or more. However, when the firing temperature is excessively high, a sintering phenomenon may occur in which the grown crystal particles agglomerate. Therefore, the firing temperature is preferably 750 °C or less.

[0114] Specifically, the firing temperature may be 550 °C or more, or 580 °C or more, or 600 °C or more; and 750 °C or less, or 720 °C or less, or 700 °C or less. Preferably, the firing temperature may be 580 °C to 750 °C, or 580 °C to 720 °C, or 600 °C to 720 °C, or 600 °C to 700 °C.

[0115] The firing is carried out at the firing temperature for 2 to 20 hours. The firing time can be adjusted in consideration of the time required for the foreign elements to be introduced into the lithium cobalt oxide in the form of an alloy or doping to stabilize the crystal. Specifically, the firing time can be 2 hours or more, or 3 hours or more, or 4 hours or more; and 20 hours or less, or 19 hours or less, or 18 hours or less. Preferably, the firing time can be 3 to 20 hours, or 3 to 19 hours, or 4 to 19 hours, or 4 to 18 hours.

[0116] The lithium transition metal oxide obtained in the second stage has a cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm and a maximum particle size (D max ) and minimum particle size (D min ) ratio (D max / D min ) as determined by laser diffraction scattering particle size distribution measurement. Optionally, a step of pulverizing and classifying the lithium transition metal oxide so that it falls within the range of the D50 value may be performed.

[0117] Optionally, a step of washing and drying the compound represented by Chemical Formula 1 obtained in the second stage may be performed.

[0118] As a non-limiting example, the washing step can be performed by mixing the compound of Chemical Formula 1 and the washing liquid at a weight ratio of 1:2 to 1:10 and stirring. As the washing liquid, distilled water, ammonia water, etc. can be used. The drying can be performed by heat treatment at a temperature of 100°C to 200°C or 100°C to 180°C for 1 to 10 hours.

[0119] III. Cathode Additive for Lithium Secondary Battery According to another embodiment of the invention, a cathode additive for a lithium secondary battery containing the lithium transition metal oxide is provided.

[0120] The lithium transition metal oxide can minimize the side reaction with the electrolyte and suppress the gas generation at the positive electrode during charge and discharge of the lithium secondary battery. Therefore, the positive electrode additive for the lithium secondary battery containing the lithium transition metal oxide enables the improvement of the safety and life characteristics of the lithium secondary battery.

[0121] The positive electrode additive for the lithium secondary battery containing the lithium transition metal oxide has the property of irreversibly raising lithium during charge and discharge of the lithium secondary battery. Therefore, the positive electrode additive for the lithium secondary battery can be included in the positive electrode for the lithium secondary battery and serve as sacrificial positive electrode materials for prelithiation.

[0122] Matters regarding the lithium transition metal oxide are replaced with the content described in the item of "I. Lithium transition metal oxide".

[0123] The lithium transition metal oxide has a composition in which two or more different elements are alloyed or doped into Li6CoO4 and introduced.

[0124] The lithium transition metal compound contains a fourth-period transition metal as a main element among the different elements.

[0125] And the lithium transition metal compound contains one or more elements selected from the group consisting of a group 2 element, a group 13 element, a group 14 element, a fifth-period transition metal, and a sixth-period transition metal as sub-elements among the different elements.

[0126] Specifically, the fourth-period transition metal contains one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0127] The Group 2 element contains one or more selected from the group consisting of Mg, Ca, Sr, and Ba; the Group 13 element contains one or more selected from the group consisting of Al, Ga, and In; the Group 14 element contains one or more selected from the group consisting of Si, Ge, and Sn; the Group 5 transition metal contains one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; and the Group 6 transition metal contains one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

[0128] Preferably, from the aspects of the ease of alloying or doping with lithium cobalt oxide and the stabilization of the crystal phase, Zn, which is a Group 4 transition metal as the main element among the heterogeneous elements, may be included; and one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W may be included as the sub-elements.

[0129] The heterogeneous elements may be contained in an amount of 5 mol% to 80 mol% based on the total metal elements excluding lithium from the lithium transition metal oxide.

[0130] The Group 4 transition metal among the heterogeneous elements may be contained in an amount of 10 mol% to 70 mol% based on the total metal elements excluding lithium from the lithium transition metal oxide.

[0131] One or more heterogeneous elements selected from the group consisting of the Group 2 element, the Group 13 element, the Group 14 element, the Group 5 transition metal, and the Group 6 transition metal among the heterogeneous elements may be contained in an amount of 1 mol% to 20 mol% based on the total metal elements excluding lithium from the lithium transition metal oxide.

[0132] The lithium transition metal oxide is represented by the following Chemical Formula 1: [Chemical Formula 1] Li6Co 1-x-y Zn x M y O4 In Chemical Formula 1, M is a Group 2 element, a Group 13 element, a Group 14 element, a Period 5 transition metal, or a Period 6 transition metal, x is from 0.1 to 0.7, y is from 0.01 to 0.2.

[0133] Preferably, in Chemical Formula 1, M can be one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

[0134] Preferably, the lithium transition metal oxide is Li6Co 0.77 Zn 0.2 Al 0.03 O4, Li6Co 0.76 Zn 0.2 Al 0.04 O4, Li6Co 0.75 Zn 0.2 Al 0.05 O4, Li6Co 0.7 Zn 0.25 Al 0.05 O4, Li6Co 0.65 Zn 0.25 Al 0.1 O4, Li6Co 0.67 Zn 0.3 Al 0.03 O4, Li6Co 0.66 Zn 0.3 Al 0.04 O4, Li6Co 0.65 Zn 0.3 Al 0.05 O4, Li6Co 0.6 Zn 0.3 Al 0.1 O4, Li6Co 0.77 Zn 0.2 Mg 0.03 O4, Li6Co 0.76 Zn 0.2 Mg 0.04 O4, Li6Co 0.75 Zn 0.2 Mg 0.05 O4, Li6Co 0.7 Zn 0.25 Mg 0.05 O4, Li6Co 0.67 Zn 0.3 Mg 0.03 O4, Li6Co 0.66 Zn0.3 Mg 0.04 O4, Li6Co 0.65 Zn 0.3 Mg 0.05 O4, Li6Co 0.77 Zn 0.2 Ti 0.03 O4, Li6Co 0.76 Zn 0.2 Ti 0.04 O4, Li6Co 0.75 Zn 0.2 Ti 0.05 O4, Li6Co 0.72 Zn 0.25 Ti 0.03 O4, Li6Co 0.67 Zn 0.3 Ti 0.03 O4, Li6Co 0.66 Zn 0.3 Ti 0.04 O4, Li6Co 0.65 Zn 0.3 Ti 0.05 O4, Li6Co 0.77 Zn 0.2 Zr 0.03 O4, Li6Co 0.76 Zn 0.2 Zr 0.04 O4, Li6Co 0.75 Zn 0.2 Zr 0.05 O4, Li6Co 0.72 Zn 0.25 Zr 0.03 O4, Li6Co 0.67 Zn 0.3 Zr 0.03 O4, Li6Co 0.66 Zn 0.3 Zr 0.04 O4, Li6Co 0.65 Zn 0.3 Zr 0.05 O4, Li6Co 0.77 Zn 0.2 Nb 0.03 O4, Li6Co 0.76 Zn 0.2 Nb 0.04 O4, Li6Co 0.75 Zn 0.2 Nb 0.05 O4, Li6Co 0.67 Zn 0.3 Nb 0.03O4, Li6Co 0.66 Zn 0.3 Nb 0.04 O4, Li6Co 0.65 Zn 0.3 Nb 0.05 O4, Li6Co 0.77 Zn 0.2 W 0.03 O4, Li6Co 0.76 Zn 0.2 W 0.04 O4, Li6Co 0.75 Zn 0.2 W 0.05 O4, Li6Co 0.67 Zn 0.3 W 0.03 O4, Li6Co 0.66 Zn 0.3 W 0.04 O4 and Li6Co 0.65 Zn 0.3 W 0.05 It may contain one or more compounds selected from the group consisting of O4.

[0135] The lithium transition metal oxide has a cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm and a maximum particle size (D max ) and a minimum particle size (D min ) ratio (D max / D min ) as measured by laser diffraction scattering particle size distribution measurement.

[0136] The lithium transition metal oxide has a maximum particle size (D max ) of 30.0 μm to 90.0 μm and a minimum particle size (D min ) of 1.0 μm to 5.0 μm as measured by laser diffraction scattering particle size distribution measurement.

[0137] And the lithium transition metal oxide has a cumulative 5% particle size (D5) of 3.0 μm to 10.0 μm and a cumulative 95% particle size (D95) of 20.0 μm to 45.0 μm as measured by laser diffraction scattering particle size distribution measurement.

[0138] IV. Cathode for Lithium Secondary Battery According to another embodiment of the invention, a cathode for a lithium secondary battery is provided.

[0139] The positive electrode for the lithium secondary battery may include a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide.

[0140] Also, the positive electrode for the lithium secondary battery may include a positive electrode active material, a binder, a conductive material, and an additive for the positive electrode of the lithium secondary battery.

[0141] The lithium transition metal oxide and the additive for the positive electrode of the lithium secondary battery have the property of irreversibly raising lithium during charge and discharge of the lithium secondary battery. Therefore, the lithium transition metal oxide and the additive for the positive electrode of the lithium secondary battery can be included in the positive electrode for the lithium secondary battery and serve as sacrificial positive electrode materials for prelithiation.

[0142] Preferably, the positive electrode for the lithium secondary battery includes a positive electrode material containing a positive electrode active material, a conductive material, the sacrificial positive electrode material, and a binder; and a current collector supporting the positive electrode material.

[0143] Here, the sacrificial positive electrode material is the lithium transition metal oxide or the additive for the positive electrode of the lithium secondary battery. Matters regarding the sacrificial positive electrode material are replaced with the contents described in the items of "I. Lithium Transition Metal Oxide" and "III. Additive for Positive Electrode of Lithium Secondary Battery".

[0144] As the battery goes to a high-capacity battery, the ratio of the negative electrode active material in the negative electrode must be increased more in order to increase the capacity of the battery. Therefore, the amount of lithium consumed in the SEI layer also increases accordingly. Therefore, after calculating the amount of lithium consumed in the SEI layer of the negative electrode, the amount of the sacrificial positive electrode material to be applied to the positive electrode can be calculated inversely to determine the design capacity of the battery.

[0145] According to one embodiment, the sacrificial positive electrode material may be included in an amount of more than 0% by weight and 15% by weight or less based on the total weight of the positive electrode material.

[0146] To compensate for the irreversible lithium consumed in the formation of the SEI layer, the content of the sacrificial anode material is preferably more than 0% by weight based on the total weight of the cathode material.

[0147] However, when the sacrificial anode material is contained in an excessive amount, the content of the cathode active material showing a reversible charge-discharge capacity decreases, the capacity of the battery decreases, and residual lithium in the battery is plated on the anode, which may induce a short circuit of the battery or inhibit the safety. Therefore, the content of the sacrificial anode material is preferably 15% by weight or less based on the total weight of the cathode material.

[0148] Specifically, the content of the sacrificial anode material can be more than 0% by weight, or 0.5% by weight or more, or 1% by weight or more, or 2% by weight or more, or 3% by weight or more; and 15% by weight or less, or 12% by weight or less, or 10% by weight or less based on the total weight of the cathode material.

[0149] Preferably, the content of the sacrificial anode material can be 0.5% by weight to 15% by weight, or 1% by weight to 15% by weight, or 1% by weight to 12% by weight, or 2% by weight to 12% by weight, or 2% by weight to 10% by weight, or 3% by weight to 10% by weight based on the total weight of the cathode material.

[0150] As the cathode active material, compounds known to be applicable to lithium secondary batteries in the technical field to which the present invention belongs can be used without particular limitation.

[0151] As non-limiting examples, the cathode active material is NCM (Li[Ni,Co,Mn]O2), NCMA (Li[Ni,Co,Mn,Al]O2), LiCoO2, LiNiO2, LiMnO2, LiMn2O2, LiNi 1-d Co d O2, LiCo 1-d Mn d O2, LiNi 1-d Mn d O2 (where 0≦d<1), Li(Ni a Co b Mnc )O4(0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-e Ni e O4, LiMn 2-e Co e O4 (where 0 < e < 2 above), LiCoPO4, and LiFePO4, etc. can be used. As the positive electrode active material, one or a mixture of two or more of the above-described examples can be used.

[0152] According to one embodiment, the positive electrode active material may be contained in an amount of 80% to 95% by weight based on the total weight of the positive electrode material.

[0153] Specifically, the content of the positive electrode active material may be 80% by weight or more, or 82% by weight or more, or 85% by weight or more based on the total weight of the positive electrode material; and 95% by weight or less, or 93% by weight or less, or 90% by weight or less.

[0154] Preferably, the content of the positive electrode active material may be 82% to 95% by weight, or 82% to 93% by weight, or 85% to 93% by weight, or 85% to 90% by weight based on the total weight of the positive electrode material.

[0155] The conductive material is used to impart conductivity to the electrode.

[0156] The conductive material can be used without particular limitation as long as it does not cause a chemical change in the battery and has electron conductivity. As non-limiting examples, the conductive material can be carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; graphite such as natural graphite and artificial graphite; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide, potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. As the conductive material, one or a mixture of two or more of the above-described examples can be used.

[0157] The content of the conductive material can be adjusted within a range that exhibits appropriate conductivity while not inducing a decrease in the capacity of the battery. Preferably, the content of the conductive material can be 1 wt% to 10 wt% or 1 wt% to 5 wt% based on the total weight of the positive electrode material.

[0158] The binder is used to make the positive electrode material adhere well to the current collector.

[0159] As non-limiting examples, the binder can be polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, etc. As the binder, one kind or a mixture of two or more kinds of the above-mentioned examples can be used.

[0160] The content of the binder can be adjusted within a range that exhibits appropriate adhesiveness while not inducing a decrease in the capacity of the battery. Preferably, the content of the binder can be 1 wt% to 10 wt% or 1 wt% to 5 wt% based on the total weight of the positive electrode material.

[0161] As the current collector, materials known to be applicable to the positive electrode of a lithium secondary battery in the technical field to which the present invention belongs can be used without particular limitation.

[0162] As non-limiting examples, as the current collector, stainless steel; aluminum; nickel; titanium; fired carbon; or those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used.

[0163] Preferably, the current collector can have a thickness of 3 μm to 500 μm. In order to enhance the adhesion of the positive electrode material, the current collector may have fine irregularities formed on its surface. The current collector can have various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0164] The positive electrode for the lithium secondary battery can be formed by laminating a positive electrode material containing the positive electrode active material, the conductive material, the sacrificial anode material, and the binder on the current collector.

[0165] V. Lithium Secondary Battery According to another embodiment of the invention, There is provided a lithium secondary battery including the positive electrode for the lithium secondary battery; a negative electrode; a separator; and an electrolyte.

[0166] The lithium secondary battery includes a positive electrode including the lithium transition metal oxide or the additive for the positive electrode of the lithium secondary battery. Thereby, gas generation at the positive electrode during charge and discharge of the lithium secondary battery can be suppressed, and improved safety and life characteristics can be exhibited. And the lithium secondary battery can exhibit a high discharge capacity, excellent output characteristics, and a capacity retention rate.

[0167] Thereby, the lithium secondary battery can be used as an energy supply source having improved performance and safety in the field of portable electronic devices such as mobile phones, notebook computers, tablet computers, mobile batteries, digital cameras; and in the field of transportation means such as electric vehicles, electric bicycles, and personal mobility devices.

[0168] The lithium secondary battery may include an electrode assembly wound with a separator interposed between a positive electrode and a negative electrode, and a case in which the electrode assembly is incorporated. And the positive electrode, the negative electrode, and the separator are impregnated with an electrolyte.

[0169] The lithium secondary battery can have various forms such as square, cylindrical, and pouch types.

[0170] The matters regarding the positive electrode are replaced with the contents described in the item of "IV. Positive Electrode for Lithium Secondary Battery".

[0171] The negative electrode may include a negative electrode material containing a negative electrode active material, a conductive material, and a binder; and a current collector that supports the negative electrode material.

[0172] The negative electrode active material may include a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping with lithium, and a transition metal oxide.

[0173] Examples of the material capable of reversibly intercalating and deintercalating lithium ions include crystalline carbon, amorphous carbon, or a mixture thereof as a carbonaceous material. Specifically, the carbonaceous material may be natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch-based carbon fiber, meso-carbon microbeads, petroleum or coal tar pitch-derived cokes, soft carbon, and hard carbon.

[0174] The alloy of lithium metal may be an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd.

[0175] The substances capable of being doped and de-doped with lithium can be Si, Si-C composite, SiOx (0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Si is excluded), Sn, SnO2, Sn-R alloy (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Sn is excluded), etc. And as the substances capable of being doped and de-doped with lithium, at least one of the above examples can be mixed with SiO2 and used. Q and R can be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, etc.

[0176] And the transition metal oxide can be vanadium oxide, lithium vanadium oxide, lithium titanate, etc.

[0177] Preferably, the negative electrode may contain one or more negative electrode active materials selected from the group consisting of carbonaceous materials and silicon compounds.

[0178] Here, the carbonaceous material is one or more substances selected from the group consisting of natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, carbon microspheres, petroleum or coal-based coke, softened carbon, and hardened carbon exemplified previously. And the silicon compound can be a compound containing Si exemplified previously, that is, Si, Si-C composite, SiOx (0 < x < 2), the Si-Q alloy, a mixture thereof, or a mixture of at least one of them and SiO2.

[0179] According to one embodiment, the negative electrode active material may be contained in an amount of 85% by weight to 98% by weight based on the total weight of the negative electrode material.

[0180] Specifically, the content of the negative electrode active material may be 85% by weight or more, or 87% by weight or more, or 90% by weight or more based on the total weight of the negative electrode material; and may be 98% by weight or less, or 97% by weight or less, or 95% by weight or less.

[0181] Preferably, the content of the negative electrode active material may be 85% by weight to 97% by weight, or 87% by weight to 97% by weight, or 87% by weight to 95% by weight, or 90% by weight to 95% by weight based on the total weight of the negative electrode material.

[0182] For the conductive material, the binder contained in the negative electrode material, and the current collector, the content described in the item of "IV. Positive electrode for lithium secondary battery" is substituted.

[0183] The separator separates the positive electrode and the negative electrode and provides a lithium ion movement path. The separator can be used without particular limitation as long as it is known to be applicable to the separator of a lithium secondary battery in the technical field to which the present invention belongs. The separator preferably has a low resistance to the ion movement of the electrolyte and excellent wettability to the electrolyte.

[0184] Specifically, the separator may be a porous polymer film made of a polyolefin-based polymer such as polyethylene, polypropylene, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methacrylate copolymer, etc. The separator may be a multilayer film in which two or more layers of the porous polymer film are laminated. The separator may be a non-woven fabric containing glass fiber, polyethylene terephthalate fiber, etc. And the separator may be coated with a ceramic component or a polymer substance to ensure heat resistance or mechanical strength.

[0185] On the one hand, as long as the electrolyte is known to be applicable to lithium secondary batteries in the technical field to which the present invention belongs, it can be used without particular limitation. For example, the electrolyte can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc.

[0186] Specifically, the electrolyte may contain a non-aqueous organic solvent and a lithium salt.

[0187] As long as the non-aqueous organic solvent can serve as a medium through which ions involved in the electrochemical reaction of the battery can move, it can be used without particular limitation.

[0188] Specifically, the non-aqueous organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; an ether solvent such as dibutyl ether and tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene and fluorobenzene; a carbonate solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); an alcohol solvent such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms and may contain a double bond, ring, or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolane, etc.

[0189] Among the above examples, a carbonate solvent can preferably be used as the non-aqueous organic solvent.

[0190] In particular, considering the charge-discharge performance of the battery and the compatibility with the sacrificial anode material, a mixture of a cyclic carbonate having ionic conductivity and a high dielectric constant (e.g., ethylene carbonate, propylene carbonate) and a linear carbonate having a low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) can be preferably used as the non-aqueous organic solvent. In this case, it is advantageous for the expression of the above-described performance to mix and use the cyclic carbonate and the linear carbonate at a volume ratio of 1:1 to 1:9.

[0191] Further, as the non-aqueous organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1:2 to 1:10; or a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) at a volume ratio of 1 to 3:1 to 9:1 can be preferably used.

[0192] The lithium salt contained in the electrolyte dissolves in the non-aqueous organic solvent and acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery, and plays a role in promoting the movement of lithium ions between the positive electrode and the negative electrode.

[0193] Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiN(SO2F)2 (LiFSI, lithium bis(fluorosulfonyl)imide), LiCl, LiI, and LiB(C2O4)2, etc. Preferably, the lithium salt can be LiPF6, LiFSI, and mixtures thereof.

[0194] The lithium salt can be contained in the electrolyte at a concentration of 0.1M to 2.0M. The lithium salt contained in the above concentration range exhibits excellent electrolyte performance by imparting appropriate conductivity and viscosity to the electrolyte.

[0195] Optionally, the electrolyte may contain additives for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, improving the discharge capacity of the battery, and the like.

[0196] For example, the additives may be haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, trimethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like. The additives may be contained in an amount of 0.1% by weight to 5% by weight based on the total weight of the electrolyte.

Advantages of the Invention

[0197] The lithium transition metal oxide according to the present invention can maintain a lattice structure stabilized by the introduction of a different element, thereby minimizing side reactions with the electrolyte and suppressing gas generation during charge and discharge of the lithium secondary battery. The positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide enables improvement in the safety and life characteristics of the lithium secondary battery.

Brief Description of the Drawings

[0198]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0199] Hereinafter, the operations and effects of the invention will be specifically described with reference to specific embodiments of the invention. However, this is presented as an exemplification for assisting in the understanding of the invention. It is not intended that the scope of the invention be limited in any sense by the following embodiments, and it is obvious to those of ordinary skill in the art that various changes and modifications are possible within the scope of the present invention and the scope of the technical idea.

[0200] Example 1 (1) Synthesis of lithium transition metal oxide Li2O, CoO, ZnO, and MgO were solid-phase mixed in a molar ratio of Li:Co:Zn:Mg = 6:0.77:0.2:0.03 to prepare a raw material mixture.

[0201] After heating the raw material mixture at a heating rate of 1.6 °C / min for 6 hours under an Ar atmosphere, it was calcined at 600 °C for 12 hours to obtain a lithium transition metal oxide of Li6Co 0.77 Zn 0.2 Mg 0.03 O4.

[0202] The lithium transition metal oxide was pulverized using a jaw crusher and then classified using a sieve shaker.

[0203] The lithium transition metal oxide and distilled water were mixed at a weight ratio of 1:2 and stirred to wash the lithium transition metal oxide. The washed lithium transition metal oxide was heat-treated at 180 °C for 1 hour to be dried.

[0204] (2) Manufacture of lithium secondary battery As a positive electrode additive, the lithium transition metal oxide (Li6Co 0.77 Zn 0.2 Mg 0.03O4), carbon black as the conductive material and polyvinylidene fluoride (PVdF) as the binder were mixed in a weight ratio of 95:3:2 in an organic solvent (N-methylpyrrolidone) to produce a positive electrode material slurry. The positive electrode material slurry was applied to one side of a current collector, which was an aluminum foil with a thickness of 15 μm, and rolled and dried to produce a positive electrode. For reference, in this experiment, no positive electrode active material was added to the positive electrode material. Those with the addition of a positive electrode active material are presented in Example 6 below.

[0205] As the negative electrode active material, natural graphite, as the conductive material, carbon black, and as the binder, carboxymethyl cellulose (CMC) were mixed in a weight ratio of 95:3:2 in an organic solvent (N-methylpyrrolidone) to produce a negative electrode material slurry. The negative electrode material slurry was applied to one side of a current collector, which was a copper foil with a thickness of 15 μm, and rolled and dried to produce a negative electrode.

[0206] A non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:4:3 was prepared. A lithium salt with a concentration of 0.7 M LiPF6 and 0.5 M LiFSI was dissolved in the non-aqueous organic solvent to produce an electrolyte.

[0207] An electrode assembly was manufactured with a porous polyethylene, a separator, interposed between the positive electrode and the negative electrode, and the electrode assembly was positioned inside the case. The electrolyte was injected into the case to manufacture a pouch cell type lithium secondary battery.

[0208] Example 2 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.77 Zn 0.2 Al 0.03 O4 and (2) as a positive electrode additive was manufactured in the same manner as in Example 1, except that Al2O3 was used instead of MgO.

[0209] Example 3 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.77 Zn 0.2 Ti 0.03 O4 and (2) as a positive electrode additive was manufactured in the same manner as Example 1 except that TiO2 was used instead of MgO.

[0210] Example 4 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.77 Zn 0.2 Zr 0.03 O4 and (2) as a positive electrode additive was manufactured in the same manner as Example 1 except that ZrO2 was used instead of MgO.

[0211] Example 5 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.77 Zn 0.2 Nb 0.03 O4 and (2) as a positive electrode additive was manufactured in the same manner as Example 1 except that Nb2O5 was used instead of MgO.

[0212] Example 6 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.7 Zn 0.25 Al 0.05 O4 and (2) as a positive electrode additive was manufactured in the same manner as Example 1 except that a raw material mixture obtained by solid-phase mixing Li2O, CoO, ZnO, and Al2O3 at a molar ratio of Li:Co:Zn:Al = 6:0.7:0.25:0.05 was used.

[0213] Example 7 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.7 Zn 0.25 Mg 0.05 O4 and (2) as a positive electrode additive was manufactured in the same manner as Example 6 except that MgO was used instead of Al2O3.

[0214] Example 8 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a raw material mixture obtained by solid-phase mixing Li2O, CoO, ZnO, and TiO2 in a molar ratio of Li:Co:Zn:Ti = 6:0.72:0.25:0.03 was used. This battery contains (1) a lithium transition metal oxide of Li6Co 0.72 Zn 0.25 Ti 0.03 O4 and (2) as a positive electrode additive.

[0215] Example 9 A lithium secondary battery was manufactured in the same manner as in Example 8, except that ZrO2 was used instead of TiO2. This battery contains (1) a lithium transition metal oxide of Li6Co 0.72 Zn 0.25 Zr 0.03 O4 and (2) as a positive electrode additive.

[0216] Example 10 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a raw material mixture obtained by solid-phase mixing Li2O, CoO, ZnO, and Al2O3 in a molar ratio of Li:Co:Zn:Al = 6:0.65:0.3:0.05 was used. This battery contains (1) a lithium transition metal oxide of Li6Co 0.65 Zn 0.3 Al 0.05 O4 and (2) as a positive electrode additive.

[0217] Example 11 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a raw material mixture obtained by solid-phase mixing Li2O, CoO, ZnO, and Al2O3 in a molar ratio of Li:Co:Zn:Al = 6:0.65:0.25:0.1 was used. This battery contains (1) a lithium transition metal oxide of Li6Co 0.65 Zn 0.25 Al 0.1 O4 and (2) as a positive electrode additive.

[0218] Example 12 A lithium secondary battery containing (1) a lithium transition metal oxide of Li6Co 0.6 Zn 0.3 Al 0.1 O4 and (2) as a cathode additive was manufactured in the same manner as in Example 1, except that a raw material mixture obtained by solid-phase mixing Li2O, CoO, ZnO, and Al2O3 in a molar ratio of Li:Co:Zn:Al = 6:0.6:0.3:0.1 was used.

[0219] Example 13 A lithium secondary battery was manufactured in the same manner as in Example 6, except that a cathode active material was further added during the manufacture of the cathode and the composition of the anode active material was changed during the manufacture of the anode. Specifically, an NCMA (Li[Ni,Co,Mn,Al]O2)-based compound, NTA-X12M, L&F) as a cathode active material, the lithium transition metal oxide (Li6Co 0.7 Zn 0.25 Al 0.05 O4) as a cathode additive, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in an organic solvent (N-methylpyrrolidone) at a weight ratio of 93.8:1.2:3:2 to produce a cathode material slurry. The cathode material slurry was applied to one surface of a current collector, which was an aluminum foil with a thickness of 15 μm, and rolled and dried to produce a cathode.

[0220] A mixture of natural graphite and SiO (weight ratio = 9:1) as an anode active material, carbon black as a conductive material, and carboxymethyl cellulose (CMC) as a binder were mixed in an organic solvent (N-methylpyrrolidone) at a weight ratio of 95:3:2 to produce an anode material slurry. The anode material slurry was applied to one surface of a current collector, which was a copper foil with a thickness of 15 μm, and rolled and dried to produce an anode.

[0221] An electrode assembly was manufactured with a porous polyethylene, which is a separator, interposed between the cathode and the anode, and the electrode assembly was placed inside a case. The electrolyte was injected into the case to manufacture a lithium secondary battery in the form of a pouch cell.

[0222] Comparative Example 1 A lithium secondary battery containing (1) a lithium transition metal oxide which is Li6CoO4 and (2) as a cathode additive was produced in the same manner as in Example 1, except that Li2O and CoO were mixed at a molar ratio of Li:Co = 6:1 without adding ZnO and MgO.

[0223] Comparative Example 2 A lithium secondary battery containing (1) a lithium transition metal oxide which is Li6Co 0.7 Zn 0.3 O4 and (2) as a cathode additive was produced in the same manner as in Example 1, except that MgO was not added and Li2O, CoO and ZnO were mixed at a molar ratio of Li:Co:Zn = 6:0.7:0.3.

[0224] Comparative Example 3 During the production of the cathode, a lithium secondary battery was produced in the same manner as in Example 13, except that Li6Co 0.7 Zn 0.25 Al 0.05 O4 was used instead of Li6CoO4 obtained in Comparative Example 1 as a cathode additive.

[0225] Comparative Example 4 During the production of the cathode, a lithium secondary battery was produced in the same manner as in Example 13, except that Li6Co 0.7 Zn 0.25 Al 0.05 O4 was used instead of Li6Co 0.7 Zn 0.3 O4 obtained in Comparative Example 2 as a cathode additive.

[0226] Comparative Example 5 During the production of the cathode, an NCMA (Li[Ni,Co,Mn,Al]O2) - based compound, NTA - X12M, L&F) was used as the cathode active material, and the above - mentioned lithium transition metal oxide (Li6Co 0.7 Zn 0.25 Al 0.05A lithium secondary battery was manufactured in the same manner as in Example 13, except that DN2O (Li2NiO2, POSCO Chemical) was used instead of O4), carbon black was used as a conductive material, and polyvinylidene fluoride (PVdF) was used as a binder, and they were mixed at a weight ratio of 91.2:3.8:3:2.

[0227] Comparative Example 6 A lithium secondary battery was manufactured in the same manner as in Example 13, except that the positive electrode additive was not added during the production of the positive electrode.

[0228] Test Example 1 The particle size distribution of the lithium transition metal oxides obtained from Examples 1 to 12 and Comparative Examples 1 and 2 was measured using a laser diffraction / scattering particle size distribution analyzer (model name: Partica LA-960V2, manufacturer: HORIBA). At this time, the measurement was carried out using N-methyl pyrrolidon (NMP) as a dispersion medium for the lithium transition metal oxide.

[0229]

Table 1

[0230] Referring to Table 1 above, it is confirmed that the lithium transition metal oxides of the examples simultaneously satisfy the D50 value of 10.0 μm to 25.0 μm and the D max / D min value.

[0231] Referring to Comparative Examples 1 and 2, it is observed that when Zn is introduced into Li6CoO4, the D50 value of the particles tends to increase.

[0232] And a difference appears in the particle size distribution depending on the additional introduced element. In particular, when Al is additionally introduced into the lithium transition metal oxide into which Zn has been introduced, the D min value tends to increase and the D max value tends to decrease. For example, in the cases of Examples 2, 6, 10, 11, and 12 into which Al has been introduced, the D is less than 30 μmmax / D min shows a value, which is D in Examples 1, 3, 4, 5, 7, and 9 where Mg, Ti, Zr, or Nb was introduced max / D min and it can be confirmed that this is smaller than the D value. In the case of Example 8 where Ti was introduced, D is less than 30 μm max / D min shows a value, but D is relatively large compared to other oxides max (showing a value of 87.7 μm).

[0233] Test Example 2 For the lithium secondary batteries of Examples 1 to 12, Comparative Examples 1 and 2, the cumulative gas generation amount due to charge - discharge cycle accumulation was measured by the following method, and the gas generation amount based on the measured cumulative charge capacity is shown in Table 2, Figures 1 and 2. The cumulative gas generation amount due to high - temperature storage time is shown in Table 3.

[0234] (1) Measurement of Formation (initial charge) capacity and charge - discharge capacity The lithium secondary battery in pouch cell form was charged at a constant current - constant voltage up to 4.25 V at 0.1 C and discharged at a constant current up to 2.5 V at 45 °C, with a 20 - minute rest between charge and discharge cycles. After that, the formation capacity and charge - discharge capacity were measured.

[0235] (2) Measurement of cumulative gas generation amount due to charge - discharge accumulation After operating the lithium secondary battery under the charge - discharge conditions of (1) above, when about to measure the gas generation amount, the pouch cell at the time point was recovered in a discharged state for a while. Using a hydrometer (MATSUHAKU, TWD - 150DM), the weight difference between the original weight of the pouch cell and its weight in water was measured to calculate the change in volume inside the pouch cell, and the gas generation amount per weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0236] (3) Measurement of cumulative gas generation amount due to high - temperature storage The pouch cell - type lithium secondary battery was charged with constant current - constant voltage up to 4.25 V at 0.1 C under the temperature condition of 45 °C, then recovered, the formation capacity was measured, and then it was stored in a 60 °C chamber. The lithium secondary battery was taken out of the chamber at one - week intervals, and the difference in weight between the original weight of the pouch cell and the weight in water was measured using a hydrometer (MATSUHAKU, TWD - 150DM) to calculate the change in volume within the pouch cell. The amount of gas generation per weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0237] Table 2 below shows the cumulative gas generation amounts after formation (0 th charge - discharge), 1 st , 2 nd , 10 th , 30 th and 50 th cumulative cycles.

[0238]

Table 2

[0239] As shown in Table 2 and FIG. 1 above, in Examples 1 - 5, the initial charge capacity was smaller than that in Comparative Examples 1 and 2. However, after 50 th cycles, the cumulative gas generation amounts in all of Examples 1 - 5 showed a significantly excellent gas reduction effect within 1 mL / g. In particular, Example 1 had the largest initial charge capacity among the examples, and the cumulative gas generation amount was also relatively small. Example 2 had a somewhat lower initial charge capacity, but it was confirmed that it had the lowest cumulative gas generation amount and an excellent gas reduction effect.

[0240] As shown in Table 2 and FIG. 2 above, in the case of Ti and Zr, the additional gas reduction effect due to the addition of different elements was relatively small. Referring to Examples 6, 10, 11, and 12, it was confirmed that the higher the molar content of Al, the more excellent the gas reduction effect. Table 3 below shows the cumulative gas generation amounts after 1 week, 2 weeks, 3 weeks, and 4 weeks of storage at 60 °C after formation (0 th charge - discharge).

[0241]

Table 3

[0242] As shown in Table 3 above, it was confirmed that Examples 1 to 5 had a significantly superior gas reduction effect compared to Comparative Examples 1 and 2, with the cumulative gas generation amount within 1 mL / g during high-temperature storage at 60°C.

[0243] Referring to Examples 6 to 12, in the case of lithium transition metal oxides into which Al was introduced, it was confirmed that they exhibited an excellent effect in reducing gas during high-temperature storage.

[0244] Test Example 3 For the lithium secondary batteries of Examples 13 and Comparative Examples 3 to 6 in which the positive electrode active material and the positive electrode additive were mixed and applied, the capacity retention (cycle retention) and the cumulative gas generation amount due to cumulative charge and discharge were measured by the following method, and the measured capacity retention and cumulative gas generation amount are shown in FIG. 3 and Table 4.

[0245] (1) Measurement of Formation (initial charge) capacity and charge and discharge capacity A lithium secondary battery in pouch cell form was charged at a constant current - constant voltage up to 4.25 V at 0.1 C and discharged at a constant current up to 2.5 V under a temperature condition of 45°C, with a 20-minute rest between charge and discharge to perform cycles. After that, the formation capacity and the charge and discharge capacity up to 100 th cycles were measured.

[0246] (2) Measurement of cumulative gas generation amount due to cumulative charge and discharge After operating the lithium secondary battery under the charge and discharge conditions of (1) above, when it was about to measure the gas generation amount, the pouch cell at the time was recovered in a discharged state for a while. Using a hydrometer (MATSUHAKU, TWD - 150DM), the weight difference between the original weight of the pouch cell and the weight in water was measured to calculate the volume change in the pouch cell, and the volume change amount was divided by the weight of the electrode active material to calculate the gas generation amount per weight.

[0247] (3) Measurement of the cumulative gas generation amount by high-temperature storage The pouch cell-shaped lithium secondary battery was charged at a constant current-constant voltage up to 4.25 V at 0.1 C under the temperature condition of 45 °C, then recovered, the formation capacity was measured, and then it was stored in a 60 °C chamber. The lithium secondary battery was taken out of the chamber at one-week intervals, and the difference in weight between the original weight of the pouch cell and the weight in water was measured using a hydrometer (MATSUHAKU, TWD-150DM) to calculate the change in volume in the pouch cell, and the amount of gas generation per weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0248] Table 4 below shows the formation (0 th charge and discharge) capacity, and the cumulative gas generation amount after 50 th and 100 th cumulative cycles thereafter and the discharge capacity retention rate after 100 th cycles.

[0249]

Table 4

[0250] As shown in Table 4 and FIG. 3 above, the discharge capacities of Example 13 and Comparative Examples 3 to 5 were shown to be larger than those of Comparative Example 6 to which no positive electrode additive (sacrificial anode material) was applied. This can be considered that the sacrificial anode material compensates for the irreversible lithium consumed in the formation of the SEI layer at the negative electrode.

[0251] On the contrary, in the case of Comparative Example 6, since there is no sacrificial anode material to compensate for the irreversible lithium, the discharge capacity decreased by consuming lithium in the positive electrode material, showing a discharge capacity of 201.3 mAh / g.

[0252] The cumulative gas generation amount in 100 th cycles of Example 13 was 0.07 mL / g, which is less than 0.24 mL / g of Comparative Example 3 and 0.16 mL / g of Comparative Example 4, and is also less than 0.20 mL / g of Comparative Example 6 to which no sacrificial anode material was applied. This is because in Example 13, Zn of Comparative Example 4 was introduced into Li6Co 0.7 Zn0.3 By additionally introducing Al into O4, CoO2 formed after the initial charge is more effectively stabilized than when only Zn is introduced, effectively preventing side reactions with the electrolyte, and it can be considered that this suppresses additional gas generation.

[0253] 50 of Comparative Example 5 th The cumulative gas generation amount at 50 cycles is the lowest at 0.02 mL / g, but from 50 th cycles to 100 th cycles, the gas generation increase amount is 0.09 mL / g, and there is a possibility that gas generation may continue to increase thereafter. This is the same for Comparative Example 3. On the other hand, in the case of Example 13, from 50 th cycles to 100 th cycles, the gas generation increase amount is 0.02 mL / g, and it can be seen that gas generation is suppressed as the charge-discharge cycles continue.

[0254] In Example 13, Comparative Example 3, and Comparative Example 4 to which the Co-based sacrificial anode material was applied, the capacity retention rate at 100 th cycles was shown to be 88.2% or more. Comparative Example 5 to which the Ni-based sacrificial anode material was applied and Comparative Example 6 to which no sacrificial anode material was applied had capacity retention rates of 86.3% and 86.2% respectively, which were significantly lower than that of Example 13. In particular, in the case of Example 13 where Al was additionally introduced, it was confirmed that the capacity retention rate was greatly improved at 91.7%. It can be considered that this is because, as seen from the cumulative gas generation amount above, by additionally introducing Al, the crystal phase after the initial charge is stabilized, preventing side reactions with the electrolyte.

[0255] Thus, when applying the Co-based sacrificial anode material, particularly the sacrificial anode material having the composition of Chemical Formula 1, to a lithium secondary battery including an actual positive electrode material, it can be confirmed that not only the initial discharge capacity is compensated and the gas generation amount in the battery is suppressed, but also the capacity retention rate after 100 th cycles is excellent.

[0256] Table 5 below shows formation (0 thIt shows the cumulative gas generation amounts after storage at 72°C for 1 week, 2 weeks, 3 weeks, and 4 weeks after (charging).

[0257]

Table 5

[0258] As shown in Table 5 above, in Example 13, the cumulative gas generation amount after 4 weeks was the lowest at 0.15 mL / g. This can be said to be because, similar to the charge-discharge cycle results, the foreign elements introduced into Li6CoO4 effectively stabilized the CoO2 formed after the initial charge, preventing side reactions with the electrolyte and suppressing additional gas generation caused thereby.

[0259] Also, although less gas was generated in Example 13 than in Comparative Example 6 where no sacrificial anode material was applied, this could be an experimental error, or it is expected that the positive electrode additive contained in the lithium secondary battery may not only suppress gas generation but also absorb the generated gas.

[0260] As described above, the present invention has been described with limited examples and drawings, but the present invention is not limited thereby, and it goes without saying that various modifications and variations are possible within the equivalent scope of the technical idea of the present invention and the scope of the claims described below by those having ordinary knowledge in the technical field to which the present invention belongs.

Claims

**Claim 1**: A lithium transition metal oxide represented by the following Chemical Formula 1, [Chemical Formula 1] Li6Co1−x−yZnxMyO4 In the Chemical Formula 1, M is a Group 2 element, a Group 13 element, a Group 14 element, a transition metal of the fifth period, or a transition metal of the sixth period, x is from 0.1 to 0.7, y is from 0.01 to 0.2, The cumulative 50% particle size (D50) of 10.0 μm to 25.0 μm, and the ratio (D ｍａｘ / D ｍｉｎ ), where D ｍａｘ is the maximum particle size and D ｍｉｎ is the minimum particle size, of lithium transition metal oxide, as determined by laser diffraction scattering particle size distribution measurement. **Claim 2** The lithium transition metal oxide has a cumulative 5% particle size (D5) of 3.0 μm to 10.0 μm and a cumulative 95% particle size (D95) of 20.0 μm to 45.0 μm as measured by laser diffraction scattering particle size distribution measurement. The lithium transition metal oxide according to Claim 1. **Claim 3** M is at least one selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W. The lithium transition metal oxide according to Claim 1 or 2. **Claim 4** The lithium transition metal oxide is Li ６ Co ０．７７ Zn ０．２ Al ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ Al ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ Al ０．０５ O ４ 、Li ６ Co ０．７ Zn ０．２５ Al ０．０５ O ４ 、Li ６ Co ０．６５ Zn ０．２５ Al ０．１ O ４ 、Li ６ Co ０．６７ Zn ０．３ Al ０．０３ O ４ 、Li ６ Co ０．６６ Zn ０．３ Al ０．０４ O ４ 、Li ６ Co ０．６５ Zn ０．３ Al ０．０５ O ４ 、Li ６ Co ０．６ Zn ０．３ Al ０．１ O ４ 、Li ６ Co ０．７７ Zn ０．２ Mg ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ Mg ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ Mg ０．０５ O ４ 、Li ６ Co ０．７ Zn ０．２５ Mg ０．０５ O ４ 、Li ６ Co ０．６７ Zn ０．３ Mg ０．０３ O ４ 、Li ６ Co ０．６６ Zn ０．３ Mg ０．０４ O ４ 、Li ６ Co ０．６５ Zn ０．３ Mg ０．０５ O ４ 、Li ６ Co ０．７７ Zn ０．２ Ti ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ Ti ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ Ti ０．０５ O ４ 、Li ６ Co ０．７２ Zn ０．２５ Ti ０．０３ O ４ 、Li ６ Co ０．６７ Zn ０．３ Ti ０．０３ O ４ 、Li ６ Co ０．６６ Zn ０．３ Ti ０．０４ O ４ 、Li ６ Co ０．６５ Zn ０．３ Ti ０．０５ O ４ 、Li ６ Co ０．７７ Zn ０．２ Zr ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ Zr ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ Zr ０．０５ O ４ 、Li ６ Co ０．７２ Zn ０．２５ Zr ０．０３ O ４ 、Li ６ Co ０．６７ Zn ０．３ Zr ０．０３ O ４ 、Li ６ Co ０．６６ Zn ０．３ Zr ０．０４ O ４ 、Li ６ Co ０．６５ Zn ０．３ Zr ０．０５ O ４ 、Li ６ Co ０．７７ Zn ０．２ Nb ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ Nb ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ Nb ０．０５ O ４ 、Li ６ Co ０．６７ Zn ０．３ Nb ０．０３ O ４ 、Li ６ Co ０．６６ Zn ０．３ Nb ０．０４ O ４ 、Li ６ Co ０．６５ Zn ０．３ Nb ０．０５ O ４ 、Li ６ Co ０．７７ Zn ０．２ W ０．０３ O ４ 、Li ６ Co ０．７６ Zn ０．２ W ０．０４ O ４ 、Li ６ Co ０．７５ Zn ０．２ W ０．０５ O ４ 、Li ６ Co ０．６７ Zn ０．３ W ０．０３ O ４ 、 Li ６ Co ０．６６ Zn ０．３ W ０．０４ O ４ 、 and Li ６ Co ０．６５ Zn ０．３ W ０．０５ O ４ The lithium transition metal oxide according to claim 1 or 2, comprising one or more compounds selected from the group consisting of **Claim 5** A first step of solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element oxide, and A second step of firing the mixture obtained in the first step in an inert atmosphere at a temperature of 550°C to 750°C to obtain the lithium transition metal oxide according to any one of Claims 1 to 4 A method for producing a lithium transition metal oxide, comprising: **Claim 6** In the second step, the mixture obtained in the first step is heated in an inert atmosphere at a heating rate of 1.4°C / min to 2.0°C / min and fired at a temperature of 550°C to 750°C for 2 hours to 20 hours. The method for producing a lithium transition metal oxide according to Claim 5. **Claim 7** A positive electrode additive for a lithium secondary battery, comprising the lithium transition metal oxide according to any one of Claims 1 to 4. **Claim 8** A positive electrode for a lithium secondary battery, comprising a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide according to any one of Claims 1 to 4. **Claim 9** A positive electrode for a lithium secondary battery, comprising a positive electrode active material, a binder, a conductive material, and the positive electrode additive for a lithium secondary battery according to Claim 7. **Claim 10** A lithium secondary battery, comprising the positive electrode for a lithium secondary battery according to Claim 8 or 9, a negative electrode, a separator, and an electrolyte. **Claim 11** The negative electrode contains at least one negative electrode active material selected from the group consisting of a carbonaceous material and a silicon compound. The lithium secondary battery according to Claim 10.

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