Positive electrode active material and method for producing the same

Abstract

The present invention relates to a method for manufacturing a positive electrode active material, which can minimize surface deterioration of the positive electrode active material occurring during a washing process, effectively control residual lithium, and form a uniform coating layer on the surface of the positive electrode active material, and to a positive electrode active material manufactured by the same, and the method includes the steps of: (A) preparing a lithium transition metal oxide; (B) mixing the lithium transition metal oxide with a first washing solution to wash the lithium transition metal oxide with water for a first time, and then performing a first filtration; and (C) washing and filtering the lithium transition metal oxide that has undergone step (B). (D) performing a second washing and a second filtration simultaneously with a second washing solution using a filtration device capable of simultaneous filtration; and (C) drying the lithium transition metal oxide that has been subjected to steps (C) and then mixing a coating element-containing raw material with the dried lithium transition metal oxide and heat treating the mixture to form a coating layer, wherein the coating element-containing raw material contains a boron-containing raw material and one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0171783, filed December 3, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material and a method for producing the same. [Background technology]

[0003] Nickel-based positive electrode active materials are manufactured by mixing a nickel-based positive electrode active material precursor with a lithium-containing raw material and then calcining the mixture. During this process, unreacted lithium-containing raw material and by-products such as LiOH and Li2CO3 remain on the surface of the positive electrode active material.

[0004] In particular, nickel-based positive electrode active materials with high nickel content have the problem of large amounts of residual lithium. These by-products can react with the electrolyte to cause problems with the long-term performance of the battery (e.g., reduced long-term life, increased resistance, etc.) and stability (e.g., gas generation, etc.). They can also cause gelation during the electrode slurry manufacturing process.

[0005] To prevent this, in existing manufacturing processes for positive electrode active materials, a positive electrode active material precursor and a lithium-containing raw material are mixed and calcined to produce a positive electrode active material, and then the positive electrode active material is washed with a washing solution (e.g., deionized water, distilled water, etc.) to control the residual lithium. Meanwhile, in order to effectively control the residual lithium, a method has been proposed in which a large amount of washing solution is used in the washing process, but the use of a large amount of washing solution can cause process problems and can lead to problems such as reduced battery performance due to deterioration of the surface of the positive electrode active material.

[0006] Furthermore, in the case of nickel-based positive electrode active materials with a high nickel content, as the charge-discharge cycle of a battery containing such materials progresses, the movement of lithium within the positive electrode active material causes repeated contraction and expansion, which leads to cracks, which have a negative impact on the long-term performance of the battery.

[0007] Therefore, there is a need for a positive electrode active material and a manufacturing method thereof that can effectively control residual lithium, suppress deterioration of the positive electrode active material, and improve the long-term performance of the battery when applied to the battery. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above problems, and aims to provide a cathode active material and a manufacturing method thereof that can minimize deterioration of battery performance by minimizing surface deterioration of the cathode active material that may occur during a water washing process during manufacturing the cathode active material, effectively controlling residual lithium, and forming a uniform coating layer on the surface of the cathode active material. [Means for solving the problem]

[0009] The present invention provides a method for producing a positive electrode active material, a positive electrode active material, and a positive electrode.

[0010] (1) The present invention provides a method for producing a positive electrode active material, comprising the steps of: (A) preparing a lithium transition metal oxide; (B) mixing the lithium transition metal oxide with a first washing solution to perform a first water wash on the lithium transition metal oxide, followed by a first filtration; (C) simultaneously performing a second water wash and a second filtration on the lithium transition metal oxide that has undergone step (B) with a second washing solution using a filtration device capable of simultaneous water washing and filtration; and (D) drying the lithium transition metal oxide that has undergone step (C), and then mixing a coating element-containing raw material with the dried lithium transition metal oxide and heat-treating it to form a coating layer, wherein the coating element-containing raw material includes a boron-containing raw material and one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O.

[0011] (2) The present invention provides the method for producing a positive electrode active material according to (1) above, wherein the lithium transition metal oxide contains nickel in an amount of 70 mol % or more of all metals other than lithium.

[0012] (3) The present invention provides the method for producing a positive electrode active material according to (1) or (2), wherein the content of the second washing solution is 10 to 50 parts by weight per 100 parts by weight of the first washing solution.

[0013] (4) The present invention provides the method for producing a positive electrode active material according to any one of (1) to (3), wherein the content of the first washing solution is 50 parts by weight to 150 parts by weight per 100 parts by weight of the lithium transition metal oxide.

[0014] (5) The present invention provides the method for producing a positive electrode active material according to any one of (1) to (4), wherein the content of the second washing solution is 5 parts by weight to 50 parts by weight per 100 parts by weight of the lithium transition metal oxide.

[0015] (6) The present invention provides the method for producing a positive electrode active material according to any one of (1) to (5), wherein the sum of the content of the first washing solution and the content of the second washing solution is 55 parts by weight to 150 parts by weight per 100 parts by weight of the lithium transition metal oxide.

[0016] (7) The present invention provides the method for producing a positive electrode active material according to any one of (1) to (6), wherein the one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O are added in an amount of 160 ppm to 500 ppm by weight based on the dried lithium transition metal oxide.

[0017] (8) The present invention provides a positive electrode active material comprising: a lithium transition metal oxide; and a coating layer formed on the lithium transition metal oxide, wherein the coating layer contains a Li-BO solid solution, and the Li-BO solid solution contains 50 wt % to 60 wt % of BO, 2 wt % to 7 wt % of LiB2O3, and 1 wt % to 5 wt % of Li2B3O6.

[0018] (9) The present invention provides the positive electrode active material according to (8), wherein the lithium transition metal oxide contains nickel in an amount of 70 mol % or more of all metals other than lithium.

[0019] (10) The present invention provides the positive electrode active material according to (8) or (9), wherein the ratio of the content of LiB2O3 to the content of BO2 is 0.05 to 0.20.

[0020] (11) The present invention provides the positive electrode active material according to any one of (8) to (10) above, wherein the ratio of the content of Li2B3O6 to the content of BO2 is 0.01 to 0.10.

[0021] (12) The present invention provides a positive electrode containing the positive electrode active material according to any one of (8) to (11) above. [Effects of the Invention]

[0022] In the present invention, the surface is controlled by the water washing process in step (C), and then a coating layer is formed on the surface-controlled cathode active material in step (D) using a boron-containing raw material and one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O. This minimizes surface deterioration of the cathode active material that occurs during the water washing process, effectively controls residual lithium, and forms a uniform coating layer on the surface of the cathode active material. Therefore, batteries using the cathode active material produced by the method of the present invention have excellent performance, particularly excellent electrochemical performance and thermal stability. DETAILED DESCRIPTION OF THE INVENTION

[0023] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0024] In this specification, the terms "comprises," "includes," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and are to be understood as not precluding the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0025] The present invention will now be described in further detail.

[0026] Method for producing positive electrode active material The present inventors discovered that it is possible to minimize surface deterioration of a positive electrode active material that occurs during a water washing process in the manufacturing process of the positive electrode active material, effectively control residual lithium, and form a uniform coating layer on the surface of the positive electrode active material, thereby completing the present invention.

[0027] A method for producing a positive electrode active material according to the present invention includes the steps of (A) preparing a lithium transition metal oxide, (B) first washing the lithium transition metal oxide by mixing the lithium transition metal oxide with a first washing solution and then first filtering the mixture, (C) simultaneously washing the lithium transition metal oxide after step (B) with a second washing solution and second filtering the lithium transition metal oxide using a filtration device capable of simultaneous washing and filtering, and (D) drying the lithium transition metal oxide after step (C), and then mixing a coating element-containing raw material with the dried lithium transition metal oxide and heat-treating the dried lithium transition metal oxide to form a coating layer, wherein the coating element-containing raw material includes a boron-containing raw material and one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O.

[0028] Each step of the method for producing a positive electrode active material will be specifically described below.

[0029] (A) Step The method for producing a positive electrode active material according to the present invention includes the step of preparing a lithium transition metal oxide.

[0030] The step of preparing the lithium transition metal oxide may include mixing a positive electrode active material precursor with a lithium-containing raw material, followed by calcining to produce the lithium transition metal oxide.

[0031] The positive electrode active material precursor may have a composition represented by, for example, the following chemical formula A or B.

[0032] [Chemical formula A] [Ni x Co y M1 z M2 w ](OH)2

[0033] [Chemical formula B] [Ni x Co y M1 z M2 w ]O·OH

[0034] In Chemical Formula A and Chemical Formula B, M1 may be one or more selected from Mn and Al, and M2 may be one or more selected from Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y.

[0035] The x represents the atomic fraction of nickel among the metal elements in the precursor, and may be 0.7≦x<1, 0.7≦x≦0.98, or 0.7≦x≦0.95.

[0036] The y represents the atomic fraction of cobalt among the metal elements in the precursor, and 0 <y≦0.3または0.01≦y≦0.3であることができる。

[0037] The z represents the element fraction of the M1 element among the metal elements in the precursor, and 0 <z≦0.3または0.01≦z≦0.3であることができる。

[0038] The w means the element fraction of the M2 element among the metal elements in the precursor, and may be 0≦w≦0.2, 0≦w≦0.1, 0≦w≦0.05, or 0≦w≦0.02.

[0039] The lithium-containing raw material may be, for example, at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), LiNO3, CH3COOLi, and Li2(COO)2, and preferably lithium carbonate (Li2CO3), lithium hydroxide (LiOH), or a combination thereof.

[0040] When preparing the positive electrode active material, the positive electrode active material precursor and the lithium-containing raw material may be mixed in a molar ratio of 1:1 to 1:1.625 or 1:1 to 1:1.15. If the lithium-containing raw material is mixed in an amount less than this range, the capacity of the resulting positive electrode active material may be reduced. If the lithium-containing raw material is mixed in an amount greater than this range, unreacted Li may remain as a by-product, resulting in a reduction in capacity and separation of the positive electrode active material particles after firing (inducing an agglomeration phenomenon of the positive electrode active material).

[0041] The calcination can be performed at a temperature of 700°C to 1000°C. If the calcination temperature is below 700°C, the raw materials may remain in the particles due to insufficient reaction, which may reduce the high-temperature stability of the battery, and the volume density and crystallinity may decrease, resulting in reduced structural stability. On the other hand, if the calcination temperature exceeds 1000°C, uneven particle growth may occur, making particle crushing difficult and resulting in reduced capacity. On the other hand, in consideration of controlling the particle size, capacity, stability, and reducing lithium-containing by-products of the produced positive electrode active material, the calcination temperature is more preferably 700°C to 980°C.

[0042] The calcination can be carried out for 5 to 35 hours. If the calcination time is less than 5 hours, the reaction time may be too short, making it difficult to obtain a highly crystalline positive electrode active material, while if it exceeds 35 hours, the particle size may become too large, resulting in a decrease in production efficiency.

[0043] According to the present invention, the lithium transition metal oxide may contain 70 mol % or more of nickel among all metals other than lithium. Specifically, the lithium transition metal oxide may have a composition represented by the following Chemical Formula 1:

[0044] [Chemical formula 1] Li 1+a Ni x1 Co y1 M1 z1 M2 w1 O2

[0045] In the above Chemical Formula 1, 0 ≦ a ≦ 0.3, 0.7 ≦ x1 < 1.0, 0 < y1 ≦ 0.3, 0 < z1 ≦ 0.3, 0 ≦ w1 ≦ 0.2, and x1 + y1 + z1 + w1 = 1. M1 is one or more selected from Mn and Al, and M2 can be one or more selected from Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y.

[0046] The above x1 represents the atomic fraction of nickel among the metal elements other than lithium in the lithium transition metal oxide, and it can be 0.7 ≦ x1 < 1, 0.7 ≦ x1 ≦ 0.98, or 0.7 ≦ x1 ≦ 0.95.

[0047] The above y1 represents the atomic fraction of cobalt among the metal elements other than lithium in the lithium transition metal oxide, and it can be 0 < y1 ≦ 0.3 or 0.01 ≦ y1 ≦ 0.3.

[0048] The above z1 represents the elemental fraction of the M1 element among the metal elements other than lithium in the lithium transition metal oxide, and it can be 0 < z1 ≦ 0.3 or 0.01 ≦ z1 ≦ 0.3.

[0049] The above w1 represents the elemental fraction of the M2 element among the metal elements other than lithium in the lithium transition metal oxide, and it can be 0 ≦ w1 ≦ 0.2, 0 ≦ w1 ≦ 0.1, 0 ≦ w1 ≦ 0.05, or 0 ≦ w1 ≦ 0.02.

[0050] (B) step and (C) step The method for manufacturing a positive electrode active material according to the present invention includes a step of mixing the lithium transition metal oxide with a first washing solution to perform first washing on the lithium transition metal oxide and then performing first filtration (step (B)), and a step of simultaneously performing second washing and second filtration on the lithium transition metal oxide after step (B) using a filtration device capable of simultaneously performing washing and filtration with a second washing solution (step (C)).

[0051] When the lithium transition metal oxide that has undergone step (B) is subjected to a second washing and a second filtration simultaneously with a second washing solution using a filtration device capable of simultaneous washing and filtration, the ions remaining on the surface of the positive electrode active material are easily removed, which is advantageous in terms of preventing surface deterioration of the positive electrode active material and reducing residual lithium, compared to the case of mixing the lithium transition metal oxide with the washing solution, washing with water, and then filtering twice as in step (B).

[0052] Furthermore, when step (B) and step (C) are performed in this order, unnecessary ions on the surface of the positive electrode active material can be removed more quickly than when step (C) is performed first and then step (B).

[0053] The filtering device capable of simultaneously performing washing and filtering may be, but is not limited to, a funnel filter, a filter press, or the like.

[0054] Here, the content of the second washing solution may be 10 to 50 parts by weight based on 100 parts by weight of the first washing solution. When the content of the second washing solution satisfies this range, surface deterioration of the positive electrode active material that occurs during the washing process can be minimized and residual ions on the surface of the positive electrode active material can be effectively controlled. Therefore, a battery using the positive electrode active material prepared by the method according to the present invention can have excellent performance, particularly excellent electrochemical performance and thermal stability.

[0055] The present invention includes steps (B) and (C) in the water washing process, which not only reduces the amount of water used, but also minimizes surface deterioration of the cathode active material that occurs during the water washing process and effectively controls residual lithium, thereby enabling batteries using the cathode active material prepared by the method of the present invention to have excellent performance.

[0056] According to the present invention, even when a lithium transition metal oxide having a high nickel content as represented by Chemical Formula 1 is used, by performing a water washing process as in the present invention, it is possible to minimize surface deterioration of the cathode active material that occurs during the water washing process and effectively control residual lithium, thereby providing a cathode active material with excellent performance.

[0057] According to the present invention, the content of the first washing solution may be 50 parts by weight to 150 parts by weight, specifically 50 parts by weight to 100 parts by weight, relative to 100 parts by weight of the lithium transition metal oxide. When the content of the first washing solution is within this range, unnecessary ions on the surface of the positive electrode active material can be sufficiently removed, and lithium inside the positive electrode active material can be prevented from being released.

[0058] According to the present invention, the content of the second washing solution may be 5 to 50 parts by weight, specifically 10 to 30 parts by weight, relative to 100 parts by weight of the lithium transition metal oxide. Furthermore, the sum of the content of the first washing solution and the content of the second washing solution may be 55 to 150 parts by weight, specifically 60 to 130 parts by weight, and more specifically 60 to 125 parts by weight, relative to 100 parts by weight of the lithium transition metal oxide. In this case, residual ions on the surface of the positive electrode active material can be effectively removed, and surface deterioration of the positive electrode active material that occurs during the washing process can be minimized.

[0059] The solvents of the first washing solution and the second washing solution may each independently be one or more selected from deionized water, distilled water, ethanol, and industrial water. Specifically, the solvents of the first washing solution and the second washing solution may be deionized water and / or distilled water. In this case, lithium is easily dissolved, which may be advantageous for removing residual lithium present on the surface.

[0060] The first water washing may be performed for 5 to 30 minutes, specifically 5 to 20 minutes, and more specifically 5 to 15 minutes. When the first water washing time is within this range, only the remaining lithium on the surface can be removed, and dissolution of the lithium inserted inside can be minimized.

[0061] The first water washing can be carried out at a temperature of 5° C. to 30° C., specifically 5° C. to 25° C. When the first water washing is carried out at a temperature within this range, it is advantageous in controlling lithium carbonate, which is easily dissolved in the washing solution at low temperatures.

[0062] The second water washing may be performed for 1 minute to 30 minutes, specifically 1 minute to 20 minutes, and more specifically 1 minute to 15 minutes. The second water washing may be performed at a temperature of 5° C. to 30° C., specifically 5° C. to 25° C. When the time and temperature of the second water washing step are within the above ranges, it is advantageous in controlling ions present on the surface of the positive electrode active material.

[0063] (D) Step The method for producing a cathode active material according to the present invention includes the steps of drying the lithium transition metal oxide obtained in step (C), mixing a coating element-containing raw material with the dried lithium transition metal oxide, and heat-treating the mixture to form a coating layer. The coating element-containing raw material includes a boron-containing raw material and one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O. This allows the production of a cathode active material having a coating layer containing a Li-BO solid solution formed on the surface of the lithium transition metal oxide. The Li-BO solid solution may contain 50% to 60% by weight of BO2, 2% to 7% by weight of LiB2O3, and 1% to 5% by weight of Li2B3O6.

[0064] The drying step is a step for removing moisture from the positive electrode active material that has been subjected to the water washing step, and can be performed at a temperature of 100° C. to 150° C. for 12 hours or more.

[0065] The boron-containing source material may be acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide containing B, for example, boric acid (H3BO3).

[0066] The boron-containing raw material may be added in an amount of 200 ppm to 2000 ppm by weight based on the dried lithium transition metal oxide. When the content of the boron-containing raw material is within this range, the capacity of the battery may be improved, and the resulting coating layer may suppress direct reaction between the electrolyte and the lithium transition metal oxide, thereby improving the long-term performance characteristics of the battery.

[0067] According to the present invention, the one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O may be added in an amount of 160 ppm to 500 ppm, specifically 160 ppm to 400 ppm, and more specifically 160 ppm to 300 ppm by weight relative to the dried lithium transition metal oxide. When the content of the one or more lithium-containing raw materials selected from LiOH, Li2CO3, and Li2O is within this range, the boron-containing raw materials may all participate in the reaction (i.e., the lithium-containing raw material and the boron-containing raw material all react), leaving no reactants, and the coating layer containing a Li-BO solid solution may be more easily formed.

[0068] The coating element-containing raw material may further include, as needed, acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or oxyhydroxides of Zr, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, Y, or combinations thereof.

[0069] The heat treatment can be carried out at a temperature of 200°C to 400°C. When the heat treatment temperature is within this range, a coating layer can be formed while maintaining the structural stability of the transition metal oxide. The heat treatment can be carried out for 1 hour to 10 hours. When the heat treatment time is within this range, an appropriate coating layer can be formed and production efficiency can be improved.

[0070] positive electrode active material The present invention also provides a positive electrode active material produced by the above-described method.

[0071] Specifically, the cathode active material according to the present invention includes a lithium transition metal oxide and a coating layer formed on the lithium transition metal oxide, the coating layer including a Li-BO solid solution, which may include 50 to 60 wt% of BO, 2 to 7 wt% of LiB2O3, and 1 to 5 wt% of Li2B3O6. In this case, the coating layer is stable, and the electrochemical performance and thermal stability of a battery including the cathode active material are excellent.

[0072] The Li-BO solid solution may further contain LiBO3, LiBO4, B3O5, etc. in addition to BO2, LiBO3, and LiBO6. Here, the LiBO3, LiBO4, and B3O5 may be contained in the Li-BO solid solution in amounts of 2% to 3% by weight, 30% to 35% by weight, and 2% to 7% by weight, respectively.

[0073] According to the present invention, the lithium transition metal oxide may contain 70 mol % or more of nickel among all metals other than lithium. Specifically, the lithium transition metal oxide may have a composition represented by Chemical Formula 1, as described above in the method for manufacturing a positive electrode active material.

[0074] According to the present invention, the ratio of the LiB2O3 content to the BO2 content may be 0.05 to 0.20. When the ratio of the LiB2O3 content to the BO2 content is within this range, the coating layer of a battery including the cathode active material according to the present invention is stable, and the battery including the cathode active material has excellent electrochemical performance and thermal stability. Specifically, the ratio of the LiB2O3 content to the BO2 content may be 0.07 to 0.12, which further improves the rate characteristics, life characteristics, and gas generation of the battery.

[0075] According to the present invention, the ratio of the Li2B3O6 content to the BO2 content may be 0.01 to 0.10. When the ratio of the Li2B3O6 content to the BO2 content is within this range, the coating layer is stable, and a battery including the positive electrode active material exhibits excellent electrochemical performance and thermal stability. Specifically, the ratio of the Li2B3O6 content to the BO2 content may be 0.02 to 0.05, in order to further improve the rate characteristics, life characteristics, and gas generation of the battery.

[0076] The coating layer may have a thickness of 5 nm to 10 nm. In this case, since the coating layer has a thin and uniform surface, the rate characteristics or life characteristics of a battery including the positive electrode active material according to the present invention can be improved.

[0077] positive electrode The present invention can also provide a positive electrode for a lithium secondary battery, which contains the above-mentioned positive electrode active material.

[0078] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector and including the above-described positive electrode active material.

[0079] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. It can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0080] The positive electrode active material layer may contain a conductive material and a binder in addition to the positive electrode active material.

[0081] The positive electrode active material may be contained in an amount of 80 wt % to 99 wt %, more specifically 85 wt % to 98 wt %, based on the total weight of the positive electrode active material layer. When contained in the above content range, excellent capacity characteristics can be exhibited.

[0082] The conductive material is used to impart conductivity to the electrode. Any conductive material can be used without particular limitations as long as it does not cause chemical changes in the resulting battery and has electronic conductivity. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials can be used alone or in combination. The conductive material can be present in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer.

[0083] The binder serves to improve adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include 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, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0084] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except for using the above-described positive electrode active material. Specifically, the positive electrode can be manufactured by coating a positive electrode composite, which is manufactured by mixing or dispersing the above-described positive electrode active material and, optionally, a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. Here, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the positive electrode composite on a separate support, peeling it from the support, and laminating the resulting film on the positive electrode current collector.

[0085] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used may be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity during subsequent application to fabricate a positive electrode, taking into consideration the coating thickness of the slurry and manufacturing yield.

[0086] Lithium secondary battery The present invention also provides an electrochemical device including the positive electrode. The electrochemical device may be, for example, a battery or a capacitor, and more specifically, a lithium secondary battery.

[0087] Specifically, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0088] The lithium secondary battery may further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

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

[0090] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys can be used. The negative electrode current collector typically has a thickness of 3 μm to 500 μm. As with the positive electrode current collector, the surface of the current collector can be formed with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0091] The negative electrode active material layer includes a negative electrode active material, and optionally a binder and a conductive material.

[0092] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); and composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. These may be used alone or in combination. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons are soft carbon and hard carbon, while typical high-crystalline carbons are amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0093] The negative electrode active material may be contained in an amount of 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

[0094] The binder is a component that helps bind the conductive material, active material, and current collector together, and is typically added in an amount of 0.1 to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0095] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 10 wt % or less, preferably 5 wt % or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0096] The negative electrode active material layer can be manufactured by coating a negative electrode composite, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent, on a negative electrode current collector and drying the coating. Alternatively, the negative electrode composite can be cast on a separate support, peeled from the support, and then laminating the resulting film on the negative electrode current collector.

[0097] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations. In particular, a separator that exhibits low resistance to ion movement in the electrolyte and excellent humidification ability for the electrolyte solution is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0098] Furthermore, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the production of lithium secondary batteries, but are not limited to these.

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

[0100] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethanol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred, as they have high ionic conductivity and a high dielectric constant, which can enhance the charge / discharge performance of batteries. In this case, the cyclic carbonate and linear carbonate should be mixed in a volume ratio of about 1:1 to about 1:9, which allows the electrolyte to exhibit excellent performance.

[0101] The lithium salt can be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The lithium salt is preferably used at a concentration in the range of 0.1M to 2.0M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0102] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, to improve battery life characteristics, suppress battery capacity reduction, and improve battery discharge capacity. In this case, the additives may be contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0103] As described above, the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and life characteristics, and is therefore useful in 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, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0105] The battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0106] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

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

[0108] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms without departing from the spirit or scope of the present invention.

[0109] Manufacturing example Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 A precursor having a composition represented by (OH)2 and LiOH were mixed in a molar ratio of 1:1.05, and then calcined at 780°C for 10 hours in an oxygen atmosphere to obtain Li[Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 ]O2 was prepared.

[0110] Examples and Comparative Examples Example 1 100 parts by weight of the lithium transition metal oxide prepared in the Preparation Example was mixed with 100 parts by weight of deionized water (first washing solution), washed for 5 minutes at 25°C, and then filtered for 5 minutes using a filter press. Then, 25 parts by weight of deionized water (second washing solution) was passed through a filter press at 25°C for 2 minutes using a filter press, washed for 2 minutes, and then filtered. The mixture was then dried in a vacuum oven at 130°C for 12 hours or more. H3BO3 and LiOH were mixed with the dried lithium transition metal oxide at 1000 ppm and 160 ppm by weight, respectively, and then heat-treated in an air atmosphere at 300°C for 5 hours to produce a cathode active material in which a coating layer containing a Li-BO solid solution was formed on the lithium transition metal oxide.

[0111] Example 2 A positive electrode active material was prepared in the same manner as in Example 1, except that H3BO3 and LiOH were mixed with the dried lithium transition metal oxide in amounts of 1000 ppm and 224 ppm by weight, respectively, based on the dried lithium transition metal oxide.

[0112] Example 3 A positive electrode active material was prepared in the same manner as in Example 1, except that H3BO3 and LiOH were mixed with the dried lithium transition metal oxide in amounts of 1000 ppm and 288 ppm by weight, respectively, based on the dried lithium transition metal oxide.

[0113] Comparative Example 1 100 parts by weight of the lithium transition metal oxide prepared in Preparation Example was mixed with 100 parts by weight of deionized water, washed for 5 minutes at 25°C, filtered for 5 minutes using a filter press, and dried for 12 hours or more in a vacuum oven at 130°C. H3BO3 was mixed with the dried lithium transition metal oxide in an amount of 1000 ppm by weight based on the dried lithium transition metal oxide, and then heat-treated at 300°C for 5 hours in an air atmosphere to prepare a cathode active material in which a coating layer containing a Li-BO solid solution was formed on the lithium transition metal oxide.

[0114] Comparative Example 2 100 parts by weight of the lithium transition metal oxide prepared in Preparation Example was mixed with 100 parts by weight of deionized water, washed for 5 minutes at 25°C, filtered for 5 minutes using a filter press, and dried for 12 hours or more in a vacuum oven at 130°C. H3BO3 and LiOH were mixed with the dried lithium transition metal oxide in amounts of 1000 ppm and 224 ppm by weight, respectively, based on the dried lithium transition metal oxide, and then heat-treated at 300°C for 5 hours in an air atmosphere to prepare a cathode active material in which a coating layer containing a Li-BO solid solution was formed on the lithium transition metal oxide.

[0115] Comparative Example 3 A positive electrode active material was prepared in the same manner as in Example 1, except that only H3BO3 was mixed with the dried lithium transition metal oxide in an amount of 1000 ppm by weight based on the dried lithium transition metal oxide.

[0116] Comparative Example 4 100 parts by weight of the lithium transition metal oxide prepared in the Preparation Example was mixed with 100 parts by weight of deionized water (first washing solution), washed for 5 minutes at 25°C, and then filtered for 5 minutes using a filter press. 25 parts by weight of deionized water (second washing solution) was then mixed with 100 parts by weight of the lithium transition metal oxide, washed for 5 minutes at 25°C, and then filtered for 5 minutes using a filter press. The mixture was then dried in a vacuum oven at 130°C for 12 hours or more. H3BO3 and LiOH were mixed with the dried lithium transition metal oxide at 1000 ppm and 160 ppm by weight, respectively, and then heat-treated in an air atmosphere at 300°C for 5 hours to produce a cathode active material in which a coating layer containing a Li-BO solid solution was formed on the lithium transition metal oxide.

[0117] [Table 1]

[0118] Experimental example Experimental Example 1: Confirmation of the type and content of Li-BO solid solution The surface of the positive electrode active materials prepared in the examples and comparative examples was analyzed to confirm the type and content of the Li-BO solid solution contained in the coating layer, which are shown in Table 2. Specifically, the surface of the positive electrode active materials was analyzed by secondary ion mass spectrometry (SIMS), using a TOF-SIMS5 manufactured by IonTOF (Germany), under the following conditions:

[0119] Negative mode: 1) Primary Ion: Bi3 + 30 keV 2)Field of View: 100μm×100μm 3) Raster size: 256 μm × 256 μm 4) Cycle time: 100 μs 5) Scan: 15 times

[0120] [Table 2] Experimental Example 2: Half-cell Characterization Lithium secondary batteries were produced using the positive electrode active materials produced in the examples and comparative examples, and the charge / discharge capacity, capacity retention rate at high temperature, and resistance increase rate of each lithium secondary battery were evaluated.

[0121] Specifically, each of the positive electrode active materials prepared in the Examples and Comparative Examples was mixed with a carbon black conductive material and a PVdF binder in a weight ratio of 97.5:1.0:1.5 in NMP solvent to prepare a positive electrode slurry. The positive electrode slurry was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare a positive electrode. Meanwhile, a Li metal disk was used as the negative electrode active material. An electrode assembly was fabricated by interposing a separator between the positive and negative electrodes, and then the assembly was placed inside a battery case. An electrolyte solution was then injected into the case to fabricate a lithium secondary battery. The electrolyte solution was prepared by dissolving 1M LiPF6 in an EC / EMC / DMC (3 / 3 / 4, vol%) organic solvent.

[0122] The lithium secondary battery prepared as described above was charged at a constant current of 0.1 C at 25°C until the voltage reached 4.3 V, and then discharged at a constant current of 0.1 C until the voltage reached 3.0 V. The charge and discharge capacities are shown in Table 3 below. To confirm rate characteristics, the lithium secondary battery prepared as described above was charged and discharged at a constant current of 0.1 C, 2.0 C, and 0.33 C at 25°C in the range of 3.0 to 4.3 V to obtain discharge capacity values ​​at each C-rate. The percentage of the discharge capacity value at a constant current of 2.0 C relative to the discharge capacity value at a constant current of 0.1 C and the percentage of the discharge capacity value at a constant current of 0.33 C relative to the discharge capacity value at a constant current of 0.1 C are shown in Table 3 below.

[0123] The capacity of the lithium secondary battery was measured by repeating 30 charge-discharge cycles, in which the battery was charged at a constant current of 0.33 C at 45°C in the range of 3.0 to 4.3 V until the voltage reached 4.3 V, and then discharged at a constant current of 0.33 C until the voltage reached 3.0 V. The capacity retention rate was calculated as the ratio of the 30th cycle capacity to the 1st cycle capacity, and this is shown in Table 3 below. The voltage drop for 60 seconds after the start of discharge in each cycle was measured, and this was divided by the applied current value to measure the resistance at high temperature. The increase rate of the 30th cycle resistance to the 1st cycle resistance is shown in Table 3 below.

[0124] [Table 3]

[0125] It can be seen that the batteries including the cathode active materials of Examples 1 to 3 manufactured by the manufacturing method according to the present invention have superior rate characteristics and capacity retention rates and lower resistance increase rates than the batteries including the cathode active materials of Comparative Examples 1 to 4. In particular, it can be seen that the battery including the cathode active material of Example 2 has superior rate characteristics and capacity retention rates and lower resistance increase rates.

[0126] Experimental Example 3: Evaluation of high temperature storage of monocell and evaluation of volume change Mono-cells were manufactured using the positive electrode active materials manufactured in the examples and comparative examples, and high-temperature storage evaluation and volume change evaluation were carried out for each.

[0127] Specifically, positive electrode active materials prepared in the Examples and Comparative Examples were mixed with carbon black conductive material and PVdF binder in an NMP solvent in a weight ratio of 97.5:1.0:1.5 to prepare positive electrode slurry. The positive electrode slurry was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare a positive electrode. Negative electrode active materials (a 9:1 mixture of natural graphite and artificial graphite), conductive material, additives, and binder were mixed in an NMP solvent in a weight ratio of 95.6:1.0:2.3:1.1 to prepare negative electrode slurry. The negative electrode was then applied to one side of a copper current collector, dried, and rolled to prepare a negative electrode. An electrode assembly was prepared by interposing a separator between the positive and negative electrodes. The electrodes were then laminated at 80°C to properly bond them together, and aluminum and nickel tabs were welded. The assembly was then placed in an aluminum pouch and filled with electrolyte to prepare a monocell. Here, the electrolyte used was prepared by dissolving 0.7M LiPF6 in an EC / EMC (3 / 7, vol%) organic solvent.

[0128] -High temperature storage rating (Initial HPPC (Hybrid Pulse Power Characterization)) The mono cell prepared as described above was charged at 25°C for 3 hours at a current of 0.1C, and then one side of the pouch was opened, vacuum degassed, and resealed. It was then charged and discharged three times at a current of 0.33C, followed by charging at a current of 0.33C. It was then discharged to SOC 50, and a current of 2.5C was applied for 10 seconds while measuring the voltage, from which the resistance was calculated. The capacity value of the initial HPPC in Table 4 below indicates the discharge capacity value after the third cycle.

[0129] (High temperature storage RPT) After HPPC evaluation, the mono cells were charged to SOC 100 and then stored in a 60°C oven for one week. After one week, they were charged and discharged three times at a current of 0.33C in a room temperature chamber, and the capacity and resistance were measured from the discharge data of the third cycle. After the measurements, the cells were stored in a 60°C oven again, and then removed every week and evaluated in the same way as the first week.

[0130] The results of the high temperature storage evaluation are shown in Table 4 below.

[0131] In Table 4 below, the retention rate indicates the ratio of the capacity maintained to the capacity at 0 weeks, and the increase rate indicates the ratio of the resistance increased to the resistance at 0 weeks.

[0132] [Table 4]

[0133] -Evaluation of volume changes The mono-cell fabricated as described above was charged at 25°C for 3 hours at a current of 0.1C. One side of the pouch was then opened, vacuum degassed, and resealed. It was then charged at a current of 0.33C three times and charged again at a current of 0.33C. The charged mono-cell was opened, the negative electrode was separated, and three positive electrodes and three separators were stacked alternately. The stack was then placed in an aluminum pouch and filled with electrolyte to prepare a cell for volume measurement. The electrolyte used was a 0.7M LiPF6 solution dissolved in an organic solvent (EC / EMC, 3 / 7, vol%). The fabricated cells were stored in an oven at 60°C and then removed at weekly intervals. The volume change rate at room temperature for 12 weeks was measured. The volume change rate for each cell relative to the initial value is shown in Table 5.

[0134] [Table 5]

[0135] The mono-cells containing the positive electrode active materials of Examples 1 to 3 manufactured by the manufacturing method according to the present invention have superior high-temperature storage characteristics and smaller mono-cell volume changes than the mono-cells containing the positive electrode active materials of Comparative Examples 1 to 4, and therefore it can be confirmed that the amount of gas generation is lower. In particular, it can be confirmed that the mono-cell containing the positive electrode active material of Example 2 has a significantly lower amount of gas generation.

[0136] That is, in the method for producing a positive electrode active material of the present invention, the surface is controlled by the water washing step in step (C), and the surface of the positive electrode active material is controlled in step (D). LiOH, Li 2 CO 3 and Li 2 In particular, By forming a coating layer using one or more lithium-containing raw materials selected from LiOH and Li2CO3, it is possible to minimize surface deterioration of the cathode active material that occurs during the water washing process, effectively control residual lithium, and form a uniform coating layer on the surface of the cathode active material. As a result, it is found that batteries using the cathode active material prepared by the method of the present invention have excellent performance, particularly excellent electrochemical performance and thermal stability.

Claims

1. (A) providing a lithium transition metal oxide; (B) mixing the lithium transition metal oxide with a first washing solution to first wash the lithium transition metal oxide with water, and then performing a first filtration; (C) performing a second washing and a second filtration simultaneously on the lithium transition metal oxide that has been subjected to step (B) using a filtration device capable of simultaneously washing with water and filtering with a second washing solution; (D) drying the lithium transition metal oxide obtained in step (C), and then mixing the dried lithium transition metal oxide with a coating element-containing raw material and heat-treating the mixture to form a coating layer; The coating element-containing raw material is a boron-containing raw material, LiOH, Li ２ CO ３ and Li ２ O, the sum of the content of the first washing solution and the content of the second washing solution is 55 parts by weight to 150 parts by weight per 100 parts by weight of the lithium transition metal oxide.

2. The method for producing a positive electrode active material according to claim 1 , wherein the lithium transition metal oxide contains nickel in an amount of 70 mol % or more of all metals other than lithium.

3. 2. The method for producing a positive electrode active material according to claim 1, wherein the content of the second washing solution is 10 parts by weight to 50 parts by weight with respect to 100 parts by weight of the first washing solution.

4. 2. The method for producing a positive electrode active material according to claim 1, wherein the content of the first washing solution is 50 parts by weight to 150 parts by weight with respect to 100 parts by weight of the lithium transition metal oxide.

5. 2. The method for producing a positive electrode active material according to claim 1, wherein the content of the second washing solution is 5 to 50 parts by weight based on 100 parts by weight of the lithium transition metal oxide.

6. The LiOH, Li ２ CO ３ and Li ２ 2. The method for producing a positive electrode active material according to claim 1, wherein the one or more lithium-containing raw materials selected from O are added in an amount of 160 ppm to 500 ppm by weight based on the dried lithium transition metal oxide.

7. a lithium transition metal oxide; a coating layer formed on the lithium transition metal oxide, The coating layer includes a Li—B—O solid solution, and the Li—B—O solid solution is BO ２ 50% by weight to 60% by weight of LiB ２ O ３ 2% by weight to 7% by weight, Li ２ B ３ O ６ A positive electrode active material comprising 1% by weight to 5% by weight of the above.

8. The positive electrode active material according to claim 7 , wherein the lithium transition metal oxide contains nickel in an amount of 70 mol % or more of all metals other than lithium.

9. The BO ２ LiB relative to the content of ２ O ３ The cathode active material according to claim 7, wherein the ratio of the contents of is 0.05 to 0.

20.

10. The BO ２ Li relative to the content of ２ B ３ O ６ The cathode active material according to claim 7, wherein the ratio of the contents of is 0.01 to 0.

10.

11. A positive electrode comprising the positive electrode active material according to any one of claims 7 to 10.

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