Lithium transition metal oxide, cathode additive for lithium secondary battery, and 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 suppress gas generation during charging and discharging of a lithium secondary battery by minimizing side reactions with an electrolyte.

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 documents of the Korean patent applications are incorporated herein by reference in their entirety.

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

Background Art

[0003] With the increasing multifunctionality of electronic devices and the accompanying 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 cathode active material with 80% or more of Ni is applied as a cathode material in a lithium secondary battery, and a metal or metal - based anode active material such as SiO, Si, or SiC is applied together with a carbon - based anode active material such as natural graphite or artificial graphite to the anode.

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

[0006] Therefore, various solutions have been studied to increase the capacity of lithium secondary batteries or reduce the 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 for prelithiation within the battery have been proposed.

[0008] As an example, there 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 process with the electrochemical lithiation method.

[0009] As another example, there is a method of coating the negative electrode with lithium metal or lithium silicide (Li x Si) 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 corresponding to the amount of lithium consumed at the negative electrode. However, since the amount of the additional positive electrode material increases due to the low capacity of the positive electrode material itself, the energy density of the final battery and the capacity per unit weight will decrease by the amount of the increasing positive electrode material.

[0011] Therefore, the material suitable for pre-lithiation of the battery at the positive electrode must have the irreversible property that the lithium released during the first charging is at least twice or more as much as that of the existing positive electrode material and does not react with lithium during subsequent discharging. An additive that satisfies such conditions is called a sacrificial positive electrode material.

[0012] In the case of a commercial battery, after injecting an electrolyte into a case containing a laminated positive electrode, a separator, and a negative electrode, it goes through a formation process of first performing a charge / discharge operation. During this process, a reaction occurs to form a SEI layer on the negative electrode, and gas is generated by the decomposition of the electrolyte. In the formation process, the sacrificial positive electrode material releases lithium and reacts with the electrolyte while being decomposed, and gases such as N2, O2, and CO2 generated during this process are recovered by a gas pocket removal process.

[0013] As the sacrificial positive electrode 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 positive electrode material. Among them, Li6CoO4 has the best electrical conductivity and good electrochemical characteristics for use as a sacrificial positive electrode material.

[0014] Li6CoO4 is desorbed and decomposed step by step in the formation process, and the crystal phase collapses. In this process, O2 gas is always generated. Ideally, no additional gas should be generated during the charge-discharge cycles after the formation process. If continuous gas is generated during charge-discharge, the pressure inside the battery increases, the distance between the electrodes becomes larger, and the battery capacity and energy density decrease. In severe cases, the battery may not withstand the pressure and rupture, leading to the possibility of an explosion accident.

[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 cycles.

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 including the positive electrode additive for a lithium secondary battery.

[0022] Further, the present invention provides a lithium secondary battery including the positive electrode for a secondary battery.

Means for Solving the Problems

[0023] According to one embodiment of the present invention, a lithium transition metal oxide represented by the following Chemical Formula 1 and having a lattice parameter of a unit lattice satisfying the following Formulas 1 and 2 is provided: [Chemical Formula 1] Li6Co 1-x M x O4 In the Chemical Formula 1, M is one or more elements selected from the group consisting of a Group 2 element, a Group 13 element, a Group 14 element, a transition metal of the 4th period, a transition metal of the 5th period, and a transition metal of the 6th period, x is 0.05 to 0.80; [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above Formulas 1 and 2, a, b, and c are lattice parameters of the lithium transition metal oxide obtained by an X-ray diffraction Rietveld refinement method using CuKα rays.

[0024] According to another embodiment of the present invention, a first step of obtaining a raw material mixture by solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element M oxide; a second step of firing the mixture obtained in the first step in an inert atmosphere and at a temperature of 550°C to 750°C to obtain a compound represented by the following Chemical Formula 1, and a method for producing the lithium transition metal oxide is provided.

[0025] According to still another embodiment of the present 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 present 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 present 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 present 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 a lithium secondary battery, the positive electrode for a 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 the ordinary or dictionary meanings, and should be construed as meanings and concepts conforming to the technical idea of the present invention based on the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way.

[0031] Unless otherwise defined in this specification, all technical terms and scientific terms have the same meaning as generally 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 merely used to effectively describe specific examples and are not intended to limit the present invention.

[0032] As used herein, the singular forms also include the plural forms unless the context clearly indicates the contrary meaning.

[0033] As used herein, the meaning of "comprising" does not exclude the presence or addition of other specific features, regions, integers, steps, operations, elements and / or components while embodying a specific feature, region, integer, step, operation, element and / or component.

[0034] Since the present invention can be modified in various ways and can have various forms, specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and it should be understood to include all modifications, equivalents or alternatives included in the spirit and technical scope of the present invention.

[0035] In this specification, for example, when the positional relationship between two parts such as "on ~", "above ~", "below ~", "on the side of ~" is described, unless the expressions "immediately" or "directly" are used, one or more other parts may be located between the two parts.

[0036] In this specification, for example, when the temporal sequence relationship such as "after ~", "subsequent to ~", "next to ~", "before ~" is described, unless the expressions "immediately" or "directly" are used, it can also include non - continuous cases.

[0037] In this specification, the term "at least one" should be understood to include all combinations that can be presented from one or more related items.

[0038] As used herein, the term "positive electrode additive" refers to a substance that has an irreversible property such that lithium desorbs more than twice as much as the existing positive electrode material during the initial charging of the battery and does not react with lithium during subsequent discharging. The positive electrode additive can also be referred to as sacrificial positive electrode materials. Since the positive electrode additive compensates for lithium loss, as a result, the lost capacity of the battery is recovered, the capacity of the battery increases, and the generation of gas is suppressed to prevent the battery from exploding, thereby improving the life characteristics and safety of the battery.

[0039] As used herein, the term "stabilization of crystal phase" 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 amorphous CoO2, a side reaction between CoO2 and the electrolyte can be prevented, and the generation of gas can be suppressed.

[0040] I. Lithium transition metal oxide According to one embodiment of the present invention, there is provided a lithium transition metal oxide represented by the following Chemical Formula 1 and having a lattice parameter of a unit lattice satisfying the following Formulas 1 and 2: [Chemical Formula 1] Li6Co 1-x M x O4 In Chemical Formula 1, M is one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, transition metals of the fourth period, transition metals of the fifth period, and transition metals of the sixth period, x is 0.05 to 0.80; [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above Formulas 1 and 2, a, b, and c are the lattice constants of the lithium transition metal oxide obtained by the X-ray diffraction Rietveld refinement method using CuKα radiation.

[0041] As a result of the inventors' continuous research, it has been confirmed that the lithium transition metal oxide represented by Chemical Formula 1 and satisfying Formulas 1 and 2 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. This is presumably because a more stabilized crystal phase is maintained by introducing a foreign element M into the lithium transition metal oxide and satisfying a specific range of lattice constants. Therefore, the lithium transition metal oxide can improve the safety and life characteristics of a lithium secondary battery.

[0042] The lithium transition metal oxide represented by Chemical Formula 1 and satisfying Formulas 1 and 2 above can stabilize the crystal phase compared to lithium cobalt oxides such as Li6CoO4. In the present invention, the stabilization of the crystal phase means suppressing the oxidizing property of amorphous CoO2 formed after the initial charge of a lithium secondary battery containing the lithium cobalt oxide.

[0043] 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 for no amorphous pattern to be observed. In the formation process, Li6CoO4 is initially oxidized to Co 2+ cations to Co 4+ cations, and then gas is generated by oxidizing O 2- anions. When charging is completed, it becomes a composition of CoO2 (Co 4+ ), but since it does not show crystallinity in the said composition, no pattern is observed.

[0044] Co 4+ In the case of cations, they are left as they are, or during discharge (reduction reaction), Co 2+ cations or Co 3+Since the oxidizing property of the tendency to be reduced to a cation is large, 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. After that, when charge-discharge cycles are performed, Co reduced during charging 2+ cations and Co 3+ cations become Co 4+ is oxidized to a cation, and Co becomes a cation again during discharging 4+ cations become Co 2+ cations and Co 3+ is reduced to a cation, and gases are continuously generated due to the side reactions.

[0045] In order to suppress such side reactions, it is necessary to suppress the oxidizing property of 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.

[0046] The different element M in Chemical Formula 1 has an oxidation number fixed during charge and discharge of the battery and can be expected to lower the average oxidation number of Co 4+ cations. Therefore, the oxidizing property of Co 4+ cations is suppressed, and the generation of gases due to the side reactions is suppressed. In particular, the lithium transition metal oxide has a lattice constant satisfying the above formulas 1 and 2 and can maintain a more stable crystal phase during charge and discharge of the lithium secondary battery.

[0047] The lithium transition metal oxide represented by Chemical Formula 1 has a composition in which a different element M is introduced by alloying or doping Li6CoO4.

[0048] Here, the "alloy" means a material in which the different element M is introduced at 10 mol% or more based on the total metal elements excluding lithium in the lithium transition metal oxide. And the "doping" means a material in which the different element M is introduced at less than 10 mol% based on the total metal elements excluding lithium in the lithium transition metal oxide.

[0049] In the above Chemical Formula 1, M of the different elements is one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, transition metals of the 4th period, transition metals of the 5th period, and transition metals of the 6th period.

[0050] Specifically, the Group 2 elements include one or more selected from the group consisting of Mg, Ca, Sr, and Ba; the Group 13 elements include one or more selected from the group consisting of Al, Ga, and In; the Group 14 elements include one or more selected from the group consisting of Si, Ge, and Sn; the transition metals of the 4th period include one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; the transition metals of the 5th period include one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; the transition metals of the 6th period include one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

[0051] Preferably, from the aspects of the ease of alloying or doping with lithium cobalt oxide and the stabilization of the crystal phase, the M can be one or more elements selected from the group consisting of Zn, Al, Mg, Ti, Zr, Nb, and W. Zn, Al, Mg, Ti, Zr, Nb, and W are easily substituted at the Co site in the anti-fluorite lattice structure, which is the crystal phase of Li6CoO4, and have the property that their oxidation numbers do not change. For example, since there is a Li6ZnO4 crystal phase for Zn, an alloy with Li6CoO4 is also easily formed, and its oxidation number also remains 2+, so the oxidation property of Co after the initial charge 4+ can be effectively suppressed.

[0052] More preferably, the M can be one or more elements selected from the group consisting of Zn, Al, and Mg. Even more preferably, the M can be Zn.

[0053] The M of the heterogeneous element is selected considering whether it exists within the anti-fluorite lattice structure of lithium cobalt oxide and whether it has a fixed oxidation number during charge and discharge of the battery.

[0054] For example, in the cases of Li5FeO4 and Li6MnO4 that do not satisfy the composition of Chemical Formula 1, 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+. Therefore, when mixing and firing raw materials such as CoO, MnO, and Fe2O3 which are raw materials of the lithium cobalt oxide, Mn or Fe is oxidized, and Co 2+ cations are reduced and Co which is not a single crystal phase anti-fluorite lattice structure 0 , that is, Co metal is generated. Even if alloyed Li6CoO4 of a single crystal phase is generated, in the case of Mn or Fe, since the oxidation number easily changes within the operating voltage, it is difficult to suppress the oxidizing property of Co 4+ cations after the initial charge.

[0055] In Chemical Formula 1, x is 0.05 to 0.80.

[0056] That is, in the lithium transition metal oxide of Chemical Formula 1, the heterogeneous element M is contained in an amount of 5 mol% to 80 mol% based on the total metal elements excluding lithium.

[0057] In order to exhibit the stabilizing effect of the crystal phase, the content of the heterogeneous element M is preferably 5 mol% or more based on the total metal elements excluding lithium. However, when an excessive amount of the heterogeneous element 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 heterogeneous element M is preferably 80 mol% or less based on the total metal elements excluding lithium.

[0058] Specifically, the content of the different element M 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 can be 80 mol% or less, or 70 mol% or less, or 60 mol% or less.

[0059] Preferably, the content of the different element M can be 10 mol% - 80 mol%, or 10 mol% - 70 mol%, or 15 mol% - 70 mol%, or 15 mol% - 60 mol% based on the total metal elements excluding lithium.

[0060] On the other hand, two or more different elements are introduced into the lithium transition metal oxide. As a non-limiting example, one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W and Zn are introduced together as the different element M.

[0061] The stabilizing effect of the crystal phase of the lithium transition metal oxide is expected to be proportional to the content of the different element. However, as the introduction amount of different elements such as Zn which is electrochemically inactive increases, the initial charge capacity relatively decreases, and the electrical conductivity shows a decreasing trend. Therefore, by introducing Zn as the main element of the different element M and introducing one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W as the secondary elements together, the stabilizing effect of the crystal phase can be expressed, and excellent battery performance can be ensured.

[0062] At this time, among the different elements, the contents of the main element and the secondary element are determined in consideration of the degree of manifestation of the above-described effects. As a non-limiting example, the different element includes a main element that is 4 mol% - 70 mol% and a secondary element that is 1 mol% - 10 mol% based on the total metal elements excluding lithium in the lithium transition metal oxide.

[0063] Preferably, the lithium transition metal oxide is Li6Co 0.95 Zn 0.05 O4, Li6Co 0.9 Zn 0.1O4, Li6Co 0.85 Zn 0.15 O4, Li6Co 0.8 Zn 0.2 O4, Li6Co 0.75 Zn 0.25 O4, Li6Co 0.7 Zn 0.3 O4, Li6Co 0.65 Zn 0.35 O4, Li6Co 0.6 Zn 0.4 O4, Li6Co 0.55 Zn 0.45 O4, Li6Co 0.5 Zn 0.5 O4, Li6Co 0.45 Zn 0.55 O4, Li6Co 0.4 Zn 0.6 O4, Li6Co 0.35 Zn 0.65 O4, Li6Co 0.3 Zn 0.7 O4, Li6Co 0.25 Zn 0.75 O4, Li6Co 0.2 Zn 0.8 O4;Li6Co 0.95 Al 0.05 O4, Li6Co 0.9 Al 0.1 O4, Li6Co 0.85 Al 0.15 O4, Li6Co 0.8 Al 0.2 O4, Li6Co 0.75 Al 0.25 O4, Li6Co 0.7 Al 0.3 O4, Li6Co 0.65 Al 0.35 O4, Li6Co 0.6 Al 0.4 O4, Li6Co 0.55 Al 0.45 O4, Li6Co 0.5 Al 0.5 O4, Li6Co 0.45 Al 0.55 O4, Li6Co 0.4 Al 0.6 O4, Li6Co 0.35 Al 0.65 O4, Li6Co 0.3 Al0.7 O4, Li6Co 0.25 Al 0.75 O4, Li6Co 0.2 Al 0.8 O4; Li6Co 0.95 Mg 0.05 O4, Li6Co 0.9 Mg 0.1 O4, Li6Co 0.85 Mg 0.15 O4, Li6Co 0.8 Mg 0.2 O4, Li6Co 0.75 Mg 0.25 O4, Li6Co 0.7 Mg 0.3 O4, Li6Co 0.65 Mg 0.35 O4, Li6Co 0.6 Mg 0.4 O4, Li6Co 0.55 Mg 0.45 O4, Li6Co 0.5 Mg 0.5 O4, Li6Co 0.45 Mg 0.55 O4, Li6Co 0.4 Mg 0.6 O4, Li6Co 0.35 Mg 0.65 O4, Li6Co 0.3 Mg 0.7 O4, Li6Co 0.25 Mg 0.75 O4, Li6Co 0.2 Mg 0.8 O4; Li6Co 0.95 Ti 0.05 O4, Li6Co 0.9 Ti 0.1 O4, Li6Co 0.85 Ti 0.15 O4, Li6Co 0.8 Ti 0.2 O4, Li6Co 0.75 Ti 0.25 O4, Li6Co 0.7 Ti 0.3 O4, Li6Co 0.65 Ti 0.35 O4, Li6Co 0.6 Ti 0.4 O4, Li6Co 0.55 Ti 0.45 O4, Li6Co0.5 Ti 0.5 O4, Li6Co 0.45 Ti 0.55 O4, Li6Co 0.4 Ti 0.6 O4, Li6Co 0.35 Ti 0.65 O4, Li6Co 0.3 Ti 0.7 O4, Li6Co 0.25 Ti 0.75 O4, Li6Co 0.2 Ti 0.8 O4; Li6Co 0.95 Zr 0.05 O4, Li6Co 0.9 Zr 0.1 O4, Li6Co 0.85 Zr 0.15 O4, Li6Co 0.8 Zr 0.2 O4, Li6Co 0.75 Zr 0.25 O4, Li6Co 0.7 Zr 0.3 O4, Li6Co 0.65 Zr 0.35 O4, Li6Co 0.6 Zr 0.4 O4, Li6Co 0.55 Zr 0.45 O4, Li6Co 0.5 Zr 0.5 O4, Li6Co 0.45 Zr 0.55 O4, Li6Co 0.4 Zr 0.6 O4, Li6Co 0.35 Zr 0.65 O4, Li6Co 0.3 Zr 0.7 O4, Li6Co 0.25 Zr 0.75 O4, Li6Co 0.2 Zr 0.8 O4; Li6Co 0.95 Nb 0.05 O4, Li6Co 0.9 Nb 0.1 O4, Li6Co 0.85 Nb 0.15 O4, Li6Co 0.8 Nb 0.2 O4, Li6Co 0.75 Nb 0.25O4, Li6Co 0.7 Nb 0.3 O4, Li6Co 0.65 Nb 0.35 O4, Li6Co 0.6 Nb 0.4 O4, Li6Co 0.55 Nb 0.45 O4, Li6Co 0.5 Nb 0.5 O4, Li6Co 0.45 Nb 0.55 O4, Li6Co 0.4 Nb 0.6 O4, Li6Co 0.35 Nb 0.65 O4, Li6Co 0.3 Nb 0.7 O4, Li6Co 0.25 Nb 0.75 O4, Li6Co 0.2 Nb 0.8 O4; Li6Co 0.95 W 0.05 O4, Li6Co 0.9 W 0.1 O4, Li6Co 0.85 W 0.15 O4, Li6Co 0.8 W 0.2 O4, Li6Co 0.75 W 0.25 O4, Li6Co 0.7 W 0.3 O4, Li6Co 0.65 W 0.35 O4, Li6Co 0.6 W 0.4 O4, Li6Co 0.55 W 0.45 O4, Li6Co 0.5 W 0.5 O4, Li6Co 0.45 W 0.55 O4, Li6Co 0.4 W 0.6 O4, Li6Co 0.35 W 0.65 O4, Li6Co 0.3 W 0.7 O4, Li6Co 0.25 W 0.75 O4 and Li6Co 0.2 W 0.8 It may contain one or more compounds selected from the group consisting of O4.

[0064] On the one hand, the lithium transition metal oxide has lattice parameters of a unit lattice that satisfy the following formulas 1 and 2: [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above formulas 1 and 2, a, b, and c are the lattice parameters of the lithium transition metal oxide obtained by the X-ray diffraction Rietveld refinement method using CuKα radiation.

[0065] The lithium transition metal oxide according to an embodiment of the present invention has an anti-fluorite lattice structure. In particular, the lithium transition metal oxide has an a-axis lattice constant of 6.53200 Å to 6.54400 Å; a b-axis lattice constant that is the same as the value of the a-axis lattice constant; and a c-axis lattice constant of 4.64930 Å to 4.65330 Å.

[0066] The lattice constants are determined by the X-ray diffraction Rietveld refinement method using CuKα radiation as a radiation source for the lithium transition metal oxide.

[0067] By satisfying the values of the lattice constants according to the above formulas 1 and 2, the structural stability of the crystal lattice including the unit lattice is improved. Further, when the battery is charged and discharged, the strain applied to the crystal structure of the lithium transition metal oxide is reduced, and a stable crystal structure can be maintained even when a large amount of lithium ions are sacrificed by prelithiation.

[0068] Preferably, the lithium transition metal oxide has an a-axis lattice constant of 6.54400 Å or less, or 6.54380 Å or less, or 6.54360 Å or less, or 6.54350 Å or less, or 6.54330 Å or less; and 6.53200 Å or more, or 6.53205 Å or more, or 6.53210 Å or more.

[0069] Preferably, the lithium transition metal oxide has an a-axis lattice constant of 6.53200 Å to 6.54400 Å, or 6.53205 Å to 6.54400 Å, or 6.53205 Å to 6.54380 Å, or 6.53205 Å to 6.54360 Å, or 6.53205 Å to 6.54350 Å, or 6.53210 Å to 6.54350 Å, or 6.53210 Å to 6.54330 Å.

[0070] Preferably, the lithium transition metal oxide has a c-axis lattice constant of 4.64930 Å or more, or 4.64935 Å or more, or 4.64940 Å or more, or 4.64945 Å or more; and 4.65330 Å or less, or 4.65328 Å or less, or 4.65326 Å or less.

[0071] Preferably, the lithium transition metal oxide has a c-axis lattice constant of 4.64930 Å to 4.65330 Å, or 4.64935 Å to 4.65330 Å, or 4.64935 Å to 4.65328 Å, or 4.64940 Å to 4.65328 Å, or 4.64940 Å to 4.65326 Å, or 4.64945 Å to 4.65326 Å.

[0072] And the lithium transition metal oxide has a unit cell volume (V) of 198.350 Å 3 ~199.170 Å 3 The unit cell volume (V) is also determined by the X-ray diffraction Rietveld refinement method (XRD Rietveld refinement method) using CuKα radiation as the target line for the lithium transition metal oxide.

[0073] Specifically, the lithium transition metal oxide has a unit cell volume (V) of 198.350 Å 3 or more, or 198.360 Å 3 or more, or 198.370 Å 3 or more, or 198.380 Å 3 or more; and 199.170 Å 3 or less, or 199.160 Å 3 or less, or 199.150 Å 3 or less, or 199.140 Å 3 or less.

[0074] Preferably, the lithium transition metal oxide has a unit cell volume (V) of 198.350 Å 3 to 199.170 Å 3 or 198.360 Å 3 to 199.170 Å 3 or 198.360 Å 3 to 199.160 Å 3 or 198.370 Å 3 to 199.160 Å 3 or 198.370 Å 3 to 199.150 Å 3 or 198.380 Å 3 to 199.150 Å 3 or 198.380 Å 3 to 199.140 Å 3 or less.

[0075] The lithium transition metal oxide has the property of irreversibly releasing 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.

[0076] II. Method for Producing Lithium Transition Metal Oxide According to another embodiment of the present invention, a first step of obtaining a raw material mixture by solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element M oxide; 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 a compound represented by the following Chemical Formula 1, is included, and a method for producing the lithium transition metal oxide is provided: [Chemical Formula 1] Li6Co 1-x M x O4 In the Chemical Formula 1, M is one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, transition metals of the fourth period, transition metals of the fifth period, and transition metals of the sixth period, x is 0.05 to 0.80.

[0077] In the first step, a raw material mixture containing a lithium oxide, a cobalt oxide, and a heterogeneous element M oxide is prepared.

[0078] As the lithium oxide, an oxide containing lithium such as Li2O can be used without particular limitation.

[0079] Also, as the cobalt oxide, an oxide containing cobalt such as CoO can be used without particular limitation.

[0080] Matters regarding the heterogeneous element M are replaced with the content described in the item of "I. Lithium Transition Metal Oxide". As the heterogeneous element oxide, oxides containing the heterogeneous element M such as ZnO, Mg, Al2O3, TiO2, ZrO2, NbO2, and WO3 can be used without particular limitation.

[0081] The raw material mixture is prepared by solid-phase mixing the lithium oxide, the cobalt oxide, and the heterogeneous element oxide according to the stoichiometric ratio of Chemical Formula 1.

[0082] In the second step, the raw material mixture obtained in the first step is fired in an inert atmosphere at a temperature of 550°C to 750°C to obtain a compound represented by Chemical Formula 1.

[0083] The second stage is carried out in an inert atmosphere formed using an inert gas such as Ar, N2, Ne, and He.

[0084] In the second stage, it is preferable to heat the mixture obtained in the first stage at a heating rate of 1.4 °C / min to 2.0 °C / min in an inert atmosphere until the firing temperature is reached.

[0085] When the heating rate is excessively slow, crystal seeds are gradually formed, 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 too 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 size of the particles also becomes relatively small. Therefore, the heating rate is preferably 2.0 °C / min or less.

[0086] Specifically, the heating rate can 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 can 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.

[0087] The firing is carried out at a temperature of 550 °C to 750 °C.

[0088] To generate crystal seeds at an appropriate rate, the firing temperature is preferably 550 °C or more. However, when the firing temperature is too high, a sintering phenomenon occurs in which the grown crystal particles agglomerate. Therefore, the firing temperature is preferably 750 °C or less.

[0089] Specifically, the firing temperature can be 550°C or higher, or 580°C or higher, or 600°C or higher; and 750°C or lower, or 720°C or lower, or 700°C or lower. Preferably, the firing temperature can be 580°C to 750°C, or 580°C to 720°C, or 600°C to 720°C, or 600°C to 700°C.

[0090] The firing is carried out for 2 hours to 20 hours at the firing temperature. 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 longer, or 3 hours or longer, or 4 hours or longer; and 20 hours or shorter, or 19 hours or shorter, or 18 hours or shorter. Preferably, the firing time can be 3 hours to 20 hours, or 3 hours to 19 hours, or 4 hours to 19 hours, or 4 hours to 18 hours.

[0091] The compound of Chemical Formula 1 obtained in the second step has a cumulative 50% particle size (D50) of 1 μm to 30 μm by laser diffraction scattering particle size distribution measurement. If necessary, a step of pulverizing and classifying can be performed so that the compound of Chemical Formula 1 falls within the range of the D50 value.

[0092] In order to prevent the side reaction with the electrolyte from intensifying due to a very large specific surface area, the D50 value is preferably 1 μm or more. However, if the particle size is too large, it is difficult to uniformly coat the positive electrode material containing the compound of Chemical Formula 1 on the current collector, and damage to the current collector can be induced during the rolling process after drying. Therefore, the D50 value is preferably 30 μm or less.

[0093] Specifically, the compound of Chemical Formula 1 has a D50 value of 1 μm or more, or 3 μm or more, or 5 μm or more; and 30 μm or less, or 27 μm or less, or 25 μm or less. Preferably, the compound of Chemical Formula 1 has a D50 value of 3 μm to 30 μm, or 3 μm to 27 μm, or 5 μm to 27 μm, or 5 μm to 25 μm.

[0094] If necessary, a step of washing and drying the compound represented by Chemical Formula 1 obtained in the second step can be performed.

[0095] As a non-limiting example, the washing step can be performed by a method of mixing the compound of Chemical Formula 1 and a washing liquid at a weight ratio of 1:2 to 1:10 and stirring. As the washing liquid, distilled water, aqueous ammonia, etc. can be used. The drying can be performed by a method of heat treatment at a temperature of 100 °C to 200 °C or 100 °C to 180 °C for 1 hour to 10 hours.

[0096] Through the above-described series of steps, a lithium transition metal oxide represented by Chemical Formula 1 and having lattice constants of the unit lattice satisfying the above Formulas 1 and 2 is produced.

[0097] III. Cathode Additive for Lithium Secondary Battery According to another embodiment of the present invention, a cathode additive for a lithium secondary battery is provided, which contains a lithium transition metal oxide represented by the following Chemical Formula 1 and having lattice parameters of a unit lattice satisfying the following Formulas 1 and 2: [Chemical Formula 1] Li6Co 1-x M x O4 In the above Chemical Formula 1, M is one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, transition metals of the fourth period, transition metals of the fifth period, and transition metals of the sixth period, x is 0.05 to 0.80; [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above Formula 1 and Formula 2, a, b, and c are lattice constants of the lithium transition metal oxide obtained by an X-ray diffraction Rietveld refinement method using CuKα rays.

[0098] The lithium transition metal oxide represented by the above Chemical Formula 1 and satisfying the above Formula 1 and Formula 2 can minimize the side reaction with the electrolyte and suppress gas generation at the positive electrode during charge and discharge of the lithium secondary battery. Therefore, the positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide enables improvement of the safety and life characteristics of the lithium secondary battery.

[0099] The positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide has a characteristic of irreversibly releasing lithium during charge and discharge of the lithium secondary battery. Therefore, the positive electrode additive for a lithium secondary battery is included in the positive electrode for a lithium secondary battery and can serve as sacrificial positive electrode materials for prelithiation.

[0100] Matters regarding the lithium transition metal oxide are replaced with the content described in the item of "I. Lithium Transition Metal Oxide".

[0101] The lithium transition metal oxide represented by the above Chemical Formula 1 has a composition in which a different element M is introduced by being alloyed or doped into Li6CoO4.

[0102] In the above Chemical Formula 1, the different element M is one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, transition metals of the fourth period, transition metals of the fifth period, and transition metals of the sixth period.

[0103] Specifically, the Group 2 element includes one or more selected from the group consisting of Mg, Ca, Sr, and Ba; the Group 13 element includes one or more selected from the group consisting of Al, Ga, and In; the Group 14 element includes one or more selected from the group consisting of Si, Ge, and Sn; the Period 4 transition metal includes one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; the Period 5 transition metal includes one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; and the Period 6 transition metal includes one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

[0104] Preferably, from the aspects of the ease of alloying or doping with lithium cobalt oxide and the stabilization of the crystal phase, M can be one or more elements selected from the group consisting of Zn, Al, Mg, Ti, Zr, Nb, and W.

[0105] Based on the total metal elements excluding lithium in the lithium transition metal oxide of Chemical Formula 1, the hetero element M is contained in an amount of 5 mol% to 80 mol%.

[0106] Two or more hetero elements are introduced into the lithium transition metal oxide.

[0107] Preferably, the lithium transition metal oxide is Li6Co 0.95 Zn 0.05 O4, Li6Co 0.9 Zn 0.1 O4, Li6Co 0.85 Zn 0.15 O4, Li6Co 0.8 Zn 0.2 O4, Li6Co 0.75 Zn 0.25 O4, Li6Co 0.7 Zn 0.3 O4, Li6Co 0.65 Zn 0.35 O4, Li6Co 0.6 Zn 0.4 O4, Li6Co 0.55 Zn0.45 O4, Li6Co 0.5 Zn 0.5 O4, Li6Co 0.45 Zn 0.55 O4, Li6Co 0.4 Zn 0.6 O4, Li6Co 0.35 Zn 0.65 O4, Li6Co 0.3 Zn 0.7 O4, Li6Co 0.25 Zn 0.75 O4, Li6Co 0.2 Zn 0.8 O4; Li6Co 0.95 Al 0.05 O4, Li6Co 0.9 Al 0.1 O4, Li6Co 0.85 Al 0.15 O4, Li6Co 0.8 Al 0.2 O4, Li6Co 0.75 Al 0.25 O4, Li6Co 0.7 Al 0.3 O4, Li6Co 0.65 Al 0.35 O4, Li6Co 0.6 Al 0.4 O4, Li6Co 0.55 Al 0.45 O4, Li6Co 0.5 Al 0.5 O4, Li6Co 0.45 Al 0.55 O4, Li6Co 0.4 Al 0.6 O4, Li6Co 0.35 Al 0.65 O4, Li6Co 0.3 Al 0.7 O4, Li6Co 0.25 Al 0.75 O4, Li6Co 0.2 Al 0.8 O4; Li6Co 0.95 Mg 0.05 O4, Li6Co 0.9 Mg 0.1 O4, Li6Co 0.85 Mg 0.15 O4, Li6Co 0.8 Mg 0.2 O4, Li6Co0.75 Mg 0.25 O4, Li6Co 0.7 Mg 0.3 O4, Li6Co 0.65 Mg 0.35 O4, Li6Co 0.6 Mg 0.4 O4, Li6Co 0.55 Mg 0.45 O4, Li6Co 0.5 Mg 0.5 O4, Li6Co 0.45 Mg 0.55 O4, Li6Co 0.4 Mg 0.6 O4, Li6Co 0.35 Mg 0.65 O4, Li6Co 0.3 Mg 0.7 O4, Li6Co 0.25 Mg 0.75 O4, Li6Co 0.2 Mg 0.8 O4; Li6Co 0.95 Ti 0.05 O4, Li6Co 0.9 Ti 0.1 O4, Li6Co 0.85 Ti 0.15 O4, Li6Co 0.8 Ti 0.2 O4, Li6Co 0.75 Ti 0.25 O4, Li6Co 0.7 Ti 0.3 O4, Li6Co 0.65 Ti 0.35 O4, Li6Co 0.6 Ti 0.4 O4, Li6Co 0.55 Ti 0.45 O4, Li6Co 0.5 Ti 0.5 O4, Li6Co 0.45 Ti 0.55 O4, Li6Co 0.4 Ti 0.6 O4, Li6Co 0.35 Ti 0.65 O4, Li6Co 0.3 Ti 0.7 O4, Li6Co 0.25 Ti 0.75 O4, Li6Co 0.2 Ti 0.8O4; Li6Co 0.95 Zr 0.05 O4, Li6Co 0.9 Zr 0.1 O4, Li6Co 0.85 Zr 0.15 O4, Li6Co 0.8 Zr 0.2 O4, Li6Co 0.75 Zr 0.25 O4, Li6Co 0.7 Zr 0.3 O4, Li6Co 0.65 Zr 0.35 O4, Li6Co 0.6 Zr 0.4 O4, Li6Co 0.55 Zr 0.45 O4, Li6Co 0.5 Zr 0.5 O4, Li6Co 0.45 Zr 0.55 O4, Li6Co 0.4 Zr 0.6 O4, Li6Co 0.35 Zr 0.65 O4, Li6Co 0.3 Zr 0.7 O4, Li6Co 0.25 Zr 0.75 O4, Li6Co 0.2 Zr 0.8 O4; Li6Co 0.95 Nb 0.05 O4, Li6Co 0.9 Nb 0.1 O4, Li6Co 0.85 Nb 0.15 O4, Li6Co 0.8 Nb 0.2 O4, Li6Co 0.75 Nb 0.25 O4, Li6Co 0.7 Nb 0.3 O4, Li6Co 0.65 Nb 0.35 O4, Li6Co 0.6 Nb 0.4 O4, Li6Co 0.55 Nb 0.45 O4, Li6Co 0.5 Nb 0.5 O4, Li6Co 0.45 Nb 0.55 O4, Li6Co 0.4 Nb0.6 O4, Li6Co 0.35 Nb 0.65 O4, Li6Co 0.3 Nb 0.7 O4, Li6Co 0.25 Nb 0.75 O4, Li6Co 0.2 Nb 0.8 O4; Li6Co 0.95 W 0.05 O4, Li6Co 0.9 W 0.1 O4, Li6Co 0.85 W 0.15 O4, Li6Co 0.8 W 0.2 O4, Li6Co 0.75 W 0.25 O4, Li6Co 0.7 W 0.3 O4, Li6Co 0.65 W 0.35 O4, Li6Co 0.6 W 0.4 O4, Li6Co 0.55 W 0.45 O4, Li6Co 0.5 W 0.5 O4, Li6Co 0.45 W 0.55 O4, Li6Co 0.4 W 0.6 O4, Li6Co 0.35 W 0.65 O4, Li6Co 0.3 W 0.7 O4, Li6Co 0.25 W 0.75 O4 and Li6Co 0.2 W 0.8 It may contain one or more compounds selected from the group consisting of O4.

[0108] The lithium transition metal oxide has an anti-fluorite lattice structure. In particular, the lithium transition metal oxide has an a-axis lattice constant of 6.53200 Å to 6.54400 Å; a b-axis lattice constant equal to the value of the a-axis lattice constant; and a c-axis lattice constant of 4.64930 Å to 4.65330 Å.

[0109] And the lithium transition metal oxide is 198.350 Å3 ~199.170 Å 3 has a unit cell volume (V) that is

[0110] IV. Cathode for Lithium Secondary Battery According to another embodiment of the present invention, a cathode for a lithium secondary battery is provided.

[0111] The cathode for the lithium secondary battery may include a cathode active material, a binder, a conductive material, and the lithium transition metal oxide.

[0112] Also, the cathode for the lithium secondary battery may include a cathode active material, a binder, a conductive material, and an additive for the cathode of the lithium secondary battery.

[0113] The lithium transition metal oxide and the additive for the cathode of the lithium secondary battery have the property of irreversibly releasing lithium during charge and discharge of the lithium secondary battery. Therefore, the lithium transition metal oxide and the additive for the cathode of the lithium secondary battery are included in the cathode for the lithium secondary battery and can serve as sacrificial positive electrode materials for prelithiation.

[0114] Preferably, the cathode for the lithium secondary battery includes a cathode material including a cathode active material, a conductive material, the sacrificial positive electrode material, and a binder, and a current collector that supports the cathode material.

[0115] Here, the sacrificial positive electrode material is the lithium transition metal oxide or the additive for the cathode 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 Cathode of Lithium Secondary Battery".

[0116] In order to increase the battery capacity as the battery goes to a high-capacity battery, the ratio of the negative electrode active material in the negative electrode must be further increased, and thereby, 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 design capacity of the battery can be determined by calculating backward the amount of the sacrificial anode material applied to the positive electrode side.

[0117] According to one embodiment, the sacrificial anode material is 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.

[0118] In order 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 positive electrode material.

[0119] However, when the sacrificial anode material is contained in excess, the content of the positive electrode active material showing a reversible charge-discharge capacity decreases, the capacity of the battery decreases, and the remaining lithium in the battery plates on the negative electrode, inducing a short circuit of the battery or inhibiting the safety. Therefore, the content of the sacrificial anode material is preferably 15% by weight or less based on the total weight of the positive electrode material.

[0120] Specifically, the content of the sacrificial anode material may 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 positive electrode material.

[0121] Preferably, the content of the sacrificial anode material may 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 positive electrode material.

[0122] As the positive electrode active material, any compound applicable to a lithium secondary battery in the technical field to which the present invention pertains can be used without particular limitation.

[0123] As a non-limiting example, the positive electrode 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 Mn c )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), LiCoPO4, and LiFePO4, etc. can be used. As the positive electrode active material, one or a mixture of two or more of the above examples can be used.

[0124] According to one embodiment, the positive electrode active material is contained in an amount of 80% to 95% by weight based on the total weight of the positive electrode material.

[0125] Specifically, the content of the positive electrode active material can be 80% by weight or more, or 82% by weight or more, or 85% by weight or more; and 95% by weight or less, or 93% by weight or less, or 90% by weight or less based on the total weight of the positive electrode material.

[0126] Preferably, the content of the positive electrode active material can be 82% to 98% by weight, or 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.

[0127] The conductive material is used to impart conductivity to the electrode.

[0128] As the conductive material, any material that does not cause chemical changes in the battery and has electron conductivity can be used without particular limitation. As non-limiting examples, the conductive material can be carbon-based materials 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 and 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 examples can be used.

[0129] The content of the conductive material is adjusted within a range that does not induce a decrease in the battery capacity while exhibiting an appropriate level of conductivity. Preferably, the content of the conductive material can be 0.5 wt% to 10 wt%, or 1 wt% to 10 wt%, or 1 wt% to 5 wt% based on the total weight of the positive electrode material.

[0130] The binder is used to adhere the positive electrode material well to the current collector. 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 polymer (EPDM), sulfonated EPDM, styrene - butadiene rubber (SBR), fluororubber, etc. As the binder, one or a mixture of two or more of the above examples can be used.

[0131] The content of the binder is adjusted within a range that does not induce a decrease in the battery capacity while exhibiting an appropriate level of adhesiveness. Preferably, the content of the binder can be 0.5 wt% to 10 wt%, or 1 wt% to 10 wt%, or 1 wt% to 5 wt% based on the total weight of the positive electrode material.

[0132] As the current collector, any material applicable to the positive electrode of a lithium secondary battery in the technical field to which the present invention pertains can be used without particular limitation.

[0133] As non-limiting examples, as the current collector, stainless steel; aluminum; nickel; titanium; fired carbon; or those obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0134] Preferably, the current collector has 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, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0135] The positive electrode for a lithium secondary battery is 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.

[0136] V. Lithium Secondary Battery According to another embodiment of the present invention, A lithium secondary battery including the positive electrode for a lithium secondary battery, a negative electrode, a separator, and an electrolyte is provided.

[0137] The lithium secondary battery includes a positive electrode containing the lithium transition metal oxide or the positive electrode additive for the lithium secondary battery. Therefore, gas generation at the positive electrode during charge and discharge of the lithium secondary battery is 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 capacity retention rate.

[0138] Therefore, the lithium secondary battery is 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, etc.; and in the field of means of transportation such as electric vehicles, electric bikes, and personal mobility devices.

[0139] The lithium secondary battery includes an electrode assembly wound through a separator 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.

[0140] The lithium secondary battery can have various forms such as square, cylindrical, and pouch-shaped.

[0141] Matters regarding the positive electrode are replaced with the content described in the item of "IV. Positive Electrode for Lithium Secondary Battery".

[0142] 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 supporting the negative electrode material.

[0143] Examples of 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 dopable and dedopable with lithium, and a transition metal oxide.

[0144] Examples of substances that can reversibly intercalate and deintercalate lithium ions include carbonaceous substances, such as crystalline carbon, amorphous carbon, or mixtures thereof. Specifically, the carbonaceous substance can 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, etc.

[0145] The alloy of the lithium metal can 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.

[0146] The substances capable of doping and undoping 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 doping and undoping 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.

[0147] And the transition metal oxide can be vanadium oxide, lithium vanadium oxide, lithium titanate, etc.

[0148] Preferably, the negative electrode contains one or more negative electrode active materials selected from the group consisting of carbonaceous materials and silicon compounds.

[0149] 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 described above. And the silicon compound can be a compound containing Si described above, 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 these and SiO2.

[0150] According to one embodiment, the negative electrode active material is contained in an amount of 85% by weight to 98% by weight based on the total weight of the negative electrode material.

[0151] 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; and 98% by weight or less, or 97% by weight or less, or 95% by weight or less based on the total weight of the negative electrode material.

[0152] 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.

[0153] Regarding the conductive material, the binder, and the current collector contained in the negative electrode material, the description in the item of "IV. Positive electrode for lithium secondary battery" is applicable instead.

[0154] The separator separates the positive electrode and the negative electrode and provides a migration path for lithium ions. As the separator, any material applicable to the separator of a lithium secondary battery in the technical field to which the present invention pertains can be used without particular limitation. The separator preferably has a low resistance to the ion migration of the electrolyte and excellent wettability to the electrolyte.

[0155] 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, or ethylene-methacrylate copolymer. 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 nonwoven fabric containing glass fiber, polyethylene terephthalate fiber, or the like. And the separator may be coated with a ceramic component or a polymer substance to ensure heat resistance or mechanical strength.

[0156] On the one hand, as the electrolyte, any electrolyte applicable to lithium secondary batteries in the technical field to which the present invention pertains 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.

[0157] Specifically, the electrolyte may contain a non-aqueous organic solvent and a lithium salt.

[0158] As the non-aqueous organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move can be used without particular limitation.

[0159] 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; a nitrile such as R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms and containing a double bond aromatic ring or an ether bond); an amide such as dimethylformamide; a dioxolane such as 1,3-dioxolane; and sulfolane, etc.

[0160] Among the above examples, it is preferable to use a carbonate solvent as the non-aqueous organic solvent.

[0161] In particular, considering the charge-discharge performance of the battery and the compatibility with the sacrificial anode material, as the non-aqueous organic solvent, it is preferable to use a mixture of a cyclic carbonate (e.g., ethylene carbonate, propylene carbonate) having high ionic conductivity and high dielectric constant and a linear carbonate having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate). 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.

[0162] Also, as the non-aqueous organic solvent, it is preferable to use 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.

[0163] 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.

[0164] 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.

[0165] The lithium salt is contained in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt contained within the above concentration range can exhibit excellent electrolyte performance by imparting appropriate conductivity and viscosity to the electrolyte.

[0166] Optionally, the electrolyte contains 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.

[0167] For example, the additives may be haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, triamide hexaline, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like. The additives are contained at 0.1% by weight to 5% by weight based on the total weight of the electrolyte.

Effects of the Invention

[0168] The lithium transition metal oxide according to the present invention can minimize side reactions with the electrolyte and suppress gas generation during charge and discharge of a lithium secondary battery by maintaining a lattice structure in which different elements are introduced and stabilized. The positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide can improve the safety and life characteristics of the lithium secondary battery.

Brief Description of the Drawings

[0169]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0170] Hereinafter, the actions and effects of the invention will be specifically described by way of specific examples of the invention. However, this is presented as an exemplification for assisting the understanding of the invention. It is not intended that the scope of the rights of the invention be limited in any sense by the following examples, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the scope of the technical idea.

[0171] Example 1 (1) Synthesis of Lithium Transition Metal Oxide Li2O, CoO, and ZnO were solid-phase mixed at a molar ratio of Li:Co:Zn = 6:0.7:0.3 to prepare a raw material mixture.

[0172] After heating the raw material mixture at a heating rate of 1.6 °C / min for 6 hours in an Ar atmosphere, it was calcined at 600 °C for 12 hours to obtain a lithium transition metal oxide of Li6Co 0.7 Zn 0.3 O4.

[0173] After pulverizing the lithium transition metal oxide using a jaw crusher, it was classified using a sieve shaker.

[0174] (2) Manufacture of Lithium Secondary Battery As a positive electrode additive, the lithium transition metal oxide (Li6Co 0.7 Zn 0.3O4), 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 then rolled and dried to produce a positive electrode. On the other hand, no positive electrode active material was added to the positive electrode material in this experiment. When a positive electrode active material was added, it was presented in Example 8 below.

[0175] As the negative electrode active material, natural graphite, carbon black as the conductive material, and carboxymethyl cellulose (CMC) as the binder 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 then rolled and dried to produce a negative electrode.

[0176] 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 of 0.7 M concentration of LiPF6 and 0.5 M concentration of LiFSI was dissolved in the non-aqueous organic solvent to produce an electrolyte.

[0177] An electrode assembly was manufactured with a porous polyethylene, which was a separator, between the positive electrode and the negative electrode, and the electrode assembly was placed inside the case. The electrolyte was injected into the case to manufacture a lithium secondary battery in the form of a pouch cell.

[0178] Example 2 A lithium transition metal oxide of (1) Li6Co 0.7 Mg 0.3 O4 and (2) a lithium secondary battery containing this as a positive electrode additive were manufactured in the same manner as in Example 1 except that MgO was used instead of ZnO.

[0179] Example 3 A lithium transition metal oxide of (1) Li6Co 0.7 Al0.3 A lithium transition metal oxide which is O4, and (2) a lithium secondary battery containing this as a cathode additive were produced.

[0180] Example 4 (1) Li6Co 0.9 Zn 0.1 A lithium transition metal oxide which is O4, and (2) a lithium secondary battery containing this as a cathode additive were produced.

[0181] Example 5 (1) Li6Co 0.8 Zn 0.2 A lithium transition metal oxide which is O4, and (2) a lithium secondary battery containing this as a cathode additive were produced.

[0182] Example 6 (1) Li6Co 0.6 Zn 0.4 A lithium transition metal oxide which is O4, and (2) a lithium secondary battery containing this as a cathode additive were produced.

[0183] Example 7 (1) Li6Co 0.5 Zn 0.5 A lithium transition metal oxide which is O4, and (2) a lithium secondary battery containing this as a cathode additive were produced.

[0184] Example 8 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode active material was further added during the manufacture of the positive electrode and the composition of the negative electrode active material was changed during the manufacture of the negative electrode.

[0185] Specifically, an NCMA (Li[Ni, Co, Mn, Al]O2)-based compound, NTA-X12M, L&F) as a positive electrode active material, the lithium transition metal oxide (Li6Co 0.7 Zn 0.3 O4) as a positive electrode 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 positive electrode material slurry. The positive electrode 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 positive electrode.

[0186] A mixture of natural graphite and SiO (weight ratio = 9:1) as a negative electrode 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 a negative electrode material slurry. The negative electrode 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 a negative electrode.

[0187] An electrode assembly was manufactured with a porous polyethylene, which is a separator, between the positive electrode and the negative electrode, 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.

[0188] Example 9 A lithium secondary battery including (1) a lithium transition metal oxide of Li6Co 0.7 Zn 0.3 O4 and (2) using this as a positive electrode additive was manufactured in the same manner as in Example 1, except that the raw material mixture was heated at a rate of 1.6 °C / min in an Ar atmosphere and then calcined at 600 °C for 6 hours.

[0189] Example 10 The raw material mixture was heated at a rate of 1.6 °C / min under an Ar atmosphere and then calcined at 600 °C for 18 hours. Except for this, a lithium transition metal oxide which is Li6Co 0.7 Zn 0.3 O4 and (2) a lithium secondary battery containing this as a cathode additive were manufactured in the same manner as in Example 1.

[0190] Example 11 The raw material mixture was heated at a rate of 1.9 °C / min under an Ar atmosphere and then calcined at 700 °C for 12 hours. Except for this, a lithium transition metal oxide which is Li6Co 0.7 Zn 0.3 O4 and (2) a lithium secondary battery containing this as a cathode additive were manufactured in the same manner as in Example 1.

[0191] Comparative Example 1 A lithium transition metal oxide which is Li6CoO4 and (2) a lithium secondary battery containing this as a cathode additive were manufactured in the same manner as in Example 1, except that ZnO was not added and Li2O and CoO were mixed at a molar ratio of Li:Co = 6:1.

[0192] Comparative Example 2 During the manufacture of the cathode, a lithium secondary battery was manufactured in the same manner as in Example 8, except that Li6Co 0.7 Zn 0.3 O4 was used instead of the Li6CoO4 obtained in Comparative Example 1 as the cathode additive.

[0193] Comparative Example 3 During the manufacture of the cathode, a lithium secondary battery was manufactured in the same manner as in Example 8, except that an NCMA (Li[Ni, Co, Mn, Al]O2)-based compound, NTA-X12M, L&F) was used as the cathode active material, DN20 (Li2NiO2, POSCO Chemical) was used instead of the lithium transition metal oxide (Li6Co 0.7 Zn 0.3 O4) as the cathode additive, carbon black was used as the conductive material, and polyvinylidene fluoride (PVdF) was used as the binder and they were mixed at a weight ratio of 91.2:3.8:3:2.

[0194] Comparative Example 4 A lithium secondary battery was manufactured in the same manner as in Example 8, except that the positive electrode additive was not added during the production of the positive electrode.

[0195] Comparative Example 5 A lithium transition metal oxide of (1) Li6Co 0.7 Zn 0.3 O4 and (2) a lithium secondary battery containing this as a positive electrode additive were manufactured in the same manner as in Example 1, except that the temperature of the raw material mixture was raised at a rate of 0.5 °C / min in an Ar atmosphere and then calcined at 600 °C for 6 hours.

[0196] Comparative Example 6 A lithium transition metal oxide of (1) Li6Co 0.7 Zn 0.3 O4 and (2) a lithium secondary battery containing this as a positive electrode additive were manufactured in the same manner as in Example 1, except that the temperature of the raw material mixture was raised at a rate of 5.0 °C / min in an Ar atmosphere and then calcined at 600 °C for 6 hours.

[0197] Comparative Example 7 A lithium transition metal oxide of (1) Li6Co 0.7 Zn 0.3 O4 and (2) a lithium secondary battery containing this as a positive electrode additive were manufactured in the same manner as in Example 1, except that the temperature of the raw material mixture was raised at a rate of 10.0 °C / min in an Ar atmosphere and then calcined at 600 °C for 6 hours.

[0198] Test Example 1 X-ray diffraction analysis (model name: D8 ENDEAVOR, manufacturer: Bruker) using CuKα radiation as the radiation source was performed on the lithium transition metal oxides obtained in Examples 1 to 7 and Comparative Example 1. The profiles obtained by the X-ray diffraction analysis were calculated by the Rietveld refinement method to obtain the lattice constant values and volume values of the unit cell.

[0199]

Table 1

[0200] Referring to Table 1 above, it was confirmed that the lithium transition metal oxides of Examples 1 to 7 had the composition of Chemical Formula 1 above and satisfied the values of the lattice constants of Formula 1 and Formula 2 above. In contrast, since the lithium transition metal oxide of Comparative Example 1 did not contain a foreign element and did not have the composition of Chemical Formula 1, it was confirmed that the value of the lattice constant did not satisfy Formula 1 and Formula 2 above.

[0201] Then, referring to Examples 1 and 4 to 7, it was shown that as the introduction amount of the foreign element increased, the value of the a-axis lattice constant decreased relatively, and the value of the c-axis lattice constant increased relatively.

[0202] Furthermore, referring to Examples 1, 9, and 10, as the firing time for the raw material mixture increased, the values of the a-axis and c-axis lattice constants showed a tendency to gradually decrease. Even in the case of Example 11 where the firing temperature was increased to 700 °C, the value of the lattice constant did not decrease significantly compared to Example 1.

[0203] On the contrary, in the case of Comparative Example 5 where the heating rate was slowed down, excessive crystal growth of the lithium transition metal oxide occurred, and the values of the a-axis and c-axis lattice constants decreased significantly compared to Example 1. And in the cases of Comparative Examples 6 and 7 where the heating rate was increased, since the crystal growth time of the lithium transition metal oxide was relatively insufficient compared to Example 1 and the crystallinity decreased, it was confirmed that the values of the a-axis and c-axis lattice constants increased compared to Example 1.

[0204] Test Example 2 An experiment was conducted to confirm the initial charge capacity of a lithium secondary battery and the cumulative gas generation amount based on the cumulative charge and discharge capacity, which vary depending on the necessity of introducing a foreign element into Li6CoO4 and the type of foreign element.

[0205] Here, the irreversible capacity is defined as "charge capacity - discharge capacity = irreversible capacity", and the cumulative irreversible capacity is defined as the sum of the irreversible capacities for each charge-discharge cycle.

[0206] For the lithium secondary batteries of Examples 1 to 3 and Comparative Example 1, the cumulative gas generation amount due to charge-discharge cycles was measured by the following method, and the gas generation amount based on the measured cumulative charge capacity is shown in a graph in FIG. 1.

[0207] (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, and rested for 20 minutes between charge and discharge to perform cycles, and then the formation capacity and charge-discharge capacity were measured.

[0208] (2) Measurement of cumulative gas generation amount due to charge-discharge 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 difference between the original weight of the pouch cell and the weight in water was measured, the change in volume in the pouch cell was calculated, and the gas generation amount per unit weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0209] The cumulative gas generation amounts after formation (0 th charge-discharge), 1 st , 2 nd , 10 th , 30 th and 50 th cumulative cycles are shown in Table 2 below.

[0210]

Table 2

[0211] As shown in Table 2 and FIG. 1 above, the formation capacity of Comparative Example 1 is the most excellent at 903.0 mAh / g, but continuous gas generation was observed, and it was found that the cumulative gas generation amount after 50 th cycles was 10 mL / g or more, which was much more than that in Examples 1 to 3. From this, it was considered that in Comparative Example 1, during the continuous charge and discharge, the actual charge capacity expression of Li6CoO4 and the charge capacity due to the side reaction with the electrolyte were mixed, and it was found that the oxidation reaction of the electrolyte occurred due to this, resulting in the generation of decomposition gas of the electrolyte.

[0212] On the contrary, in Examples 1 to 3, although the formation capacity is smaller than that of Comparative Example 1, it was found that the cumulative gas generation amount in 50 th cycles is also smaller than that of Comparative Example 1. In particular, Example 1, despite having the same molar ratio of different elements as Examples 2 and 3, the cumulative gas generation amount in 50 th cycles is 0.76 mL / g, and when compared with the gas generation amounts of 6.02 mL / g and 6.13 mL / g in Examples 2 and 3, it showed a much better gas generation reduction effect. From this, it was found that among the lithium cobalt oxides alloyed with different elements, the lithium cobalt oxide alloyed with Zn effectively stabilized the crystal phase, thereby reducing the gas generation due to the side reaction with the electrolyte.

[0213] In the case of Example 9 where the firing time was shortened to 6 hours, compared with Example 1 where the firing time was 12 hours, the crystallinity was somewhat insufficient and the formation capacity was lower than that of Example 1, and the cumulative gas generation amount in 50 th cycles is considered to be relatively high.

[0214] In the case of Example 10 where the firing time was increased to 18 hours and Example 11 where the firing temperature was increased to 700 °C, it was found that the formation capacity was larger than that of Example 1 and the cumulative gas generation amount in 50 th cycles was low. This is considered to be due to the increase in crystallinity accompanying the increase in firing time or firing temperature.

[0215] In the case of Comparative Example 5, due to the longer heating-up time, excessive crystal growth occurred, the particle size increased, and the formation capacity appeared to be somewhat lower than that of Example 1 due to the resulting decrease in specific surface area. On the other hand, in the cases of Comparative Example 6 and Comparative Example 7 where the heating-up time was shorter, although the particle size became smaller, the formation capacity was considered to decrease due to the reduction in crystallinity. Also, in the cases of Comparative Example 6 and Comparative Example 7, due to the instability caused by the reduction in crystallinity, the cumulative gas generation amount after 50 th cycles showed a slightly increasing trend compared to Example 1.

[0216] Test Example 3 An experiment was conducted to confirm the initial charge capacity of a lithium secondary battery and the cumulative gas generation amount due to the cumulative charge-discharge capacity, which vary depending on the introduction amount of Zn, one of the foreign elements, into Li6CoO4. Also, an experiment was carried out to confirm the cumulative gas generation amount due to high-temperature storage after formation.

[0217] For the lithium secondary batteries of Example 1, Examples 4 to 7, and Comparative Example 1, the cumulative gas generation amount due to the cumulative charge-discharge cycles was measured by the following method, and the gas generation amount according to the measured cumulative charge capacity was shown in the graphs of Table 3 and Figure 2. The cumulative gas generation amount according to the high-temperature storage time is shown in Table 4.

[0218] (1) Measurement of Formation (Initial Charge) Capacity and Charge-Discharge Capacity A pouch-type lithium secondary battery was charged at a constant current-constant voltage up to 4.25 V at 0.1 C under a temperature condition of 45 °C and discharged at a constant current up to 2.5 V. After performing cycles with a 20-minute rest between charge and discharge, the formation capacity and charge-discharge capacity were measured.

[0219] (2) Measurement of Cumulative Gas Generation Amount due to Cumulative Charge-Discharge After operating the lithium secondary battery under the charge-discharge conditions of (1) above, when attempting to measure the gas generation amount, the pouch cell was recovered in a discharged state for a while. Using a hydrometer (MATSUHAKU, TWD-150DM), the difference between the original weight of the pouch cell and the weight in water was measured, the change in volume within the pouch cell was calculated, and the gas generation amount per weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0220] (3) Measurement of cumulative gas generation amount due to high-temperature storage The lithium secondary battery in the form of a pouch cell was charged at a constant current-constant voltage up to 4.25 V at 0.1C under the temperature condition of 45°C, then recovered and the formation capacity was measured, and then stored in a chamber at 60°C. The lithium secondary battery was taken out of the chamber at one-week intervals, and using a hydrometer (MATSUHAKU, TWD-150DM), the difference between the original weight of the pouch cell and the weight in water was measured, the change in volume within the pouch cell was calculated, and the gas generation amount per weight was calculated by dividing the change in volume by the weight of the electrode active material.

[0221] As shown in Table 3 below after formation (0 th charge-discharge), 1 st , 2 nd , 10 th , 30 th and 50 th show the cumulative gas generation amounts after cumulative cycles.

[0222]

Table 3

[0223] As shown in Table 3 above and Figure 2, as the Zn content in Li6CoO4 increased, the formation capacity and the gas generation amount decreased. This is because, unlike Co which is oxidized from Co to CO during the initial charge while Zn is substituted at the Co site in Li6CoO4, Zn does not change its oxidation number from Zn 2+ so it does not contribute to the charge capacity. 4+ to CO 2+ from Zn

[0224] 50 after Example 1 th The cumulative gas generation amount after the cycle is 0.76 mL / g, which is within 1 mL / g. In the case of Example 6 and Example 7, the gas generation amount is smaller than that of Example 1, but the initial charge capacity has decreased. In the case of Example 1, considering comprehensively from the aspects of the initial charge capacity, 50 th The cumulative gas generation amount after the cycle, and the electrical conductivity of the particles, it seems to be the most excellent.

[0225] In the case of Example 6, the gas generation amount shows a negative value of -0.18 mL / g, which is an experimental error of the hydrometer and means that almost no actual gas generation occurs. That is, from the aspect of gas generation reduction, it seems that Example 6 is a little more excellent than Example 1.

[0226] After formation (0 th charge and discharge) in Table 4 below, the cumulative gas generation amounts after storage at 60°C for 1 week, 2 weeks, 3 weeks, and 4 weeks are shown.

[0227]

Table 4

[0228] As shown in Table 4 above, it was found that the cumulative gas generation amount during high-temperature storage at 60°C decreases as the Zn content in Li6CoO4 increases.

[0229] In particular, it was confirmed that in Example 4, the cumulative gas generation amount at the 4th week was 2.04 mL / g, which was a 78.6% decrease compared to Comparative Example 1. The cumulative gas generation amount after the 4th week in Example 1 was 0.37 mL / g, which is within 1 mL / g. Example 6 and Example 7 also showed excellent gas generation reduction effects.

[0230] Test Example 4 For Example 8 in which the positive electrode active material and the positive electrode additive were mixed and applied, and for the lithium secondary batteries of Comparative Examples 2 to 4, the capacity retention (cycle retention) and the cumulative gas generation amount due to the cumulative charge and discharge cycles were measured by the following method, and the measured capacity retention and cumulative gas generation amount are shown in FIG. 3 and Table 5.

[0231] (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 under a temperature condition of 45°C and discharged at a constant current up to 2.5 V, and after performing cycles with a 20-minute rest between charge and discharge, the formation capacity and the charge-discharge capacity up to 100 th cycles were measured.

[0232] (2) Measurement of Cumulative Gas Generation Amount due to Cumulative Charge and Discharge 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 difference between the original weight of the pouch cell and the weight in water was measured, the change in volume inside the pouch cell was calculated, and the gas generation amount per weight was calculated by dividing the change amount of volume by the weight of the electrode active material.

[0233] (3) Measurement of Cumulative Gas Generation Amount due to High-Temperature Storage 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 under a temperature condition of 45°C, and then, after being recovered and the formation capacity was measured, it was stored in a chamber at 60°C. The lithium secondary battery was taken out of the chamber at one-week intervals, and using a hydrometer (MATSUHAKU, TWD-150DM), the difference between the original weight of the pouch cell and the weight in water was measured, the change in volume inside the pouch cell was calculated, and the gas generation amount per weight was calculated by dividing the change amount of volume by the weight of the electrode active material.

[0234] In Table 5 below, the formation (0 th charge-discharge) capacity, and then 50 thand 100 th The cumulative gas generation amount after the cumulative cycles and 100 th Indicates the discharge capacity retention rate after the cycles.

[0235]

Table 5

[0236] As shown in Table 5 and Figure 3 above, the discharge capacities of Example 8, Comparative Example 2, and Comparative Example 3 were 214.9 mAh / g, 215.4 mAh / g, and 214.5 mAh / g, respectively, and were significantly larger than those of Comparative Example 4 where no sacrificial anode material was applied. This is considered to be because the sacrificial anode material compensates for the irreversible lithium consumed in the formation of the SEI layer at the negative electrode.

[0237] On the contrary, in the case of Comparative Example 4, since there is no sacrificial anode material to compensate for the irreversible lithium, the lithium in the positive electrode material is consumed, resulting in a decrease in the discharge capacity, showing a discharge capacity of 201.3 mAh / g.

[0238] 100 of Example 8 th The cumulative gas generation amount in the 100 cycles is 0.16 mL / g, which is less than 0.24 mL / g of Comparative Example 2 and also less than 0.20 mL / g of Comparative Example 3 where no sacrificial anode material was applied.

[0239] 100 of Comparative Example 3 th The cumulative gas generation amount in the 100 cycles is the least at 0.11 mL / g, but from the 50 th cycles to the 100 th cycles, the increase in gas generation is 0.09 mL / g, and thereafter, the gas generation may continue to increase. This is the same for Comparative Example 2. On the contrary, in the case of Example 8, from the 50 th cycles to the 100 th cycles, the increase in gas generation is 0.02 mL / g, and it is considered that the gas generation is suppressed as the charge-discharge cycles continue.

[0240] 100 thIn the case of the capacity retention rate in the cycle, both Example 8 and Comparative Example 2 to which the Co-based sacrificial anode material was applied are excellent at 88.2%. In the case of Comparative Example 3 to which the Ni-based sacrificial anode material was applied and Comparative Example 4 to which no sacrificial anode material was applied, the capacity retention rates were 86.3% and 86.2% respectively, which were lower than those of Example 8 and Comparative Example 2.

[0241] From this, when the Co-based sacrificial anode material, particularly the sacrificial anode material alloyed with Zn, is applied to a lithium secondary battery containing an actual cathode material, not only is the initial discharge capacity preserved and the amount of gas generated in the battery suppressed, but it is also possible to confirm that the capacity retention rate after 100 th cycles is also excellent.

[0242] The following Table 6 shows the cumulative gas generation amounts after 1 week, 2 weeks, 3 weeks, and 4 weeks of storage at 72 °C after formation (0 th charging).

[0243]

Table 6

[0244] As shown in Table 6 above, in the case of Example 8, the cumulative gas generation amount after 4 weeks was the least at 0.22 mL / g. This is considered to be because, similar to the results of the charge-discharge cycle, 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.

[0245] Also, in the case of Example 8, less gas was generated than in Comparative Example 4 to which no sacrificial anode material was applied. This may be due to experimental error or it is expected that the cathode additive contained in the lithium secondary battery not only suppresses gas generation but also absorbs the generated gas.

[0246] As described above, the present invention has been described by way of limited embodiments and drawings. However, the present invention is not limited thereby, and it goes without saying that various modifications and variations can be made by those having ordinary knowledge in the technical field to which the present invention pertains within the equivalent scope of the technical idea of the present invention and the scope of the claims described below.

Claims

1. A lithium transition metal oxide represented by the following Chemical Formula 1, wherein the lattice constants of the unit cell satisfy the following Formulas 1 and 2: [Chemical Formula 1] Li ６ Co １－ｘ M ｘ O ４ In the above Chemical Formula 1, M is one or more elements selected from the group consisting of Zn, Al, Mg, Ti, Zr, Nb, and W; x is from 0.1 to 0.7; [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above Formulas 1 and 2, a, b, and c are the lattice constants of the lithium transition metal oxide obtained by the X-ray diffraction Rietveld refinement method using CuKα radiation. A lithium transition metal oxide.

2. The lithium transition metal oxide has a unit cell volume (V) of 198.350 Å ３ to 199.170 Å ３ The lithium transition metal oxide according to claim 1.

3. The lithium transition metal oxide is Li ６ Co ０．９ Zn ０．１ O ４ 、Li ６ Co ０．８５ Zn ０．１５ O ４ 、Li ６ Co ０．８ Zn ０．２ O ４ 、Li ６ Co ０．７５ Zn ０．２５ O ４ 、Li ６ Co ０．７ Zn ０．３ O ４ 、Li ６ Co ０．６５ Zn ０．３５ O ４ 、Li ６ Co ０．６ Zn ０．４ O ４ 、Li ６ Co ０．５５ Zn ０．４５ O ４ 、Li ６ Co ０．５ Zn ０．５ O ４ 、Li ６ Co ０．４５ Zn ０．５５ O ４ 、Li ６ Co ０．４ Zn ０．６ O ４ 、Li ６ Co ０．３５ Zn ０．６５ O ４ 、Li ６ Co ０．３ Zn ０．７ O ４ ;Li ６ Co ０．９ Al ０．１ O ４ 、Li ６ Co ０．８５ Al ０．１５ O ４ 、Li ６ Co ０．８ Al ０．２ O ４ 、Li ６ Co ０．７５ Al ０．２５ O ４ 、Li ６ Co ０．７ Al ０．３ O ４ 、Li ６ Co ０．６５ Al ０．３５ O ４ 、Li ６ Co ０．６ Al ０．４ O ４ 、Li ６ Co ０．５５ Al ０．４５ O ４ 、Li ６ Co ０．５ Al ０．５ O ４ 、Li ６ Co ０．４５ Al ０．５５ O ４ 、Li ６ Co ０．４ Al ０．６ O ４ 、Li ６ Co ０．３５ Al ０．６５ O ４ 、Li ６ Co ０．３ Al ０．７ O ４ ;Li ６ Co ０．９ Mg ０．１ O ４ 、Li ６ Co ０．８５ Mg ０．１５ O ４ 、Li ６ Co ０．８ Mg ０．２ O ４ 、Li ６ Co ０．７５ Mg ０．２５ O ４ 、Li ６ Co ０．７ Mg ０．３ O ４ 、Li ６ Co ０．６５ Mg ０．３５ O ４ 、Li ６ Co ０．６ Mg ０．４ O ４ , Li ６ Co ０．５５ Mg ０．４５ O ４ , Li ６ Co ０．５ Mg ０．５ O ４ , Li ６ Co ０．４５ Mg ０．５５ O ４ , Li ６ Co ０．４ Mg ０．６ O ４ , Li ６ Co ０．３５ Mg ０．６５ O ４ , Li ６ Co ０．３ Mg ０．７ O ４ ; Li ６ Co ０．９ Ti ０．１ O ４ , Li ６ Co ０．８５ Ti ０．１５ O ４ , Li ６ Co ０．８ Ti ０．２ O ４ , Li ６ Co ０．７５ Ti ０．２５ O ４ , Li ６ Co ０．７ Ti ０．３ O ４ , Li ６ Co ０．６５ Ti ０．３５ O ４ , Li ６ Co ０．６ Ti ０．４ O ４ , Li ６ Co ０．５５ Ti ０．４５ O ４ , Li ６ Co ０．５ Ti ０．５ O ４ , Li ６ Co ０．４５ Ti ０．５５ O ４ , Li ６ Co ０．４ Ti ０．６ O ４ , Li ６ Co ０．３５ Ti ０．６５ O ４ , Li ６ Co ０．３ Ti ０．７ O ４ ; Li ６ Co ０．９ Zr ０．１ O ４ , Li ６ Co ０．８５ Zr ０．１５ O ４ , Li ６ Co ０．８ Zr ０．２ O ４ , Li ６ Co ０．７５ Zr ０．２５ O ４ , Li ６ Co ０．７ Zr ０．３ O ４ , Li ６ Co ０．６５ Zr ０．３５ O ４ , Li ６ Co ０．６ Zr ０．４ O ４ , Li ６ Co ０．５５ Zr ０．４５ O ４ , Li ６ Co ０．５ Zr ０．５ O ４ , Li ６ Co ０．４５ Zr ０．５５ O ４ , Li ６ Co ０．４ Zr ０．６ O ４ , Li ６ Co ０．３５ Zr ０．６５ O ４ , Li ６ Co ０．３ Zr ０．７ O ４ ; Li ６ Co ０．９ Nb ０．１ O ４ , Li ６ Co ０．８５ Nb ０．１５ O ４ 、Li ６ Co ０．８ Nb ０．２ O ４ 、Li ６ Co ０．７５ Nb ０．２５ O ４ 、Li ６ Co ０．７ Nb ０．３ O ４ 、Li ６ Co ０．６５ Nb ０．３５ O ４ 、Li ６ Co ０．６ Nb ０．４ O ４ 、Li ６ Co ０．５５ Nb ０．４５ O ４ 、Li ６ Co ０．５ Nb ０．５ O ４ 、Li ６ Co ０．４５ Nb ０．５５ O ４ 、Li ６ Co ０．４ Nb ０．６ O ４ 、Li ６ Co ０．３５ Nb ０．６５ O ４ 、Li ６ Co ０．３ Nb ０．７ O ４ ;Li ６ Co ０．９ W ０．１ O ４ 、Li ６ Co ０．８５ W ０．１５ O ４ 、Li ６ Co ０．８ W ０．２ O ４ 、Li ６ Co ０．７５ W ０．２５ O ４ 、Li ６ Co ０．７ W ０．３ O ４ , Li ６ Co ０．６５ W ０．３５ O ４ , Li ６ Co ０．６ W ０．４ O ４ , Li ６ Co ０．５５ W ０．４５ O ４ , Li ６ Co ０．５ W ０．５ O ４ , Li ６ Co ０．４５ W ０．５５ O ４ , Li ６ Co ０．４ W ０．６ O ４ , Li ６ Co ０．３５ W ０．６５ O ４ , and Li ６ Co ０．３ W ０．７ O ４ The lithium transition metal oxide according to claim 1 or 2, comprising one or more compounds selected from the group consisting of

4. A first step of obtaining a raw material mixture by solid-phase mixing a lithium oxide, a cobalt oxide, and a heterogeneous element M oxide; A second step of heating the mixture obtained in the first step in an inert atmosphere at a heating rate of 1.4 °C / min to 2.0 °C / min and firing at a temperature of 550 °C to 750 °C to obtain a compound represented by the following Chemical Formula 1. A method for producing a lithium transition metal oxide, comprising: [Chemical Formula 1] Li ６ Co １－ｘ M ｘ O ４ In the above Chemical Formula 1, M is one or more elements selected from the group consisting of Zn, Al, Mg, Ti, Zr, Nb, and W; x is from 0.1 to 0.

7. A method for producing a lithium transition metal oxide.

5. 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 4.

6. A positive electrode additive for a lithium secondary battery, comprising a lithium transition metal oxide represented by the following Chemical Formula 1, wherein the lattice constants of the unit cell satisfy the following Formulas 1 and 2: [Chemical Formula 1] Li ６ Co １－ｘ M ｘ O ４ In the above Chemical Formula 1, M is one or more elements selected from the group consisting of Zn, Al, Mg, Ti, Zr, Nb, and W; x is from 0.1 to 0.7; [Formula 1] 6.53200 Å ≤ a = b ≤ 6.54400 Å [Formula 2] 4.64930 Å ≤ c ≤ 4.65330 Å In the above Formulas 1 and 2, a, b, and c are the lattice constants of the lithium transition metal oxide obtained by the X-ray diffraction Rietveld refinement method (XRD Rietveld refinement method). A positive electrode additive for a lithium secondary battery.

7. The lithium transition metal oxide has a unit cell volume (V) of 198.350 Å ３ to 199.170 Å ３ The positive electrode additive for a lithium secondary battery according to claim 6, having the above volume (V).

8. The lithium transition metal oxide is Li ６ Co ０．９ Zn ０．１ O ４ 、Li ６ Co ０．８５ Zn ０．１５ O ４ 、Li ６ Co ０．８ Zn ０．２ O ４ 、Li ６ Co ０．７５ Zn ０．２５ O ４ 、Li ６ Co ０．７ Zn ０．３ O ４ 、Li ６ Co ０．６５ Zn ０．３５ O ４ 、Li ６ Co ０．６ Zn ０．４ O ４ 、Li ６ Co ０．５５ Zn ０．４５ O ４ 、Li ６ Co ０．５ Zn ０．５ O ４ 、Li ６ Co ０．４５ Zn ０．５５ O ４ 、Li ６ Co ０．４ Zn ０．６ O ４ 、Li ６ Co ０．３５ Zn ０．６５ O ４ 、Li ６ Co ０．３ Zn ０．７ O ４ ;Li ６ Co ０．９ Al ０．１ O ４ 、Li ６ Co ０．８５ Al ０．１５ O ４ 、Li ６ Co ０．８ Al ０．２ O ４ 、Li ６ Co ０．７５ Al ０．２５ O ４ 、Li ６ Co ０．７ Al ０．３ O ４ 、Li ６ Co ０．６５ Al ０．３５ O ４ 、Li ６ Co ０．６ Al ０．４ O ４ 、Li ６ Co ０．５５ Al ０．４５ O ４ 、Li ６ Co ０．５ Al ０．５ O ４ 、Li ６ Co ０．４５ Al ０．５５ O ４ 、Li ６ Co ０．４ Al ０．６ O ４ 、Li ６ Co ０．３５ Al ０．６５ O ４ 、Li ６ Co ０．３ Al ０．７ O ４ ;Li ６ Co ０．９ Mg ０．１ O ４ 、Li ６ Co ０．８５ Mg ０．１５ O ４ 、Li ６ Co ０．８ Mg ０．２ O ４ 、Li ６ Co ０．７５ Mg ０．２５ O ４ 、Li ６ Co ０．７ Mg ０．３ O ４ 、Li ６ Co ０．６５ Mg ０．３５ O ４ 、Li ６ Co ０．６ Mg ０．４ O ４ , Li ６ Co ０．５５ Mg ０．４５ O ４ , Li ６ Co ０．５ Mg ０．５ O ４ , Li ６ Co ０．４５ Mg ０．５５ O ４ , Li ６ Co ０．４ Mg ０．６ O ４ , Li ６ Co ０．３５ Mg ０．６５ O ４ , Li ６ Co ０．３ Mg ０．７ O ４ ; Li ６ Co ０．９ Ti ０．１ O ４ , Li ６ Co ０．８５ Ti ０．１５ O ４ , Li ６ Co ０．８ Ti ０．２ O ４ , Li ６ Co ０．７５ Ti ０．２５ O ４ , Li ６ Co ０．７ Ti ０．３ O ４ , Li ６ Co ０．６５ Ti ０．３５ O ４ , Li ６ Co ０．６ Ti ０．４ O ４ , Li ６ Co ０．５５ Ti ０．４５ O ４ , Li ６ Co ０．５ Ti ０．５ O ４ , Li ６ Co ０．４５ Ti ０．５５ O ４ , Li ６ Co ０．４ Ti ０．６ O ４ , Li ６ Co ０．３５ Ti ０．６５ O ４ , Li ６ Co ０．３ Ti ０．７ O ４ ; Li ６ Co ０．９ Zr ０．１ O ４ , Li ６ Co ０．８５ Zr ０．１５ O ４ , Li ６ Co ０．８ Zr ０．２ O ４ , Li ６ Co ０．７５ Zr ０．２５ O ４ , Li ６ Co ０．７ Zr ０．３ O ４ , Li ６ Co ０．６５ Zr ０．３５ O ４ , Li ６ Co ０．６ Zr ０．４ O ４ , Li ６ Co ０．５５ Zr ０．４５ O ４ , Li ６ Co ０．５ Zr ０．５ O ４ , Li ６ Co ０．４５ Zr ０．５５ O ４ , Li ６ Co ０．４ Zr ０．６ O ４ , Li ６ Co ０．３５ Zr ０．６５ O ４ , Li ６ Co ０．３ Zr ０．７ O ４ ; Li ６ Co ０．９ Nb ０．１ O ４ , Li ６ Co ０．８５ Nb ０．１５ O ４ 、Li ６ Co ０．８ Nb ０．２ O ４ 、Li ６ Co ０．７５ Nb ０．２５ O ４ 、Li ６ Co ０．７ Nb ０．３ O ４ 、Li ６ Co ０．６５ Nb ０．３５ O ４ 、Li ６ Co ０．６ Nb ０．４ O ４ 、Li ６ Co ０．５５ Nb ０．４５ O ４ 、Li ６ Co ０．５ Nb ０．５ O ４ 、Li ６ Co ０．４５ Nb ０．５５ O ４ 、Li ６ Co ０．４ Nb ０．６ O ４ 、Li ６ Co ０．３５ Nb ０．６５ O ４ 、Li ６ Co ０．３ Nb ０．７ O ４ ;Li ６ Co ０．９ W ０．１ O ４ 、Li ６ Co ０．８５ W ０．１５ O ４ 、Li ６ Co ０．８ W ０．２ O ４ 、Li ６ Co ０．７５ W ０．２５ O ４ 、Li ６ Co ０．７ W ０．３ O ４ , Li ６ Co ０．６５ W ０．３５ O ４ , Li ６ Co ０．６ W ０．４ O ４ , Li ６ Co ０．５５ W ０．４５ O ４ , Li ６ Co ０．５ W ０．５ O ４ , Li ６ Co ０．４５ W ０．５５ O ４ , Li ６ Co ０．４ W ０．６ O ４ , Li ６ Co ０．３５ W ０．６５ O ４ , and at least one compound selected from the group consisting of Li ６ Co ０．３ W ０．７ O ４ The positive electrode additive for a lithium secondary battery according to claim 6 or 7, comprising one or more compounds selected from the group consisting of.

9. A positive electrode for a lithium secondary battery, comprising a positive electrode active material, a binder, a conductive material, and a lithium transition metal oxide according to any one of claims 1 to 3.

10. A positive electrode for a lithium secondary battery, comprising a positive electrode active material, a binder, a conductive material, and a positive electrode additive for a lithium secondary battery according to any one of claims 6 to 8.

11. A lithium secondary battery, comprising the positive electrode for a lithium secondary battery according to claim 9 or 10, a negative electrode, a separator, and an electrolyte.

12. The lithium secondary battery according to claim 11, wherein the negative electrode contains one or more negative electrode active materials selected from the group consisting of a carbonaceous material and a silicon compound.

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