Manufacturing method of positive electrode active material precusor

Abstract

The present invention relates to a method for manufacturing a bimodal-type positive electrode active material precursor, comprising: (A) a step of forming a transition metal hydroxide through a precipitation reaction using an aqueous solution of a transition metal, a solution containing ammonium ions, and an aqueous basic solution; and (B) a step of first washing some of the transition metal hydroxides with a neutral solution to obtain a coarse-type positive electrode active material precursor, and second washing the remaining transition metal hydroxides with a solution having a pH of 3 to 5 to obtain a small-type positive electrode active material precursor having an average particle size (D50) smaller than that of the coarse-type positive electrode active material precursor.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a positive electrode active material precursor. Background Technology

[0003] With the increasing technological development and demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly rising. Among secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0004] Lithium transition metal composite oxides are used as cathode active materials for lithium secondary batteries; among these, lithium cobalt composite metal oxides such as LiCoO2, which exhibit high operating voltage and excellent capacity characteristics, are primarily used. However, LiCoO2 has very poor thermal properties due to the descaling of its crystal structure caused by lithium removal. Furthermore, because the aforementioned LiCoO2 is expensive, there are limitations to its mass use as a power source in fields such as electric vehicles.

[0005] As materials to replace the above LiCoO2, lithium manganese composite metal oxides (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4, etc.), or lithium nickel composite metal oxides (LiNiO2, etc.) have been developed. Among these, research and development on lithium nickel composite metal oxides is being conducted more actively, as they have a high reversible capacity of about 200 mAh / g, making it easy to implement large-capacity batteries. However, the above LiNiO2 has inferior thermal stability compared to LiCoO2, and there was a problem in that if an internal short circuit occurs due to external pressure or the like while charged, the positive active material itself decomposes, causing the battery to rupture and ignite. Accordingly, as a method to improve the low thermal stability while maintaining the excellent reversible capacity of the above LiNiO2, a lithium composite transition metal oxide in which a portion of Ni is substituted with Co, Mn, or Al has been developed.

[0006] However, lithium composite transition metal oxides have the problem of low capacity. Therefore, to increase the capacity of lithium composite transition metal oxides, methods such as increasing the nickel content or increasing the packing density per unit volume of the cathode active material have been studied.

[0007] Conventionally, to manufacture high-density cathode active materials with a high packing density per unit volume, a method was used in which small particle size precursors (controlled to a short reaction time) and large particle size precursors (controlled to a long reaction time) were prepared by varying the reaction times, and then the prepared precursors were mixed and calcined to produce a bimodal cathode active material, or the prepared precursors were each calcined and mixed to produce a bimodal cathode active material.

[0008] However, in this case, since small particle size precursors and large particle size precursors must be manufactured through different cycle manufacturing processes with different reaction times, there is a problem that manufacturing time and manufacturing costs increase.

[0009] Therefore, there is a need to develop a method for manufacturing cathode active material precursors that can reduce manufacturing time and costs. The problem to be solved

[0011] The present invention aims to solve the above-mentioned problems by providing a method for manufacturing a bimodal cathode active material precursor that can reduce manufacturing time and costs, i.e., improve productivity, by simultaneously manufacturing large and small particle cathode active material precursors in a single manufacturing cycle. means of solving the problem

[0013] The present invention comprises: (A) a step of forming a transition metal hydroxide through a precipitation reaction using an aqueous transition metal solution, an ammonium ion-containing solution, and a basic aqueous solution; and (B) a step of first washing some of the transition metal hydroxides with a neutral solution to obtain a coarse-type cathode active material precursor, and second washing the remaining transition metal hydroxides with a solution having a pH of 3 to 5 to obtain an average particle size (D) greater than that of the coarse-type cathode active material precursor. 50 The present invention provides a method for manufacturing a bimodal type positive electrode active material precursor, comprising the step of obtaining a small particle positive electrode active material precursor. Effects of the invention

[0015] The present invention relates to the average particle size (D) in one cycle of the manufacturing process when manufacturing a positive electrode active material precursor. 50 Including a washing process capable of controlling ), average particle size (D 50 Different allotropic cathode active material precursors and microparticle cathode active material precursors can be easily manufactured. Since the bimodal cathode active material precursor can be manufactured in a single manufacturing cycle, manufacturing time and manufacturing costs can be reduced.

[0016] In addition, since the manufacturing of the small particle cathode active material precursor occurs simultaneously with the manufacturing of the allotrope cathode active material precursor and is performed under different conditions, productivity can be improved. Brief explanation of the drawing

[0018] Figure 1 is an SEM image of the covalent cathode active material precursor prepared in Example 1. Figure 2 is an SEM image of the small particle cathode active material precursor prepared in Example 1. Figure 3 is an SEM image of the covalent cathode active material precursor prepared in Comparative Example 1. Figure 4 is an SEM image of the small particle cathode active material precursor prepared in Comparative Example 1. Figure 5 is a graph showing the particle size distribution of the bimodal cathode active material precursor prepared in Example 1. Figure 6 is a graph showing the particle size distribution of the bimodal type cathode active material precursor prepared in Comparative Example 1. Specific details for implementing the invention

[0019] The present invention will be described in more detail below.

[0020] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0021] In this specification, 'average particle size (D 50' )' can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The above average particle size (D 50 ) can be measured, for example, using the laser diffraction method. For example, the average particle size (D) of the positive electrode active material. 50 The measurement method of ) involves dispersing particles of the positive electrode active material in a dispersion medium, introducing them into a commercially available laser diffraction particle size measuring device (e.g., HORIBA LA-960), irradiating them with ultrasound of approximately 28 kHz at an output of 60 W, and then determining the average particle size (D) corresponding to 50% of the volume accumulation in the measuring device. 50 ) can be produced.

[0023] Method for manufacturing a bimodal type positive electrode active material precursor

[0024] First, a method for manufacturing a bimodal type positive electrode active material precursor according to the present invention will be described.

[0026] A method for manufacturing a bimodal-type positive electrode active material precursor according to the present invention comprises: (A) a step of forming a transition metal hydroxide through a precipitation reaction using an aqueous transition metal solution, an ammonium ion-containing solution, and a basic aqueous solution; and (B) a step of first washing some of the transition metal hydroxides with a neutral solution to obtain a coarse-type positive electrode active material precursor, and second washing the remaining transition metal hydroxides with a solution having a pH of 3 to 5 to obtain an average particle size (D) greater than that of the coarse-type positive electrode active material precursor. 50 ) includes the step of obtaining a small particle positive electrode active material precursor.

[0028] Hereinafter, each step of the present invention will be described in detail.

[0030] (A) Step

[0031] The above step (A) is a step of forming a transition metal hydroxide through a precipitation reaction using an aqueous transition metal solution, an ammonium ion-containing solution, and a basic aqueous solution.

[0032] Specifically, the above step (A) is a step of introducing reaction raw materials including a transition metal aqueous solution, an ammonium ion-containing solution, and a basic aqueous solution into a reactor to form nuclei of transition metal hydroxide particles through a precipitation reaction, and then growing the transition metal hydroxide particles to form a transition metal hydroxide.

[0034] The above transition metal aqueous solution may contain nickel in an amount of 70 mol% or more, specifically 80 mol% or more, of the total content of the transition metal elements. In this case, the charge / discharge capacity of the positive electrode active material is large, and consequently, the charge / discharge capacity of the secondary battery containing the above positive electrode active material may be large.

[0035] In addition, the above transition metal aqueous solution may contain 0 mol% to 20 mol% of manganese and 0 mol% to 10 mol% of cobalt among the total content of the transition metal elements, and the content of manganese may be greater than the content of cobalt.

[0037] The above transition metal aqueous solution may include nickel-containing raw materials, cobalt-containing raw materials, and manganese-containing raw materials.

[0038] The above nickel-containing raw material, cobalt-containing raw material, manganese-containing raw material, etc., are not particularly limited as long as they can be dissolved in water.

[0039] For example, the nickel-containing raw material may be a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be Ni(OH)2, NiO, NiOOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O2ㆍ2H2O, Ni(NO3)2ㆍ6H2O, NiSO4, NiSO4ㆍ6H2O, nickel fatty acid salts, nickel halides, or combinations thereof, but are not limited thereto.

[0040] 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, CoSO4, Co(SO4)2ㆍ7H2O or a combination thereof, but is not limited thereto.

[0041] The above 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, manganese oxides such as Mn2O3, MnO2, Mn3O4, etc.; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid, manganese fatty acid; manganese oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0042] The above transition metal aqueous solution may be prepared by adding a nickel-containing raw material, a cobalt-containing raw material, and a manganese-containing raw material, etc., to a solvent, specifically water, or a mixed solvent of an organic solvent that can be uniformly mixed with water (e.g., alcohol, etc.).

[0043] The composition of the final cathode active material precursor can be controlled by adjusting the concentrations of the nickel-containing raw material, cobalt-containing raw material, and manganese-containing raw material included in the above transition metal aqueous solution. For example, by adjusting the concentrations of the raw materials, a cathode active material precursor can be manufactured in which the nickel (Ni) content of the total metal content is 70 mol% or more, and in this case, high capacity characteristics can be achieved by including high-Ni nickel.

[0045] The above ammonium ion-containing solution may include one or more selected from NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3. In this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.) may be used as the solvent.

[0047] The above basic aqueous solution may include one or more selected from NaOH, KOH, and Ca(OH)2. In this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.) may be used as the solvent.

[0049] The above step (A) can be performed by first introducing deionized water into the reactor, then purging the reactor with an inert gas to remove dissolved oxygen in the water and creating a non-oxidizing atmosphere inside the reactor, and then introducing an ammonium ion-containing solution and a basic aqueous solution up to a certain volume of the reactor to adjust the pH inside the reactor to pH 11 to 13.

[0051] The above transition metal hydroxide can be prepared under a pH of 11 to 13.

[0052] For example, the nucleation of the transition metal hydroxide particles can be performed at a pH of 12 or higher, specifically at a pH of 12 to 13. More specifically, it can be performed at a pH of 12 to 12.5. When the pH is within the above range, only particle nuclei are formed and little growth of the particles may occur. In addition, the growth of the transition metal hydroxide particles can be performed at a pH of less than 12, specifically at a pH of 10 or higher and less than 12. More specifically, it can be performed at a pH of 11 or higher and less than 12. When the pH is within the above range, little new particle nuclei are generated, and the growth of already generated particle nuclei occurs preferentially.

[0054] (B) Step

[0055] Step (B) above involves first washing some of the transition metal hydroxides with a neutral solution to obtain a coarse-type positive electrode active material precursor, and secondly washing the remaining transition metal hydroxides with a solution having a pH of 3 to 5 to obtain an average particle size (D) greater than that of the coarse-type positive electrode active material precursor. 50 This is the step of obtaining a small particle positive electrode active material precursor.

[0056] The present invention relates to the average particle size (D) in one cycle of the manufacturing process when manufacturing a positive electrode active material precursor. 50 A bimodal cathode active material precursor can be manufactured in a single cycle of manufacturing process by including step (B), which includes a washing process capable of controlling ). Accordingly, manufacturing time and manufacturing costs can be reduced, and productivity can be improved.

[0057] By removing by-products remaining in the transition metal hydroxide through a first washing process of some of the transition metal hydroxides with a neutral solution, a precursor of an alternative cathode active material can be obtained.

[0058] And, through a second washing process of the remaining transition metal hydroxide with a solution having a pH of 3 to 5, residual by-products remaining in the transition metal hydroxide are removed, and at the same time, the transition metal hydroxide is dissolved to reduce its size, so that the average particle size (D) is smaller than that of the aforementioned covalent anode active material precursor. 50 A small particle cathode active material precursor can be obtained. In this case, by adjusting the pH of the solution having a pH of 3 to 5, which is the washing solution of the second washing step, the average particle size (D) of the small particle cathode active material precursor 50 ) can be controlled. Meanwhile, the transition metal hydroxide dissolved in the second washing solution can be recycled.

[0059] In addition, the above-mentioned small particle cathode active material precursor may be obtained by washing the remaining transition metal hydroxide a second time with a solution having a pH of 3 to 5, and then washing it a third time with a neutral solution. The third washing may be a process for removing acids and impurities that may remain after the second washing.

[0061] The above-mentioned partial transition metal hydroxide may be 60% to 80% by mass of the total mass of the transition metal hydroxide, specifically 65% ​​to 75% by mass, and more specifically 65% ​​to 70% by mass.

[0062] The remaining transition metal hydroxide may be 20% to 40% by mass of the total mass of the transition metal hydroxide, specifically 25% to 35% by mass, and more specifically 25% to 30% by mass. If the content of the partial transition metal hydroxide and the content of the remaining transition metal hydroxide are within the above ranges, it may be advantageous in terms of the filling rate of the bimodal cathode active material.

[0064] The neutral solution, which is the rinsing solution for the first wash, may be one or more selected from industrial water, distilled water, deionized water, methanol, ethanol, and propanol. Specifically, the neutral solution may be industrial water. In this case, since discarded industrial water is recycled, manufacturing costs can be reduced.

[0065] The first washing may be performed at 40°C to 80°C, specifically at 50°C to 75°C, and more specifically at 60°C to 70°C. When the first washing is performed within the above temperature range, impurities dissolve well in the washing solution, so washing can occur effectively.

[0066] The first washing may be performed for 1 to 10 hours, specifically 2 to 8 hours, and more specifically 5 to 7 hours. When the first washing is performed within the above time range, impurities can be sufficiently washed away and productivity can be improved.

[0068] The solution having a pH of 3 to 5, which is the rinsing solution of the second wash, may be one or more selected from an aqueous acetic acid solution, an aqueous phosphoric acid solution, an aqueous sulfuric acid solution, and an aqueous nitric acid solution. Specifically, the solution having a pH of 3 to 5 may be an aqueous acetic acid solution, an aqueous phosphoric acid solution, and an aqueous sulfuric acid solution, and more specifically, an aqueous acetic acid solution and an aqueous phosphoric acid solution. In this case, the pH can be easily adjusted to 3 to 5.

[0069] The above second washing may be performed at 20°C to 30°C, that is, at room temperature, in order to prevent the pH from changing with temperature.

[0070] The above second washing may be performed for 1 to 10 hours, specifically 2 to 8 hours, and more specifically 3 to 6 hours. By adjusting the time for performing the above second washing, the average particle size (D) of the small particle cathode active material precursor 50) can be controlled. In particular, when the second washing is performed within the above time range, it does not take long to remove the solution after washing, that is, to filter under reduced pressure, so that a difference in particle size due to filtration time may not occur.

[0072] The above third wash is a process for removing acid and impurities that may remain after the second wash, and can be performed under the same solution, temperature, and time conditions as the above first wash.

[0074] The above-mentioned allotropic active material precursor has an average particle size (D 50 ) may be 8㎛ to 12㎛, specifically 9㎛ to 11㎛, and more specifically 10㎛ to 10.5㎛. The above-mentioned small particle cathode active material precursor has an average particle size (D 50 ) may be 3㎛ to 7㎛, specifically 4㎛ to 6㎛, and more specifically 4.5㎛ to 5.5㎛. The average particle size (D) of the large and small particle cathode active material precursors. 50 If ) is within the above range, the small particle positive active material precursor is properly distributed between the large particle positive active material precursors, so the filling rate can be excellent.

[0076] The bimodal precursor according to the present invention has an average particle size (D) of the above-mentioned range 50 By including an allele active material precursor and a microparticle cathode active material precursor having ), the relative average particle size (D) within the empty space of the allele cathode active material precursor particles 50 The small particle cathode active material precursor is positioned therein, which can further increase the packing density per unit volume. Accordingly, the capacity and lifespan characteristics of a battery containing a cathode active material prepared from a bimodal precursor according to the present invention can be excellent.

[0078] Bimodal type positive electrode active material precursor

[0079] The present invention provides a bimodal cathode active material precursor prepared by the above-described method for preparing a bimodal cathode active material.

[0080] The above-described bimodal cathode active material precursor comprises a coarse cathode active material precursor and a small particle cathode active material precursor, and the weight ratio of the coarse cathode active material precursor to the small particle cathode active material precursor may be 60:40 to 80:20. In this case, the cathode active material precursor may be appropriately distributed between the coarse cathode active material precursors, so that the filling rate may be excellent.

[0081] Average particle size (D) of the above-mentioned allotropic active material precursor and microparticle cathodic active material precursor 50 Since ) is the same as described above in the method for manufacturing a bimodal cathode active material, a detailed explanation is omitted.

[0083] positive active material

[0084] The present invention can provide a bimodal cathode active material prepared using a bimodal cathode active material precursor prepared by the above-described method for preparing a bimodal cathode active material.

[0085] The above-mentioned bimodal cathode active material can be manufactured by mixing the above-mentioned bimodal cathode active material precursor with a lithium raw material and then calcining it.

[0086] Examples of the above lithium raw materials include lithium-containing carbonates (e.g., lithium carbonate, etc.), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O), etc.), hydroxides (e.g., lithium hydroxide, etc.), nitrates (e.g., lithium nitrate (LiNO3), etc.), chlorides (e.g., lithium chloride (LiCl), etc.), and one of these alone or a mixture of two or more of these may be used.

[0087] Meanwhile, the mixing of the bimodal cathode active material precursor and the lithium raw material can be carried out as a solid-state mixture, and the mixing ratio of the bimodal cathode active material precursor and the lithium raw material can be determined within a range that satisfies the atomic fraction of each component in the bimodal cathode active material finally manufactured. For example, the bimodal cathode active material precursor and the lithium raw material can be mixed in an amount such that the molar ratio of transition metal to Li is 1:0.9 to 1:1.2, specifically 1:0.98 to 1:1.1. When the bimodal cathode active material precursor and the lithium raw material are mixed within the above range, a bimodal cathode active material exhibiting excellent capacity characteristics can be manufactured.

[0088] The above firing may be performed at 600°C to 1000°C, specifically at 700°C to 900°C, and the firing time may be 5 hours to 30 hours, specifically at 8 hours to 15 hours, but is not limited thereto.

[0090] anode

[0091] The present invention provides a positive electrode comprising the above-described bimodal positive electrode active material.

[0093] The above positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer comprises the bimodal positive electrode active material.

[0094] As the bimodal cathode active material has been described above, a detailed explanation is omitted, and only the remaining components are described in detail below.

[0096] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0098] The above positive active material layer may, together with the above bimodal positive active material, optionally include a conductive material and a binder as needed.

[0099] At this time, the bimodal type positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive electrode active material layer. Excellent capacity characteristics can be exhibited when included within the above-mentioned content range.

[0100] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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 fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0101] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0103] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described bimodal anode active material. Specifically, it may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-described bimodal anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, and then drying and rolling.

[0104] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0106] In addition, the anode may also be manufactured by casting the composition for forming the anode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto an anode current collector.

[0108] electrochemical device

[0109] The present invention provides an electrochemical device comprising the anode described above.

[0110] The above electrochemical device may specifically be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0111] Specifically, the above lithium secondary battery comprises a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is identical to the one described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0112] Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0114] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0115] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0117] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0118] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may 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; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity 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 microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0119] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0120] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0121] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, specifically 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0123] The above-mentioned negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, or by casting the composition for forming a negative electrode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0125] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0127] In addition, the above electrolytes may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used when manufacturing lithium secondary batteries, but are not limited to these.

[0128] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0129] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0131] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0133] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0135] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0136] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same may be provided.

[0137] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0138] There are no specific restrictions on the external shape of the above lithium secondary battery, but it may be a cylindrical type using a can, a prismatic type, a pouch type, or a coin type.

[0139] The above lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0140] Examples of the above-mentioned medium-to-large devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, but are not limited to these.

[0142] The present invention will be explained in more detail below through specific embodiments.

[0144] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0146] Examples and Comparative Examples

[0147] Example 1

[0148] A transition metal aqueous solution with a concentration of 2.4 M was prepared by mixing NiSO4, CoSO4, and MnSO4 in water in amounts such that the molar ratio of nickel:cobalt:manganese was 83:5:12.

[0149] The container containing the above transition metal aqueous solution, the container containing a 25 wt% concentration NaOH aqueous solution, and the container containing a 9 wt% concentration NH4OH aqueous solution were each connected to a batch reactor (10L).

[0150] Next, 4.3 L of deionized water was added to the reactor, and nitrogen gas was purged into the reactor at a rate of 2 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Then, 28.8 g of a 25 wt% aqueous NaOH solution and 170 g of a 9 wt% aqueous NH4OH solution were added, and the mixture was stirred at 60°C at a stirring speed of 850 rpm to adjust the pH inside the reactor to 11.8.

[0151] Subsequently, the above transition metal aqueous solution was introduced into the reactor at a rate of 1.5 L / hr, an NaOH aqueous solution at 0.54 L / hr, and an NH4OH aqueous solution at 0.06 L / hr, and a precipitation reaction was carried out for 49 hours under pH 11.8 to produce a complex transition metal hydroxide.

[0152] 70 mass% of the above composite transition metal hydroxide is washed with industrial water at 60°C for 6 hours, filtered under reduced pressure, and then dried in an oven at 130°C to obtain an average particle size (D 50 3.5 kg of a coarse-type positive electrode active material precursor with a thickness of 10.51 μm was obtained.

[0153] 30 mass% of the above complex transition metal hydroxide is washed with an aqueous acetic acid solution (pH 4) at 25°C for 6 hours, then washed with industrial water at 60°C for 6 hours, filtered under reduced pressure, and dried in an oven at 130°C to obtain an average particle size (D 50 1.5 kg of a small particle cathode active material precursor with a particle size of 5.33 μm was obtained.

[0154] In other words, the covalent anode active material precursor and the microparticle anode active material precursor were simultaneously manufactured by varying only the washing process.

[0156] The above average particle size (D 50 A coarse-shaped positive electrode active material precursor having a diameter of 10.51 μm and the average particle size (D 50 A bimodal cathode active material precursor was prepared by mixing a small particle cathode active material precursor with a particle size of 5.33 μm in a weight ratio of 7:3.

[0158] Example 2

[0159] A bimodal cathode active material was prepared using the same method as in Example 1, except that the microparticle cathode active material precursor was washed with an aqueous acetic acid solution (pH 4) at 25°C for 3 hours. At this time, the average particle size (D) of the microparticle cathode active material precursor 50 ) was 6.91㎛.

[0161] Comparative Example 1

[0162] (1) Preparation of an alternative positive electrode active material precursor

[0163] A transition metal aqueous solution with a concentration of 2.4 M was prepared by mixing NiSO4, CoSO4, and MnSO4 in water in amounts such that the molar ratio of nickel:cobalt:manganese was 83:5:12.

[0164] The container containing the above transition metal aqueous solution, the container containing a 25 wt% concentration NaOH aqueous solution, and the container containing a 9 wt% concentration NH4OH aqueous solution were each connected to a batch reactor (10L).

[0165] Next, 4.3 L of deionized water was added to the reactor, and nitrogen gas was purged into the reactor at a rate of 2 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Then, 28.8 g of a 25 wt% aqueous NaOH solution and 170 g of a 9 wt% aqueous NH4OH solution were added, and the mixture was stirred at 60°C at a stirring speed of 850 rpm to adjust the pH inside the reactor to 11.8.

[0166] Subsequently, the above transition metal aqueous solution was introduced into the reactor at a rate of 1.5 L / hr, NaOH aqueous solution at 0.54 L / hr, and NH4OH aqueous solution at 0.06 L / hr, and a precipitation reaction was carried out for 49 hours under pH 11.8 to produce a complex transition metal hydroxide.

[0167] The above complex transition metal hydroxide is washed with industrial water at 60°C for 10 hours, filtered under reduced pressure, and then dried in an oven at 130°C to obtain an average particle size (D 50 6.0 kg of a coarse-type positive electrode active material precursor with a thickness of 10.55 μm was obtained.

[0169] (2) Preparation of a precursor of a small particle positive electrode active material

[0170] A transition metal aqueous solution with a concentration of 2.4 M was prepared by mixing NiSO4, CoSO4, and MnSO4 in water in amounts such that the molar ratio of nickel:cobalt:manganese was 83:5:12.

[0171] The container containing the above transition metal aqueous solution, the container containing a 25 wt% concentration NaOH aqueous solution, and the container containing a 9 wt% concentration NH4OH aqueous solution were each connected to a batch reactor (10L).

[0172] Next, 4.3 L of deionized water was added to the reactor, and nitrogen gas was purged into the reactor at a rate of 2 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Subsequently, 28.8 g of a 25 wt% aqueous NaOH solution and 170 g of a 9 wt% aqueous NH4OH solution were added, and the mixture was stirred at a stirring speed of 1000 rpm at 60°C to adjust the pH inside the reactor to 11.8.

[0173] Subsequently, the above transition metal aqueous solution was introduced into the reactor at a rate of 0.9 L / hr, NaOH aqueous solution at 0.54 L / hr, and NH4OH aqueous solution at 0.06 L / hr, and a precipitation reaction was carried out for 1 hour at pH 11.8 to prepare a complex transition metal hydroxide.

[0174] The above complex transition metal hydroxide is washed with industrial water at 60°C for 12 hours, filtered under reduced pressure, and then dried in an oven at 130°C to obtain an average particle size (D 50 3.0 kg of a small particle cathode active material precursor with a particle size of 5.35 μm was obtained.

[0176] The above average particle size (D 50A coarse-shaped positive electrode active material precursor having a diameter of 10.55 μm and the average particle size (D 50 A bimodal cathode active material precursor was prepared by mixing a small particle cathode active material precursor with a particle size of 5.35 μm in a weight ratio of 7:3.

[0178] Experimental Example 1: Evaluation of Characteristics of Anode Active Material Precursor

[0180] The particle characteristics of the cathode active material precursors prepared in Examples 1 and 2 and Comparative Example 1 above were evaluated.

[0182] 1) Confirmation of the surface of the positive electrode active material precursor

[0183] The surface characteristics of the cathode active material precursors prepared in Example 1 and Comparative Example 1 were confirmed using a scanning electron microscope (SEM).

[0184] Figure 1 is an SEM image of the coarse-shaped cathode active material precursor prepared in Example 1, measured at a magnification of ×3.00k, and Figure 2 is an SEM image of the small-shaped cathode active material precursor prepared in Example 1, measured at a magnification of ×3.00k.

[0185] Figure 3 is an SEM image of the large-particle cathode active material precursor prepared in Comparative Example 1 measured at a magnification of ×3.00k, and Figure 4 is an SEM image of the small-particle cathode active material precursor prepared in Comparative Example 1 measured at a magnification of ×3.00k.

[0186] Referring to FIGS. 1 to 4, it can be seen that the large and small particle cathode active materials produced in one cycle of the manufacturing process of Example 1 have a uniform shape and particle size compared to the shape and particle size of the large and small particle cathode active materials produced in each different cycle of the manufacturing process of Comparative Example 1.

[0187] Accordingly, it can be seen that the method for manufacturing a positive electrode active material precursor of the present invention includes a washing process capable of controlling the average particle size in a single manufacturing cycle, thereby enabling the production of a bimodal positive electrode active material precursor with uniform particle shape and particle size of large and small particles in a single manufacturing cycle. Accordingly, it can be seen that the time and cost of manufacturing the bimodal positive electrode active material precursor can be reduced, thereby improving productivity.

[0189] 2) Evaluation of particle size distribution

[0190] The particle size distribution of the cathode active material precursors prepared in Examples 1 and 2 and Comparative Example 1 was evaluated. Specifically, using a particle size analyzer (LA-960, HORIBA), the D of the large and small particle cathode active material precursors of Examples 1, 2 and Comparative Example 1, respectively 10 , D 50 , D 90 The values ​​were measured, and the results are shown in Table 1 below.

[0191] In addition, Figures 5 and 6 each show graphs representing the particle size distribution of the bimodal cathode active material precursors prepared in Example 1 and Comparative Example 1.

[0192] Contrapositive active material precursor Subatomic particle positive electrode active material precursor D 10 D 50 D 90 (D 90 -D 10 ) / D 50 D 10 D 50 D 90 (D 90 -D 10 ) / D 50 Example 1 7.02 10.51 15.24 0.78 3.73 5.33 8.37 0.87 Example 2 7.06 10.59 15.31 0.78 3.92 6.91 10.55 0.96 Comparative Example 1 7.04 10.55 15.02 0.76 3.44 5.35 9.53 1.14

[0193] Referring to Table 1, it can be seen that the particle size distribution of the small particle and large particle cathode active material precursors of Examples 1 and 2, manufactured according to the manufacturing method of the present invention, is narrower or at the same level compared to the particle and large particle cathode active material precursor of Comparative Example 1. That is, it can be seen that the particle and small particle cathode active material precursors of Examples 1 and 2, manufactured in one cycle of the manufacturing process according to the manufacturing method of the present invention, have uniform size.

[0195] Experimental Example 2: Evaluation of initial capacity and capacity retention rate of a battery containing a positive electrode active material prepared using a positive electrode active material precursor

[0197] The bimodal cathode active material precursors prepared in Example 1 and Comparative Example 1, respectively, were each mixed with LiOH in a molar ratio of 1:1.05 and calcined at 780°C for 10 hours to prepare a cathode active material. After manufacturing a secondary battery using the cathode active material prepared above, the initial capacity and capacity retention rate of the secondary battery were confirmed.

[0198] At this time, the secondary battery was manufactured using the same method as below, except that a positive active material was prepared using the positive active material precursors of Example 1 and Comparative Example 1, respectively.

[0199] Specifically, a composition for forming an anode was prepared by mixing each of the anode active materials, a carbon black conductive material, and a PVdF binder in a weight ratio of 97.5:1.0:1.5 in an N-methylpyrrolidone (NMP) solvent. The anode forming composition was applied to one surface of an Al current collector, dried at 130°C, and then rolled to produce an anode. Meanwhile, a Li metal disk was used as the negative electrode active material. An electrode assembly was prepared by interposing a separator between the anode and the negative electrode prepared above, and then the assembly was placed inside a battery case. An electrolyte was then injected into the case to produce a lithium secondary battery.

[0200] The lithium secondary battery manufactured as described above was charged at 25°C with a constant current of 0.1C until the voltage reached 4.25V, and then discharged with a constant current of 0.1C until the voltage reached 3.0V to measure the initial charge and discharge capacities.

[0201] The above charging and discharging behavior was defined as one cycle, and this cycle was repeated 30 times to measure the capacity of the lithium secondary battery. In particular, the ratio of the capacity of the 30th cycle to the capacity of the 1st cycle was defined as the capacity retention rate and is shown in Table 2 below.

[0202] Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Capacity retention rate (%) Example 1 217.7 192.1 96.4 Comparative Example 1 216.8 191.5 96.5

[0203] Referring to Table 2, it can be confirmed that the initial charge / discharge capacity and capacity retention rate of the secondary battery prepared using the positive active material precursor of Example 1 are at the same level as Comparative Example 1, in which large-particle and small-particle precursors with the same composition as Example 1 were prepared through different manufacturing processes in different reactors and then mixed.

[0204] Consequently, in the case of Comparative Example 1, since the small particle size precursor and the large particle size precursor must be manufactured through different manufacturing cycles with different reaction times, there is a problem of increased manufacturing time and manufacturing cost, whereas in the case of Example 1, the average particle size (D 50 Including a washing process capable of controlling ), average particle size (D 50 Since different allotropic active material precursors and microparticle cathodic active material precursors can be manufactured in a single manufacturing cycle, it can be seen that the productivity of the bimodal cathodic active material precursor can be improved according to the present invention.

Claims

Claim 1 (A) a step of forming a transition metal hydroxide through a precipitation reaction using an aqueous transition metal solution, an ammonium ion-containing solution, and a basic aqueous solution; and (B) a step of first washing some of the transition metal hydroxides with a neutral solution to obtain a coarse-type cathode active material precursor, and second washing the remaining transition metal hydroxides with a solution having a pH of 3 to 5 to obtain an average particle size (D) greater than that of the coarse-type cathode active material precursor. 50 A method for manufacturing a bimodal type positive electrode active material precursor comprising the step of obtaining a small particle positive electrode active material precursor. Claim 2 A method for manufacturing a bimodal cathode active material precursor according to claim 1, wherein the partial transition metal hydroxide is 60% to 80% by mass of the total mass of the transition metal hydroxide, and the remaining transition metal hydroxide is 20% to 40% by mass of the total mass of the transition metal hydroxide. Claim 3 A method for manufacturing a bimodal type cathode active material precursor according to claim 1, wherein the neutral solution is one or more selected from industrial water, distilled water, deionized water, methanol, ethanol, and propanol. Claim 4 A method for manufacturing a bimodal type positive electrode active material precursor according to claim 1, wherein the first washing is performed at 40°C to 80°C. Claim 5 A method for manufacturing a bimodal anode active material precursor according to claim 1, wherein the first washing is performed for 1 to 10 hours. Claim 6 A method for manufacturing a bimodal type positive electrode active material precursor according to claim 1, wherein the solution having a pH of 3 to 5 is one or more selected from an aqueous acetic acid solution, an aqueous phosphoric acid solution, an aqueous sulfuric acid solution, and an aqueous nitric acid solution. Claim 7 A method for manufacturing a bimodal type positive electrode active material precursor according to claim 1, wherein the second washing is performed at 20°C to 30°C. Claim 8 A method for manufacturing a bimodal type positive electrode active material precursor according to claim 1, wherein the second washing is performed for 1 to 10 hours. Claim 9 In claim 1, the opposing positive electrode active material precursor has an average particle size (D 50 A method for manufacturing a bimodal type positive electrode active material precursor having a thickness of 8㎛ to 12㎛. Claim 10 In claim 1, the small particle anode active material precursor has an average particle size (D 50 A method for manufacturing a bimodal type positive electrode active material precursor having a thickness of 3㎛ to 7㎛.

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