Composite transition metal oxide precursor and preparing method thereof, and positive active material using same

Abstract

A composite transition metal oxide precursor according to the present invention has a structure of spherical secondary particles including a plurality of plate-shaped primary particles, wherein the primary particles may have a pore density of 22 ㎛-1 to 50 ㎛-1 on the (002) and (111) crystal planes.

Description

Complex transition metal oxide precursor and method for producing the same, and cathode active material using the precursor

[0001] The present invention relates to a complex transition metal oxide precursor, a method for producing the same, and a cathode active material using the precursor.

[0002] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid cars.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries are actively being researched and developed due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0004] A lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator, and an electrolyte that impregnates the electrode assembly. The lithium secondary battery may further include an outer packaging material, for example, in the form of a pouch, that accommodates the electrode assembly and the electrolyte.

[0005] As the application scope of lithium secondary batteries expands to large devices such as hybrid vehicles, high-nickel (high-Ni) lithium oxides with increased nickel content are becoming known as cathode active materials for securing high capacity in lithium secondary batteries. These cathode active materials can be manufactured by reacting nickel-containing precursors with lithium raw materials.

[0006] However, the positive electrode active material may cause electrode deterioration and a reduction in the lifespan of the lithium secondary battery due to a side reaction with the electrolyte. For example, if the positive electrode active material has square primary particles, anisotropic shrinkage and expansion occur in the c-axis direction during charge and discharge, and microcracks are formed inside the secondary particles, which accelerates the side reaction with the electrolyte and reduces the electrochemical effect.

[0007] One aspect of the present invention for solving the above-described problem is to provide a composite transition metal oxide precursor having excellent electrochemical properties such as cycle life characteristics and thermal stability, a method for producing the same, and a cathode active material using the precursor, by controlling the pore density in the (002) crystal plane and the (111) crystal plane of the plate-like composite transition metal oxide precursor, thereby increasing the charge / discharge speed of a battery.

[0008] The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0009] In order to achieve the above purpose, a composite transition metal oxide precursor represented by the following chemical formula 1 according to one embodiment of the present invention has a structure of a spherical secondary particle including a plurality of plate-shaped primary particles, and the primary particles have a pore density of 22 μm of the (002) crystal plane and the (111) crystal plane. -1 50㎛ -1 It could be.

[0010] [Chemical Formula 1]

[0011] Ni 1-x-y Co x Mn y O z (OH) 2-2z

[0012] (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0임.)

[0013] In addition, the pore density of the (002) crystal plane and (111) crystal plane is 30㎛. -1 40㎛ -1 It could be.

[0014] Additionally, the length of the (002) crystal plane and the (111) crystal plane may be 1.2 μm or less.

[0015] Additionally, the above complex transition metal oxide precursor may have an average particle diameter (D50) of 2 µm to 6 µm.

[0016] In addition, a method for producing a composite transition metal oxide precursor represented by the chemical formula 1 according to one embodiment of the present invention may include a step of producing a nickel-manganese-cobalt precursor by co-precipitation reaction of a metal solution containing a nickel raw material, a manganese raw material, and a cobalt raw material; and a step of oxidizing the nickel-manganese-cobalt precursor.

[0017] Additionally, the above coprecipitation reaction can be performed at a temperature of 40°C to 70°C under an inert atmosphere such as nitrogen or argon.

[0018] Additionally, the oxidation can be performed by heat treatment at 450°C to 550°C for 3 to 7 hours under an air or oxygen atmosphere.

[0019] According to one embodiment of the present invention, the positive electrode active material represented by the following chemical formula 2 may include the above-described complex transition metal oxide precursor.

[0020] [Chemical Formula 2]

[0021] Li a (Ni 1-x-y Co x Mn y ) 2-a O2

[0022] (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0, 1≤a≤1.5임.)

[0023] In addition, the above complex transition metal oxide precursor has a pore density of 30㎛ on the (002) crystal plane and (111) crystal plane of the primary particle. -1 40㎛ -1 It could be.

[0024] Additionally, the above complex transition metal oxide precursor may have an average particle diameter (D50) of 2 µm to 6 µm.

[0025] The positive electrode according to one embodiment of the present invention may include the positive electrode active material.

[0026] A lithium secondary battery according to one embodiment of the present invention may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0027] According to the present invention, by controlling the pore density in the (002) crystal plane and the (111) crystal plane of a plate-shaped complex transition metal oxide precursor, the charge / discharge speed of a battery can be increased, and a complex transition metal oxide precursor having excellent electrochemical properties such as life characteristics and thermal stability, a method for producing the same, and a cathode active material using the precursor can be provided.

[0028] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0029] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0030] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0031] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense. For example, singular expressions herein include plural expressions unless the context clearly indicates otherwise.

[0032] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0033] Hereinafter, a composite transition metal oxide precursor according to one embodiment of the present invention will be described in detail.

[0034] A composite transition metal oxide precursor according to one embodiment of the present invention is represented by the following chemical formula 1 and has a structure of spherical secondary particles including a plurality of plate-shaped primary particles, wherein the primary particles have a pore density of 22 μm on the (002) crystal plane and the (111) crystal plane. -1 50㎛ -1It could be.

[0035] The above complex transition metal oxide precursor can be represented by the following chemical formula 1.

[0036] [Chemical Formula 1]

[0037] Ni 1-x-y Co x Mn y O z (OH) 2-2z

[0038] (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0임.)

[0039] Among the elements excluding the hydroxyl group in the above complex transition metal oxide precursor, Ni may be included in the largest amount (molar ratio or atomic %). For example, in the above chemical formula 1, the content of Ni may be 0.80 or more, preferably 0.86 or more, and more preferably 0.88 or more.

[0040] The above-mentioned composite transition metal oxide precursor may have a spherical secondary particle form in which a plurality of plate-shaped primary particles are aggregated.

[0041] The above primary particle has a plate-like structure, and the pore density of the (002) crystal plane and the (111) crystal plane, which are the side surfaces of the crystal structure, is 22㎛. -1 50㎛ -1 It can be, preferably 30㎛ -1 40㎛ -1 It is.

[0042] The above pore density refers to the average value of the number of pores existing within the vertical line length of the (002) crystal plane and the (111) crystal plane of the primary particle of the complex transition metal oxide precursor.

[0043] When the pore density of the (002) crystal plane and the (111) crystal plane is within the above range, the interior of the composite transition metal oxide precursor has a uniform pore distribution, so that the occurrence of crystal defects in the precursor can be suppressed. In addition, the occurrence of crystal defects in the positive electrode active material manufactured using the composite transition metal oxide precursor can be suppressed. When the pore density of the (002) crystal plane and the (111) crystal plane is within the above range, the occurrence of crystal defects in the positive electrode active material manufactured using the composite transition metal oxide precursor can be suppressed. -1 If less than , phase separation of nickel, cobalt, and manganese in the complex transition metal oxide precursor may occur, forming lithium metal oxides with a spinel or rock salt structure as well as a layered structure during firing, which may adversely affect the firing quality. Accordingly, this may act as a defect in the crystal structure during charge and discharge, reducing capacity and efficiency.

[0044] The pore density of the above (002) crystal plane and (111) crystal plane is 50㎛. -1 If it exceeds , the hydrogen and hydroxyl groups remaining in the lattice in the section where the oxidation of the precursor has relatively less occurred can act as defects that hinder the insertion of lithium during the synthesis of the positive electrode active material, thereby reducing the capacity and efficiency of the lithium secondary battery.

[0045] In addition, the length of the side surface of the plate-shaped primary particle of the above-mentioned complex transition metal oxide precursor, i.e., the (002) crystal plane and the (111) crystal plane, may be 1.2 μm or less, and preferably 1.0 μm or less.

[0046] The secondary particles, which are formed by agglomerating multiple primary particles, have a spherical shape.

[0047] The above secondary particles may have an average particle diameter (D50) of 2 µm to 6 µm, and preferably 3 µm to 4 µm. When the average particle diameter is within the above range, the stability of the positive electrode active material manufactured using the composite transition metal oxide precursor is improved, efficient diffusion of lithium ions is possible, so that the movement of lithium ions is smooth during charging and discharging, the initial charge and discharge efficiency characteristics of the positive electrode active material can be improved, and the capacity and output of the lithium secondary battery can be improved.

[0048] Therefore, in the present invention, by controlling the pore density of the side surfaces of the plate-shaped primary particles, i.e., the (002) crystal plane and the (111) crystal plane, and thereby controlling the average particle diameter of the secondary particles within the above range, a lithium secondary battery with improved initial efficiency and capacity characteristics can be manufactured.

[0049] Hereinafter, a method for manufacturing a composite transition metal oxide precursor according to one embodiment of the present invention will be described.

[0050] A method for producing a composite transition metal oxide precursor according to one embodiment of the present invention may include a step of producing a nickel-manganese-cobalt precursor by co-precipitation reaction of a metal solution containing a nickel raw material, a manganese raw material, and a cobalt raw material; and a step of oxidizing the nickel-manganese-cobalt precursor.

[0051] The above nickel-manganese-cobalt transition metal precursor can be manufactured according to a manufacturing method well known in the art.

[0052] For example, the nickel-manganese-cobalt precursor can be prepared by adding an ammonium cation-containing complex forming agent and a basic compound to a metal solution containing a nickel-containing raw material, a cobalt-containing raw material, and a manganese-containing raw material, and performing a co-precipitation reaction.

[0053] The nickel-containing raw material may be, for example, a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be, but is not limited to, Ni(OH)2, NiO, NiOOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O2ㆍ2H2O, Ni(NO3)2ㆍ6H2O, NiSO4, NiSO4ㆍ6H2O, fatty acid nickel salt, nickel halide or a combination thereof.

[0054] The above cobalt-containing raw material may be a cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, Co(SO4)2ㆍ7H2O or a combination thereof, but is not limited thereto.

[0055] The manganese-containing raw material may be, for example, a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide or a combination thereof, and specifically, may be, but is not limited to, a manganese oxide such as Mn2O3, MnO2, Mn3O4; a manganese salt such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, manganese fatty acid salt; manganese oxyhydroxide, manganese chloride or a combination thereof.

[0056] The above metal solution may be prepared by adding a nickel-containing raw material, a cobalt-containing raw material, and a manganese-containing raw material to a solvent, specifically, water, or a mixed solvent of an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water, or may be prepared by mixing an aqueous solution of a nickel-containing raw material, an aqueous solution of a cobalt-containing raw material, and an aqueous solution of a manganese-containing raw material.

[0057] The above ammonium cation-containing complex forming agent may be, for example, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof, but is not limited thereto. Meanwhile, the above ammonium cation-containing complex forming agent may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0058] The basic compound may be a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. The basic compound may also be used in the form of an aqueous solution, and in this case, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that is uniformly miscible with water.

[0059] The above basic compound is added to adjust the pH of the reaction solution, and can be added in an amount such that the pH of the metal solution becomes 9 to 12, preferably 10 to 11.

[0060] Meanwhile, the coprecipitation reaction can be performed at a temperature of 40°C to 70°C under an inert atmosphere such as nitrogen or argon.

[0061] Nickel-manganese-cobalt hydroxide particles are produced by the above process and precipitated within the reaction solution. The precipitated nickel-manganese-cobalt hydroxide particles can be separated and dried using a conventional method to obtain a nickel-manganese-cobalt precursor.

[0062] Next, a composite transition metal oxide precursor can be prepared through a step of oxidizing the nickel-manganese-cobalt precursor.

[0063] Here, oxidation refers to a broad concept in which a reactant combines with oxygen or loses hydrogen or electrons from the reactant. This oxidation step can be performed by heat treating the nickel-manganese-cobalt precursor in an air or oxygen atmosphere.

[0064] In the present invention, the pore density of the (002) crystal plane and the (111) crystal plane of the primary particle of the composite transition metal oxide precursor can be controlled through the step of oxidizing the nickel-manganese-cobalt precursor, and therefore, the atmosphere, temperature, and time range during the heat treatment in the oxidation step are most important.

[0065] In the above oxidation step, the air or oxygen atmosphere is not particularly limited.

[0066] In addition, in the oxidation step, it is preferable that the heat treatment be performed at a temperature ranging from 450°C to 550°C for 3 to 7 hours, and more preferably, it is performed at a temperature ranging from 450°C to 500°C for 4 to 6 hours.

[0067] If the temperature is less than 450°C during the above heat treatment, sufficient oxidation treatment does not occur, making it difficult to control the pore density of the (002) crystal plane and (111) crystal plane of the primary particles of the composite transition metal oxide precursor within the range intended by the present invention. As a result, the electrochemical performance may be reduced due to the occurrence of crystal defects in the composite transition metal oxide precursor or the positive electrode active material, or the performance of the lithium secondary battery may be deteriorated, such as the electrolyte penetrating into the positive electrode active material and continuously causing side reactions.

[0068] Additionally, when the temperature exceeds 550℃, crystal defects may occur in the complex transition metal oxide precursor or positive electrode active material.

[0069] In addition, if the heat treatment time is less than 3 hours, sufficient oxidation treatment may not occur, making it difficult to control the pore density of the (002) crystal plane and (111) crystal plane of the primary particles of the complex transition metal oxide precursor, and thus the performance of the positive electrode active material and lithium secondary battery including the precursor may deteriorate.

[0070] In addition, if it exceeds 7 hours, crystal defects may occur in the complex transition metal oxide precursor or positive electrode active material due to excessive oxidation treatment, or the capacity and life characteristics of the lithium secondary battery may deteriorate.

[0071] Below, a positive electrode active material according to one embodiment of the present invention is described.

[0072] A cathode active material according to one embodiment of the present invention may include the above-described complex transition metal oxide precursor. More specifically, the cathode active material may be represented by the following chemical formula 2.

[0073] [Chemical Formula 2]

[0074] Li a (Ni 1-x-y Co x Mn y ) 2-a O2

[0075] (In the above chemical formula 2, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0, 1≤a≤1.5임.)

[0076] The above positive electrode active material may be an active material of a nickel-rich system in which the content of nickel (Ni) among the total transition metal is 80% or more, and preferably 86% or more and less than 90%.

[0077] The average particle diameter of the above-mentioned positive electrode active material is not particularly limited as long as it is within a typical range that can be used as an active material. For example, it may be in the range of 2 μm to 15 μm, and preferably in the range of 3 μm to 6 μm.

[0078] The positive electrode active material of the present invention can be manufactured according to a conventional method known in the art, and can be manufactured, for example, by a dry method, a wet method, or a combination thereof.

[0079] For example, a method for manufacturing the above-mentioned positive electrode active material can be produced by mixing the above-mentioned composite transition metal oxide precursor and lithium raw material and then heat-treating the reaction mixture.

[0080] Since the above complex transition metal oxide precursor is the same as described above, a detailed description thereof is omitted here.

[0081] The above lithium raw material can be used without limitation as various lithium raw materials known in the relevant technical field, and for example, lithium-containing carbonates (e.g., lithium carbonate, etc.), lithium-containing hydrates (e.g., lithium hydroxide I hydrate (LiOH·H2O)), lithium-containing hydroxides (e.g., lithium hydroxide, etc.), lithium-containing nitrates (e.g., lithium nitrate (LiNO3)), lithium-containing chlorides (e.g., lithium chloride (LiCl)), etc.) can be used.

[0082] In addition, the mixing ratio of the complex transition metal oxide precursor and the lithium raw material can be appropriately controlled within a conventional range known in the art, and for example, the lithium raw material and the complex transition metal oxide precursor can be included so that the molar ratio of lithium:transition metal is 1.0 or more, preferably 1.0 to 1.1, and more preferably 1.03 to 1.07.

[0083] Meanwhile, in addition to the lithium raw material and the composite transition metal oxide precursor, a doping raw material may be further included to improve the stability and properties of the positive electrode active material. As such a doping raw material, oxides, hydroxides, sulfides, oxyhydroxides, halides, or mixtures thereof containing one or more elements selected from among W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo may be used.

[0084] A reaction mixture containing the above components may be prepared by putting each component into a mixer or the like and mixing them in a solid state, but is not limited thereto.

[0085] Next, the reaction mixture is subjected to a primary heat treatment at 700°C to 1,000°C for 1 to 10 hours under an oxygen atmosphere.

[0086] When the first heat treatment is performed in the above temperature range, the low-density lithium raw material melts and adheres to the complex transition metal oxide precursor, forming a plastic mixture with a reduced volume compared to the reaction mixture.

[0087] Specifically, the volume of the plastic mixture formed by the first heat treatment in the above temperature range is 20% to 50%, for example, 20% to 40%, of the volume of the reaction mixture before the first heat treatment. If the first heat treatment temperature is less than 700℃, there is almost no change in the structure of the raw material, the complex transition metal oxide precursor, even after the first heat treatment, and the plastic mixture is formed in a form in which lithium is unevenly attached to the surface, so the volume reduction effect may be minimal. Therefore, if the first heat treatment temperature is less than 700℃, the productivity improvement effect is reduced, and the quality uniformity of the cathode active material ultimately produced also deteriorates. On the other hand, if the first heat treatment temperature exceeds 1,000℃, crystal growth occurs rapidly during the first heat treatment, making it difficult to control the crystal growth and the characteristics of the final cathode product.

[0088] Meanwhile, the first heat treatment can be performed for 1 to 10 hours, and preferably for 3 to 7 hours. When the first heat treatment time is within the above range, moisture and gases generated during the heat treatment can be sufficiently removed, and there is an advantage in that it is easy to control crystal growth in the second heat treatment.

[0089] Additionally, the primary heat treatment can be performed in an oxygen atmosphere. Unnecessary gases such as CO2 are generated during the sintering process of the lithium raw material and the composite transition metal oxide precursor, which can deteriorate the properties of the resulting positive electrode active material. Therefore, the primary heat treatment can be performed in an oxygen atmosphere to address the aforementioned issues.

[0090] Additionally, after the above first heat treatment, a crushing or classification step may be additionally performed as needed.

[0091] At this time, the crushing or classification can be performed by a general crushing or classification method known in the art, and can be performed by, for example, a ball mill, a jet mill, or a sieving method. When the crushing or classification step is performed, the tap density of the plastic mixture increases, so that a larger amount of the plastic mixture can be obtained, and the plastic mixtures are homogeneously mixed during the crushing or classification process, so that the quality uniformity of the positive electrode active material can be further improved.

[0092] After the above first heat treatment and the crushing or classification step, a second heat treatment is performed at 500°C to 800°C for 2 hours and 10 hours under an oxygen atmosphere.

[0093] The above secondary heat treatment can be performed in an oxygen atmosphere or an air atmosphere, and the secondary heat treatment is performed at a temperature of 500°C to 800°C, preferably 600°C to 700°C, to form a positive electrode active material.

[0094] In addition, the secondary heat treatment may be performed for 2 to 10 hours, and preferably for 3 to 7 hours. When the secondary heat treatment time is within the above range, crystal growth occurs sufficiently, and thus, when applied to a battery, the lifespan characteristics and storage characteristics may be excellent.

[0095] Hereinafter, a positive electrode including the positive electrode active material and a lithium secondary battery including the same according to one embodiment of the present invention will be described.

[0096] A positive electrode according to one embodiment of the present invention may include the positive electrode active material. In this case, the positive electrode is required to include a positive electrode active material prepared from the above-described composite transition metal oxide precursor. The positive electrode active material itself is used as the positive electrode active material, or a positive electrode mixture obtained by mixing the positive electrode active material with a binder, a positive electrode mixture paste obtained by further adding a solvent, and a positive electrode formed by further applying the positive electrode mixture to a current collector are also included within the scope of the positive electrode material of the present invention.

[0097] The above positive electrode is formed on the positive electrode current collector and the positive electrode current collector, and may include a positive electrode active material layer including the positive electrode active material.

[0098] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0099] In addition, the positive electrode active material layer may include a conductive agent and a binder along with the positive electrode active material described above. The conductive agent is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and has electronic conductivity may be used without particular limitation. Specifically, 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, carbon fiber, or carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc. may be used. The conductive agent may typically be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer.

[0100] The above binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specifically, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof can be used. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer.

[0101] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method. For example, the positive electrode can be manufactured by mixing a positive electrode active material, a binder, and / or a conductive agent in a solvent to prepare a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0102] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0103] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry onto a separate support, then peeling the film from the support and laminating the resulting film onto a positive electrode current collector.

[0104] In addition, a secondary battery according to one embodiment of the present invention may include the positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the positive electrode is as described above.

[0105] The above negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0106] The above negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0107] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0108] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specifically, 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 alloy, Sn alloy, or Al alloy; SiO β (0<β<2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used.

[0109] In addition, a metallic lithium thin film may be used as the negative active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbon material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0110] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular restrictions. Specifically, examples thereof 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, carbon fiber, and carbon nanotube; 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, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may typically be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the negative electrode active material layer.

[0111] The above binder serves to improve adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specifically, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the negative electrode active material layer.

[0112] The above-described negative electrode active material layer may be manufactured by, for example, applying a negative electrode slurry containing a negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling it off from the support.

[0113] Meanwhile, in the secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0114] In addition, examples of the electrolyte used in the present invention include, but are not limited to, 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 manufacture of secondary batteries.

[0115] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0116] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may 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; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R represents a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0117] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be 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 0.1M to 5.0M, preferably 0.1M to 3.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0118] In addition to the electrolyte components, the electrolyte may further include additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. For example, the additives may include haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, either singly or in mixtures, but are not limited thereto. The additives may be included in an amount of 0.1 wt% to 10 wt%, preferably 0.1 wt% to 5 wt%, based on the total weight of the electrolyte.

[0119] Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended only to illustrate the present invention and the scope of the present invention is not limited to these examples.

[0120] Example 1

[0121] (Manufacture of complex transition metal oxide precursors)

[0122] Under a temperature condition of 70℃, a 25 wt% sodium hydroxide (NaOH) aqueous solution and 28 wt% ammonia water were added to the reactor so that the pH became 11, and then the solution in the reactor was bubbled with nitrogen (N2) gas while stirring at a constant speed to remove dissolved oxygen and create a non-oxidizing atmosphere inside the reactor.

[0123] A transition metal aqueous solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water at a composition of 89:4:7 (molar ratio of Ni:Co:Mn). The transition metal aqueous solution was added to the reactor so that the molar concentration of ammonia water to the molar concentration of the transition metal aqueous solution was 1.2, and a coprecipitation reaction was performed for 48 hours to prepare a nickel-cobalt-manganese precursor. During this time, the pH of the solution in the reactor was maintained at 10 to 11. Afterwards, the nickel-cobalt-manganese precursor was washed and filtered and dried in an oven at 120°C for 12 hours. The nickel-cobalt-manganese precursor was oxidized by heat treatment at 450°C for 5 hours under an argon (Ar) atmosphere, thereby obtaining a composite transition metal oxide precursor composed of spherical secondary particles in which plate-like primary particles are aggregated.

[0124] The average particle diameter (D50) of the complex transition metal oxide precursor obtained in this way was 3 to 4 μm.

[0125] (Manufacturing of positive electrode active materials)

[0126] The obtained complex transition metal oxide precursor was mixed with lithium hydroxide in a molar ratio of 1:1.02, and the temperature was increased to 890°C at a heating rate of 2°C / min, followed by a primary heat treatment in a kiln maintained in an oxygen atmosphere by passing oxygen at a rate of 25 L / min for 5 hours at 890°C and 8 hours at 800°C. After the primary heat treatment, the kiln was naturally cooled to room temperature, and subjected to pulverization, washing with water, and a secondary heat treatment at 680°C for 6 hours to obtain a cathode active material.

[0127] (Lithium secondary battery manufacturing)

[0128] A secondary battery was manufactured using the positive electrode active material obtained above.

[0129] Specifically, a positive electrode slurry was prepared by mixing the positive electrode active material, Denka Black as a conductive agent, and PVDF as a binder in a mass ratio of 93:5:2. The positive electrode slurry was coated on an aluminum current collector (thickness: 20 μm), vacuum-dried at 100°C, and then rolled to prepare a positive electrode.

[0130] The cathode used lithium metal (Li metal) with a thickness of 1.2 mm.

[0131] The positive and negative electrodes manufactured as described above were notched into circular shapes having diameters of Φ14 and Φ16, respectively, and laminated, and a separator (polyethylene, thickness 13 ㎛) notched into Φ19 was interposed between the positive and negative electrodes to form an electrode cell. The electrode cell was placed in a coin cell outer case having a diameter of 20 mm and a height of 1.6 mm, and an electrolyte was injected to assemble it, and the electrode was aged for more than 12 hours so that the electrolyte could be impregnated into the inside of the electrode. The electrolyte used was 1 M LiPF6 dissolved in a mixed solvent of EC / EMC (30 / 70; volume ratio).

[0132] Examples 2-3 and Comparative Examples 1-4

[0133] In the above Example 1, a composite transition metal oxide precursor, a cathode active material, and a lithium secondary battery were manufactured in the same manner as in the above Example 1, except that the oxidation heat treatment temperature of the nickel-cobalt-manganese precursor was changed as shown in Table 1 below when manufacturing the composite transition metal oxide precursor.

[0134] The pore density of the composite transition metal oxide precursors manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 was measured, and the results are shown in Table 1 below.

[0135] The pore density (n / h) is an average value measured by selecting 5 point plate-shaped primary particles to be measured within a spherical complex transition metal oxide precursor, and is calculated by measuring the number of pores (n) existing within the vertical line length (h) of the (002) crystal plane and (111) crystal plane of the measured primary particles within the spherical secondary particles.

[0136] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Oxidation heat treatment temperature (℃) 450 500 550 300 350 400 600 Pore density (㎛) -1 )46.735.525.0108.492.673.213.8

[0137] In addition, a chemical charge / discharge test was performed on a lithium secondary battery manufactured using a cathode active material including a composite transition metal oxide precursor manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 (charge condition CC-CV 0.1C 4.25V, 0.05C CUT-OFF, discharge condition CC 0.1C 3V CUT-OFF), and the results are shown in Table 2 below.

[0138] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 0.1C Charge Capacity (mAh / g) 229.6 231.5 231.5 229.7 230.8 231.8 230.3 0.1C Discharge Capacity (mAh / g) 207.0 207.9 207.5 205.2 206.3 207.5 206.6 Efficiency (%) 90.2 89.8 89.6 89.4 89.4 89.5 89.7

[0139] Examples 4-6

[0140] In the above Example 2, a composite transition metal oxide precursor, a positive electrode active material, and a lithium secondary battery were manufactured in the same manner as in the above Example 2, except that the oxidation heat treatment time of the nickel-cobalt-manganese precursor was changed as shown in Table 3 below when manufacturing the composite transition metal oxide precursor.

[0141] The pore density of the complex transition metal oxide precursors manufactured in Examples 2 and 4 to 6 above was measured, and the results are shown in Table 3 below.

[0142] Example 2 Example 4 Example 5 Example 6 Oxidation heat treatment time (h) 5345 Processing density (㎛) -1 )35.538.239.636.1

[0143] In addition, a chemical charge / discharge test was performed on a lithium secondary battery manufactured using a cathode active material including a composite transition metal oxide precursor manufactured in Examples 2 and 4 to 6 (charge condition CC-CV 0.1C 4.25V, 0.05C CUT-OFF, discharge condition CC 0.1C 3V CUT-OFF), and the results are shown in Table 4 below.

[0144] Classification Example 2 Example 4 Example 5 Example 60.1C Charge capacity (mAh / g) 231.5 232.6 231.4 231.7 0.1C Discharge capacity (mAh / g) 207.9 209.3 208.7 208.7 Efficiency (%) 89.8 90.0 90.2 89.7

[0145] As shown in Table 1 and Table 3 above, when the complex transition metal oxide precursor was oxidized by heat treatment in the temperature range of 450°C to 550°C for 3 to 7 hours according to the present invention, the pore density of the (002) crystal plane and the (111) crystal plane of the primary particles of the complex transition metal oxide precursor was 22 μm. -1 50㎛ -1 It was confirmed that it represents. On the other hand, it was confirmed that when the temperature during oxidation heat treatment is too high or too low, the pore density does not satisfy the range targeted by the present invention. In addition, as shown in Table 2 and Table 4 above, it was confirmed that the lithium secondary batteries manufactured using the positive electrode active materials including the composite transition metal oxide precursors of Examples 1 to 6 according to the present invention also exhibited excellent 0.1C charge / discharge capacity and efficiency compared to the comparative examples.

[0146] Through these results, according to the present invention, the pore density of the (002) crystal plane and (111) crystal plane of the primary particle of the complex transition metal oxide precursor was 22 μm through oxidation heat treatment of the complex transition metal oxide precursor at a temperature of 450°C to 550°C for 3 to 7 hours under an air or oxygen atmosphere. -1 50㎛ -1 It was confirmed that when a cathode active material including a complex transition metal oxide precursor satisfying the pore density of the (002) crystal plane and the (111) crystal plane is applied to a lithium secondary battery, the electrochemical characteristics such as capacity, life characteristics, and thermal stability of the lithium secondary battery can be improved.

[0147] Although the embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be implemented by a person having ordinary skill in the art to which the disclosed invention pertains without departing from the gist claimed in the claims.

Claims

1. It has a structure of a spherical secondary particle containing multiple plate-shaped primary particles, The above primary particles have a pore density of 22㎛ on the (002) crystal plane and the (111) crystal plane. -1 50㎛ -1 A complex transition metal oxide precursor represented by the following chemical formula 1. [Chemical Formula 1] Ni 1-x-y What x Mn y ABOUT z (OH) 2-2z (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0임.) 2. In paragraph 1, The pore density of the above (002) crystal plane and (111) crystal plane is 30㎛. -1 40㎛ -1 A complex transition metal oxide precursor.

3. In paragraph 1, A complex transition metal oxide precursor having a length of the (002) crystal plane and the (111) crystal plane of 1.2 μm or less.

4. In paragraph 3, The above complex transition metal oxide precursor is a complex transition metal oxide precursor having an average particle diameter (D50) of 2 µm to 6 µm.

5. A step of producing a nickel-manganese-cobalt precursor by co-precipitation reaction of a metal solution containing a nickel raw material, a manganese raw material, and a cobalt raw material; and A method for producing a complex transition metal oxide precursor represented by the following chemical formula 1, comprising a step of oxidizing a nickel-manganese-cobalt precursor. [Chemical Formula 1] Ni 1-x-y What x Mn y ABOUT z (OH) 2-2z (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0임.) 6. In paragraph 5, A method for producing a complex transition metal oxide precursor, wherein the above coprecipitation reaction is performed at a temperature of 40°C to 70°C in an inert atmosphere such as nitrogen or argon.

7. In paragraph 5, A method for producing a complex transition metal oxide precursor, wherein the above oxidation is performed by heat treatment at 450°C to 550°C for 3 to 7 hours in an air or oxygen atmosphere.

8. A cathode active material represented by the following chemical formula 2, which comprises a complex transition metal oxide precursor according to Article 1. [Chemical Formula 2] Li a (Ni 1-x-y Co x Mr y ) 2-a O2 (In the above chemical formula 1, 0 <x≤0.2, 0<y≤0.2, 0≤z≤1, 0.80≤1-x-y<1.0, 1≤a≤1.5임.) 9. In paragraph 8, The above complex transition metal oxide precursor has a pore density of 30 μm on the (002) crystal plane and (111) crystal plane of the primary particle. -1 40㎛ -1 A positive electrode active material.

10. In paragraph 8, The above complex transition metal oxide precursor is a positive electrode active material having an average particle diameter (D50) of 2 µm to 6 µm.

11. A positive electrode comprising a positive electrode active material according to Article 8.

12. The anode according to Article 11, cathode, A separator interposed between the positive and negative electrodes, and A lithium secondary battery containing an electrolyte.