Positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material comprising a nickel-cobalt-manganese-based lithium transition metal oxide, a method for preparing the positive electrode active material, and a positive electrode and a secondary battery comprising the positive electrode active material, wherein the nickel content of the nickel-cobalt-manganese-based lithium transition metal oxide is more than 60 mol% of the total molar number of metals other than lithium, wherein the nickel-cobalt-manganese-based lithium transition metal oxide is doped with a doping element M 1 (wherein the doping element M 1 is a metal element including aluminum (Al) and a doping element M 2 (wherein the doping element M 2 is at least one metal element selected from the group consisting of Mg, La, Ti, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au and Si, the doping element M of the nickel-cobalt-manganese-based lithium transition metal oxide 1 The content of M is 100ppm to 10,000ppm, and the doping element M 1 and doping element M 2 The weight ratio is 50:50 to 99:1.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2018-0152743 filed in the Korean Intellectual Property Office on November 30, 2018, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode and a lithium secondary battery comprising the positive electrode active material. Specifically, the present invention relates to a positive electrode active material in which a lithium transition metal oxide with a high nickel content is doped with a specific doping element to reduce the hygroscopicity of the powder, and a positive electrode and a lithium secondary battery comprising the positive electrode active material. Background Art

[0004] With the development of technology and the increase in demand for mobile devices, the demand for secondary batteries as energy sources has increased significantly. Among these secondary batteries, lithium secondary batteries with high energy density, high voltage, long cycle life and low self-discharge rate have been commercialized and widely used.

[0005] In a lithium secondary battery in a state where an organic electrolyte solution or a polymer electrolyte solution is filled between a positive electrode and a negative electrode (each of which is formed of an active material that can insert and deinsert lithium ions), electric energy is generated through oxidation and reduction reactions when lithium ions are inserted into / deinserted from the positive electrode and the negative electrode.

[0006] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.) or lithium iron phosphate compound (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. In addition, as a method for improving low thermal stability while maintaining the excellent reversible capacity of LiNiO2, lithium composite metal oxides (hereinafter referred to as "NCM-based lithium composite transition metal oxides" or "NCA-based lithium composite transition metal oxides") have been developed to replace a portion of nickel (Ni) with cobalt (Co) or manganese (Mn) / aluminum (Al). However, due to the insufficient capacity characteristics of conventionally developed NCM-based / NCA-based lithium composite transition metal oxides, NCM-based / NCA-based lithium composite transition metal oxides are limited in application.

[0007] In order to solve this limitation, research has recently been conducted to increase the nickel (Ni) content in NCM-based / NCA-based lithium oxides. However, for NCM-based / NCA-based lithium oxides with high Ni content, the nickel in NCM-based / NCA-based lithium oxides is Ni. 3+The NCM-based / NCA-based lithium oxide exists in the form of a hydroxyl group, and its stability is poor as the Ni content increases. Therefore, since the NCM-based / NCA-based lithium oxide becomes unstable and the nickel in the NCM-based / NCA-based lithium oxide reacts with moisture in the air or the solvent in the electrolyte solution to form hydroxyl groups, there is a problem of a large amount of moisture in the positive electrode active material. In addition, when a positive electrode active material with a large amount of moisture is used, since the hydroxyl groups formed in the positive electrode active material react with the binder contained in the positive electrode active material layer to cause gelation, the uniformity of the positive electrode active material layer is reduced. Therefore, there is a problem of reduced adhesion between the electrode and the electrode, the cell capacity may not be achieved, and the output may be reduced. Summary of the invention

[0008] [Technical issues]

[0009] One aspect of the present invention provides a positive electrode active material in which moisture absorption is reduced by doping a nickel-cobalt-manganese-based lithium transition metal oxide having a high nickel content with two or more doping elements at a specific ratio.

[0010] Another aspect of the present invention provides a positive electrode for a lithium secondary battery, comprising the positive electrode active material having reduced moisture absorption.

[0011] Another aspect of the present invention provides a lithium secondary battery, which comprises the positive electrode for a lithium secondary battery.

[0012] [Technical solution]

[0013] According to one aspect of the present invention, there is provided a positive electrode active material comprising a nickel-cobalt-manganese-based lithium transition metal oxide, wherein the nickel content is more than 60 mol% of the total molar number of metals other than lithium, wherein the nickel-cobalt-manganese-based lithium transition metal oxide is doped with a doping element M 1 (Wherein the doping element M 1 is a metal element including aluminum (Al) and a doping element M 2 (Wherein the doping element M 2 is at least one metal element selected from the group consisting of magnesium (Mg), lanthanum (La), titanium (Ti), zinc (Zn), boron (B), tungsten (W), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), ruthenium (Ru), copper (Cu), cadmium (Cd), silver (Ag), yttrium (Y), scandium (Sc), gallium (Ga), indium (In), arsenic (As), antimony (Sb), platinum (Pt), gold (Au) and silicon (Si), wherein the doping element M of the nickel-cobalt-manganese-based lithium transition metal oxide is 1 The content of M is 100ppm to 10,000ppm, and the doping element M 1 and doping element M 2 The weight ratio is 50:50 to 99:1.

[0014] According to another aspect of the present invention, there is provided a positive electrode including a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector, wherein the positive electrode contains the positive electrode active material of the present invention.

[0015] According to another aspect of the present invention, a lithium secondary battery including the positive electrode of the present invention is provided.

[0016] [Beneficial Effects]

[0017] According to the present invention, hygroscopicity (in which a positive electrode active material absorbs moisture from the air) can be suppressed by doping a nickel-cobalt-manganese-based lithium transition metal oxide having a high nickel content with two or more doping elements in specific amounts and ratios.

[0018] In addition, by suppressing the moisture hygroscopicity of the positive electrode active material, the formation of lithium byproducts (such as LiOH) due to the reaction of moisture with lithium, which exists on the surface of the nickel-cobalt-manganese-based lithium transition metal oxide with a high nickel content, can be reduced. DETAILED DESCRIPTION

[0019] Hereinafter, the present invention will be described in more detail.

[0020] It should be understood that the words or terms used in the specification and claims should not be interpreted as the meanings defined in commonly used dictionaries, and it should be further understood that based on the principle that the inventor can appropriately define the concepts of words or terms in order to best explain the present invention, in the context of the relevant technology and the technical ideas of the present invention, the words or terms should be interpreted as having a meaning consistent with their meanings.

[0021] Throughout the specification, the expression "average particle size (D 50 )” can be defined as the particle size at which the cumulative volume in the particle size distribution curve is 50%. For example, the average particle size (D 50 ) can be measured using laser diffraction. Laser diffraction can generally measure particle sizes from submicron to several millimeters, and can obtain highly reproducible and high-resolution results.

[0022] <Positive Electrode Active Material>

[0023] The positive electrode active material for a secondary battery of the present invention comprises a nickel-cobalt-manganese-based lithium transition metal oxide, the nickel content of which is 60 mol% or more of the total molar number of metals other than lithium, wherein the nickel-cobalt-manganese-based lithium transition metal oxide is doped with a doping element M 1 (Wherein the doping element M 1 is a metal element including aluminum (Al) and a doping element M 2 (Wherein the doping element M 2is at least one metal element selected from the group consisting of magnesium (Mg), lanthanum (La), titanium (Ti), zinc (Zn), boron (B), tungsten (W), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), ruthenium (Ru), copper (Cu), cadmium (Cd), silver (Ag), yttrium (Y), scandium (Sc), gallium (Ga), indium (In), arsenic (As), antimony (Sb), platinum (Pt), gold (Au) and silicon (Si), wherein the doping element M of the nickel-cobalt-manganese-based lithium transition metal oxide is 1 The content of M is 100ppm to 10,000ppm, and the doping element M 1 and doping element M 2 The weight ratio is 50:50 to 99:1.

[0024] When describing the positive electrode active material in more detail, the nickel content of the nickel-cobalt-manganese-based lithium transition metal oxide of the present invention is 60 mol% or more of the total molar number of metals other than lithium. In the case where the nickel content in the nickel-cobalt-manganese-based lithium transition metal oxide is less than the above range, it may not be suitable for electrochemical devices requiring high capacity due to the reduced capacity of the positive electrode active material. As the amount of nickel increases within the above range, batteries including nickel may exhibit high capacity characteristics. However, as the amount of nickel increases, the amount of cobalt and / or manganese decreases relatively, and thus the charging and discharging efficiency may decrease. Therefore, based on the total molar number of transition metals other than lithium, the nickel content of the positive electrode active material is 60 mol% or more, preferably 60 mol% to 90 mol%, more preferably 70 mol% to 90 mol%, and most preferably 80 mol% to 85 mol%.

[0025] In addition, based on the total molar number of metal elements other than lithium, the cobalt content of the nickel-cobalt-manganese-based lithium transition metal oxide may be 0 mol% to 35 mol%, preferably 3 mol% to 20 mol%, and most preferably 5 mol% to 10 mol%. In the case where the amount of cobalt exceeds this range and is greater than 35 mol%, a large amount of cobalt may increase the total cost of raw materials and the reversible capacity may be somewhat reduced.

[0026] In addition, the manganese content of the nickel-cobalt-manganese-based lithium transition metal oxide may be 0 mol% to 35 mol%, preferably 3 mol% to 20 mol%, and most preferably 5 mol% to 10 mol%, based on the total molar number of metal elements other than lithium. When the manganese content is within the above range, the structural stability of the active material can be improved.

[0027] In addition, the nickel-cobalt-manganese-based lithium transition metal oxide is doped with a doping element M 1 and M 2 .

[0028] In this case, the doping element M 1is a metal element including Al, and doped with an element M 2 It may include at least one selected from the group consisting of Mg, La, Ti, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au and Si, may preferably include at least one selected from the group consisting of Mg, La and Ti, may more preferably include at least two selected from the group consisting of Mg, La and Ti, may most preferably include all of Mg, La and Ti.

[0029] For example, since the nickel-cobalt-manganese-based lithium transition metal oxide contains the doping element M 1 , thus improving the structural stability of the nickel-cobalt-manganese-based lithium transition metal oxide, thereby inhibiting moisture hygroscopicity (the positive electrode active material absorbs moisture from the air).

[0030] However, in the NiCoMn-based lithium transition metal oxides, only the doping element M 1 In this case, the capacity retention rate may be poor.

[0031] According to the present invention, due to the use of a specific ratio of doping elements M 1 and M 2 Doping nickel-cobalt-manganese-based lithium transition metal oxides can not only suppress the moisture absorption of the positive electrode active material due to improved structural stability, but also achieve the effect of improving capacity characteristics.

[0032] For example, due to the inclusion of doping elements M 1 The structural stability of the nickel-cobalt-manganese-based lithium transition metal oxide is improved, so the capacity characteristics can be improved when the nickel-cobalt-manganese-based lithium transition metal oxide is used in a battery.

[0033] Based on 100 parts by weight of the total weight of the nickel-cobalt-manganese-based lithium transition metal oxide, the doping element M 1 The content of M can be 100 ppm to 10,000 ppm, preferably 1,000 ppm to 10,000 ppm, and most preferably 3,000 ppm to 5,000 ppm. 1 When the amount satisfies the above range, the effect of suppressing moisture absorption can be maximized.

[0034] For example, in the doping element M 1 When the amount of M is less than the above range, the effect of suppressing the moisture absorption of the positive electrode active material may not be achieved. 1 When the amount is greater than the above range, the energy density is reduced, and thus when the nickel-cobalt-manganese-based lithium transition metal oxide is used in a battery, the life characteristics may be reduced.

[0035] In addition, the doping element M1 and M 2 The weight ratio of M can be 50:50 to 99:1, preferably 60:40 to 80:20, and most preferably 70:30 to 80:20. 1 and M 2 In the case where the above weight ratio is satisfied, the hygroscopicity of the positive electrode active material can be further suppressed, and when the positive electrode active material is used in a battery, the capacity characteristics can be improved.

[0036] In contrast, in the case of doping element M 1 With doping element M 2 The weight ratio exceeds the above range and the doping element M 1 When the ratio is greater than the above range, the capacity characteristics may be reduced. 1 If the ratio is smaller than the above range, the effect of suppressing the moisture absorption of the positive electrode active material by doping with the doping element may be reduced.

[0037] Preferably, the nickel-cobalt-manganese-based lithium transition metal oxide is represented by Formula 1 below.

[0038] [Formula 1]

[0039] Li 1+a [Ni x Co y Mn z M 1 w M 2 v ]O2

[0040] In formula 1, M 1 It is a doping element substituted at the transition metal site of the nickel-cobalt-manganese-based lithium transition metal oxide, and may be a metal element including Al.

[0041] Nickel-cobalt-manganese-based lithium transition metal oxides including doping elements M 1 and doping element M 2 , wherein the doping element M 2 is at least one metal element selected from the group consisting of Mg, La, Ti, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au and Si. 1 is Al, and M 2 It may include at least one metal element selected from the group consisting of Mg, La and Ti, and most preferably, M 1 is Al, and M 2 Including all of Mg, La and Ti.

[0042] 1 + a represents the molar ratio of lithium in the nickel-cobalt-manganese-based lithium transition metal oxide, and a can satisfy 0 ≤ a ≤ 0.3, for example, 0 ≤ a ≤ 0.15.

[0043] x represents the molar ratio of nickel element in the nickel-cobalt-manganese-based lithium transition metal oxide, and x can satisfy 0.60 ≤ x < 1, preferably satisfy 0.60 ≤ x ≤ 0.90, more preferably satisfy 0.70 ≤ x ≤ 0.90, and most preferably satisfy 0.80 ≤ x ≤ 0.85.

[0044] y represents the molar ratio of cobalt in the nickel-cobalt-manganese-based lithium transition metal oxide, and y can satisfy 0 < y < 0.35, for example, 0 < y ≤ 0.1.

[0045] z represents the molar ratio of manganese in the nickel-cobalt-manganese-based lithium transition metal oxide, and y can satisfy 0 < z < 0.35, for example, 0 < z ≤ 0.1.

[0046] When the molar ratios x, y, and z of the transition metals in the nickel-cobalt-manganese-based lithium transition metal oxide satisfy the above ranges, a positive electrode active material with excellent energy density and high-capacity characteristics can be obtained.

[0047] w represents the molar ratio of the doping element M 1 in the nickel-cobalt-manganese-based lithium transition metal oxide, and w can satisfy 0 < w ≤ 0.01, preferably satisfy 0.002 ≤ w ≤ 0.007, more preferably satisfy 0.003 ≤ w ≤ 0.006, and most preferably satisfy 0.003 ≤ w ≤ 0.005. When the molar ratio of the doping element M 1 in the nickel-cobalt-manganese-based lithium transition metal oxide satisfies the above range, a positive electrode active material with suppressed moisture hygroscopicity can be obtained.

[0048] v represents the molar ratio of the doping element M 2 in the nickel-cobalt-manganese-based lithium transition metal oxide, and v can satisfy 0 < v ≤ 0.005, preferably satisfy 0.001 ≤ v ≤ 0.005, more preferably satisfy 0.002 ≤ v ≤ 0.004, and most preferably satisfy 0.002 ≤ w ≤ 0.003. When the molar ratio of the doping element M 2 in the nickel-cobalt-manganese-based lithium transition metal oxide satisfies the above range, a positive electrode active material with improved capacity retention rate can be obtained.

[0049] When the molar ratios w and v of the doping elements in the nickel-cobalt-manganese-based lithium transition metal oxide satisfy the above ranges w ≥ v and 1 ≤ w / v ≤ 15, not only can the moisture hygroscopicity be suppressed, but also a positive electrode active material with improved capacity retention rate can be obtained.

[0050] Specifically, the nickel-cobalt-manganese-based lithium transition metal oxide represented by Formula 1 can be Li 1+a [Nix Co y Mn z Al w (Mg v1 La v2 Ti v3 )]O2 (wherein v1+v2+v3=v, and w:(v1+v2+v3)=50:50 to 99:1), but the present invention is not limited thereto.

[0051] For nickel-cobalt-manganese-based lithium transition metal oxides, after the positive electrode active material is placed in an environment with a relative humidity (RH) of 60% and a temperature of 25°C for 1 day, the total amount of lithium by-products (including at least one of lithium hydroxide and lithium carbonate) present on the surface of the positive electrode active material can be less than 0.5 parts by weight, for example, 0.1 parts by weight to 0.4 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material.

[0052] For the present invention, by doping element M 1 and M 2 The positive electrode active material whose moisture absorption is suppressed by doping, since the side reaction between the positive electrode active material and moisture in the air or the side reaction between the positive electrode active material and the electrolyte solution is reduced as the structural stability of the positive electrode active material is improved, the hydroxyl groups present in the positive electrode active material are reduced, thereby reducing the amount of lithium hydroxide formed by the reaction of hydroxyl groups with lithium present on the surface of the positive electrode active material.

[0053] Preferably, the positive electrode active material may satisfy the relationship 1:

[0054] [Equation 1]

[0055] 1.0≤(A1 / A0)≤1.8

[0056] In Relationship 1, A1 is the amount of lithium carbonate present on the surface of the positive electrode active material measured after the positive electrode active material is placed in an environment with a relative humidity (RH) of 60% and a temperature of 25°C for 1 day, and A0 is the initial amount of lithium carbonate present on the surface of the positive electrode active material measured before the positive electrode active material is placed.

[0057] For example, as described above, since moisture absorption is suppressed, the amount of lithium hydroxide formed is reduced, and therefore, since the amount of reaction between LiOH and CO2 is also reduced, the amount of lithium carbonate can also be reduced.

[0058] In addition, the nickel-cobalt-manganese-based lithium transition metal oxide may also include a coating, the coating comprising at least one coating element selected from the group consisting of Al, Ti, W, B, fluorine (F), phosphorus (P), Mg, Ni, Co, Fe, Cr, V, Cu, calcium (Ca), Zn, zirconium (Zr), niobium (Nb), molybdenum (Mo), strontium (Sr), Sb, bismuth (Bi), Si and sulfur (S). For example, since the contact between the nickel-cobalt-manganese-based lithium transition metal oxide represented by Formula 1 and the electrolyte solution contained in the lithium secondary battery is blocked by the coating to inhibit the occurrence of side reactions, the nickel-cobalt-manganese-based lithium transition metal oxide can be used in the battery to improve the life characteristics.

[0059] In the case where a coating element is further included as described above, the amount of the coating element in the coating layer may be 100 ppm to 10,000 ppm, for example 200 ppm to 5,000 ppm, based on the total weight of the nickel-cobalt-manganese-based lithium transition metal oxide. For example, when the amount of the coating element included is within the above range based on the total weight of the nickel-cobalt-manganese-based lithium transition metal oxide, the occurrence of side reactions with the electrolyte solution can be more effectively suppressed, and the life characteristics can be more improved when the nickel-cobalt-manganese-based lithium transition metal oxide is used in a battery.

[0060] The coating layer may be formed on the entire surface of the nickel-cobalt-manganese-based lithium transition metal oxide or may be partially formed. Specifically, when the coating layer is partially formed on the surface of the nickel-cobalt-manganese-based lithium transition metal oxide, the formation area of ​​the coating layer may be 5% or more and less than 100%, for example, 20% or more and less than 100%, relative to the total surface area of ​​the nickel-cobalt-manganese-based lithium transition metal oxide.

[0061] The average particle size (D 50 ) can be 8 μm to 15 μm, preferably 9 μm to 14 μm, and most preferably 10 μm to 13 μm. The average particle size (D 50 )When the above range is met, excellent electrode density and energy density can be achieved.

[0062] <Method for preparing positive electrode active material>

[0063] Commercially available nickel-cobalt-manganese-based lithium transition metal oxides may be purchased and used as the positive electrode active material, or the positive electrode active material may be prepared by a method known in the art for preparing nickel-cobalt-manganese-based lithium transition metal oxides.

[0064] For example, the nickel-cobalt-manganese-based lithium transition metal oxide represented by Formula 1 can be prepared by mixing a nickel-cobalt-manganese-based precursor, a lithium raw material, and a doping element M 1 Raw materials and doping elements M 2 The raw materials are mixed and then sintered.

[0065] The nickel-cobalt-manganese-based precursor may include nickel-manganese-cobalt hydroxide, oxyhydroxide, carbonate or organic complex, or contain a doping element M 2 For example, the nickel-cobalt-manganese-based precursor can be [Ni x Co y Mn z ](OH)2 or [Ni y Co z Mn w ]O·OH, but the nickel-cobalt-manganese-based precursor is not limited thereto.

[0066] The lithium raw material can be a lithium-containing carbonate (such as lithium carbonate, etc.), a hydrate (such as lithium hydroxide monohydrate (LiOH·H2O), etc.), a hydroxide (such as lithium hydroxide, etc.), a nitrate (such as lithium nitrate (LiNO3)), etc.) or a chloride (such as lithium chloride (LiCl)), but the lithium raw material is not limited to these.

[0067] Doping element M 1 The raw material may include an Al-containing oxide, hydroxide, oxyhydroxide, sulfate, carbonate, halide, sulfide, acetate or carboxylate, or a combination thereof, for example, Al2(SO4)3, AlCl3, Al-isopropoxide and Al(NO3)3, but the doping element M 1 The raw materials are not limited thereto.

[0068] Doping element M 2 The raw material may include at least one doping element M 2 (M 2 Oxides, hydroxides, oxyhydroxides, carbonates, sulfates, halides, sulfides, acetates or carboxylates selected from the group consisting of Mg, La, Ti, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au and Si, or combinations thereof, for example, may include MgO, Mg(OH)2, MgSO4, Mg(NO3)2, TiO2 and La2CO3, but the doping element M 2 The raw materials are not limited thereto.

[0069] The sintering may be performed at 600° C. to 1,000° C. (eg, 700° C. to 900° C.) for 5 hours to 30 hours (eg, 10 hours to 20 hours).

[0070] In the case where the positive electrode active material includes a coating layer, the coating raw material is added and mixed after sintering, and then a heat treatment process may be further performed.

[0071] The coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate or carboxylate containing at least one element (hereinafter referred to as "coating element") selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si and S, or a combination thereof, for example, ZnO, Al2O3, Al(OH)3, Al2(SO4)3, AlCl3, Al-isopropoxide, Al(NO3)3, TiO2, WO3, AlF3, H2BO3, HBO2, H3BO3, H2B4O7, B2O3, C6H5B(OH)2, (C6H5O)3B, (CH3(CH2)3O)3B, C3H9B3O6, (C3H7O3)B, Li3WO4, (NH4) 10 W 12 O 41 ·5H2O and NH4H2PO4, but the coating material is not limited thereto.

[0072] The coating layer may be formed using a method known in the art, for example, a wet coating method, a dry coating method, a plasma coating method, or atomic layer deposition (ALD) may be used.

[0073] The heat treatment for forming the coating layer may be performed at 100° C. to 700° C. (eg, 300° C. to 450° C.) for 1 hour to 15 hours (eg, 3 hours to 8 hours).

[0074] <Positive electrode>

[0075] Next, the positive electrode for a lithium secondary battery of the present invention will be described.

[0076] The positive electrode of the present invention includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector, wherein the positive electrode active material layer contains the positive electrode active material of the present invention and, if necessary, contains a conductive agent and / or a binder.

[0077] In this case, since the positive electrode active material is the same as that described above, a detailed description thereof will be omitted, and only the remaining configuration will be described below.

[0078] The content of the positive electrode active material may be 80 to 99 parts by weight, for example 85 to 98.5 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material layer. When the content of the positive electrode active material is within the above range, excellent capacity characteristics may be obtained.

[0079] There is no specific limitation on the positive electrode current collector, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium or silver, etc., can be used. In addition, the thickness of the positive electrode current collector can generally be 3 μm to 500 μm, and small irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, various shapes of positive electrode current collectors can be used, such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0080] The conductive agent is used to provide conductivity to the electrode, wherein any conductive agent can be used without specific limitation, as long as it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of the conductive agent can be graphite, such as natural graphite and artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black and carbon fiber; powder or fiber of metals such as copper, nickel, aluminum and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives, and any one of them or a mixture of two or more thereof can be used. The content of the conductive agent can generally be 0.1 to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

[0081] The binder improves the adhesion between the positive active material particles and the adhesion between the positive active material and the current collector. Specific examples of the binder can be polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber or various copolymers thereof, and any one of them or a mixture of two or more thereof can be used. Based on the total weight of 100 parts by weight of the positive active material layer, the content of the binder can be 0.1 parts by weight to 15 parts by weight.

[0082] The positive electrode can be prepared according to a typical method for preparing a positive electrode, except that the above-mentioned positive electrode active material is used. Specifically, a positive electrode material mixture prepared by dissolving or dispersing the positive electrode active material and an optional binder and / or conductive agent in a solvent is coated on a positive electrode current collector, and then the positive electrode is prepared by drying and rolling the coated positive electrode current collector.

[0083] The solvent may be a commonly used solvent in the art. The solvent may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone or water, and any one thereof or a mixture of two or more thereof may be used. Considering the coating thickness and manufacturing yield of the slurry, if the cathode material mixture can be adjusted to have an appropriate viscosity, the amount of the solvent used may be sufficient.

[0084] In addition, as another method, the positive electrode may be prepared by casting the positive electrode material mixture on a separate support and then laminating a film separated from the support on a positive electrode current collector.

[0085] <Lithium Secondary Battery>

[0086] In addition, the present invention can prepare an electrochemical device comprising a positive electrode. The electrochemical device can be specifically a battery or a capacitor, for example, a lithium secondary battery.

[0087] The lithium secondary battery specifically includes a positive electrode, a negative electrode disposed opposite to the positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the same as described above, and its detailed description will be omitted, and only the remaining configuration will be described below.

[0088] In addition, the lithium secondary battery may further selectively include a battery container accommodating an electrode assembly including a positive electrode, a negative electrode, and a separator, and a sealing member sealing the battery container.

[0089] In a lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0090] The negative electrode current collector may not be specifically limited as long as it has high conductivity and does not cause adverse chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or copper or stainless steel surface-treated with one of carbon, nickel, titanium or silver, and aluminum-cadmium alloys may be used. In addition, the thickness of the negative electrode current collector may generally be 3 μm to 500 μm, and similar to the positive electrode current collector, tiny irregularities may be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. For example, various shapes of negative electrode current collectors may be used, such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0091] The negative electrode active material layer selectively contains a binder and a conductive agent in addition to the negative electrode active material.

[0092] As the negative electrode active material, a compound capable of reversibly inserting and deinserting lithium can be used. Specific examples of the negative electrode active material may be: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal substances capable of alloying with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), Si alloy, Sn alloy, or Al alloy; metal oxides that can be doped and dedoped with lithium, such as SiO β (0<β<2), SnO2, vanadium oxide and lithium vanadium oxide; or a composite comprising a metal substance and a carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one of them or a mixture of two or more thereof can be used. In addition, a metallic lithium film can be used as a negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as carbon materials. Typical examples of low-crystalline carbon can be soft carbon and hard carbon, and typical examples of high-crystalline carbon can be amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-type carbon fibers, mesophase carbon microbeads, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch.

[0093] The content of the negative electrode active material may be 80 parts by weight to 99 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material layer.

[0094] The binder is a component that helps the bonding between the conductive agent, the active material and the current collector, wherein the amount of the binder added is generally 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material layer. Examples of binders may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber and various copolymers thereof.

[0095] The conductive agent is a component for further improving the conductivity of the negative electrode active material, wherein the amount of the conductive agent added may be 10 parts by weight or less, for example, 5 parts by weight or less, based on 100 parts by weight of the total weight of the negative electrode active material layer. The conductive agent is not specifically limited as long as it has conductivity and does not cause adverse chemical changes in the battery, for example, conductive materials such as the following may be used: graphite, such as natural graphite or artificial graphite; carbon black, such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fibers or metal fibers; metal powders, such as fluorocarbon powders, aluminum powders, and nickel powders; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or polyphenylene derivatives.

[0096] For example, the negative electrode active material layer can be manufactured as follows: a negative electrode forming composition prepared by dissolving or dispersing the negative electrode active material and optional binder and conductive agent in a solvent is coated on the negative electrode collector, and the coated negative electrode collector is dried; or the negative electrode forming composition is cast on a separate support, and a film layer separated from the support is then stacked on the negative electrode collector.

[0097] In lithium secondary batteries, the diaphragm separates the negative electrode from the positive electrode and provides a mobile channel for lithium ions, wherein any diaphragm can be used as the diaphragm without specific restrictions, as long as it is commonly used in lithium secondary batteries, specifically, a diaphragm with high moisture retention capacity for electrolytes and low resistance to the transfer of electrolyte ions can be used. Specifically, a porous polymer film can be used, for example, a porous polymer film prepared by polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers or ethylene / methacrylate copolymers, or a laminated structure with two or more layers thereof. In addition, a typical porous non-woven fabric can be used, for example, a non-woven fabric formed by high melting point glass fiber or polyethylene terephthalate fiber. In addition, a coated diaphragm comprising a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and a diaphragm with a single layer or multilayer structure can be selectively used.

[0098] In addition, the electrolyte used in the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used to prepare a lithium secondary battery, but the electrolyte is not limited thereto.

[0099] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0100] Any organic solvent can be used as the organic solvent without specific restrictions, as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; or carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (wherein R is a linear, branched or cyclic C2-C20 hydrocarbon group, and may include a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolanes; or cyclopentane sulfone. Among these solvents, carbonate solvents are preferred, such as a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant and a low-viscosity straight-chain carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that can more preferably improve the charge / discharge performance of the battery. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte solution may be excellent.

[0101] Lithium salts can be used without specific restrictions, as long as they are compounds that can provide lithium ions for lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI or LiB(C2O4)2 can be used as lithium salts. The lithium salt can be used in a concentration range of 0.1M to 2.0M. In the case of lithium salts containing a concentration within the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance can be obtained, and lithium ions can be effectively moved.

[0102] In order to improve the life characteristics of the battery, suppress the reduction of the battery capacity and increase the discharge capacity of the battery, in addition to the above-mentioned electrolyte components, at least one additive may be added to the electrolyte, such as halogenated alkylene carbonate compounds (such as difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glycol dimethyl ether, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidinones, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol or aluminum chloride. In this case, the content of the additive may be 0.1 to 5 parts by weight based on 100 parts by weight of the total weight of the electrolyte.

[0103] As described above, since the lithium secondary battery including the cathode active material of the present invention stably exhibits excellent discharge capacity, output characteristics and life characteristics, the lithium secondary battery is suitable for portable devices such as mobile phones, notebook computers and digital cameras and electric vehicles such as hybrid electric vehicles (HEVs).

[0104] Therefore, according to another embodiment of the present invention, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the battery module are provided.

[0105] The battery module or battery pack can be used as a power source for at least one of the following large and medium-sized devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0106] The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical type using a can, a prismatic type, a pouch type, or a coin type may be used.

[0107] The lithium secondary battery of the present invention can be used not only in a battery cell used as a power source for small-sized devices but also as a unit cell in a large or medium-sized battery module including a plurality of battery cells.

[0108] Hereinafter, the present invention will be described in detail according to specific embodiments. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these exemplary embodiments are provided so that the description will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0109] Example

[0110] Example 1

[0111] NiSO4, CoSO4, MnSO4, AlCl3, MgCl2, TiCl4 and LaCl3 were dissolved in ion exchange water in an amount of 8:1:1:0.03:0.004:0.004:0.002 in a molar ratio of nickel:cobalt:manganese:aluminum:magnesium:lanthanum:titanium to prepare a 0.01 M transition metal aqueous solution.

[0112] The container containing the aqueous solution of the transition metal powder was connected to a 10L batch reactor set at 50°C. In addition, a 0.2M aqueous ammonium solution and a 0.1% aqueous sodium hydroxide solution were prepared and connected to the batch reactor. 1L of ion exchange water was placed in the reactor, and then the reactor was purged with nitrogen at a rate of 10L / min to remove dissolved oxygen in the water and form a non-oxidizing atmosphere in the reactor.

[0113] After that, a transition metal aqueous solution, a sodium hydroxide aqueous solution and an ammonium aqueous solution were added at a rate of 100 mL / min, 50 mL / min and 100 mL / min, respectively, and a coprecipitation reaction was performed for 5 hours to precipitate transition metal hydroxide particles. The precipitated transition metal hydroxide particles were separated, washed, and then dried at 80°C for 3 hours to obtain a positive electrode active material precursor.

[0114] The positive electrode active material precursor prepared above and LiOH were mixed so that the molar ratio of metal (Me):lithium (Li) was 1:1.05, and the mixture was sintered at 1000° C. for 5 hours in an oxygen atmosphere to prepare a positive electrode active material.

[0115] Example 2

[0116] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3 and MgCl2 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:magnesium of 8:1:1:0.03:0.004 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0117] Example 3

[0118] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3 and LaCl3 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:lanthanum of 8:1:1:0.03:0.002 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0119] Example 4

[0120] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3 and TiCl4 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:titanium of 8:1:1:0.03:0.004 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0121] Example 5

[0122] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3, MgCl2 and LaCl3 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:magnesium:lanthanum of 8:1:1:0.03:0.004:0.002 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0123] Example 6

[0124] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3, MgCl2 and TiCl4 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:magnesium:titanium of 8:1:1:0.03:0.004:0.004 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0125] Example 7

[0126] The positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3, TiCl4 and LaCl3 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:titanium:lanthanum of 8:1:1:0.03:0.004:0.002 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0127] Comparative Example 1

[0128] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4 and MnSO4 were dissolved in ion exchange water in an amount of 8:1:1 molar ratio of nickel:cobalt:manganese to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0129] Comparative Example 2

[0130] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4 and AlCl3 were dissolved in ion exchange water in an amount of 8:1:1:0.03 in a molar ratio of nickel:cobalt:manganese:aluminum to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0131] Comparative Example 3

[0132] A positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, MgCl2, TiCl4 and LaCl3 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:magnesium:lanthanum:titanium of 8:1:1:0.004:0.004:0.002 to prepare a transition metal aqueous solution, and the transition metal aqueous solution was used.

[0133] Comparative Example 4

[0134] The positive electrode active material was prepared in the same manner as in Example 1, except that NiSO4, CoSO4, MnSO4, AlCl3, MgCl2, TiCl4 and LaCl3 were dissolved in ion exchange water in a molar ratio of nickel:cobalt:manganese:aluminum:magnesium:lanthanum:titanium of 8:1:1:0.01:0.01:0.01:0.01 to prepare a 0.01 M transition metal aqueous solution, and the transition metal aqueous solution was used.

[0135] Experimental Example 1: Measuring water absorption

[0136] The moisture absorption amounts of the positive electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated.

[0137] Specifically, the positive electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were placed in the air under the same conditions (including humidity 60% and temperature 25° C.), and the moisture content of each positive electrode active material just after the positive electrode active material was prepared and after the positive electrode active material was placed for 24 hours was analyzed using a moisture absorption measuring instrument (Karl Fischer moisture determination, Mettler Toledo GmbH, Germany), and the results are presented in Table 1 below.

[0138] Table 1

[0139] Just after preparation (ppm) After moisture absorption (ppm) Example 1 181 584 Example 2 175 654 Example 3 173 666 Example 4 180 589 Example 5 168 595 Example 6 183 640 Example 7 166 598 Comparative Example 1 167 994 Comparative Example 2 147 664 Comparative Example 3 168 1004 Comparative Example 4 170 764

[0140] As shown in Table 1, it can be confirmed that the moisture absorption amount of the positive electrode active materials prepared in Examples 1 to 7 is as excellent as the moisture absorption amount of the positive electrode active material doped with only Al as in Comparative Example 2. In particular, it can be confirmed that the moisture absorption amount thereof is significantly improved compared with the case where Al is not contained as a doping element as in Comparative Examples 1, 3 and 4.

[0141] Experimental Example 2: Measurement of Residual Lithium

[0142] pH titration was performed using a pH metrohm as a pH meter to measure the amount of residual lithium on the surface of each positive active material prepared in Examples 1 to 6 and Comparative Examples 1, 2, and 4. Specifically, 10 g of each positive active material powder prepared in Examples 1 to 7 and Comparative Examples 1 to 4 was stirred with 100 mL of distilled water. The pH titration was performed while adding a 0.1 N HCl solution to the solution.

[0143] pH titration was performed immediately after the positive electrode active material was prepared, and the amount of residual lithium on the surface of the positive electrode active material in this case was recorded. After that, pH titration was performed after the positive electrode active material was placed at 25°C and 60% RH for 24 hours after preparation, and the amount of residual lithium on the surface of the positive electrode active material in this case was recorded. The results are presented in Table 2 below.

[0144] Table 2

[0145]

[0146] As shown in Table 2, for the positive electrode active materials prepared in Examples 1 to 6 and Comparative Example 2, it can be confirmed that the amount of lithium carbonate formed after moisture absorption is reduced compared with the positive electrode active material prepared in Comparative Example 1.

[0147] For the positive electrode active material prepared in Comparative Example 4, it was confirmed that since Al was not included as a doping element, the amount of lithium carbonate formed after moisture absorption was greater than that of Examples 1 to 6 and Comparative Example 2 containing Al.

[0148] Experimental Example 3: Capacity Measurement

[0149] Lithium secondary batteries were prepared using the positive electrode active materials prepared in Examples 1 to 3 and 5 and Comparative Examples 1 to 4, and then the capacity characteristics of the respective secondary batteries were compared.

[0150] In this case, a secondary battery was prepared in the same manner as described below, except that the positive active materials prepared in Examples 1 to 3 and 5 and Comparative Examples 1 to 4 were used. Specifically, each positive active material, carbon black conductive agent and polyvinylidene fluoride binder prepared in Examples 1 to 3 and 5 and Comparative Examples 1 to 4 were mixed in an N-methylpyrrolidone solvent at a weight ratio of 97:1:2 to prepare a positive electrode forming composition. An 8 μm thick aluminum current collector was coated with the positive electrode forming composition, dried, and then rolled to prepare a positive electrode. Subsequently, artificial graphite as a negative electrode active material, a carbon black conductive agent, and carboxymethyl cellulose and styrene-butadiene rubber as a binder were mixed in a weight ratio of 95:1:1:3 and added to pure water as a solvent to prepare a negative electrode active material slurry. A 15 μm thick copper current collector was coated with the negative electrode active material slurry, dried, and then rolled to prepare a negative electrode. The positive electrode and negative electrode prepared as above are stacked with a polypropylene / polyethylene separator by a conventional method to prepare a polymer battery. Thereafter, the polymer battery is placed in a battery casing, and an electrolyte solution of 1M LiPF6 dissolved in a mixed solvent (in which ethylene carbonate, diethyl carbonate and dimethyl carbonate are mixed) is injected therein to prepare each lithium secondary battery corresponding to Examples 1 to 3 and 5 and Comparative Examples 1 to 4.

[0151] Each lithium secondary battery prepared in Examples 1 to 3 and 5 and Comparative Examples 1 to 4 was charged to 4.25V at a constant current of 0.2C at 25°C, and the charging was cut off at 0.005C. After that, each lithium secondary battery was discharged to 2.5V at a constant current of 0.2C, and the discharge capacity in this case was measured. Subsequently, the secondary batteries prepared in Examples 1 to 3 and 5 and Comparative Examples 1 to 4 thus obtained were placed at 25°C and 60% RH for 24 hours to prepare samples that absorbed moisture, and the capacity after moisture absorption was measured. The secondary battery just prepared was prepared separately to measure the capacity just prepared, and the results are presented in Table 3 below.

[0152] Table 3

[0153] Capacity just after preparation (mAh / g) Capacity after water absorption (mAh / g) Example 1 208.2 206.8 Example 2 208.3 206.5 Example 3 207.5 205.0 Example 5 208.3 206.1 Comparative Example 1 209.3 204.5 Comparative Example 2 207.7 205.8 Comparative Example 3 208.1 206.4 Comparative Example 4 208.0 206.1

[0154] As shown in Table 3, it can be confirmed that the capacity characteristics after water absorption of the secondary batteries of Examples 1 to 3 and 5 are higher than that of Comparative Example 1 not containing a doping element. It can be confirmed that the secondary batteries of Examples 1 to 3 and 5 containing an additional doping element and Al exhibit better capacity after water absorption than Comparative Example 2 doped with only Al as a doping element.

Claims

1. A positive electrode active material comprising a nickel-cobalt-manganese-based lithium transition metal oxide, wherein the nickel content of the nickel-cobalt-manganese-based lithium transition metal oxide is 60 mol% or more of the total molar number of metals other than lithium, in, The nickel-cobalt-manganese-based lithium transition metal oxide is doped with a doping element M 1 and doping element M 2 , The doping element M of the nickel-cobalt-manganese-based lithium transition metal oxide 1 The content is 100ppm to 10,000ppm, and The doping element M contained 1 and the doping element M 2 The weight ratio is 50:50 to 99:1; Wherein the lithium transition metal oxide is represented by Formula 1: [Formula 1] Li 1+a [Ni x Co y Mr z M 1 w M 2 v ]O2 Wherein, in Formula 1, M 1 is a metal element including Al, M 2 is Ti, and optionally at least one element selected from the group consisting of Mg, La, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au and Si, and 0 ≤ a ≤ 0.3, 0.60 ≤ x < 1, 0 < y < 0.35, 0 < z < 0.35, 0 < w ≤ 0.01, 0 < v ≤ 0.005, and 1 < w / v ≤ 15.

2. The positive electrode active material according to claim 1, wherein M 2 They are Mg, La and Ti.

3. The positive electrode active material according to claim 1, wherein The positive electrode active material satisfies Relationship 1: [Relationship 1] 1.0 ≤ (A1 / A0) ≤ 1.8 Wherein, A1 is the amount of lithium carbonate present on the surface of the positive electrode active material measured after the positive electrode active material is placed in an environment with a relative humidity (RH) of 60% and a temperature of 25°C for 1 day, and A0 is the initial amount of lithium carbonate present on the surface of the positive electrode active material measured before the positive electrode active material is placed.

4. The positive electrode active material according to claim 3, wherein After the positive electrode active material is placed in an environment with a relative humidity (RH) of 60% and a temperature of 25°C for 1 day, based on the total weight of 100 parts by weight of the positive electrode active material, the total amount of lithium by-products including at least one of lithium hydroxide and lithium carbonate present on the surface of the positive electrode active material is 0.5 part by weight or less.

5. The positive electrode active material according to claim 1, wherein The average particle size D of the positive electrode active material 50 8μm to 15μm.

6. A positive electrode, comprising: A positive electrode current collector, and a positive electrode active material layer formed on the positive electrode current collector, Wherein, the positive electrode active material layer contains the positive electrode active material according to any one of claims 1 to 5. 7 . A lithium secondary battery comprising the positive electrode according to claim 6 .

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