Method for manufacturing a positive electrode active material for lithium secondary batteries and a lithium secondary battery containing a positive electrode active material manufactured using the same.

Abstract

This embodiment relates to a method for producing a positive electrode active material for a lithium secondary battery and a lithium secondary battery containing the same. A method for producing a positive electrode active material for a lithium secondary battery according to one embodiment includes the steps of: preparing a metal hydroxide containing nickel, cobalt, and manganese; mixing the metal hydroxide, lithium raw material, and dope raw material to produce a mixture; pre-calcining the mixture to obtain a pre-calcined product; calcining the pre-calcined product in a three-stage process: a first-stage calcination, a second-stage calcination, and a third-stage calcination to obtain a calcined product in single-particle form; and mixing the calcined product and a coating raw material, followed by heat treatment to obtain a metal oxide with a coating layer formed thereon, wherein the second-stage calcination may be performed at a higher temperature than the first-stage calcination, and the third-stage calcination may be performed at a lower temperature than the first-stage calcination.

Description

[Technical Field]

[0001] This embodiment relates to a method for producing a positive electrode active material for lithium secondary batteries and a lithium secondary battery containing a positive electrode active material produced using this method. [Background technology]

[0002] In recent years, the explosive demand for electric vehicles and the increasing need for longer driving ranges have led to a global surge in the development of high-capacity, high-energy-density secondary batteries to meet these demands. In particular, high-nickel NCM cathode materials with high nickel content are being used to satisfy these requirements.

[0003] However, increasing the nickel content reduces particle strength, leading to microcracks during charging and discharging. Furthermore, this increases the specific surface area of ​​the positive electrode material, resulting in increased reaction with the electrolyte and thus increased gas generation. Additionally, structural instability leads to unstable nickel. 3+ is stable Ni 2+ The phenomenon of positive ion mixing (cation mixing), which is reduced to stable NiO, increases. Therefore, there are problems with actually applying this to positive electrode active materials for lithium-ion batteries for electric vehicles and energy storage.

[0004] To solve this problem, a proposed solution involves manufacturing a cathode material in the form of single particles, where the size of the primary particles is maximized, rather than in a multi-particle form where primary particles are aggregated into secondary particles.

[0005] However, generally, manufacturing single-particle cathode materials requires firing at higher temperatures compared to multi-particle materials. This can lead to over-firing, causing crystal defects in the layered structure and degrading electrochemical properties such as capacitance and power output.

[0006] Furthermore, lowering the firing temperature to solve this problem resulted in insufficient growth of crystal grain size within a single particle, leading to a deterioration in particle strength and lifetime characteristics. [Overview of the project] [Problems that the invention aims to solve]

[0007] This embodiment aims to provide a method for producing a positive electrode active material for lithium secondary batteries that has excellent electrochemical properties and improved lifespan and resistance characteristics, and a lithium secondary battery containing the same. [Means for solving the problem]

[0008] A method for producing a positive electrode active material for a lithium secondary battery according to one embodiment includes the steps of: preparing a metal hydroxide containing nickel, cobalt, and manganese; mixing the metal hydroxide, lithium raw material, and dope raw material to produce a mixture; pre-calcining the mixture to obtain a pre-calcined product; performing a three-stage calcination process on the pre-calcined product to obtain a calcined product in single-particle form; and mixing the calcined product with a coating raw material and then heat-treating it to obtain a metal oxide on which a coating layer has been formed, wherein the step of obtaining the calcined product may be performed at a higher temperature than the first calcination, and the third calcination may be performed at a lower temperature than the first calcination.

[0009] Lithium secondary batteries according to other embodiments may include a positive electrode containing the positive electrode active material for lithium secondary batteries according to one embodiment described above. [Effects of the Invention]

[0010] According to this embodiment, the primary, secondary, and third stages of firing are performed in a three-step process. By including a second stage of firing performed at a higher temperature than the first stage and a third stage of firing performed at a lower temperature than the first stage, the crystal structure can be stabilized and the particle strength can be improved.

[0011] As a result, in this embodiment, it is possible to realize a cathode active material that, while in single-particle form, has excellent electrochemical properties and improved lifespan and resistance characteristics. [Modes for carrying out the invention]

[0012] The terms First, Second, and Third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the First Part, component, region, layer, or section described below may be referred to as the Second Part, component, region, layer, or section, without exceeding the scope of the present invention.

[0013] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the text explicitly indicates the opposite. The meaning of “includes” as used in this specification is to embody specific characteristics, regions, integers, steps, elements, and / or components, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0014] When one part is described as being "on top of" or "above" another part, it means that it is located above or above the other part, or that the other part may be interposed between them. In contrast, when one part is described as being "directly on top of" another part, it means that the other part is not interposed between them.

[0015] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are to be interpreted as having the meaning consistent with the relevant technical literature and the present disclosures, and not as ideal or highly formal unless otherwise defined.

[0016] Also, unless otherwise specifically referred to, % means weight %, and 1 ppm is 0.0001 weight %.

[0017] As used herein, the term "these combinations" described in Markush format expressions means one or more mixtures or combinations selected from the group consisting of the components described in the Markush format expressions, and means including one or more selected from the group consisting of the components.

[0018] Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0019] Method for manufacturing a positive electrode active material for a lithium secondary battery As described above, in the single-particle form of the positive electrode active material, overfiring may occur, defects may occur in the layered crystal structure, or the particle strength may decrease, thereby causing problems of reduced high-temperature life and resistance characteristics.

[0020] However, in this embodiment, the single-particle form of the positive electrode active material is manufactured by a method in which the firing in the three-step (STEP) process is carried out in three steps, i.e., the first step, the second step, and the third step, with the firing in the second step being carried out at a temperature higher than that in the first step and the firing in the third step being carried out at a temperature lower than that in the first step, thereby solving such problems.

[0021] Specifically, a method for manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment may include the steps of: preparing a metal hydroxide containing nickel, cobalt, and manganese; mixing the metal hydroxide, a lithium raw material substance, and a doping raw material substance to produce a mixture; pre-firing the mixture to obtain a pre-fired product; firing the pre-fired product in a three-stage process including a first-stage firing, a second-stage firing, and a third-stage firing to obtain a fired product in a single-particle form; and after mixing the fired product and a coating raw material substance, performing heat treatment to obtain a metal oxide having a coating layer formed thereon.

[0022] At this time, in the step of obtaining the fired product, the second-stage firing may be performed at a temperature higher than that of the first-stage firing, and the third-stage firing may be performed at a temperature lower than that of the first-stage firing. By performing the second-stage firing process at a high temperature for a short time as in this embodiment and then performing the third-stage firing process, it is possible to improve the particle strength and at the same time realize a positive electrode active material in a single-particle form with a stabilized crystallization structure.

[0023] In this specification, a single particle may include at least one of a single crystal structure composed of one particle and a form in which about 2 to 20 or about 2 to 10 particles are aggregated, and when observing a cross-section of the powder through a scanning electron microscope (SEM), it can be distinguished as one lump. Here, one particle means one grain or crystallite.

[0024] The active material in the single-particle form as in this embodiment has a smaller surface area compared to the positive electrode active material in the form of secondary particles formed by aggregation of dozens to hundreds of primary particles in the prior art. Therefore, the amount of gas generated due to side reactions with the electrolyte is reduced, and since the particle strength is large, particle cracking during rolling can be suppressed, and crack generation due to repeated charging and discharging can be reduced. As a result, compared to secondary particles, there are advantages in terms of longer life and higher safety, and high energy density of the electrode can be realized.

[0025] First, the step of preparing metal hydroxides containing nickel, cobalt, and manganese is performed.

[0026] In this case, the nickel-containing metal hydroxide can be produced, for example, by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a transition metal-containing solution containing a nickel raw material, selectively a cobalt raw material, and / or a manganese raw material, and causing a coprecipitation reaction.

[0027] The nickel raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the nickel raw material is a nickel-containing sulfate, acetate, nitrate, halogen compound, sulfide, hydroxide, oxide or oxyhydroxide, and may, but is not limited to, NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof.

[0028] The aforementioned cobalt raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the cobalt raw material may be cobalt-containing sulfates, acetates, nitrates, halogen compounds, sulfides, hydroxides, oxides, or oxyhydroxides, and may specifically be, but not limited to, CoSO4, CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or combinations thereof.

[0029] The manganese raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the manganese raw material may be manganese-containing sulfates, acetates, nitrates, halogen compounds, sulfides, hydroxides, oxides, oxyhydroxides, or combinations thereof, and may, but is not limited to, manganese salts such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate salts, manganese citrate, and manganese fatty acid salts, manganese oxides such as Mn2O3, MnO2, and Mn3O4, oxyhydroxides, manganese chloride, or combinations thereof.

[0030] The transition metal-containing solution may be prepared by adding a nickel raw material and, selectively, a cobalt raw material or a manganese raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol) that can be homogeneously mixed with water.

[0031] The complexing agent-containing solution plays a role in complex formation, and the complexing agent may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof. On the other hand, the complexing agent-containing solution can be used in the form of an aqueous solution, in which case water or a mixture of water and an organic solvent that can be homogeneously mixed with water (e.g., alcohol) can be used as the solvent.

[0032] Next, the metal hydroxide, lithium raw material, and dope raw material are mixed to produce a mixture.

[0033] The lithium raw material is not particularly limited as long as it is OH or LiOH·H2O, which is commonly used in the industry, but may be, for example, Li2CO3 or Li. In this embodiment, LiOH·H2O can be used as the lithium raw material.

[0034] At this time, the mixture can be manufactured such that the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) is in the range of 1.0 to 1.1, or 1.01 to 1.08.

[0035] The doping raw material may include an Al raw material, a Y raw material, and a Zr raw material.

[0036] The aforementioned Al raw material may include, but is not limited to, at least one of Al(OH)3, Al2(SO4)3, Al(NO)3, Al2O3, and AlCl3.

[0037] The aforementioned Y raw material may include, but is not limited to, at least one of Y2O3, Y(SO4)2, Y2(SO4)3, and Y(NO3)3.

[0038] The aforementioned Zr raw material may include, but is not limited to, at least one of ZrO2, Zr(SO4)2, ZrS2, and Zr(NO3)4.

[0039] The Al raw material can be added and mixed in a content range of 200 to 1,800 ppm or 500 to 1,500 ppm based on 100 g of the metal hydroxide.

[0040] The aforementioned Y raw material can be added and mixed in a content range of 400 to 2,000 ppm or 700 to 1,700 ppm based on 100 g of the metal hydroxide.

[0041] The Zr raw material can be added and mixed in, for example, in a content range of 1,200 to 2,800 ppm or 1,500 to 2,500 ppm based on 100 g of the metal hydroxide.

[0042] When the input content of Al raw material, Y raw material, and Zr raw material satisfies the above range, a positive electrode active material with improved capacity retention and resistance characteristics can be manufactured.

[0043] Next, the mixture is pre-fired to obtain a pre-fired product.

[0044] The aforementioned pre-sintering can be carried out at a temperature of 650°C to 770°C for 2 to 12 hours, or at a temperature of 680°C to 740°C for 3 to 10 hours. By performing the pre-sintering process in this manner, the production volume of the positive electrode active material can be increased while maintaining the electrochemical properties, thereby improving economic efficiency.

[0045] Subsequently, the pre-fired product is subjected to a 3-step process in which it undergoes a first-stage firing, a second-stage firing, and a third-stage firing to obtain a single-particle shaped product.

[0046] The first stage of firing can be carried out at a temperature of 870°C to 930°C for 2 to 6 hours, or at a temperature of 880°C to 920°C for 3 to 5 hours.

[0047] The second firing stage can be carried out at a temperature of 890°C to 960°C for 0.5 to 2 hours, or at a temperature of 900°C to 940°C for 0.5 to 1.5 hours.

[0048] The third stage of firing can be carried out at a temperature of 750°C to 870°C for 5 to 14 hours, or at a temperature of 780°C to 840°C for 7 to 12 hours.

[0049] Specifically, in this embodiment, the second stage of firing is performed at a higher temperature than the first stage, and the third stage of firing is performed at a lower temperature than the first stage. By performing the second stage of firing, which is carried out at a high temperature for a short time, that is, by performing a three-stage firing process including a shooting section, it is possible to realize a single-particle positive electrode active material in which particle strength is improved and the crystal structure is stabilized.

[0050] Next, the calcined product and the coating raw material are mixed, and then heat-treated to obtain a metal oxide with a coating layer formed on top.

[0051] The coating raw material may include a Co coating raw material and an Al coating raw material.

[0052] The aforementioned Co coating raw material may include, but is not limited to, at least one of Co(OH)2, CoO, Co3O4, CoCO3, cobalt acetate, and cobalt oxalate.

[0053] The Al coating raw material may include, but is not limited to, at least one of Al(OH)3, Al2(SO4)3, Al(NO)3, Al2O3, and AlCl3.

[0054] Here, the Co coating raw material can be added and mixed in a content range of 1.5 mol% to 3 mol% or 2.0 mol% to 2.8 mol% based on the total weight of the calcined product.

[0055] The Al coating raw material can be added and mixed in a content range of 500 ppm to 1,500 ppm or 800 ppm to 1,200 ppm based on the total weight of the calcined product.

[0056] When the content of the Co coating raw material and the Al coating raw material satisfies the above range, interfacial side reactions with the positive electrode active material and electrolyte can be suppressed, and a lithium secondary battery with improved capacity and resistance characteristics can be manufactured.

[0057] The heat treatment in the step of obtaining the metal oxide on which the coating layer is formed can be carried out, for example, at 660°C to 760°C for 3 to 8 hours, or at 690°C to 750°C for 4 to 6 hours. When the heat treatment process satisfies the above conditions, the amount of lithium remaining on the surface can be reduced while simultaneously stabilizing the surface structure.

[0058] In this embodiment, after the step of obtaining the fired product as needed, the step of crushing the fired product can be further included. That is, after obtaining the fired product, a crushing step can be included before the coating step.

[0059] The step of crushing can be performed after cooling the fired product to 50-200°C. When cooling to the cooling temperature, the reaction between external moisture and the fired product can be suppressed, and the increase in residual lithium can be suppressed.

[0060] The crushing can be performed by a method commonly used in the industry.

[0061] The crushing can be performed, for example, using a rotor mill, ball mill, pin mill, jet mill, bead mill, roll mill equipment, but is not limited thereto.

[0062] The metal oxide formed with a coating layer in the form of single particles produced by such a method can be represented by the following Chemical Formula 1.

[0063] [Chemical Formula 1] Li a [Ni x Co y Mn z M1 w1 M2 w2 O2

[0064] In Chemical Formula 1, 0.8 ≤ a ≤ 1.2, 0.8 ≤ x ≤ 0.99, 0 < y ≤ 0.06, 0 < z ≤ 0.14, 0 < w1 ≤ 0.1, 0 ≤ w2 ≤ 0.05, x + y + z + w1 + w2 = 1, M1 is Al, Y, and Zr, and M2 includes one or more of B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, and Sr.

[0065] In chemical formula 1, the nickel content is 0.8 moles or more, more specifically, in the range of 0.8 moles to 0.99 moles, 0.82 to 0.95 moles, or 0.82 to 0.93 moles, based on 1 mole of total transition metals contained in the nickel-containing metal oxide on which the coating layer is formed. When the nickel content satisfies the above range, a high-capacity battery can be realized.

[0066] Furthermore, the total content of M1 and M2, which are doped elements of chemical formula 1, can be greater than 0 and less than or equal to 0.2 moles, more specifically, in the range of 0.0005 moles to 0.1 moles, 0.0005 moles to 0.08 moles, 0.0005 moles to 0.04 moles, or 0.001 moles to 0.03 moles, based on a total of 1 mole of nickel, cobalt, manganese, and the doped elements. The content of the doped elements in the chemical formula refers to the amount of doped elements contained in the final obtained positive electrode active material.

[0067] On the other hand, the average particle size (D50) of the positive electrode active material in this embodiment can be 3 μm or more, more specifically, in the range of 3 μm to 6 μm. When the average particle size of the single-particle positive electrode active material satisfies the above range, a lithium secondary battery with excellent electrochemical properties such as lifetime characteristics and resistance increase rate can be realized. At the same time, the energy density per unit volume can also be increased, which has a very advantageous effect.

[0068] The positive electrode active material of this embodiment has a very low fine particle generation rate. Specifically, when the positive electrode active material is subjected to five presses on a 0.01 mm press gauge using a roll press, the total value of fine particles smaller than 1 μm can be 2% or less. When the fine particle generation rate meets the above range, high-temperature life and resistance characteristics can be improved.

[0069] positive electrode In other embodiments, a current collector and a positive electrode are provided, which is located on one surface of the current collector and includes a positive electrode active material layer containing the positive electrode active material manufactured according to the above-described embodiment.

[0070] The characteristics of the positive electrode active material constituting the positive electrode active material layer are as described above. Therefore, a detailed explanation of the positive electrode active material will be omitted.

[0071] The current collector can be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc.

[0072] On the other hand, the positive electrode active material layer may include a binder and a conductive material.

[0073] At this time, the binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, recycled cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these can be used, but are not limited to these. The binder can be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0074] The conductive material is used to impart conductivity to the electrodes and can be used in the battery without any special restrictions as long as it does not induce chemical changes 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 powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these can be used alone or in mixtures of two or more, but this is not limited to these examples. The conductive material can usually be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0075] The positive electrode can be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used.

[0076] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which includes the positive electrode active material described above and optionally a binder, conductive material, or solvent, onto a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0077] The solvent is a solvent commonly used in the art, and includes dimethyl cellulose sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these can be used alone or a mixture of two or more. The amount of solvent used is sufficient to dissolve or disperse the cathode active material, conductive material, and binder, taking into consideration the coating thickness and production yield of the slurry, and to have a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing.

[0078] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0079] Lithium-ion battery Another embodiment provides a lithium secondary battery including the positive electrode.

[0080] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, wherein the positive electrode is as described above. The lithium secondary battery may also selectively further include a battery container housing the electrode assembly including the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0081] In the lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0082] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treatments with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can also typically have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0083] The negative electrode active material layer may selectively include a binder and a conductive material along with the negative electrode active material. The negative electrode active material layer can also be manufactured, for example, by applying a negative electrode active material layer forming composition containing the negative electrode active material and selectively a binder and a conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0084] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples 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, or Al alloys; metallic oxides capable of doping and dedoping with lithium, such as SiOβ (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. Any one or a mixture of two or more of these can be used. Furthermore, a metallic lithium thin film can also be used as the negative electrode active material. In addition, all carbon materials, including low-crystalline carbon and high-crystalline carbon, can be used. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon micro beads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0085] The binder and conductive material may be the same as those described earlier for the positive electrode.

[0086] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0087] Furthermore, in the lithium secondary battery, the electrolyte can be 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, which can be used in the manufacture of lithium secondary batteries, and is not limited to these.

[0088] Specifically, the organic liquid electrolyte may contain an organic solvent and a lithium salt.

[0089] The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propyl methyl carbonate). Carbonate solvents such as necarbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2-C20, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Of these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, when the cyclic carbonate and linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte can be improved.

[0090] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, exhibits excellent electrolyte performance, and lithium ions can move effectively.

[0091] As described above, the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and thus is useful in portable devices such as mobile phones, notebook personal computers, digital cameras, and the field of electric vehicles such as hybrid electric vehicles (HEVs).

Examples

[0092] Hereinafter, examples of the present invention will be described in detail. However, this is presented as an illustration, and the present invention is not limited thereby. The present invention is defined by the scope of the claims described below.

[0093] Example 1 (1) Production of positive electrode active material Ni 0.90 Co 0.03 Mn 0.07 After preparing a precursor having a (OH)2 composition, LiOH·H2O (Samden Chemical, battery grade) as a lithium raw material substance, Y2O3, ZrO2, and Al(OH)3 as doping raw material substances were uniformly mixed with the precursor to produce a mixture.

[0094] At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.05, and doping raw materials were added so that the total weight of the precursor was 2000 ppm of Zr, 1200 ppm of Y, and 1000 ppm of Al.

[0095] The mixture was placed in a firing furnace under an oxygen atmosphere and pre-fired at 680°C for 6.5 hours to obtain the pre-fired product. Subsequently, the obtained pre-fired product was placed in a firing furnace under an oxygen atmosphere and fired at 890°C for 3 hours (1 st After step (2), bake at 940°C for 1 hour. nd (step) and then bake at 780℃ for 11 hours (3 rd The fired product was obtained by firing using a 3-step method.

[0096] The calcined material was crushed to obtain single-particle metal oxides doped with Al, Y, and Zr.

[0097] The obtained single-particle metal oxide was dry-mixed with Co(OH)2 and Al(OH)3 as coating raw materials, and then heat-treated in an oxygen atmosphere at 700°C for 5 hours to produce a positive electrode active material with a coating layer formed on top. At this time, the Co(OH)2 and Al(OH)3 were added and mixed based on the single-particle metal oxide, with Co at a content of 2.5 mol% and Al at a content of 1000 ppm.

[0098] Comparative Example 1 Pre-fired at 680°C for 6.5 hours, and after obtaining the pre-fired product, the obtained pre-fired product was placed in a firing furnace under an oxygen atmosphere, and the temperature was increased to 890°C for 4 hours (1 st After step (2), bake at 780°C for 11 hours. nd A single-particle positive electrode active material was produced in the same manner as in Example 1, except that the firing process was carried out using the method described in step 1.

[0099] Experimental Example 1 - Measurement of Particle Splitting Degree The degree of particle cracking was measured using the positive electrodes manufactured in Example 1 and Comparative Example 1, and the results are shown in Table 1 below.

[0100] Specifically, 10 g of positive electrode active material was mixed with 3.5 g of NMP, cast onto 20 μm thick aluminum foil (70 mm x 210 mm), and then dried in a convection oven at 120°C for 30 minutes. After that, a sample was prepared by covering the aluminum foil coated with positive electrode active material with another aluminum foil of the same size.

[0101] The aforementioned sample was subjected to five presses using a roll press to a press gauge of 0.01 mm, after which 2 g of active material particles were obtained. The amount of fine powder generated was analyzed using the obtained active material particles by performing particle size analysis with a Malvern (MS3000) analyzer. The degree of particle fracture was indicated by the total vol% value of fine powder particles smaller than 1 μm in the particle size analysis results.

[0102] [Table 1]

[0103] Referring to Table 1, it can be seen that in Example 1, which is a positive electrode active material manufactured in a 3-step process, the fine particle generation rate is significantly lower compared to Comparative Example 1, which is a positive electrode active material manufactured in a 2-step process.

[0104] Experimental Example 2 - Measurement of Residual Lithium The residual lithium in the cathode active materials produced in Example 1 and Comparative Example 1 was measured using a METTLER TOLEDO T50 model. The results are shown in Table 2 below.

[0105] [Table 2]

[0106] Referring to Table 2, it can be seen that the residual lithium content of the positive electrode active material produced by Example 1 is lower than that of the positive electrode active material produced by Comparative Example 1.

[0107] Experimental Example 3 - Measurement of Crystal Grain Size The crystal grain size, c-axis, and a-axis values ​​were measured for the positive electrode active materials produced in Example 1 and Comparative Example 1 as follows. The results are shown in Table 3 below.

[0108] 1) Sample structure analysis using Rigaku's smart lab equipment

[0109] 2) Smart lab equipment configuration Goniometer radius: 300.0 mm Rotating anode x-ray tube(DPTA-II) Theta_s arm:BB Slit CBO(cross beam optics for Cu target) Soller slit 5.0 deg, 10mm Incident slit Theta_d arm:8.0mm Receiving slit Diffracted beam monochromator(DBM)unit for D / teX Ultra, D / teX Ultra Sample stage: ASC-6 (auto sample changer), Reflection knife edge

[0110] 2) Apply 45kV, 200mA (9kW) to the Cu anode to generate X-rays.

[0111] 3) Equipped optics: Incident slit 1 / 2 degree, Receiving slit 8.0 mm setting

[0112] 4) XRD measurement with Scan 10-80°, Step 0.02°, 10° / min.

[0113] 5) The crystal grain size was calculated using Rigaku's SmartLab Studio IIx64v4.2.82.0S / W.

[0114] 6) Calculations are performed using WPPF (Whole Powder Pattern Fitting) in S / W.

[0115] [Table 3]

[0116] Referring to Table 3, it can be confirmed that the crystal grain size of the positive electrode active material produced by Example 1 is 190 nm or larger, while the crystal grain size of the positive electrode active material produced by Comparative Example 1 is less than 190 nm.

[0117] Experimental Example 4 - Particle Size Distribution Measurement Span and Dn10 values ​​were measured for the cathode active materials produced in Example 1 and Comparative Example 1. Specifically, particle size analysis was performed using Microtrac's S3500 equipment.

[0118] - Sample quantity: 0.02g - Dispersant: 10 wt.% (NaPO3) 6: 0.5 g -Pure water: 5g - External ultrasound: 1 min - Measurement conditions

[0119] I. SDC -SDC Control Parameters Number of Rinses: 3 Deaeration Cycles: 1 • Flow rate: 40

[0120] Analysis - Particle Information ·Particle Characteristics:Refractive Index1.55 - Fluid Information ·Fluid Characteristics:Refractive Index(1.333)

[0121] H. Forming -Setzero Time:10 - Measurement Run Run Time: 10 • Number of Runs: 3

[0122] The results are shown in Table 4 below.

[0123] [Table 4]

[0124] Referring to Table 4, Example 1, manufactured using the same method as this example, has a Span value of 0.9 or less and a Dn10 value of 1.5 or more. In contrast, Comparative Example 1 has a Span value exceeding 0.9 and a Dn10 of less than 1.5. Therefore, it can be confirmed that the positive electrode active material of Example 1 has superior particle size uniformity compared to Comparative Example 1, resulting in less fine particle generation and superior single-crystal ducting.

[0125] The present invention is not limited to the embodiments described above and can be manufactured in a variety of different forms. A person with ordinary skill in the art to which the present invention belongs will understand that it can be implemented in other specific forms without altering the technical idea or essential features of the present invention. Therefore, the embodiments described above should be understood in all respects as illustrative and not limiting.

Claims

1. Steps to prepare metal hydroxides containing nickel, cobalt, and manganese; A step of mixing the metal hydroxide, lithium raw material and dope raw material to produce a mixture; A step of pre-calcining the mixture and obtaining the pre-calcined product; The aforementioned pre-fired product is subjected to a three-stage firing process: a first-stage firing, a second-stage firing, and a third-stage firing to obtain a single-particle shaped product; and The steps include: mixing the calcined product and the coating raw material, then heat-treating to obtain a metal oxide in which a coating layer has been formed; A method for producing a positive electrode active material for a lithium secondary battery, wherein the step of obtaining the calcined product is to perform a second calcination at a higher temperature than the first calcination, and a third calcination at a lower temperature than the first calcination.

2. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the first stage of firing is carried out at a temperature in the range of 870°C to 930°C for 2 to 6 hours.

3. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the second stage of firing is carried out at a temperature in the range of 890°C to 960°C for 0.5 hours to 2 hours.

4. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the third stage of firing is carried out at a temperature in the range of 750°C to 870°C for 5 to 14 hours.

5. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the pre-firing is carried out at a temperature in the range of 650°C to 770°C for 3 to 10 hours.

6. In the step of producing the aforementioned mixture, The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the doping raw material includes an Al raw material, a Y raw material, and a Zr raw material.

7. The aforementioned Al raw material is A method for producing a positive electrode active material for a lithium secondary battery according to claim 6, wherein the material is added and mixed in a content range of 500 ppm to 1,500 ppm based on the aforementioned metal hydroxide.

8. The aforementioned Y raw material is A method for producing a positive electrode active material for a lithium secondary battery according to claim 6, wherein the material is added and mixed in a content range of 400 ppm to 2,000 ppm based on the aforementioned metal hydroxide.

9. The aforementioned Zr raw material is A method for producing a positive electrode active material for a lithium secondary battery according to claim 6, wherein the metal hydroxide is added and mixed in a content range of 1,200 ppm to 2,800 ppm based on the aforementioned metal hydroxide.

10. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the coating raw material includes a Co coating raw material and an Al coating raw material.

11. The aforementioned Co coating raw material is A method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the material is added and mixed in a content range of 1.5 mol% to 3 mol% based on 100 g of the calcined product.

12. The aforementioned Al coating raw material is A method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the calcined product is added and mixed in a content range of 500 ppm to 1,500 ppm based on 100 g of the calcined product.

13. The aforementioned Co coating raw material is Co(OH) ２ CoO, Co ３ O ４ CoCO ３ A method for producing a positive electrode active material for a lithium secondary battery according to claim 10, comprising at least one of cobalt acetate and cobalt oxalate.

14. The Al coating raw material substance is Al(OH) ３ , Al ２ (SO ４ ) ３ , Al(NO) ３ , Al ２ O ３ and at least one of AlCl ３ , the method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 10

15. The heat treatment in the step of obtaining the metal oxide on which the coating layer is formed is, A method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the process is carried out at 660°C to 760°C for 3 to 8 hours.

16. The metal oxide on which the coating layer is formed is represented by the following chemical formula 1, the method for producing a positive electrode active material for a lithium secondary battery according to claim 1: [Chemical formula 1] Li ａ [Ni ｘ Co ｙ Mn ｚ M1 ｗ１ M2 ｗ２ ]O ２ In the above chemical formula 1, 0.8 ≤ a ≤ 1.2, 0.8 ≤ x ≤ 0.99, 0 < y ≤ 0.06, 0 < z ≤ 0.14, 0 < w1 ≤ 0.05, 0 ≤ w2 ≤ 0.05, x + y + z + w1 + w2 = 1, M1 is Al, Y and Zr, and M2 contains one or more of B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La and Sr.

17. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is subjected to five pressurization steps using a roll press with a press gauge of 0.01 mm, and the sum of fine particles smaller than 1 μm is 2 vol% or less.

18. A positive electrode for a lithium secondary battery comprising a positive electrode active material manufactured according to any one of claims 1 to 17.

19. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 18.

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