Method for preparing positive electrode active material precursor

Abstract

One aspect of the present invention provides a method for preparing a positive electrode active material precursor having a narrow particle size distribution in a reproducible manner.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2022-0116495 filed in the Korean Intellectual Property Office on September 15, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The invention relates to a method for preparing a positive electrode active material precursor. Background Art

[0004] As the technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources has increased significantly. Among these secondary batteries, lithium secondary batteries with high energy density, high voltage, long cycle life and low self-discharge rate have been commercialized and widely used.

[0005] Lithium transition metal oxides have been used as positive electrode active materials for lithium secondary batteries, and among these oxides, lithium cobalt oxides such as LiCoO2, which have high operating voltage and excellent capacity characteristics, are mainly used. However, LiCoO2 has very poor thermal properties due to an unstable crystal structure caused by delithiation and is expensive, so there are limitations in using a large amount of LiCoO2 as a power source for applications such as electric vehicles.

[0006] Lithium manganese oxide (LiMnO2 or LiMn2O4), lithium iron phosphate compounds (LiFePO4, etc.), or lithium nickel oxide (LiNiO2, etc.) have been developed as materials to replace LiCoO2. Among these materials, lithium nickel oxide, which can easily realize large-capacity batteries due to its high reversible capacity of about 200 mAh / g, has been more actively studied and developed. However, the problem with LiNiO2 is that the thermal stability of LiNiO2 is worse than that of LiCoO2, and when an internal short circuit occurs due to external pressure in a charged state, the positive electrode active material itself decomposes, causing rupture and fire of the battery.

[0007] Therefore, as a method to improve the low thermal stability while maintaining the excellent reversible capacity of LiNiO2, LiNiO2 in which a portion of nickel is replaced by cobalt has been developed. 1-α Co α O2 (α = 0.1 to 0.3), or a nickel-cobalt-manganese lithium composite metal oxide in which a portion of nickel is replaced by Mn and Co (hereinafter referred to as "NCM-based lithium oxide"). In addition, lithium transition metal oxides having a concentration gradient of metal composition have been proposed, thereby solving the stability problem caused by the dissolution of metal elements while having excellent output characteristics.

[0008] Examples of methods for preparing positive electrode active materials include: preparing a positive electrode active material precursor by using a continuous stirred tank reactor (CSTR), and then sintering the positive electrode active material precursor with a lithium raw material to prepare a positive electrode active material; and preparing a positive electrode active material precursor by using a batch reactor, and then sintering the positive electrode active material precursor with a lithium raw material to prepare a positive electrode active material. The continuous stirred tank reactor discharges a precursor composed of particles while adding a raw material and performing coprecipitation, and for a batch reactor, the raw material is added according to the volume of the reactor and the reaction continues for a predetermined time, and the precursor is discharged after the reaction is completed.

[0009] Generally, the productivity of the positive electrode active material precursor prepared by using a continuous stirred tank reactor can be improved by introducing raw materials, co-precipitating the raw materials and discharging the precursor at the same time. However, since the introduction of raw materials and the discharge of products are carried out simultaneously and continuously, the residence time and reaction time of the positive electrode active material precursor produced in the reactor may deviate, so there is a problem of uneven size and particle size distribution of the positive electrode active material precursor particles produced.

[0010] In addition, the positive active material precursor prepared using a batch reactor has a uniform particle size and particle size distribution, but when a batch reactor is used to prepare the precursor, the precursor seed formation step and the precursor particle growth step are carried out simultaneously in the reactor, so it is difficult to reproduce or predict the same particle size distribution and average particle size for each reaction. In addition, during large-scale production by a batch reactor, the larger the reactor, the faster the rotation speed of the agitator, so there are difficulties in terms of equipment. Due to the imperfect equipment used, the possibility of seed quality dispersion is high, which causes problems in quality reproducibility and ultimately causes problems in product quality.

[0011] [Prior art literature]

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent Application Publication No. 2012-0049227 Summary of the invention

[0014] Technical issues

[0015] One aspect of the present invention provides a method for preparing a positive electrode active material precursor having a narrow particle size distribution in a reproducible manner.

[0016] Technical Solution

[0017] According to one aspect of the present invention, there is provided a method for preparing a positive electrode active material precursor, the method using a reaction device in which a reactor and a continuous pulverizer are connected, the method comprising the following steps:

[0018] (S1) introducing a reaction solution including a solution containing a transition metal, a solution containing ammonium ions, and an alkaline aqueous solution into a reactor to form and discharge positive electrode active material precursor seeds; and

[0019] (S2) introducing the positive electrode active material precursor seeds discharged from the reactor into a continuous pulverizer, and discharging the positive electrode active material precursor seeds and introducing them into the reactor again,

[0020] Wherein step (S1) and step (S2) are performed simultaneously.

[0021] Beneficial Effects

[0022] According to the present invention, a positive electrode active material precursor having uniform size and narrow particle size distribution can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram showing a reaction apparatus used in the present invention.

[0024] Figure 2 The SEM image of Example 1 is shown.

[0025] Figure 3 A SEM image of Comparative Example 1 is shown.

[0026] Figure 4 A SEM image of Comparative Example 2 is shown. DETAILED DESCRIPTION

[0027] Hereinafter, the present invention will be described in more detail to help understanding of the present invention.

[0028] The terms or words used in this specification and claims should not be interpreted as limited to the conventional or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical spirit based on the principle that the inventor can appropriately define the concepts of the terms in order to interpret the present invention in the best manner.

[0029] In this manual, D5, D 50 and D 95 It can be defined as the particle size corresponding to 5%, 50% and 95% of the cumulative volume in the particle size distribution curve (particle size distribution curve). 50 and D 95For example, laser diffraction can be used for measurement. Laser diffraction can generally measure particle sizes ranging from a few nanometers to a few millimeters, and can obtain highly reproducible and high-resolution results. In this specification, the average particle size refers to D 50 .

[0030] The method for preparing a positive electrode active material precursor of the present invention uses a reaction device in which a reactor and a continuous pulverizer are connected, and the method comprises the following steps:

[0031] (S1) introducing a reaction solution including a solution containing a transition metal, a solution containing ammonium ions, and an alkaline aqueous solution into a reactor to form and discharge positive electrode active material precursor seeds; and

[0032] (S2) introducing the positive electrode active material precursor seeds discharged from the reactor into a continuous pulverizer, and then discharging the positive electrode active material precursor seeds and introducing them into the reactor again,

[0033] The above steps (S1) and (S2) are performed simultaneously.

[0034] Hereinafter, the present invention will be described in detail.

[0035] Step (S1)

[0036] In step (S1), a reaction solution including a transition metal-containing solution, an ammonium ion-containing solution, and an alkaline aqueous solution is introduced into a reactor to form and discharge positive electrode active material precursor seeds.

[0037] Figure 1 Schematically shows a reaction device that can be used in a method for preparing a positive electrode active material precursor according to one embodiment of the present invention. Figure 1 , the preparation method of the present invention uses a reaction device in which a reactor 100 and a continuous pulverizer 200 are connected.

[0038] In step ( S1 ), a reaction solution including a solution containing a transition metal, a solution containing ammonium ions, and an alkaline aqueous solution is introduced into the reactor 100 , and positive electrode active material precursor seeds are formed in the reactor 100 .

[0039] The reactor 100 may be used without limitation to the reactor type, such as a batch reactor, a continuous stirred tank reactor (CSTR), and a continuous filter tank reactor (CFTR). More specifically, a reactor such as a continuous filter tank reactor (CFTR) in which a filtration device is provided inside the reactor may be used.

[0040] The positive electrode active material precursor seeds formed in step (S1) may refer to seeds formed by agglomeration of the nuclei of the positive electrode active material precursor particles in the form of primary particles, wherein the nuclei of the positive electrode active material precursor particles in the form of primary particles are generated when a coprecipitation reaction is started by introducing a transition metal aqueous solution, an ammonium cation, and an alkaline aqueous solution. As will be described later, after the seeds pass through a continuous pulverizer and are then reintroduced into a reactor, the seeds may agglomerate to form a core of the positive electrode active material precursor.

[0041] The solution containing transition metals 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 solution containing transition metals may contain acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides or oxyhydroxides of the above transition metals, and there is no particular limitation on these materials as long as they can be dissolved in water.

[0042] For example, cobalt (Co) may be contained as Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or Co(SO4)2·7H2O, and any one thereof or a mixture of two or more thereof may be used. In addition, nickel (Ni) may be contained as Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, a fatty acid nickel salt, or a nickel halide, and any one thereof or a mixture of two or more thereof may be used. In addition, manganese (Mn) may be contained as manganese oxides such as Mn2O3, MnO2, and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarbonate, manganese citrate, and fatty acid manganese salts; oxyhydroxides and manganese chlorides, and any one thereof or a mixture of two or more thereof may be used.

[0043] On the other hand, when the final prepared precursor also contains a second metal element (M) other than 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), a raw material containing the second metal element can be optionally added when preparing a solution containing metal ions. The raw material containing the second metal element may include acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides or oxyhydroxides containing the second metal element, and one or a mixture of two or more thereof can be used. For example, when the second metal element is Zr, zirconium oxide, etc. can be used.

[0044] The ammonium ion-containing solution may contain at least one 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, etc.) that can be uniformly mixed with water can be used.

[0045] The alkaline aqueous solution may include at least one selected from hydrates of alkali metals, hydroxides of alkali metals, hydrates of alkaline earth metals and hydroxides of alkaline earth metals. For example, the alkaline aqueous solution may include NaOH, KOH, Ca(OH)2, etc. As the solvent, water or a mixture of water and an organic solvent (specifically alcohol, etc.) that can be uniformly mixed with water may be used.

[0046] The content of the ammonium ion-containing solution may be 4 parts by weight to 100 parts by weight, preferably 4 parts by weight to 30 parts by weight, based on 100 parts by weight of the transition metal-containing solution.

[0047] On the other hand, step (S1) can be performed at a pH of 10.5 to 12.5, an alkaline 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 seeds, an alkaline aqueous solution can be used to maintain the pH of the reaction solution at 10.5 to 12.5, preferably 11 to 12. When the content of the ammonium ion-containing solution introduced in step (S1) is within the above range, or when the pH of the reaction solution is within the above range, it may be beneficial to adjust the size of the seeds.

[0048] Step (S1) can be performed at a temperature of 10° C. to 80° C., specifically, at a temperature of 40° C. to 60° C. When the temperature is within the above range, the metal ions can be fully dissolved while preventing the introduced solution from volatilizing, thereby appropriately forming the positive electrode active material precursor seed.

[0049] Step (S2)

[0050] The positive electrode active material precursor seeds discharged from the reactor are introduced into a continuous pulverizer, then discharged and reintroduced into the reactor. Here, the positive electrode active material precursor seeds reintroduced into the reactor after passing through the continuous pulverizer through step (S2) can grow into positive electrode active material precursor particles in the reactor.

[0051] In the present invention, the rate of discharging the positive electrode active material precursor seeds from the reactor 100 in step (S1) and introducing them into the continuous pulverizer 200 in step (S2) can be at least [reactor 100 capacity (L) × 6] / [hour], specifically at least [reactor 100 capacity (L) × 8] / [hour], at least [reactor 100 capacity (L) × 10] / [hour], at least [reactor 100 capacity (L) × 12] / [hour].

[0052] Within the above range, the positive electrode active material precursor seeds are transferred from the reactor 100 to the continuous pulverizer 200 at an appropriate rate and amount, so that the effect of pulverizing the seeds into a small size and uniformly adjusting the particle size can be sufficiently exhibited.

[0053] The positive electrode active material precursor seeds formed in step ( S1 ) are not concentrated in the reactor 100 , but are pulverized in the continuous pulverizer 200 through step ( S2 ) and then introduced into the reactor 100 again.

[0054] If the reaction solution is introduced into the reactor and then reacted continuously, particle agglomeration occurs, which tends to occur seriously until the reaction progress rate in the reactor reaches 30%. In the present invention, before the reaction in the reactor 100 is significantly progressed and particle agglomeration occurs, the positive electrode active material precursor seeds are introduced into a continuous pulverizer and split into small sizes to suppress agglomeration and uniformly control the particle size.

[0055] Therefore, in the present invention, the positive electrode active material precursor seeds introduced again into the reactor 100 through the above process have a narrow and uniform particle size distribution characteristic. As a result, the particle size is small and the contact area of ​​the seeds is large, so not only can the generation efficiency of the positive electrode active material precursor be improved, but also a positive electrode active material precursor with uniform particle size can be provided in the end.

[0056] Unlike the present invention, when a positive electrode active material precursor is prepared by using an apparatus without a continuous pulverizer, a plurality of particles that are far from spherical in shape are found in the final positive electrode active material precursor, for example, particles having a tumbler-like shape, which should be removed to improve the sphericity of the precursor, and which cause a decrease in the electrode density of the positive electrode in the secondary battery.

[0057] Since the stirring force is low at the beginning of the precursor preparation reaction, the particles in the shape of a tumbler are produced by the growth of the seeds in a state where the seeds are attached to another seed. In order to solve this situation, it is necessary to increase the stirring force of the reactor or keep the introduction rate of the raw material low. However, increasing the stirring force of the reactor has obvious equipment limitations depending on the scale of the reactor.

[0058] The continuous pulverizer 200 used in the present invention can compensate for the low stirring force of the reactor, in which case it is not necessary to reduce the rate at which the raw materials are introduced into the reactor. The continuous pulverizer 200 can be used not only to suppress the phenomenon of seeds adhering to one another, but also to continuously separate the already attached seeds. Thus, D 90 and D 95 A positive electrode active material precursor with a low value.

[0059] In the present invention, step (S2) can be performed for 0.5 hours to 24 hours, specifically more than 2 hours, more than 4 hours, less than 20 hours, less than 16 hours or less than 10 hours. During the above time, the positive active material precursor seed is introduced into the continuous pulverizer 200 and discharged from the continuous pulverizer 200, and then introduced into the reactor 100 again, so that the particle size of the positive active material precursor seed can be uniformly adjusted.

[0060] In step (S1), the rotation speed of the continuous pulverizer 200 may be 500 rpm to 4,500 rpm, preferably 3,000 rpm to 3,500 rpm.

[0061] Since rpm depends on the characteristics of the machine, rpm cannot be absolute, but the size of the seeds can be adjusted by rpm adjustment. The average particle size (D 50 ) can be adjusted from 1.0 µm to 5.0 µm.

[0062] Specifically, in the present invention, the average particle size (D 50 ) can be 1.0 μm to 5.0 μm or 1.3 μm to 3.0 μm.

[0063] When the rotation speed of the continuous pulverizer 200 is within the above range, or when the size of the seeds is within the above range, the particle size of the formed positive electrode active material precursor seeds can be uniform, and therefore, there may be advantages in that positive electrode active material precursors with a narrow particle size distribution can be produced in a reproducible manner, and the sphericity and uniformity of the particles can be improved.

[0064] In the present invention, the above step (S1) and step (S2) are performed simultaneously. That is, the reaction solution is introduced into the reactor 100 to form the 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, and then crushed and discharged in the continuous pulverizer 200 and introduced again into the reactor 100. These are performed simultaneously and continuously, so that the concentration of the positive electrode active material precursor seeds in the reactor 100 can be suppressed and the particle growth can be suppressed.

[0065] Step (S3)

[0066] After step (S2), the method may further include step (S3): stopping the operation of the continuous pulverizer and growing positive electrode active material precursor particles in the reactor.

[0067] This is a step of preparing a positive electrode active material precursor using positive electrode active material precursor seeds of uniform particle size obtained in the reactor 100 through steps (S1) and (S2). In order to prevent the positive electrode active material precursor from being continuously discharged into the continuous pulverizer 200 and pulverized, the operation of the continuous pulverizer 200 is stopped after steps (S1) and (S2) are fully performed, and the positive electrode active material precursor particles are allowed to grow.

[0068] The reaction of step (S3) can be performed at a temperature of 10° C. to 80° C., for example, 50° C. When the temperature is within the above range, the metal ions can be sufficiently dissolved while preventing the introduced solution from volatilizing, thereby forming a positive electrode active material precursor with narrow and uniform particle distribution.

[0069] The span value of the positive electrode active material precursor prepared according to step (S3) of the present invention may be 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 uniform particle size can be prepared.

[0070] In addition, the present invention provides a method for preparing a positive electrode active material, the method comprising mixing the positive electrode active material precursor prepared as described above with a lithium-containing raw material, and then sintering the mixture.

[0071] As the lithium-containing raw material, for example, lithium carbonate (Li2CO3) or lithium hydroxide (LiOH) may be used, and the positive electrode active material precursor and the lithium-containing raw material may be mixed in a molar ratio of 1:1 to 1:1.15. When the molar ratio of the positive electrode active material precursor to the lithium-containing raw material is within the above range, the capacity of the positive electrode active material may be excellent, and separation of the positive electrode active material particles may not occur.

[0072] Sintering can be performed at a temperature of 700°C to 1,000°C. When the sintering temperature is within the above range, the raw material does not remain in the particles, thereby improving the high temperature stability of the battery and the volume density and crystallinity are excellent, whereby the structural stability can be excellent. In addition, the volume capacity of the battery can be excellent. On the other hand, considering the particle size control, capacity, stability and reduction of lithium-containing by-products of the prepared positive electrode active material, the sintering temperature can be more preferably in the range of 750°C to 850°C.

[0073] The sintering may be performed for 5 hours to 35 hours. When the sintering time is within the above range, a positive electrode active material with high crystallinity may be obtained, the particle size may be appropriate, and the production efficiency may be excellent.

[0074] In addition, the present invention can provide a positive electrode including the positive electrode active material prepared as described above, and a lithium secondary battery.

[0075] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector and including a positive electrode active material.

[0076] In the positive electrode, there is no particular limitation on the positive electrode collector as long as it has conductivity without causing adverse chemical changes in the battery, and for example: stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used. In addition, the thickness of the positive electrode collector can generally be 3 μm to 500 μm, and fine concavoconvexity can be formed on the surface of the positive electrode collector to improve the adhesion of the positive electrode active material. For example, the positive electrode collector can be used in various shapes such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

[0077] In addition, the positive electrode active material layer may further include a conductive material and a binder in addition to the positive electrode active material described above.

[0078] In this case, the conductive material is used to provide conductivity to the electrode, wherein any conductive material can be used without particular limitation, as long as it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of conductive materials may include the following: graphite such as natural graphite or artificial graphite; carbon materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black and carbon fiber; powder or fiber of metals such as copper, nickel, aluminum and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and any one thereof alone or a mixture of two or more thereof can be used. Based on the total weight of the positive electrode active material layer, the content of the conductive material may generally be 1% to 30% by weight.

[0079] In addition, the binder improves the adhesion between the positive active material particles and the adhesion between the positive active material and the collector. Specific examples of binders may include: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene rubber (EPDM rubber), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber or its various copolymers, and any one thereof alone or a mixture of two or more thereof may be used. Based on the gross weight of the positive active material layer, the content of the binder may be 1 wt % to 30 wt %.

[0080] In addition to using the above-mentioned positive electrode active material, the positive electrode can be prepared according to the conventional method for preparing the positive electrode. Specifically, a positive electrode active material layer-forming composition comprising the above-mentioned positive electrode active material and a selective binder and a conductive material is coated on the positive electrode collector, and then the positive electrode can be prepared by drying and rolling the coated positive electrode collector. In this case, the type and amount of the positive electrode active material, the binder and the conductive material are the same as those described above.

[0081] The solvent may be a commonly used solvent in the art. The solvent may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone or water, and any one thereof or a mixture of two or more thereof may be used. If the coating thickness and manufacturing yield of the slurry are taken into account, the solvent may dissolve or disperse the positive electrode active material, the conductive material and the binder, and may be such that a viscosity having excellent thickness uniformity may be provided during the subsequent preparation of the coating of the positive electrode is obtained, then the amount of the solvent may be sufficient.

[0082] In addition, the positive electrode can be prepared by casting the positive electrode active material layer-forming composition on a separate support and then laminating the film separated from the support on a positive electrode current collector.

[0083] The present invention can also provide an electrochemical device comprising the positive electrode. The electrochemical device can be a battery or a capacitor, for example, a lithium secondary battery.

[0084] The lithium secondary battery specifically comprises a positive electrode, a negative electrode disposed facing the positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may further selectively comprise: a battery container for accommodating an electrode assembly of the positive electrode, the negative electrode and the separator; and a sealing member for sealing the battery container.

[0085] In a lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0086] There is no particular limitation on the negative electrode current collector as long as it has high conductivity without causing adverse chemical changes in the battery, and for example: copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. In addition, the thickness of the negative electrode current collector can generally be 3 μm to 500 μm, and similar to the positive electrode current collector, fine concavoconvexity can be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0087] On the basis of the negative electrode active material, the negative electrode active material layer further selectively includes a binder and a conductive material. The negative electrode active material layer can be prepared by coating a negative electrode forming composition in the form of a slurry containing the negative electrode active material and the selective binder and the conductive material on the negative electrode current collector and drying the coated negative electrode current collector, or can be prepared by casting the negative electrode forming composition on a separate support and then laminating the film separated from the support on the negative electrode current collector.

[0088] A compound capable of reversibly inserting and deinserting lithium may be used as a negative electrode active material. Specific examples of negative electrode active materials may be: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal compounds that can form alloys with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides that can be doped and dedoped with lithium such as SiOβ (0<β<2), SnO2, vanadium oxides, and lithium vanadium oxides; or composite materials comprising metal compounds and carbonaceous materials such as Si-C composite materials or Sn-C composite materials, and any one thereof or a mixture of two or more thereof may be used. In addition, a metallic lithium film may be used as a negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as carbon materials. Typical examples of low-crystalline carbon may be soft carbon and hard carbon, and typical examples of high-crystalline carbon may be irregular, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, condensed graphite, pyrolytic carbon, mesophase pitch-type carbon fibers, mesophase carbon microbeads, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch.

[0089] Furthermore, the binder and the conductive material may be the same as those previously described in the positive electrode.

[0090] In a lithium secondary battery, a separator separates the negative electrode from the positive electrode and provides a path for the movement of lithium ions, wherein any separator can be used as the separator without particular limitation, as long as it is commonly used in lithium secondary batteries, and in particular, a separator having high moisture retention capacity for electrolytes and low resistance to the movement of electrolyte ions can be used. Specifically, a porous polymer film, for example, a porous polymer film prepared from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer; or a laminated structure having two or more layers thereof can be used. In addition, a typical porous non-woven fabric can be used, such as a non-woven fabric formed of a high melting point glass fiber or a polyethylene terephthalate fiber. In addition, a coated separator comprising a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and a separator having a single-layer or multilayer structure can be optionally used.

[0091] In addition, the electrolyte used in the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte or a molten inorganic electrolyte that can be used in the preparation of a lithium secondary battery, but the present invention is not limited thereto.

[0092] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0093] Any organic solvent can be used as the organic solvent without particular limitation, as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, the following substances can be used as organic solvents: 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; or carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitrile such as R-CN (wherein R is a linear, branched or cyclic C2-C20 hydrocarbon group and may contain a double bond, an aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolanes; or cyclopentane sulfone. Among these solvents, carbonate solvents can be used, and for example, a mixture of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) which can improve the charge and discharge performance of the battery, have high ion conductivity and high dielectric constant, and linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) with low viscosity can be used.

[0094] In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte may be excellent.

[0095] Lithium salts can be used without particular limitation, as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the following substances can be used as lithium salts: LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. Lithium salts are preferably used in a concentration range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can have suitable conductivity and viscosity, thereby showing excellent performance, and lithium ions can be effectively moved.

[0096] In order to improve the life characteristics of the battery, suppress the reduction of the battery capacity and improve the discharge capacity of the battery, in addition to the electrolyte components, the electrolyte may further include at least one additive, such as a halogenated alkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (condensed) glycol dimethyl ether, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum chloride. In this case, based on the total weight of the electrolyte, the content of the additive may be 0.1 wt % to 5 wt %.

[0097] As described above, since the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and capacity retention rate, the lithium secondary battery is suitable for portable devices such as mobile phones, notebook computers, digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0098] Therefore, the present invention can provide a battery module including the lithium secondary battery as a unit cell, and a battery pack including the battery module.

[0099] The battery module or battery pack can be used as a power source for at least one of the following medium to large devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0100] Example

[0101] Hereinafter, the present invention will be described in more detail according to Examples. However, the following Examples are intended to explain the present invention, and the scope of the present invention is not limited thereto.

[0102] Example 1

[0103] 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 2.4 M solution. In addition, an 8.0 M NaOH aqueous solution and a 5.1 M NH4OH aqueous solution were prepared.

[0104] like Figure 1 As shown in , a container containing a solution containing a transition metal and a container in which a 25 wt % NaOH aqueous solution and a 9 wt % NH 4 OH aqueous solution were prepared were each connected to a 100 L reactor.

[0105] After 28.6 L of deionized water, 0.035 mol / L of NaOH aqueous solution, and 0.22 mol / L of NH4OH aqueous solution were introduced into the reactor, nitrogen was blown into the reactor to remove dissolved oxygen in the water and to form a non-oxidizing atmosphere inside the reactor.

[0106] Thereafter, the metal solution was introduced into the reactor at a rate of 7.26 L / hour, the NaOH aqueous solution was introduced into the reactor at a rate of 4.39 L / hour, and the NH4OH aqueous solution was introduced into the reactor at a rate of 1.03 L / hour, respectively, and the reaction mixture was precipitated for 10 minutes at a pH below 12.5 to form particle seeds of nickel-cobalt-manganese hydroxide. At the same time, the particle seeds formed in the reactor were transferred to a continuous pulverizer at a rate of 1,000 L / hour ([reactor capacity × 10] / [hour]) to maintain the growth reaction of the particles, but the process of suppressing or disintegrating the agglomeration between the particles and transferring the reactants to the 100 L reactor again was carried out for 8 hours. Subsequently, when the 100 L reactor became full, the filtration system located in the reactor was operated to continuously discharge the solvent that completed the reaction to the outside of the reactor, and the transition metal-containing solution, the NaOH aqueous solution, and the NH4OH aqueous solution were continuously introduced to maintain the reaction for 32 hours. In this case, while the stirring speed was sequentially reduced, NaOH was introduced to control the pH using a pH sensor linkage method, the metal solution was introduced at a rate of 7.26 L / hour, the NaOH aqueous solution was introduced at a rate of 4.39 L / hour, and the NH4OH aqueous solution was introduced at a rate of 1.03 L / hour, and the mixture was co-precipitated while maintaining the introduction rate to prepare a precursor containing nickel-cobalt-manganese composite metal hydroxide particles.

[0107] The molar ratio of Ni:Co:Mn in the entire positive electrode active material precursor particles is 88.5:3.5:8, and the particle size is 3.5 µm.

[0108] Comparative Example 1

[0109] A continuous stirred tank reactor (CSTR) was used to prepare the nickel-cobalt-manganese composite metal hydroxide precursor.

[0110] NiSO4, CoSO4 and MnSO4 were mixed in water in an amount 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 introduced into a continuous stirred tank reactor at a rate of 7.26 L / hour, the NaOH aqueous solution was introduced into the continuous stirred tank reactor at a rate of 4.39 L / hour, and the NH4OH aqueous solution was introduced into the continuous stirred tank reactor at a rate of 1.03 L / hour. The temperature of the reactor was set to 50°C and stirred at a speed of 350 rpm to precipitate the nickel-cobalt-manganese composite metal hydroxide. The resulting nickel-cobalt-manganese composite metal hydroxide particles were separated, washed with water, and dried in an oven at 120°C to ensure the precursor.

[0111] Comparative Example 2

[0112] A nickel-cobalt-manganese composite metal hydroxide precursor was prepared in the same manner as in Example 1, except that the step of transferring the particle seeds to the continuous pulverizer at a rate of 1,000 L / hour ([reactor capacity×10] / [hour]) was not performed.

[0113] Experimental Example 1: SEM Observation

[0114] The positive electrode active material precursors prepared in Example 1, Comparative Example 1 and Comparative Example 2 were photographed using a scanning electron microscope to confirm the particle characteristics of the precursors.

[0115] Figure 2 is the SEM image of Example 1, Figure 3 is the SEM image of Comparative Example 1, Figure 4 is the SEM image of Comparative Example 2. Figure 2 As shown in , it can be confirmed that the precursor particles formed by suppressing or disintegrating the aggregation of particle cores by the continuous pulverizer in Example 1 have a spherical particle shape and a relatively uniform particle size.

[0116] On the other hand, Figure 3 As shown in , it can be confirmed that the precursor prepared using the continuous reactor as in Comparative Example 1 has a mixture of particles of large and small particle sizes. This is because when a continuous process is used as in Comparative Example 1, input and discharge of the reaction raw materials occur simultaneously, and thus the size and size distribution of the obtained precursor particles are not uniform due to deviations in the residence time of the reaction raw materials and the reaction time.

[0117] On the other hand, Figure 4 As shown in , in the case of precursor particles prepared by a continuous concentration process in which the solid content increases with reaction time as in Comparative Example 2, it can be seen that the solid content and particle growth remain constant, and therefore, the size of the precursor particles is formed relatively uniformly, but the sphericity is reduced.

[0118] Experimental Example 2: Span Value

[0119] The D5, D 50 and D 95 , the span value of the positive electrode active material precursor was calculated according to the following formula 1, and the results are shown in Table 1.

[0120] [Formula 1]

[0121] Span = (D 95 - D5) / D 50

[0122]

[0123] As shown in the above results, in Example 1 prepared according to the present invention, it was confirmed that the agglomeration between the seed particles was suppressed, and thus D 95 Low, and the span value is also low.

[0124] [reference numerals]

[0125] 100: Reactor

[0126] 200: Continuous crusher

Claims

1. A method for preparing a positive electrode active material precursor, the method using a reaction device in which a reactor and a continuous pulverizer are connected, the method comprising the following steps: (S1) introducing a reaction solution including a solution containing a transition metal, a solution containing ammonium ions, and an alkaline aqueous solution into the reactor to form and discharge positive electrode active material precursor seeds; and (S2) introducing the positive electrode active material precursor seeds discharged from the reactor into the continuous pulverizer, and then discharging the positive electrode active material precursor seeds and introducing them into the reactor again, The above steps (S1) and (S2) are performed simultaneously.

2. The method according to claim 1, further comprising the following steps after step (S2): (S3) The operation of the continuous pulverizer is stopped, and positive electrode active material precursor particles are grown in the reactor.

3. The method according to claim 1, wherein the above step (S2) is performed for 0.5 hour to 24 hours.

4. The method according to claim 1, wherein the rotation speed of the continuous pulverizer is 500 rpm to 4,500 rpm.

5. The method of claim 1, wherein the transition metal-containing solution comprises cations of one or more metals selected from the group consisting of nickel, manganese, cobalt, tungsten, molybdenum, chromium, and aluminum.

6. The method according to claim 1, wherein the ammonium ion-containing solution comprises at least one selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4 and NH4CO3. 7 . The method according to claim 1 , wherein the alkaline aqueous solution comprises at least one selected from the group consisting of hydrates of alkali metals, hydroxides of alkali metals, hydrates of alkaline earth metals, and hydroxides of alkaline earth metals.

8. The method 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 - D5) / D 50 .

Images