Method for Producing 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 the benefit of priority based on Korean Patent Application No. 10-2022-0116495 filed on September 15, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference as part of this specification.

[0002] The present invention relates to a method for manufacturing a cathode active material precursor.

Background Art

[0003] As the development and demand for technologies related to mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density, a high voltage, a long cycle life, and a low self-discharge rate have been commercialized and widely used.

[0004] As the cathode active material of a lithium secondary battery, a lithium transition metal oxide is used. Among them, lithium cobalt oxide of LiCoO2, which has a high operating voltage and excellent capacity characteristics, is mainly used. However, since LiCoO2 has very poor thermal characteristics due to the destabilization of the crystal structure by delithiation and is expensive, there is a limit to its large-scale use as a power source in fields such as electric vehicles.

[0005] As materials to be used instead of LiCoO2, lithium manganese oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), or lithium nickel oxides (such as LiNiO2) have been developed. Among them, research and development on lithium nickel oxides, which have a high reversible capacity of about 200 mAh / g and thus can easily realize a large-capacity battery, have been more actively conducted. However, LiNiO2 has inferior thermal stability compared to LiCoO2, and when an internal short circuit occurs due to external pressure or the like in the charged state, the cathode active material itself decomposes, causing problems such as battery rupture and ignition.

[0006] Therefore, as a method for maintaining the excellent reversible capacity of LiNiO₂ and improving its low thermal stability, a part of nickel is replaced with cobalt to form LiNi 1-α Co α O₂ (α = 0.1 - 0.3), or nickel cobalt manganese-based lithium composite metal oxide in which a part of nickel is replaced with Mn and Co (hereinafter referred to as "NCM-based lithium oxide") has been developed. In addition, in order to solve the problem of stability due to excellent output characteristics and elution of metal elements, etc., a lithium transition metal oxide having a concentration gradient of metal composition has also been proposed.

[0007] As a method for manufacturing such a cathode active material, typically, after manufacturing a cathode active material precursor using a Continuous Stirring Tank Reactor (CSTR), firing with a lithium raw material substance to manufacture the cathode active material, and a method of manufacturing a cathode active material precursor using a Batch Reactor and then firing with a lithium raw material substance can be mentioned. The continuous stirring reactor is a method of charging raw materials to coprecipitate and discharging the precursor formed by particles, and the batch type is a method of charging raw materials according to the volume of the reactor for a predetermined time to react and discharging the precursor after the reaction ends.

[0008] Generally, the cathode active material precursor produced using a continuous stirring reactor can improve the productivity of the cathode active material precursor by charging raw materials to coprecipitate and discharging the precursor at the same time. However, since the charging of raw materials and the discharging of products are continuously carried out at the same time, there may be a deviation in the residence time and reaction time of the cathode active material precursor generated in the reactor in the reactor. Therefore, there is a problem that the particle size and particle size distribution of the generated cathode active material precursor are non-uniform.

[0009] In addition, the precursor of the positive electrode active material produced using a batch reactor has a uniform particle size and particle diameter. However, when producing the precursor using a batch reactor, since the formation step of the precursor seed and the growth step of the precursor particles are carried out simultaneously in the reactor, it is difficult to reproduce or predict the same particle size distribution and average particle diameter for each reaction. Also, during mass production using a batch reactor, the larger the reactor, the higher the rotation speed of the stirrer must be, which is inconvenient in terms of equipment. Thus, there is a high possibility of occurrence of quality variations of the seeds due to the application of incomplete equipment, problems occur in terms of quality reproducibility, and ultimately, problems are also caused in the quality of the product.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide a method for reproducibly producing a positive electrode active material precursor having a narrow particle size distribution.

Means for Solving the Problems

[0012] The present invention is 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: (S1) introducing a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution into the reactor to form and discharge a positive electrode active material precursor seed; 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 carried out simultaneously, and provides 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 to have a uniform size and a narrow particle size distribution.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

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 limited to their 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, following 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 can each 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) of the particles. 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 results with high reproducibility and high resolution. In this specification, the average particle diameter means the above D 50 .

[0018] The method for producing a positive electrode active material precursor of the present invention uses a reaction apparatus in which a reactor and a continuous grinder are connected, and includes: (S1) a step of charging a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution into the reactor to form and discharge a positive electrode active material precursor seed; and (S2) a step of charging the positive electrode active material precursor seed discharged from the reactor into the continuous grinder, discharging it, and recharging it into the reactor. The steps (S1) and (S2) are characterized by being performed simultaneously.

[0019] Hereinafter, the present invention will be described in detail.

[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 charged into the reactor to form and discharge a positive electrode active material precursor seed.

[0021] FIG. 1 is a schematic diagram showing a reaction apparatus that can be used in the method for producing a positive electrode active material precursor according to an embodiment of the present invention. Referring to FIG. 1, the production method of the present invention uses a reaction apparatus 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 charged into 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 continuous stirred tank reactor (CSTR), or a continuous filtered tank reactor (CFTR). More specifically, a reactor equipped with a filtration device inside the reactor, for example, a continuous filtered tank reactor (CFTR), may be used.

[0024] The cathode active material precursor seeds formed in step (S1) may mean seeds formed by introducing a transition metal aqueous solution, an ammonium cation, and a basic aqueous solution, starting a coprecipitation reaction to generate nuclei of cathode active material precursor particles in the form of primary particles, and aggregating the nuclei in the form of primary particles. As will be described later, when these pass through a continuous mill and are then introduced into a reactor, they can aggregate to form the core of the cathode 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, etc., and any one or a mixture of two or more of these can be used. Also, 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, nickel fatty acid salts, or nickel halides, etc., and any one or a mixture of two or more of these can be used. Further, the manganese (Mn) can be contained in 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, etc., and any one or a mixture of two or more of these can be used.

[0027] On the one hand, when the finally produced precursor further contains other second 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 second metal element-containing raw material substance may be selectively added further during the production of the metal ion-containing solution. Examples of the second metal element-containing raw material substance include acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides or oxyhydroxides containing the second metal element, and one of these alone or a mixture of two or more thereof can be used. As an example, when the second metal element is Zr, zirconium oxide or the like can be used.

[0028] The ammonium ion-containing solution can 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 (specifically, alcohol or the like) that can be uniformly mixed with water can be used.

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

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

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

[0032] The step (S1) can be carried out under temperature conditions of 10°C to 80°C. Specifically, it can be carried out under temperature conditions of 40°C to 60°C. When the temperature conditions are within the above range, it can prevent the introduced solution from volatilizing, and the metal ions can be sufficiently dissolved, and the cathode active material precursor seed can be properly formed.

[0033] Step (S2) After the cathode active material precursor seed discharged from the reactor is put into a continuous grinder and then discharged, it is re-introduced into the reactor. Here, by step (S2), the cathode active material precursor seed re-introduced into the reactor after passing through the continuous grinder can grow into cathode active material precursor particles in the reactor.

[0034] In the present invention, the speed at which the cathode active material precursor seed is discharged from the reactor 100 in step (S1) and introduced into the continuous grinder 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, [reactor 100 capacity L×12] / [hr] or more.

[0035] Within the speed range, the cathode active material precursor seed is transferred from the reactor 100 to the continuous grinder 200 at an appropriate speed and amount, and the seed can be ground to a small size, and the effect of uniformly adjusting the particle size can be fully achieved.

[0036] The positive electrode active material precursor seeds formed in the step (S1) are not concentrated in the reactor 100, and after being pulverized by the continuous pulverizer 200 in step (S2), they are re-introduced into the reactor 100.

[0037] After introducing a reaction solution into the reactor and continuously carrying out the reaction, aggregation of particles occurs, and this particularly tends to occur severely until the reaction progress rate in the reactor reaches 30%. In the present invention, before a large amount of reaction occurs in the reactor 100 and particle aggregation occurs, the positive electrode active material precursor seeds are introduced into the continuous pulverizer and pulverized to a small size to suppress aggregation and uniformly control the particle size.

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

[0039] Unlike the present invention, when manufacturing a positive electrode active material precursor using a device not equipped with a continuous pulverizer, many particles having a form far from a spherical shape, for example, particles having a dumpling-like shape, are found in the final positive electrode active material precursor, and these must be removed in order to improve the sphericity of the precursor, which also causes a decrease in the electrode density of the positive electrode in the secondary battery.

[0040] The dumpling-like particles are formed by seeds sticking to each other due to a low stirring force at the initial stage of the precursor production reaction. To solve this, it is necessary to increase the stirring force of the reactor or maintain a low raw material input rate. However, increasing the stirring force of the reactor has clear equipment limitations depending on the scale of the reactor.

[0041] The continuous grinder 200 used in the present invention can complement the low stirring force of the reactor, in which 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 performed 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 feeding and discharging the cathode active material precursor seeds into the continuous grinder 200 during the above time and then re-feeding them into the reactor 100, it can be advantageous for adjusting the particle size of the cathode active material precursor seeds uniformly.

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

[0044] Since the 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 3.0 μm.

[0046] When the rotational speed of the continuous grinder 200 is within the above range, or when the size of the seeds is within the above range, the particle size of the formed cathode active material precursor seeds can be uniform. As a result, a cathode active material precursor with a narrow particle size distribution can be manufactured with good reproducibility, and it can have the merit of improving the sphericity and uniformity of the particles.

[0047] In the present invention, the step (S1) and the step (S2) are performed simultaneously. That is, when a reaction solution is introduced into the reactor 100 to form cathode active material precursor seeds, at the same time, after discharging some of the cathode active material precursor seeds from the reactor 100, they are ground by the continuous grinder 200, discharged, and then reintroduced into the reactor 100. These are continuously performed simultaneously, and it is possible to suppress the concentration of the cathode active material precursor seeds in the reactor 100 and the increase in the particle size.

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

[0049] This is a step of manufacturing a cathode active material precursor using the cathode active material precursor seeds with a uniform particle size obtained in the reactor 100 by the steps (S1) and (S2). In order to prevent continuous discharge and grinding in the continuous grinder 200, after the steps (S1) and (S2) are sufficiently performed, the operation of the continuous grinder 200 is stopped to grow the cathode active material precursor particles.

[0050] The step (S3) can be performed at a temperature condition of 10°C to 80°C, for example, 50°C. When the temperature condition is within the above range, metal ions can be sufficiently dissolved while preventing the volatilization of the introduced solution, and a cathode active material precursor with a narrow particle distribution and uniform can be formed.

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

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

[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 at 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 capacity of the positive electrode active material can be excellent, and the separation of the positive electrode active material particles can be prevented.

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

[0055] The firing can be performed for 5 hours to 35 hours. When the firing time is within the above range, a positive electrode active material with high crystallinity can be obtained, the particle size is appropriate, and the production efficiency can be excellent.

[0056] The present invention can also provide a positive electrode and a lithium secondary battery including the positive electrode active material produced 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 and containing 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 a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. Further, 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 enhance the adhesive force of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0059] In addition, the positive electrode active material layer can include a conductive material and a binder together with the above-described positive electrode active material.

[0060] Here, the conductive material is used to impart conductivity to the electrode, and in the battery to be formed, it can be used without particular limitation as long as it does not cause a chemical change and has electron conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Among these, one kind alone or a mixture of two or more kinds can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

[0061] In addition, the binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. Among these, one kind alone or a mixture of two or more kinds can be used. The binder can be contained in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

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

[0063] The solvent can be a solvent generally used in the art, and examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. Among these, one kind alone or a mixture of two or more kinds can be used. The amount of the solvent used is such that, considering the coating thickness of the slurry and the production yield, it can dissolve or disperse the positive electrode active material, conductive material, and binder, and then have a viscosity that can exhibit excellent thickness uniformity during coating for the production of the positive electrode.

[0064] Further, the positive electrode can also be manufactured by laminating, on a positive electrode current collector, a film obtained by casting the composition for forming the positive electrode active material layer on another support and then peeling the film from the support.

[0065] Moreover, the present invention can produce an electrochemical element including the positive electrode. Specifically, the electrochemical element can be a battery, a capacitor, etc., and more specifically, it can be a lithium secondary battery.

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

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

[0068] The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Further, 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 binding force of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0069] The negative electrode active material layer selectively contains a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer is formed by applying and drying a composition for forming a negative electrode, which contains a negative electrode active material, and selectively a binder and a conductive material, onto a negative electrode current collector, or by casting the composition for forming a negative electrode onto another support and then laminating a film obtained by peeling the film from the support onto the negative electrode current collector.

[0070] As the negative electrode active material, a compound 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; metal oxides such as SiO β (0 < β < 2), SnO2, vanadium oxides, and lithium vanadium oxides that can be doped and undoped with lithium; or composites containing the metallic compound and the carbonaceous material such as Si-C composites or Sn-C composites. Any one or a mixture of two or more of these can be used. Further, a thin film of metallic lithium can also be used as the negative electrode active material. Also, as the carbon material, both low-crystalline carbon and high-crystalline carbon can be used. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural graphite 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] Further, the binder and the conductive material are as described for the above-described 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 migration path for lithium ions. Usually, any material can be used as long as it can be used as a separator in a lithium secondary battery, and in particular, a material having low resistance to ion migration of the electrolyte and excellent electrolyte moisture retention ability is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. can be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance can also be used, and optionally, it can be used as a single-layer or multilayer structure.

[0073] Examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel 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 contain an organic solvent and a lithium salt.

[0075] As the organic solvent, any substance can be used without particular limitation as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. 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, which can enhance the charge-discharge performance of the battery, and a linear carbonate compound having low viscosity (e.g., ethylmethylcarbonate, dimethylcarbonate, or diethylcarbonate) is more preferred. In this case, by mixing the cyclic carbonate and the linear carbonate at a volume ratio of about 1:1 to about 1:9, the electrolyte can exhibit excellent performance.

[0076] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, 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 is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0077] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives such as haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride for improving the life characteristics of the battery, suppressing the capacity reduction of the battery, improving the discharge capacity of the battery, etc. At this time, the additive can be contained in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

[0078] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and life characteristics, and thus is useful in portable devices such as mobile phones, notebook personal computers, digital cameras, and in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0079] Accordingly, 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 battery module or battery pack can be used as a power source for any one or more medium to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0081] Example Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

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

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

[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 in the water and make the inside of the reactor a non-oxidizing atmosphere.

[0085] Thereafter, while feeding a metal solution into 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, a precipitation reaction was carried out at pH 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 by a continuous grinder at a rate of 1000 L / hr ([reactor capacity × 10] / [hr]) to maintain the particle growth reaction, and to suppress or unlock the aggregation of particles. The step of sending the reactants to a 100 L reactor was carried out for 8 hours. Next, when the 100 L reactor was full, the filtration system located in the reactor was activated, and while continuously discharging the reacted solvent outside the reactor, a transition metal-containing solution, the NaOH aqueous solution, and the NH4OH aqueous solution were continuously fed, and the reaction was maintained for 32 hours. Here, the reaction conditions were such that the pH was controlled by a method of feeding NaOH in a pH sensor interlocking manner while gradually decreasing the stirring speed, and a coprecipitation reaction was carried out while maintaining the feeding rate of the metal solution at 7.26 L / hr, the NaOH aqueous solution at 4.39 L / hr, and the NH4OH aqueous solution at 1.03 L / hr 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 the particle size was 3.5 μm.

[0087] Comparative Example 1 A nickel-cobalt-manganese composite metal hydroxide precursor was 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 transition metal-containing solution with a concentration of 2.4 M. The metal solution was fed into a continuous stirred tank reactor at a rate of 7.26 L / hr, and the NaOH aqueous solution was fed at a rate of 4.39 L / hr and the NH4OH aqueous solution was fed at a rate of 1.03 L / hr. The temperature of the reactor was set to 50 °C, and 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 then dried in an oven at 120 °C to obtain a 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 seeds at a rate of 1000 L / hr ([reactor volume × 10] / [hr]) using a continuous grinder was not performed.

[0090] Experimental Example 1: SEM Observation The positive electrode 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 the SEM image of Example 1, Figure 3 is the SEM image of Comparative Example 1, and Figure 4 is the SEM image of Comparative Example 2. As shown in Figure 2, in the case of the precursor particles formed by suppressing the aggregation or unlocking of particle nuclei by the continuous grinder of Example 1, it was confirmed that they had a spherical particle shape and the particle diameters were formed relatively uniformly.

[0092] On the other hand, as can be seen from FIG. 3, in the case of the precursor produced using a continuous reactor as in Comparative Example 1, it was confirmed that large and small particles were mixed. This is because, when a continuous process is used as in Comparative Example 1, the raw materials for the reaction are charged and discharged simultaneously, so the residence time of the raw materials for the reaction and the deviation of the reaction time result in non-uniform precursor particle diameters and particle sizes.

[0093] On the other hand, as can be seen from FIG. 4, in the case of the precursor particles produced by a continuous concentration process in which the solid content increases steadily with the reaction time as in Comparative Example 2, the solid content and particle growth were maintained steadily, and as a result, it was found that the particle diameter of the precursor was formed relatively uniformly, but the sphericity was poor.

[0094] Experimental Example 2: Span Value Using a particle size analyzer (S3500, manufactured by Microtrac), the D5, D 50 , D 95 of the positive electrode active material precursors formed in the examples and comparative examples were measured, and the span value of the positive electrode active material precursors was calculated by the following formula 1 and shown in Table 1.

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

[0096]

Table 1

[0097] As shown in the above results, in Example 1 produced according to the present invention, aggregation of seed particles was suppressed, D 95 was shown to be low, and it was confirmed that the span value was also lower than that of the comparative examples.

Explanation of Signs

[0098] 100 Reactor 200 Continuous grinder

Claims

1. A method for manufacturing a cathode active material precursor using a reaction apparatus in which a reactor and a continuous grinder are connected, comprising: (S1) A step of charging a reaction solution containing a transition metal-containing solution, an ammonium ion-containing solution, and a basic aqueous solution into a reactor to form and discharge a cathode active material precursor seed; (S2) A step of charging the cathode active material precursor seed discharged from the reactor into a continuous grinder, discharging it, and then recharging it into the reactor, wherein the steps (S1) and (S2) are performed simultaneously, and the method for manufacturing a cathode active material precursor.

2. After step (S2), (S3) further comprising a step of stopping the operation of the continuous grinder and growing cathode active material precursor particles in the reactor, the method for manufacturing a cathode active material precursor according to claim 1.

3. The step (S2) is performed for 0.5 to 24 hours, the method for manufacturing a cathode active material precursor according to claim 1.

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

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

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 and includes one or more selected therefrom. The method for producing a cathode active material precursor according to claim 1.

7. The basic aqueous solution contains one or more selected from hydrates of alkali metals, hydroxides of alkali metals, hydrates of alkaline earth metals, and hydroxides of alkaline earth metals, the method for manufacturing a cathode active material precursor according to claim 1.

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

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