Method for manufacturing a positive electrode active material precursor

Abstract

An object of the present invention is to provide a method for reproducibly producing a cathode active material precursor having a narrow particle size distribution.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0116495 dated September 15, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a method for producing a positive electrode active material precursor. [Background technology]

[0003] As the development and demand for mobile device technologies increase, the demand for rechargeable batteries as an energy source is rapidly growing. Among these rechargeable batteries, lithium-ion batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Lithium transition metal oxides are used as the positive electrode active material for lithium secondary batteries, and among them, lithium cobalt oxide (LiCoO2), which has a high operating voltage and excellent capacity characteristics, is mainly used. However, LiCoO2 has very poor thermal properties due to the destabilization of its crystal structure by delithiation, and it is also expensive, so there are limitations to its large-scale use as a power source in fields such as electric vehicles.

[0005] As alternatives to LiCoO2, materials such as lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4, etc.), and lithium nickel oxide (LiNiO2, etc.) have been developed. Among these, research and development on lithium nickel oxide is particularly active because it has a high reversible capacity of approximately 200 mAh / g, making it easier to realize high-capacity batteries. However, LiNiO2 has inferior thermal stability compared to LiCoO2, and if an internal short circuit occurs due to external pressure while charged, the positive electrode active material itself decomposes, causing the battery to rupture and catch fire.

[0006] Therefore, as a method to maintain the excellent reversible capacitance of LiNiO2 and improve its low thermal stability, LiNiO2 is modified by substituting some of the nickel with cobalt. 1-α Co α A nickel-cobalt-manganese lithium composite metal oxide (hereinafter referred to as "NCM lithium oxide") has been developed, in which O2 (α=0.1~0.3) or nickel is partially replaced with Mn and Co. In addition, lithium transition metal oxides with a concentration gradient of metal composition have been proposed to have excellent power characteristics and to solve the problem of stability due to the leaching of metal elements.

[0007] Typical methods for producing such positive electrode active materials include a method in which a positive electrode active material precursor is produced using a Continuous Stirring Tank Reactor (CSTR), followed by calcination with lithium raw materials to produce the positive electrode active material, and a method in which a positive electrode active material precursor is produced using a Batch Reactor, followed by calcination with lithium raw materials to produce the positive electrode active material. A Continuous Stirring Tank Reactor is a method in which raw materials are introduced, co-precipitated, and the precursor formed from particles is discharged, while a Batch Reactor is a method in which raw materials are introduced according to the volume of the reactor for a predetermined time, reacted, and then the precursor is discharged after the reaction is complete.

[0008] Generally, the productivity of cathode active material precursors produced using a continuous stirring reactor can be improved by simultaneously adding raw materials, allowing them to co-precipitate, and discharging the precursors. However, because the addition of raw materials and the discharge of products occur simultaneously and continuously, there may be deviations in the residence time and reaction time of the cathode active material precursors generated in the reactor. This results in the problem of non-uniform particle size and particle size distribution of the generated cathode active material precursors.

[0009] Furthermore, while cathode active material precursors produced using batch reactors have uniform particle size and particle size distribution, when precursors are produced using batch reactors, the precursor seed formation step and the precursor particle growth step occur simultaneously within the reactor. Therefore, it is difficult to reproduce or predict the same particle size distribution and average particle size for each reaction. In addition, during mass production using batch reactors, the larger the reactor, the faster the stirrer must rotate, which presents equipment disadvantages. Thus, the application of inadequate equipment increases the likelihood of variations in seed quality, leading to problems with quality reproducibility and ultimately causing problems with product quality. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Korean Published Patent No. 2012-0049227 [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention aims to provide a method for reproducibly producing a cathode active material precursor with a narrow particle size distribution. [Means for solving the problem]

[0012] The present invention provides a method for producing a positive electrode active material precursor using a reaction apparatus in which a reactor and a continuous grinder are connected, comprising the steps of (S1) introducing a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution into a reactor to form a positive electrode active material precursor seed and discharging it, and (S2) introducing the positive electrode active material precursor seed discharged from the reactor into a continuous grinder, discharging it, and reintroducing it into the reactor, wherein steps (S1) and (S2) are performed simultaneously, thereby providing a method for producing a positive electrode active material precursor. [Effects of the Invention]

[0013] According to the present invention, the precursor of the positive electrode active material can be manufactured so as to have a uniform size and a narrow particle size distribution.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram showing a reaction apparatus used in the present invention. [Figure 2] It is a diagram showing the SEM image of Example 1. [Figure 3] It is a diagram showing the SEM image of Comparative Example 1. [Figure 4] It is a diagram showing the SEM image of Comparative Example 2.

Modes for Carrying Out the Invention

[0015] Hereinafter, in order to contribute to the understanding of the present invention, the present invention will be described in more detail.

[0016] In the description and claims of the present invention, terms and words used should not be construed as being limited to ordinary or dictionary meanings. The inventors should interpret them in accordance with the meaning and concept consistent with the technical idea of the present invention, in accordance with the principle that they can appropriately define the concept of terms in order to explain their invention in the best way.

[0017] In this specification, D5, D 50 and D 95 each can be defined as the particle diameters corresponding to 5%, 50% and 95% of the volume cumulative amount in the particle size distribution curve (graph curve of the particle size distribution degree). The above D5, D 50 and D 95 can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle diameters in the range from several nm to about several mm, and can obtain highly reproducible and highly resolvable results. In this specification, the average particle diameter means the above D 50 .

[0018] The present invention provides a method for producing a positive electrode active material precursor, comprising the steps of (S1) introducing a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution into a reactor to form a positive electrode active material precursor seed and then discharging it, using a reaction apparatus in which a reactor and a continuous grinder are connected, and (S2) introducing the positive electrode active material precursor seed discharged from the reactor into a continuous grinder, discharging it, and then reintroducing it into the reactor, wherein steps (S1) and (S2) are performed simultaneously.

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

[0020] Step (S1) In step (S1), a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution is introduced into the reactor to form a positive electrode active material precursor seed, which is then discharged.

[0021] Figure 1 is a schematic diagram showing a reactor that can be used in a method for producing a positive electrode active material precursor according to one embodiment of the present invention. Referring to Figure 1, the production method of the present invention uses a reactor in which a reactor 100 and a continuous grinder 200 are connected.

[0022] In step (S1), a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution is added to the reactor 100, and a positive electrode active material precursor seed is formed in the reactor 100.

[0023] The reactor 100 can be used regardless of the type of reactor, such as a batch-type reactor, a continuously stirred tank reactor (CSTR), or a continuously filtered tank reactor (CFTR). More specifically, a reactor equipped with a filtration device inside, such as a continuously filtered tank reactor (CFTR), may be used.

[0024] The positive electrode active material precursor seed formed in step (S1) may refer to the seed formed when a transition metal aqueous solution, ammonium cation, and basic aqueous solution are added, a coprecipitation reaction begins, and nuclei of primary particle-shaped positive electrode active material precursor particles are generated, and these primary particle-shaped nuclei aggregate to form the seed. As will be described later, when these are passed through a continuous grinder and then put back into the reactor, they can aggregate to form the core of the positive electrode active material precursor.

[0025] The transition metal-containing solution may contain cations of one or more metals selected from nickel (Ni), manganese (Mn), cobalt (Co), tungsten (W), molybdenum (Mo), chromium (Cr), and aluminum (Al). The metal ion-containing solution may contain acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or oxyhydroxides of the metal, and is not particularly limited as long as it is soluble in water.

[0026] For example, the cobalt (Co) can be contained in Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, or Co(SO4)2·7H2O, and one or more of these can be used in mixtures. The nickel (Ni) can be contained in Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salts, or nickel halides, and one or more of these can be used in mixtures. Furthermore, the manganese (Mn) may include manganese oxides such as Mn2O3, MnO2, and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate salts, manganese citrate, and manganese fatty acid salts; oxyhydroxides, and manganese chloride, and one or more of these may be used as a mixture.

[0027] On the other hand, if the final precursor produced further contains other secondary metal elements (M) in addition to nickel (Ni), manganese (Mn), cobalt (Co), tungsten (W), molybdenum (Mo), chromium (Cr), and aluminum (Al) (for example, M is one or more elements selected from Zr, Ti, Mg, Ta, and Nb), the secondary metal element-containing raw material may be selectively added during the production of the metal ion-containing solution. Examples of the secondary metal element-containing raw material include acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or oxyhydroxides containing the secondary metal element, and one or more of these can be used individually or in mixtures of two or more. For example, if the secondary metal element is Zr, zirconium oxide can be used.

[0028] The ammonium ion-containing solution may contain one or more selected from NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3. As the solvent, water or a mixture of water and an organic solvent that is homogeneously miscible with water (specifically, an alcohol) may be used.

[0029] The basic aqueous solution may contain one or more selected from alkali metal hydrates, alkali metal hydroxides, alkaline earth metal hydrates, and alkaline earth metal hydroxides. For example, the basic aqueous solution may contain NaOH, KOH, or Ca(OH)2, and as the solvent, water or a mixture of water and an organic solvent that is homogeneously miscible with water (specifically, an alcohol) may be used.

[0030] The amount of the ammonium ion-containing solution can be 4 to 100 parts by weight, preferably 4 to 30 parts by weight, per 100 parts by weight of the transition metal-containing solution.

[0031] On the other hand, step (S1) can be carried out at a pH of 10.5 to 12.5, and a basic aqueous solution can be used to adjust the pH of the reaction solution, and in the step of forming the positive electrode active material precursor seed, it can be used to maintain the pH of the reaction solution at 10.5 to 12.5, preferably at 11 to 12. If the content of the ammonium ion-containing solution added in step (S1) is within the above range, or if the pH of the reaction solution is within the above range, it can be advantageous for adjusting the seed size.

[0032] Step (S1) can be carried out under temperature conditions of 10°C to 80°C, specifically, under temperature conditions of 40°C to 60°C. When the temperature conditions are within the above range, the introduced solution is prevented from volatilizing, the metal ions can be sufficiently dissolved, and the positive electrode active material precursor seed can be properly formed.

[0033] Step (S2) The positive electrode active material precursor seeds discharged from the reactor are fed into a continuous grinder, then discharged and reintroduced into the reactor. In step (S2), the positive electrode active material precursor seeds that have passed through the continuous grinder and been reintroduced into the reactor can grow into positive electrode active material precursor particles within the reactor.

[0034] In the present invention, the rate at which the positive electrode active material precursor seed is discharged from the reactor 100 in step (S1) and fed into the continuous pulverizer 200 in step (S2) can be [Reactor 100 capacity L × 6] / [hr] or more, specifically, it can be [Reactor 100 capacity L × 8] / [hr] or more, [Reactor 100 capacity L × 10] / [hr] or more, or [Reactor 100 capacity L × 12] / [hr] or more.

[0035] Within the aforementioned speed range, the positive electrode active material precursor seeds are transferred from the reactor 100 to the continuous grinder 200 at an appropriate speed and quantity, effectively grinding the seeds to a smaller size and uniformly adjusting the particle size.

[0036] The positive electrode active material precursor seed formed in step (S1) is not concentrated in the reactor 100, but is pulverized in the continuous pulverizer 200 in step (S2) and then reintroduced into the reactor 100.

[0037] If the reaction continues after the reaction solution is added to the reactor, particle aggregation will occur, which tends to be particularly severe until the reaction rate in the reactor reaches 30%. In this invention, before a large amount of reaction occurs in reactor 100 and particle aggregation occurs, the positive electrode active material precursor seed is introduced into a continuous pulverizer and pulverized to a small size to suppress aggregation and control the particle size uniformly.

[0038] Therefore, in the present invention, the positive electrode active material precursor seeds that are reintroduced into the reactor 100 through the above process have a narrow particle size distribution and uniform characteristics. Consequently, because the particle size is small and the contact area of ​​the seeds is large, not only is the efficiency of positive electrode active material precursor production increased, but as a result, a positive electrode active material precursor with uniform particle size can be provided.

[0039] Unlike the present invention, when producing a positive electrode active material precursor using equipment that does not have a continuous grinder, a large number of particles that are not spherical, such as those with a rounded or oval shape, are found in the final positive electrode active material precursor. These particles must be removed to improve the sphericity of the precursor, and this can also cause a decrease in the electrode density of the positive electrode in a secondary battery.

[0040] The daruma-shaped particles are formed when seeds grow together due to low stirring force in the early stages of the precursor production reaction. To resolve this, it is necessary to increase the stirring force of the reactor or maintain a low rate of raw material input. However, increasing the stirring force of the reactor has clear equipment limitations depending on the size of the reactor.

[0041] The continuous grinder 200 used in the present invention can complement the low stirring force of the reactor, and in this case, it is not necessary to reduce the raw material input rate into the reactor. In the continuous grinder 200, it can not only suppress the phenomenon of seeds sticking to each other, but also play a role in continuously separating the already stuck seeds. Thereby, D 90 、D 95 a cathode active material precursor having a low value can be produced.

[0042] In the present invention, the step (S2) can be carried out within 0.5 to 24 hours, specifically, within 2 hours or more, 4 hours or more, 20 hours or less, 16 hours or less, and 10 hours or less. After continuously inputting and discharging the cathode active material precursor seeds into the continuous grinder 200 and then re-inputting them into the reactor 100 during the above time, it can be advantageous for uniformly adjusting the particle size of the cathode active material precursor seeds.

[0043] In the step (S1), the rotation speed of the continuous grinder 200 can be 500 to 4500 rpm, and preferably, it can be 3000 to 3500 rpm.

[0044] Since the above rpm depends on the characteristics of the machine, it is not absolute, but the size of the seeds can be adjusted by adjusting the rpm. By adjusting the rpm, the average particle size (D 50 ) of the cathode active material precursor seeds can be adjusted to 1.0 to 5.0 μm.

[0045] Specifically, in the present invention, the average particle size (D 50 ) of the cathode active material precursor seeds discharged from the continuous grinder 200 can be 1.0 to 5.0 μm, or 1.3 to 3. μm.

[0046] When the rotational speed of the continuous grinder 200 is within the aforementioned range, or when the seed size is within the aforementioned range, the particle size of the formed positive electrode active material precursor seeds can be uniform. This makes it possible to reproducibly produce positive electrode active material precursors with a narrow particle size distribution, and has the advantage of improving the sphericity and uniformity of the particles.

[0047] In the present invention, steps (S1) and (S2) are performed simultaneously. That is, the reaction solution is introduced into the reactor 100 to form positive electrode active material precursor seeds, and at the same time, a portion of the positive electrode active material precursor seeds are discharged from the reactor 100, pulverized in a continuous pulverizer 200, discharged, and reintroduced into the reactor 100. These steps are performed simultaneously and continuously, which helps to concentrate the positive electrode active material precursor seeds in the reactor 100 and suppress the increase in particle size.

[0048] Step (S3) After step (S2), the process may further include step (S3) of stopping the operation of the continuous grinder and growing the positive electrode active material precursor particles in the reactor.

[0049] This is a step in which a positive electrode active material precursor is produced using a positive electrode active material precursor seed of uniform particle size obtained in the reactor 100 by steps (S1) and (S2), and in order to prevent the seed from being continuously discharged to the continuous grinder 200 and ground, the operation of the continuous grinder 200 is stopped after steps (S1) and (S2) have been sufficiently performed, and the positive electrode active material precursor particles are allowed to grow.

[0050] Step (S3) can be carried out under temperature conditions of 10°C to 80°C, for example, 50°C. When the temperature conditions are within this range, the metal ions can be sufficiently dissolved while preventing the introduced solution from volatilizing, and a positive electrode active material precursor with a narrow particle distribution and uniformity can be formed.

[0051] The positive electrode active material precursor of the present invention produced by step (S3) above may have a span value of 2.5 or less, specifically 1.5 or less, or 1.0 or less. In other words, according to the present invention, a positive electrode active material precursor with a uniform particle size can be produced.

[0052] Furthermore, the present invention provides a method for producing a positive electrode active material, which includes the step of mixing the positive electrode active material precursor produced as described above with a lithium-containing raw material and then firing it.

[0053] As the lithium-containing raw material, for example, lithium carbonate (Li2CO3) or lithium hydroxide (LiOH) can be used, and the positive electrode active material precursor and the lithium-containing raw material can be mixed in a molar ratio of 1:1 to 1:1.15. When the molar ratio of the positive electrode active material precursor and the lithium-containing raw material is within the above range, the volume of the positive electrode active material can be excellent, and separation of positive electrode active material particles can be prevented.

[0054] The firing can be carried out at a temperature of 700°C to 1000°C. When the firing temperature is within this range, no raw material remains in the particles, improving the high-temperature stability of the battery, and resulting in excellent volume density, crystallinity, and structural stability. Furthermore, the volume capacity of the battery can be improved. On the other hand, considering the control of particle size, capacity, stability, and reduction of lithium-containing by-products of the manufactured positive electrode active material, the firing temperature can more preferably be 750°C to 850°C.

[0055] The aforementioned firing can be carried out for 5 to 35 hours. When the firing time is within this range, a highly crystalline positive electrode active material can be obtained, with an appropriate particle size and excellent production efficiency.

[0056] Furthermore, the present invention can provide a positive electrode and a lithium secondary battery containing a positive electrode active material manufactured as described above.

[0057] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, which contains the positive electrode active material.

[0058] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric.

[0059] Furthermore, the positive electrode active material layer may include a conductive material and a binder in addition to the positive electrode active material described above.

[0060] Here, the conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal 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. Of these, one or more can be used. The conductive material can usually be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0061] Furthermore, the binder plays a role in improving adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0062] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material described above. Specifically, it can be manufactured by applying the positive electrode active material and, selectively, a composition for forming a positive electrode active material layer containing a binder and a conductive material onto a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0063] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these can be used alone or in a mixture of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode, taking into consideration the coating thickness of the slurry and the manufacturing yield.

[0064] Furthermore, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0065] Furthermore, the present invention can be used to manufacture an electrochemical element including the positive electrode. Specifically, the electrochemical element can be a battery, a capacitor, and more specifically, a lithium secondary battery.

[0066] Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. The lithium secondary battery may also selectively further include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0067] In the lithium secondary battery described above, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0068] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0069] The negative electrode active material layer selectively includes a binder and a conductive material along with the negative electrode active material. The negative electrode active material layer can be manufactured, for example, by coating a negative electrode forming composition containing the negative electrode active material and selectively a binder and a conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0070] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical 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.

[0071] Furthermore, the binder and conductive material are as described above for the positive electrode.

[0072] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity are particularly preferred. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof can be used. Ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0073] Furthermore, the electrolytes 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 lithium secondary batteries.

[0074] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0075] The organic solvent can be used without particular limitations as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte can exhibit excellent performance by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0076] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The lithium salt is preferably used within a concentration range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0077] In addition to the components of the electrolyte, the electrolyte may also contain one or more additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. These additives may include, for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0078] As described above, lithium secondary batteries containing the positive electrode active material according to the present invention exhibit excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making them useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0079] Therefore, the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0080] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0081] Examples The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and do not limit the scope of the present invention to these examples alone.

[0082] Example 1 NiSO4, CoSO4, and MnSO4 were added to distilled water in amounts that resulted in a molar ratio of Ni:Co:Mn of (88.5):(3.5):(8.0) to prepare a 2.4 M solution. In addition, an 8.0 M concentration NaOH aqueous solution and a 5.1 M concentration NH4OH aqueous solution were prepared.

[0083] As shown in Figure 1, a container filled with the transition metal-containing solution and containers containing a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were each connected to a 100 L reactor.

[0084] After adding 28.6 L of deionized water, 0.035 mol / L of the NaOH aqueous solution, and 0.22 mol / L of the NH4OH aqueous solution to the reactor, nitrogen gas was purged into the reactor to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor.

[0085] Subsequently, the metal solution was added to the reactor at a rate of 7.26 L / hr, the NaOH aqueous solution at a rate of 4.39 L / hr, and the NH4OH aqueous solution at a rate of 1.03 L / hr, while the precipitation reaction was carried out at a pH of 12.5 or lower for 10 minutes to form nickel-cobalt-manganese hydroxide particle seeds. At the same time, the particle seeds formed in the reactor were transferred at a rate of 1000 L / hr ([reactor capacity × 10] / [hr]) using a continuous grinder to maintain the particle growth reaction and suppress or break particle aggregation, and the reactants were then sent back to the 100 L reactor. This process was carried out for 8 hours. Next, when the 100 L reactor was full, the filtration system located inside the reactor was activated to continuously discharge the solvent that had completed the reaction to the outside of the reactor, while the transition metal-containing solution, NaOH aqueous solution, and NH4OH aqueous solution were continuously added, and the reaction was maintained for 32 hours. Here, the reaction conditions were such that the pH was controlled by adding NaOH in conjunction with a pH sensor while gradually decreasing the stirring speed, and the metal solution was added at a rate of 7.26 L / hr, the NaOH aqueous solution at a rate of 4.39 L / hr, and the NH4OH aqueous solution at a rate of 1.03 L / hr while coprecipitation was carried out to produce a precursor containing nickel-cobalt-manganese composite metal hydroxide particles.

[0086] The molar ratio of Ni:Co:Mn in the entire positive electrode active material precursor particles was 88.5:3.5:8, and its particle size was 3.5 μm.

[0087] Comparative Example 1 Nickel-cobalt-manganese composite metal hydroxide precursors were produced using a continuous stirred tank reactor (CSTR).

[0088] NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was (88.5):(3.5):(8.0) to prepare a 2.4 M transition metal-containing solution. The metal solution was added to a continuous stirring tank reactor at a rate of 7.26 L / hr, the NaOH aqueous solution at a rate of 4.39 L / hr, and the NH4OH aqueous solution at a rate of 1.03 L / hr. The reactor temperature was set to 50°C, and the nickel-cobalt-manganese composite metal hydroxide was precipitated while stirring at a speed of 350 rpm. The resulting nickel-cobalt-manganese composite metal hydroxide particles were separated, washed with water, and dried in an oven at 120°C to secure the precursor.

[0089] Comparative Example 2 A nickel-cobalt-manganese composite metal hydroxide precursor was produced in the same manner as in Example 1, except that the step of transferring the particle seed at a rate of 1000 L / hr ([reactor capacity × 10] / [hr]) using a continuous grinder was omitted.

[0090] Experimental Example 1: SEM Observation The cathode active material precursors produced in Example 1, Comparative Example 1, and Comparative Example 2 were photographed with a scanning electron microscope to confirm the particle characteristics of the precursors.

[0091] Figure 2 is an SEM image of Example 1, Figure 3 is an SEM image of Comparative Example 1, and Figure 4 is an SEM image of Comparative Example 2. As shown in Figure 2, in the case of precursor particles formed by suppression or decoupling of particle nuclei using the continuous grinder of Example 1, it was confirmed that the particles had a spherical shape and that the particle size was formed relatively uniformly.

[0092] On the other hand, as can be seen from Figure 3, in the case of the precursor produced using a continuous reactor, as in Comparative Example 1, it was confirmed that a mixture of large and small particles was present. This is because, as in Comparative Example 1, when a continuous process is used, the input and discharge of the reaction materials occur simultaneously, resulting in non-uniform precursor particle size and particle size due to deviations in the residence time and reaction time of the reaction materials.

[0093] On the other hand, as can be seen from Figure 4, in the case of precursor particles produced by a continuous concentration process in which the solid content increases steadily with reaction time, as in Comparative Example 2, the solid content and particle growth are kept constant, resulting in the formation of relatively uniform particle sizes for the precursor, but it was found that the sphericity is inferior.

[0094] Experimental Example 2: Span Values Using a particle size analyzer (S3500, Microtrac), the D5 and D5 of the cathode active material precursors formed in the examples and comparative examples were analyzed. 50 , D 95 The values ​​were measured, and the span value of the positive electrode active material precursor was calculated using Equation 1 below, as shown in Table 1.

[0095] [Formula 1] Span = (D 95 -D5) / D 50

[0096] [Table 1]

[0097] As shown above, in Example 1 produced by the present invention, aggregation of seed particles is suppressed, D 95 The values ​​were shown to be low, and we confirmed that the span values ​​were also lower compared to the comparative example. [Explanation of Symbols]

[0098] 100 reactors 200 Continuous-type pulverizer

Claims

1. A method for producing a positive electrode active material precursor using a reactor and a continuous grinder connected together, (S1) A reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution is introduced into the reactor to form a positive electrode active material precursor seed, and then discharged. (S2) The step of feeding the positive electrode active material precursor seed discharged from the reactor into a continuous grinder, then discharging it and reintroducing it into the reactor, Step (S1) and Step (S2) are performed simultaneously in a method for producing a cathode active material precursor.

2. After step (S2), (S3) The method for producing a positive electrode active material precursor according to claim 1, further comprising the step of stopping the operation of the continuous grinding machine and growing positive electrode active material precursor particles in the reactor.

3. The method for producing a positive electrode active material precursor according to claim 1, wherein step (S2) is performed for 0.5 to 24 hours.

4. The method for producing a positive electrode active material precursor according to claim 1, wherein the rotational speed of the continuous grinder is 500 to 4500 rpm.

5. The method for producing a positive electrode active material precursor according to claim 1, wherein the transition metal-containing solution contains a cation of one or more metals selected from nickel, manganese, cobalt, tungsten, molybdenum, chromium, and aluminum.

6. The ammonium ion-containing solution contains NH ４ OH, (NH ４ ) ２ SO ４ , NH ４ NO ３ , NH ４ Cl, CH ３ COONH ４ and NH ４ CO ３ The method for producing a positive electrode active material precursor according to claim 1, comprising one or more selected therefrom.

7. The method for producing a positive electrode active material precursor according to claim 1, wherein the basic aqueous solution contains one or more selected from alkali metal hydrates, alkali metal hydroxides, alkaline earth metal hydrates, and alkaline earth metal hydroxides.

8. The method for producing a positive electrode active material precursor according to claim 1, wherein the positive electrode active material precursor has a span value of 2.5 or less according to the following formula 1. [Formula 1] Span = (D ９５ -D ５ ) / D ５０

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