Precursor for positive electrode active material and method for preparing the same

Abstract

The present invention relates to a method for producing a precursor for a positive electrode active material, the method comprising: a seed formation step of forming a precursor for a positive electrode active material seed by performing a coprecipitation reaction while supplying a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to a reactor; and a particle growth step of growing a precursor for a positive electrode active material particle by performing a coprecipitation reaction while supplying a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to a reaction solution in which the precursor for a positive electrode active material seed has been formed, wherein in the particle growth step, the reaction is performed while continuously increasing the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2021-0021657, filed on February 18, 2021, the disclosure of which is incorporated herein by reference.

[0002] This invention relates to a precursor for a positive electrode active material used in secondary batteries and a method for preparing the same, and more particularly, to a precursor for a positive electrode active material and a method for preparing the same, wherein the precursor for the positive electrode active material exhibits excellent reactivity with lithium during sintering. Background Technology

[0003] With the technological advancements and increasing demands of mobile devices, the need for secondary batteries as energy sources has grown significantly. Among these secondary batteries, lithium-ion batteries, characterized by high energy density, high voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Lithium composite transition metal oxides containing two or more transition metals (such as nickel, cobalt, manganese and aluminum) have been used as positive electrode active materials for lithium secondary batteries.

[0005] Lithium complex transition metal oxides are typically prepared by adding a metal solution containing a transition metal element, an ammonium cation complexing agent, and an alkaline aqueous solution as raw materials to a continuous stirred tank reactor (CSTR) or batch reactor for co-precipitation reaction to prepare a precursor in the form of hydroxide. This precursor is then mixed with lithium raw materials, and the mixture is sintered.

[0006] In a continuous stirred tank reactor (CSTR), the precursor composed of particles is discharged while the feedstock is added and co-precipitation occurs. In contrast, in a batch reactor, the feedstock is added according to the volume of the reactor. When the reactor is full, the addition of feedstock is stopped and the reaction proceeds. The precursor is then discharged after the reaction is complete.

[0007] The advantage of using a continuous stirred tank reactor (CSTR) to prepare precursors is the high productivity because the precursor is discharged simultaneously with the addition of reactants and co-precipitation. However, since the addition of reactants and the discharge of products occur continuously, the residence time and reaction time of the precursor used to form the positive electrode active material in the reactor may vary. Therefore, a limitation is the inhomogeneity in the size and particle size distribution of the formed precursor particles. Therefore, to ensure the uniformity of precursor quality, batch reactors are primarily used for precursor preparation.

[0008] However, in the traditional batch reactor method for preparing precursors for cathode active materials, particle growth occurs after seed formation at the start of the reaction, even though the number of particles remains unchanged. Therefore, as the co-precipitation reaction time progresses, the growth rate of precursor particles slows down, while the surface density and primary particle size increase, resulting in a decrease in the surface energy of the precursor particles. For precursors with high surface density, a problem arises because the reactivity with the lithium feedstock is low during sintering, and the penetration of lithium and dopant elements into the precursor particles is suppressed, making uniform sintering difficult. Furthermore, the use of batch reactors for preparing precursors for cathode active materials also results in reduced productivity.

[0009] Therefore, there is a need to develop a precursor for positive electrode active materials that exhibits excellent reactivity with lithium feedstock during sintering. Summary of the Invention

[0010] Technical issues

[0011] An aspect of the present invention provides a method for preparing a precursor for a cathode active material by controlling the surface density of precursor particles by adjusting the supply flow rate of the raw material during the preparation of the precursor, wherein the precursor for the cathode active material exhibits excellent reactivity with lithium raw material during sintering.

[0012] Technical solution

[0013] According to one aspect of the present invention, a method for preparing a precursor for a positive electrode active material is provided, the method comprising:

[0014] Seed formation steps: Precursor seeds for the positive electrode active material are formed by co-precipitation reaction simultaneously with the supply of an aqueous transition metal solution, an ammonium cation complexing agent, and an alkaline compound to the reactor; and

[0015] Particle growth step: The precursor particles for the positive electrode active material are grown by simultaneously supplying a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to the reaction solution in which precursor seeds for the positive electrode active material have already been formed, and a co-precipitation reaction is carried out.

[0016] In the particle growth step, the reaction is carried out while the supply rate of the transition metal aqueous solution and the ammonium cation complexing agent is continuously increased.

[0017] According to another aspect of the present invention, a precursor for a positive electrode active material prepared by the above preparation method is provided.

[0018] Beneficial effects

[0019] The method for preparing precursors for positive electrode active materials according to the present invention allows for a reduction in the internal density of the precursor particles and the preparation of precursor particles with small primary particle sizes on the particle surface by continuously increasing the supply rate of the transition metal aqueous solution and the ammonium cation complexing agent as reactants during the precursor particle growth step. If the surface density and primary particle size of the precursor particles decrease, the specific surface area increases, resulting in improved reactivity with the lithium feedstock during the sintering step, thereby improving sintering uniformity and promoting better crystal structure development. Therefore, when the positive electrode active material prepared using the precursor prepared according to the method of the present invention is used in a secondary battery, an increase in reversible capacity can be achieved.

[0020] Furthermore, the method for preparing precursors for positive electrode active materials according to the present invention can achieve increased productivity because the reaction time required to form precursor particles with the desired particle size is reduced. Attached Figure Description

[0021] Figure 1 These are scanning electron microscope (SEM) images showing the surface features of the precursor prepared in Example 1;

[0022] Figure 2 These are scanning electron microscope (SEM) images showing the surface features of the precursor prepared in Example 2;

[0023] Figure 3 These are scanning electron microscope (SEM) images showing the surface features of the precursor prepared in Example 3;

[0024] Figure 4 These are scanning electron microscope (SEM) images showing the surface features of the precursor prepared from Comparative Example 1;

[0025] Figure 5 These are scanning electron microscope (SEM) images showing the surface features of the positive electrode active material and precursor prepared from Comparative Example 2;

[0026] Figure 6 It is a graph showing the specific capacity-voltage curves measured by charging / discharging secondary batteries using the positive electrode active materials prepared by Examples 1 to 3 and Comparative Example 1 at 0.1C / 0.1C;

[0027] Figure 7 This is a graph showing the high-temperature lifetime characteristics of secondary batteries using the positive electrode active materials prepared by Examples 1 to 3 and Comparative Example 1. Detailed Implementation

[0028] It will be understood that the words or terms used in the specification and claims should not be interpreted as having the meanings defined in common dictionaries, and it will also be understood that the words or terms should be interpreted as having meanings consistent with their meanings in the context of the relevant field and technical concept of the invention, based on the principle that the inventors can appropriately define the meanings of the words or terms to best interpret the invention.

[0029] Methods for preparing precursors for positive electrode active materials

[0030] As a result of extensive research conducted to develop precursors for cathode active materials that exhibit excellent reactivity with lithium during sintering, the inventors have discovered that precursor particles with low surface density and high specific surface area can be prepared by continuously increasing the feed rate during the precursor particle growth step, and that the reactivity with lithium during sintering can be increased when using the precursor, thus completing the present invention.

[0031] Specifically, the method for preparing precursors for positive electrode active materials according to the present invention is characterized in that the method comprises the following steps:

[0032] (1) Seed formation step: Precursor seeds for the positive electrode active material are formed by co-precipitation reaction simultaneously with the supply of a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to the reactor; and

[0033] (2) Particle growth step: The precursor particles for the positive electrode active material are grown by simultaneously supplying a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to the reaction solution in which precursor seeds for the positive electrode active material have already been formed.

[0034] In the particle growth step (2), the reaction is carried out while the supply rate of the transition metal aqueous solution and the ammonium cation complexing agent is continuously increased.

[0035] In this paper, the expression "continuously increasing the supply rate" refers to changing the supply flow rate of raw materials so that the curve of the supply flow rate relative to time becomes a continuous linear curve with a constant slope. This expression "continuously increasing the supply rate" is different from the concept of discontinuously and gradually increasing the supply flow rate.

[0036] The method for preparing precursors for positive electrode active materials according to the present invention will be described in more detail below.

[0037] (1) Seed formation steps

[0038] First, an aqueous solution of a transition metal, an ammonium cation complexing agent, and an alkaline compound are supplied to the reactor, and a co-precipitation reaction is carried out while stirring to form precursor seeds.

[0039] Ideally, the reactor should be a batch reactor. This is because it is difficult to control the particle size of precursor particles when using a continuous stirred tank reactor (CSTR) to prepare precursors.

[0040] The reactor may contain a mother liquor. Specifically, before supplying the aqueous transition metal solution, ammonium cation complexing agent, and basic compound as reaction raw materials, the ammonium cation complexing agent, basic compound, and water can be added to the reactor to form a mother liquor.

[0041] In this case, the ammonium cation complexing agent can be at least one selected from the following: NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3, and can be added to the reactor in the form of a solution of the above compounds dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically an alcohol, etc.) that can be uniformly mixed with water can be used as the solvent.

[0042] Next, the alkaline compound can be at least one selected from NaOH, KOH, and Ca(OH)₂, and can be added to the reactor in the form of a solution of the above compound dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically an alcohol, etc.) that can be uniformly mixed with water can be used as the solvent.

[0043] The reaction mother liquor can be prepared to have a pH of 11.0 to 12.5, for example, 11.3 to 12.3. When the pH of the reaction mother liquor meets the above range, seed formation can proceed smoothly.

[0044] After forming the reaction mother liquor by adding an ammonium cation complexing agent, an alkaline compound, and water to the reactor, oxygen in the reaction mother liquor is preferably removed by purging with nitrogen.

[0045] Next, precursor seeds are formed through the generation and spheroidization of precursor seeds by co-precipitation reaction, which is carried out while the reactor is being fed an aqueous transition metal solution, an ammonium cation complexing agent, and an alkaline compound under stirring. In this case, the aqueous transition metal solution and the ammonium cation complexing agent are supplied at a constant rate.

[0046] If an aqueous solution of a transition metal, an ammonium cation complexing agent, and an alkaline compound are supplied to a reactor containing a mother liquor and stirred, precursor nuclei in the form of primary particles are formed as the coprecipitation reaction proceeds. Simultaneously, as the primary particle nuclei aggregate and spheroidize, seeds in the form of secondary particles are formed.

[0047] In this case, the transition metal aqueous solution can contain nickel, cobalt and manganese elements, and can be formed by mixing nickel raw materials, cobalt raw materials and manganese raw materials with water.

[0048] The nickel raw materials can be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salts or nickel halides, and any one of the above materials or a mixture of two or more of them can be used.

[0049] The cobalt raw materials can be Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O or CoSO4·7H2O, and any one of the above materials or a mixture of two or more of them can be used.

[0050] Manganese raw materials can be: manganese oxides, such as Mn2O3, MnO2 and Mn3O4; manganese salts, such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate and fatty acid manganese salts; hydroxy oxides; and manganese chloride, and any one or a mixture of two or more of the above materials can be used.

[0051] If desired, aqueous solutions of transition metals may contain doping elements (M) in addition to nickel, cobalt, and manganese. 1 In this case, M 1 It may include at least one selected from the following: aluminum (Al), tungsten (W), molybdenum (Mo), chromium (Cr), zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb). When the transition metal aqueous solution also contains doping elements, improved lifetime characteristics, discharge characteristics, and / or stability can be obtained.

[0052] The transition metal aqueous solution also contains the dopant element M. 1 In this case, a dopant element M may be optionally added further during the preparation of the transition metal aqueous solution. 1 The raw materials.

[0053] M, as a doping element 1 The raw materials can use elements containing doped M. 1 The salt is selected from at least one of the following: acetate, sulfate, sulfide, hydroxide, oxide or hydroxyoxide.

[0054] Based on the total molar amount of transition metal, the transition metal aqueous solution can contain nickel raw material in such a manner that the amount of nickel is 30 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, and for example 90 mol% or more. When the amount of nickel in the transition metal aqueous solution is 70 mol% or more, the capacity characteristics can be further improved.

[0055] The ammonium cation complexing agent can be at least one selected from the following: NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3, and can be added to the reactor in the form of a solution of the above compounds dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically an alcohol, etc.) that can be uniformly mixed with water can be used as the solvent.

[0056] Furthermore, the alkaline compound can be at least one selected from NaOH, KOH, and Ca(OH)₂, and can be added to the reactor in the form of a solution of the above compound dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically an alcohol, etc.) that can be uniformly mixed with water can be used as the solvent.

[0057] The seed formation step can take anywhere from 1 to 8 hours, for example, 1 to 5 hours. If the seed formation time is too short, the number of seeds formed will be insufficient, resulting in excessively rapid particle growth, reduced sphericity, and a smaller final amount of precursor. Conversely, if the seed formation time is too long, the excessive number of seeds may lead to an excessively long reaction time required for the precursor particles to grow to the desired particle size, thus reducing productivity.

[0058] Furthermore, in the seed formation step, the pH of the reaction solution can be in the range of 11.0 to 12.5, for example, 11.3 to 12.0, and the temperature of the reaction solution can be in the range of 40°C to 65°C, for example, 50°C to 65°C. When the pH and temperature of the reaction solution meet the above ranges, nuclei of the positive electrode active material precursor are formed in the reaction solution, and the process of seed formation through nucleus aggregation can proceed smoothly. The pH of the reaction solution can be controlled by adjusting the amount of alkaline compound added using a pH sensor or similar method.

[0059] (2) Particle growth steps

[0060] When sufficient seeds are formed through the process described above, a co-precipitation reaction is carried out while supplying a transition metal aqueous solution, an ammonium cation complexing agent, and an alkaline compound to the reaction solution in which the precursor seeds have already been formed, thereby growing the positive electrode active material with precursor particles.

[0061] In the particle growth step, the reaction is carried out while the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent are continuously increased. Specifically, the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent can be continuously increased until the supply rates reach 2 to 10 times, preferably 2 to 5 times, and more preferably 3 to 5 times, the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent in the seed formation step. When the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent in the particle growth step are increased to less than twice the supply rates of the transition metal aqueous solution and the ammonium cation complexing agent in the seed formation step, the effect of increasing the specific surface area is not significant, and therefore the effect of improving sintering uniformity is reduced.

[0062] In this invention, when the supply rate of the transition metal aqueous solution and the ammonium cation complexing agent is continuously increased during the precursor particle growth step, the surface density and primary particle size of the formed precursor particles decrease as the reaction rate increases with the increase of reactants. As a result, precursor particles with a large specific surface area are prepared. If a precursor with a large specific surface area is used in the preparation of the cathode active material, the reactivity between the precursor and the lithium raw material increases during the sintering step, thereby improving the sintering uniformity. As a result, the reversible capacity of the cathode active material can be improved. When the supply rate of the reactants is increased rapidly in one go rather than continuously, precursor particles with a large specific surface area can be prepared. However, because the primary particle size of the precursor particles suddenly decreases, the difference in shrinkage rate between the seed of the precursor particles and the region formed in the particle growth step may increase during sintering, leading to cracks in the secondary particles. Therefore, this invention gradually reduces the primary particle size in the precursor particles by continuously increasing the supply rate of the reactants, thereby preventing cracks from appearing in the secondary particles during sintering.

[0063] Furthermore, by increasing the supply rate of the reaction raw materials in the particle growth step as in this invention, the reaction time required to form precursor particles with the desired particle size can be shortened, thus improving productivity.

[0064] Ideally, the rate of increase in the supply rate of the transition metal aqueous solution and the rate of increase in the supply rate of the ammonium cation complexing agent should be equal. Here, the rate of increase in the supply rate refers to the slope of the curve of the supply flow rate versus time. If the rate of increase in the supply rate of the transition metal aqueous solution and the rate of increase in the supply rate of the ammonium cation complexing agent differ, the specific surface area may increase excessively due to the decrease in particle density, or the amount of unprecipitated metal complex salt may increase, thereby reducing productivity or forming fine particles.

[0065] The aqueous solution of transition metals, ammonium cation complexing agents, and basic compounds added in the particle growth step are the same as those used in the seed formation step.

[0066] The pH of the reaction solution in the particle growth step can be in the range of 10.5 to 11.7, for example, 10.7 to 11.3, and the temperature of the reaction solution can be in the range of 40°C to 65°C, for example, 50°C to 65°C. Particle growth can proceed smoothly when the pH and temperature of the reaction solution meet these ranges. The pH of the reaction solution can be controlled by adjusting the amount of alkaline compound added using a pH sensor or similar method.

[0067] When the reactor is full during the particle growth step, after stopping the feed supply and agitation to allow the precursor particles in the reaction solution to settle, the supernatant is removed, and then the feed supply is resumed to continue the reaction. By performing the process of removing the supernatant from the reactor in the manner described above, sufficient reaction time required for precursor particle growth can be ensured, and the precursor yield can be increased. The above process can be repeated more than twice.

[0068] When the precursor particles are fully grown through the above process, the precursor particles for the positive electrode active material can be obtained by separating the precursor particles from the reaction solution, washing the precursor particles, and then drying them.

[0069] Precursors for positive electrode active materials

[0070] Next, the precursor for the positive electrode active material according to the present invention will be described.

[0071] The precursor for positive electrode active material according to the present invention is a precursor for positive electrode active material prepared by the above-described preparation method of the present invention.

[0072] The precursor for positive electrode active materials prepared according to the preparation method of the present invention has a lower surface density and a higher specific surface area than conventional precursors for positive electrode active materials.

[0073] Specifically, the precursor for the positive electrode active material according to the present invention can have a 10m 2 / g to 20m 2 / g, preferably 10m 2 / g to 18m 2 / g, more preferably 10m 2 / g to 16m 2The Brunauer-Emmett-Teller (BET) specific surface area of / g. If the BET specific surface area of the precursor satisfies the above range, the reactivity with lithium or a doping element during sintering is improved, thereby improving the sintering quality. As a result, a positive electrode active material having excellent capacity characteristics and structural stability can be prepared.

[0074] Specifically, the positive electrode active material precursor may be a hydroxide or oxyhydroxide containing nickel, cobalt, and manganese. For example, it may be a compound having a composition represented by the following [Formula 1] or [Formula 2].

[0075] [Formula 1]

[0076] [Ni a Co b Mn c M 1 d (OH)2

[0077] [Formula 2]

[0078] [Ni a Co b Mn c M 1 d O·OH

[0079] In Formula 1 and Formula 2, M 1 is at least one selected from Al, W, Mo, Cr, Zr, Ti, Mg, Ta, and Nb, and 0.8 ≤ a < 1, 0 < b < 0.2, 0 < c < 0.2, and 0 ≤ d < 0.1. Preferably, 0.85 ≤ a < 1, 0 < b < 0.15, 0 < c < 0.15, and 0 ≤ d < 0.1, and more preferably 0.9 ≤ a < 1, 0 < b < 0.1, 0 < c < 0.1, and 0 ≤ d < 0.1.

[0080] Positive electrode active material

[0081] Mix the positive electrode active material precursor according to the present invention prepared as described above with a lithium raw material, and then sinter it to prepare a positive electrode active material.

[0082] The lithium raw material can be used without particular limitation as long as it is a compound containing a lithium source, but preferably at least one selected from the following can be used: lithium carbonate (Li2CO3), lithium hydroxide (LiOH·H2O), LiNO3, CH3COOLi, and Li2(COO)2.

[0083] The precursor and lithium feedstock can be mixed in amounts such that the molar ratio of transition metal (Me) to lithium (Li) contained in the precursor is in the range of 1:1 to 1:1.2, for example, 1:1 to 1:1.1. When the lithium feedstock is mixed in a ratio smaller than the above range, the capacity of the prepared cathode active material may be reduced. When the lithium feedstock is mixed in a ratio larger than the above range, the preparation of the cathode active material may be difficult, the capacity may be reduced, and particle separation may occur after sintering because the particles are sintered during the sintering process.

[0084] In addition, if necessary, a mixture containing dopant element M can be added during sintering. 2 Materials. For example, dopant element M. 2 It may be selected from at least one of Al, W, Mo, Cr, Zr, Ti, Mg, Ta and Nb, and contains the dopant element M. 2 The material can be selected from those containing doped element M 2 It contains at least one of the following: acetate, sulfate, sulfide, hydroxide, oxide, or hydroxyoxide.

[0085] Sintering can be carried out for 5 to 20 hours in a temperature range of 700°C to 800°C, for example, for 5 to 15 hours in a temperature range of 700°C to 780°C, but the present invention is not limited thereto.

[0086] The positive electrode active material can be, for example, a lithium nickel cobalt manganese oxide represented by the following formula 3.

[0087] [Formula 3]

[0088] Li 1+p Ni x Co y Mn z M 2 w O2

[0089] In Equation 3, M 2 It can be at least one selected from Al, W, Mo, Cr, Zr, Ti, Mg, Ta and Nb.

[0090] 1+p represents the molar ratio of lithium in lithium transition metal oxides, where p can satisfy 0≤p≤0.3, for example 0≤p≤0.2.

[0091] x represents the molar ratio of nickel in all transition metals, where x can satisfy 0.80≤x<1.0, 0.85≤x<1, or 0.90≤x<1. Excellent capacity characteristics can be achieved when the nickel content meets the above range.

[0092] y represents the molar ratio of cobalt in all transition metals, where y can satisfy 0 < y < 0.20, 0 < y < 0.15, or 0 < y < 0.10.

[0093] z represents the molar ratio of manganese in all transition metals, where z can satisfy 0 < z < 0.20, 0 < z < 0.15, or 0.01 < z < 0.10.

[0094] w represents the molar ratio of M 2 in all transition metals, where w can satisfy 0 ≤ w ≤ 0.1 or 0 ≤ w ≤ 0.05.

[0095] positive electrode

[0096] In addition, the present invention provides a positive electrode for a lithium secondary battery, and the positive electrode for the lithium secondary battery includes a positive electrode active material prepared by the above method.

[0097] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and includes the above positive electrode active material.

[0098] There is no particular limitation on the positive electrode current collector as long as it has conductivity and does not cause adverse chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon; or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector usually can have a thickness of 3 μm to 500 μm, and fine concavities and convexities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various shapes such as a film, sheet, foil, net, porous body, foam body, non-woven fabric body, etc.

[0099] In addition to the positive electrode active material, the positive electrode active material layer may further include a conductive material and a binder.

[0100] In this case, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80% by weight to 99% by weight, for example, 85% by weight to 98% by weight. When the content of the positive electrode active material is within the above range, excellent capacity characteristics can be obtained.

[0101] In this context, a conductive material is used to provide conductivity to the electrode. Any conductive material can be used without particular limitation, provided it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of conductive materials include: graphite, such as natural or artificial graphite; carbonaceous materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, and carbon fibers; powders or fibers 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 or a mixture of two or more of the above materials can be used. Based on the total weight of the positive electrode active material layer, the content of the conductive material can typically range from 1% to 30% by weight.

[0102] The adhesive improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples of the adhesive can be polyvinylidene fluoride (PVDF), polyvinylidene 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 (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers of the above materials, and any one or a mixture of two or more of the above materials can be used. Based on the total weight of the positive electrode active material layer, the adhesive content can be from 1% by weight to 30% by weight.

[0103] In addition to using the aforementioned positive electrode active materials, positive electrodes can be prepared according to typical methods for preparing positive electrodes. For example, a mixture of positive electrode materials prepared by dissolving or dispersing the aforementioned positive electrode active materials, along with optional binders and conductive materials, in a solvent can be coated onto a positive electrode current collector. The positive electrode can then be prepared by drying and rolling the coated positive electrode current collector. Alternatively, the positive electrode can be prepared by casting the positive electrode material mixture onto a separate carrier and then pressing the film layer separated from the carrier onto the positive electrode current collector.

[0104] The solvent used to prepare the cathode material mixture can be a solvent commonly used in the art. Solvents may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, or water, and any one or a mixture of two or more of these solvents may be used. The amount of solvent used may be sufficient if, taking into account the coating thickness and manufacturing yield of the slurry, the solvent can dissolve or disperse the cathode active material, conductive material, and binder, and can allow for a viscosity that provides excellent thickness uniformity during subsequent coating for cathode preparation.

[0105] Lithium secondary batteries

[0106] Furthermore, in this invention, an electrochemical device comprising the positive electrode can be prepared. Specifically, the electrochemical device can be a battery or a capacitor, such as a lithium secondary battery.

[0107] A lithium secondary battery specifically includes a positive electrode, a negative electrode facing the positive electrode, a separator between the positive and negative electrodes, and an electrolyte. Since the positive electrode is the same as described above, its detailed description will be omitted, and only the remaining structures will be described in detail below.

[0108] In addition, the lithium secondary battery may optionally include: a battery container that houses an electrode assembly of a positive electrode, a negative electrode, and a separator; and a sealing member that seals the battery container.

[0109] In a lithium secondary battery, the negative electrode includes a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector.

[0110] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause adverse chemical changes in the battery. Materials used include, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon; copper or stainless steel surface-treated with one of carbon, nickel, titanium, or silver; and aluminum-cadmium alloys. Furthermore, the negative electrode current collector can typically have a thickness from 3 μm to 500 μm, and similar to the positive electrode current collector, fine irregularities can be formed on its surface 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, meshes, porous bodies, foams, and nonwoven fabrics.

[0111] In addition to the negative electrode active material, the negative electrode active material layer may optionally include a binder and a conductive material.

[0112] Compounds capable of reversibly inserting and deintercalating lithium can be used as anode active materials. Specific examples of anode active materials can be: carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; (semi-metallic) materials capable of forming alloys with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), Si alloys, Sn alloys, or Al alloys; and (semi-metallic) oxides that can be doped or undoped with lithium, such as SiO2. β(0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials containing (semi-)metallic materials and carbonaceous materials, such as Si-C composite materials or Sn-C composite materials, and any one or a mixture of two or more of the above materials may be used. Additionally, a thin film of metallic lithium may be used as the negative electrode active material. Based on the total weight of the negative electrode active material layer, the content of the negative electrode active material may be from 80% to 99% by weight.

[0113] Adhesives are components that facilitate the bonding between conductive materials, active materials, and current collectors. The adhesive content is typically from 0.1% to 10% by weight, based on the total weight of the negative electrode active material layer. Examples of adhesives include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers of the above materials.

[0114] Conductive materials are components used to further improve the conductivity of the negative electrode active material. Based on the total weight of the negative electrode active material layer, the content of the conductive material can be less than 10% by weight, for example, less than 5% by weight. There are no particular restrictions on the conductive material, as long as it is conductive and does not cause adverse chemical changes in the battery. For example, conductive materials such as: graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers; fluorinated carbon; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives.

[0115] For example, the negative electrode active material layer can be prepared by coating a mixture of negative electrode materials, prepared by dissolving or dispersing an optional binder and conductive material and the negative electrode active material in a solvent, onto a negative electrode current collector and drying the coated negative electrode current collector; or the negative electrode active material layer can be prepared by casting a mixture of negative electrode materials onto a separate carrier and then pressing the film layer separated from the carrier onto the negative electrode current collector.

[0116] In lithium-ion secondary batteries, the separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is commonly used in lithium-ion secondary batteries. In particular, separators with high electrolyte retention capacity and low resistance to electrolyte ion transfer can be used. Specifically, porous polymer membranes can be used, such as porous polymer membranes prepared from polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers); or laminated structures having two or more of the above porous polymer membranes. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. Additionally, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and separators with single-layer or multi-layer structures can optionally be used.

[0117] Furthermore, the electrolyte used in this invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used to prepare lithium secondary batteries, but this invention is not limited thereto.

[0118] Specifically, the electrolyte may contain organic solvents and lithium salts.

[0119] Any organic solvent can be used without particular limitation, as long as it can serve as a medium through which ions participating in the battery electrochemical reaction can move. Specifically, the following substances can be used as the organic solvent: 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 solvents, such as benzene and fluorobenzene; or carbonate solvents, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents, such as ethanol and isopropanol; nitriles, such as R-CN (where R is a straight-chain, branched, or cyclic C2 to C20 hydrocarbon group and may contain double bonds, aromatic rings, or ether bonds); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane; or sulfolane. Among these solvents, carbonate solvents can be used, such as mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate).

[0120] Lithium salts can be used without particular restrictions, as long as they are compounds capable of providing 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, or LiB(C2O4)2. Lithium salts can be used in concentrations ranging from 0.1 M to 4.0 M. When the concentration of the lithium salt is included within the above range, excellent electrolyte performance can be obtained because the electrolyte can have suitable conductivity and viscosity, and lithium ions can move efficiently.

[0121] To improve battery life characteristics, suppress battery capacity reduction, and increase battery discharge capacity, electrolytes may also contain additives.

[0122] The lithium secondary batteries described above can be suitably used in: portable devices such as mobile phones, laptops and digital cameras; and electric vehicles such as hybrid electric vehicles (HEVs).

[0123] Preferred implementation scheme

[0124] In the following description, embodiments of the invention will be described in detail in a manner that allows those skilled in the art to readily implement the invention. However, the invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0125] Example 1

[0126] (S-1) Distilled water, ammonia, and sodium hydroxide aqueous solution are charged into a 20L batch reactor and purged by supplying N2 gas at a rate of 4L / min. The mixture is then stirred to form a reaction mother liquor. The reactor temperature is then raised to 58°C.

[0127] (S-2) NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water in amounts such that the molar ratio of nickel:cobalt:manganese was 92:4:4 to prepare a 2.3 M transition metal aqueous solution. When the temperature of the solution in the reactor reached 58 °C, the transition metal aqueous solution and 15 wt% ammonia solution were added quantitatively at supply rates of 1200 ml / h and 108 ml / h, respectively, for 3 hours. Precursor seeds were formed by adding 25 wt% sodium hydroxide aqueous solution to maintain the pH of the reaction solution at 11.1 using a pH adjusting pump.

[0128] (S-3) After 3 hours, precursor particles were grown by continuously increasing the supply rate of the transition metal aqueous solution from 1200 ml / h to 3600 ml / h and the supply rate of ammonia from 108 ml / h to 324 ml / h for 18.5 hours. A 25% by weight sodium hydroxide aqueous solution was added using a pH adjusting pump to maintain the pH of the reaction solution at 11.1 during the reaction.

[0129] In the above process, the supply of reactants is stopped whenever the volume of the reaction solution reaches 20 L, stirring is stopped to allow the precursor intermediates to settle, leaving 10 L of reaction solution. The supernatant is then removed to restart the reaction. The average particle size D of the precursor particles is... 50 The reaction was terminated when the particle size reached 15 μm.

[0130] (S-4) After separating the precursor particles from the reaction solution, the precursor particles are washed with water, dried in a drying oven at 130°C for 12 hours, then pulverized and sieved to prepare a precursor for positive electrode active materials.

[0131] (S-5) After mixing the precursor, LiOH, Al2O3 and ZrO2 prepared as described above in such a way that the molar ratio of (Ni+Co+Mn):Li:Al:Zr is 1:1.03:0.02:0.0035, the mixture is sintered at 760°C for 10 hours to prepare the positive electrode active material.

[0132] Example 2

[0133] Except that in Example 1 (S-3), the supply rate of the transition metal aqueous solution was continuously increased from 1200 ml / h to 6000 ml / h and the supply rate of ammonia water was continuously increased from 108 ml / h to 540 ml / h while the reaction was carried out for 12.3 hours, the positive electrode active material was prepared in the same manner as in Example 1.

[0134] Example 3

[0135] Except that in Example 1 (S-3), the supply rate of the transition metal aqueous solution was continuously increased from 1200 ml / h to 9000 ml / h and the supply rate of ammonia water was continuously increased from 108 ml / h to 810 ml / h while the reaction was carried out for 8.7 hours, the positive electrode active material was prepared in the same manner as in Example 1.

[0136] Comparative Example 1

[0137] (S-1) Distilled water, ammonia, and sodium hydroxide aqueous solution are charged into a 20L batch reactor and purged by supplying N2 gas at a rate of 4L / min. The mixture is then stirred to form a reaction mother liquor. The reactor temperature is then raised to 58°C.

[0138] (S-2) NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water in amounts such that the molar ratio of nickel:cobalt:manganese was 92:4:4 to prepare a 2.3 M transition metal aqueous solution. When the temperature of the solution in the reactor reached 58 °C, the transition metal aqueous solution and 15 wt% ammonia solution were added quantitatively at supply rates of 1200 ml / h and 108 ml / h, respectively, for 40 hours. Precursor particles were formed by adding 25 wt% sodium hydroxide aqueous solution to maintain the pH of the reaction solution at 11.1 for 40 hours using a pH adjusting pump.

[0139] In the above process, the supply of reactants is stopped whenever the volume of the reaction solution reaches 20 L, stirring is stopped to allow the precursor intermediates to settle, leaving 10 L of reaction solution. The supernatant is then removed to restart the reaction. The average particle size D of the precursor particles is... 50 The reaction was terminated when the particle size reached 15 μm.

[0140] (S-3) After separating the precursor particles from the reaction solution, the precursor particles are washed with water, dried in a drying oven at 130°C for 12 hours, then pulverized and sieved to prepare a precursor for positive electrode active materials.

[0141] (S-4) After mixing the precursor, LiOH, Al2O3 and ZrO2 prepared as described above in such a way that the molar ratio of (Ni+Co+Mn):Li:Al:Zr is 1:1.03:0.02:0.0035, the mixture is sintered at 760°C for 10 hours to prepare the positive electrode active material.

[0142] Comparative Example 2

[0143] Except for the following, the positive electrode active material was prepared in the same manner as in Example 1: In Example 1 (S-3), the supply rates of the transition metal aqueous solution and the ammonia solution were not increased discontinuously but were increased to 3600 ml / h and 324 ml / h respectively at 80% of the supply flow rate to carry out the reaction for 9 hours. Then, the supply rates of the transition metal aqueous solution and the ammonia solution were further increased to 6000 ml / h and 540 ml / h respectively to carry out the reaction for 4 hours.

[0144] Experimental Example 1 - Evaluation of Precursor Powder Properties

[0145] The average particle size (D50), BET specific surface area, and tap density of the precursors for positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2, as well as the particle density of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2, were measured using the following methods. The measurement results are shown in Table 1 below.

[0146] (1) Average particle size D50: The volume-based cumulative particle size distribution was measured using a particle size distribution measuring instrument (Microtrac S3500, Microtrac Corporation).

[0147] (2) BET specific surface area: The specific surface area is measured by the BET method, in which the specific surface area is calculated based on the amount of nitrogen adsorbed at the liquid nitrogen temperature (77K) using Bell Japan's BELSORP-mini II.

[0148] (3) Tap density: After weighing 50g of the positive electrode active material precursor and placing it in a special container, the volume was measured by tapping 3000 times, and the tap density was calculated by dividing the weight by the volume. The SEISHIN Enterprise KYT-4000 was used as the measuring device.

[0149] (4) Particle density: After 5g of positive electrode active material was placed in a mold with a diameter of 22mm and pressurized with a pressure of 2 tons to prepare granules, the volume of the granules was measured, and the particle density was calculated by dividing the weight by the volume. The HPRM-A2 (HANTECH) was used as the measuring device.

[0150] [Table 1]

[0151]

[0152] As shown in Table 1, compared with the precursor for positive electrode active material prepared by the method of the comparative example where the reaction was carried out under conditions where the supply rate was not changed, the precursor for positive electrode active material prepared by the method of Examples 1 to 3, in which the supply rate of the raw material was continuously increased during the particle growth step, had a higher specific surface area. Furthermore, it was confirmed that the higher the increase in supply rate, the greater the increase in specific surface area.

[0153] Although density usually decreases as the specific surface area of ​​particles increases, the precursors of Examples 1 to 3 of the present invention still exhibit a tap density comparable to that of the precursor of Comparative Example 1, despite the increase in the specific surface area of ​​the precursors. It can also be confirmed that the particle density of the positive electrode active material prepared using the precursors of Examples 1 to 3 of the present invention is not significantly different from that of Comparative Example 1.

[0154] In Comparative Example 2, where the supply rate was increased only once rather than continuously, the specific surface area and tap density of the precursor were similar to those of the Example, but the particle density of the sintered positive electrode active material was significantly reduced, which was believed to be due to particle cracks generated during sintering.

[0155] Furthermore, in Examples 1 to 3 and Comparative Examples 1 and 2, precursor particle samples were collected when the added flow rate was equivalent to 20% of the total supply flow rate of the transition metal aqueous solution added throughout the process, and the surface characteristics of the precursor particles were confirmed by scanning electron microscopy (SEM) analysis. Additionally, the surface characteristics of the final precursor particles prepared by the methods of Examples 1 to 3 and Comparative Examples 1 and 2 were confirmed by scanning electron microscopy (SEM) analysis.

[0156] SEM images of the precursors for the positive electrode active materials prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 are shown below. Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 In. Figures 1 to 5 In the diagram, (A) is a SEM image showing the surface of the precursor particles when the added flow rate is equivalent to 20% of the total supply flow rate of the transition metal aqueous solution, and (B) is a SEM image showing the surface of the final precursor particles. Furthermore, SEM images of the positive electrode active material prepared in Comparative Example 2 are shown below. Figure 5 In (C).

[0157] refer to Figures 1 to 5 It can be confirmed that the surface density and primary particle size of the cathode active material precursors prepared in Examples 1 to 3 are reduced compared to the precursor prepared in Comparative Example 1. Furthermore, for Examples 1 to 3, the surface density and primary particle size of the final precursor particles and the precursor particles collected at an added flow rate equivalent to 20% of the total supply flow rate of the transition metal aqueous solution showed almost no change. However, for Comparative Example 1, it can be confirmed that the surface density and primary particle size of the final precursor particles were significantly increased compared to the precursor particles collected at an added flow rate equivalent to 20% of the total supply flow rate of the transition metal aqueous solution. (Reference) Figure 5 (C) When the method of Comparative Example 2, in which the supply rate is increased in a stepwise manner instead of continuously, is adopted, it can be confirmed that cracks occur in the sintered positive electrode active material. This is believed to be because when the supply flow rates of the transition metal aqueous solution and the ammonium cation complexing agent are increased discontinuously and rapidly, the density inside the particles changes rapidly, and the degree of particle shrinkage changes during sintering.

[0158] Experimental Example 2 - Capacity Characteristic Evaluation

[0159] A positive electrode slurry was prepared by mixing each of the positive electrode active materials, conductive materials, and PVDF binders prepared in Examples 1 to 3 and Comparative Example 1 in N-methyl-2-pyrrolidone (NMP) at a weight ratio of 97.5:1:1.5. The slurry was coated onto an aluminum current collector using a doctor blade, dried, and then rolled to prepare the positive electrode.

[0160] An electrode assembly was fabricated by stacking a polyethylene separator and a lithium metal anode on a positive electrode prepared as described above, and an electrolyte was injected to fabricate a coin cell. As the electrolyte, a solution of 1 M LiPF6 dissolved in an organic solvent in a volume ratio of ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) was used.

[0161] Each coin cell prepared as described above was charged at 25°C with a constant current at a rate of 0.1C until the voltage reached 4.25V, and then charged at a constant voltage until the current dropped below 0.05C. Each coin cell was then discharged at a constant current of 0.1C until the voltage reached 2.5V, and the charging capacity and discharging capacity were measured.

[0162] Furthermore, after charging each coin cell prepared as described above at 25°C with a constant current at a rate of 0.2C until the voltage becomes 4.25V and then charging at a constant voltage until the current becomes below 0.05C, each coin cell is discharged at a constant current of 0.2C until the voltage reaches 2.5V, and the charging capacity and discharging capacity are measured.

[0163] The measurement results are shown in Table 2 below. Figure 6 middle. Figure 6 It is a graph showing the specific capacity-voltage curve during 0.1C charging / 0.1C discharging.

[0164] [Table 2]

[0165]

[0166] Refer to [Table 2] and Figure 6 It can be confirmed that the charge / discharge capacity of the secondary battery prepared using the positive electrode active material of Examples 1 to 3 is better than that of the secondary battery prepared using the positive electrode active material of Comparative Example 1.

[0167] Experimental Example 3 - High Temperature Cycling Characteristics

[0168] The coin cell battery prepared in Experimental Example 2 was charged at 45°C with a constant current of 0.33C to 4.25V, and then charged at a constant voltage until the current dropped below 0.05C. Subsequently, each coin cell battery was discharged at a constant current of 0.33C to 2.5V. This charging and discharging cycle was defined as one cycle, and after repeating this cycle 30 times, the capacity retention rate of the lithium secondary batteries of Examples 1 to 3 and Comparative Example 1 after 30 cycles was measured. In this case, the capacity retention rate after 30 cycles is the percentage of the discharge capacity after 30 cycles to the discharge capacity after the first cycle.

[0169] The measurement results are shown in Table 3 below. Figure 7 middle.

[0170] [Table 3]

[0171] Capacity retention rate after 30 cycles [%) Comparative Example 1 93.5 Example 1 94.6 Example 2 94.2 Example 3 92.9

[0172] Refer to [Table 3] and Figure 7 It can be confirmed that, compared with the secondary battery using the positive electrode active material of Comparative Example 1, the secondary batteries using the positive electrode active materials of Examples 1 and 2 respectively have a higher capacity retention rate after 30 cycles.

Claims

1. A method for preparing a precursor for a positive electrode active material, the method comprising: A seed formation step: forming seeds of a precursor for a positive electrode active material by performing a coprecipitation reaction while supplying an aqueous solution of a transition metal, an ammonium cation complexing agent, and an alkaline compound to a reactor; and A particle growth step: growing precursor particles of a positive electrode active material by performing a coprecipitation reaction while supplying an aqueous solution of a transition metal, an ammonium cation complexing agent, and an alkaline compound to a reaction solution in which the seeds of the precursor for a positive electrode active material have been formed, wherein, in the particle growth step, the reaction is performed while continuously increasing the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent, wherein the aqueous solution of the transition metal contains nickel, cobalt, and manganese elements, and contains 30 mol% or more of nickel among all transition metal elements, wherein the ammonium cation complexing agent is at least one selected from the following: NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3, wherein the alkaline compound is at least one selected from the following: NaOH, KOH, and Ca(OH)2.

2. The method according to claim 1, wherein, In the particle growth step, the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent are continuously increased until the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent in the particle growth step reach 2 to 10 times the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent in the seed formation step, respectively.

3. The method according to claim 1, wherein, In the particle growth step, the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent are continuously increased until the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent in the particle growth step reach 2 to 5 times the supply rates of the aqueous solution of the transition metal and the ammonium cation complexing agent in the seed formation step, respectively.

4. The method according to claim 1, wherein, In the particle growth step, the rate of increase in the supply rate of the aqueous solution of the transition metal is equal to the rate of increase in the supply rate of the ammonium cation complexing agent.

5. The method according to claim 1, wherein, The seed formation step is performed for 1 hour to 8 hours.

6. The method according to claim 1, wherein, The aqueous solution of the transition metal contains 70 mol% or more of nickel among all transition metal elements.

7. The method according to claim 1, wherein, In the seed formation step, the alkaline compound is added in an amount such that the pH of the reaction solution is maintained at 11.0 to 12.

5.

8. The method according to claim 1, wherein, In the particle growth step, the alkaline compound is added in an amount such that the pH of the reaction solution is maintained at 10.5 to 11.

7.

9. The method according to claim 1, wherein, In the seed formation step and the particle growth step, the temperature of the reaction solution is in the range of 40°C to 65°C.

10. A precursor for a positive electrode active material, the precursor being prepared by the method according to any one of claims 1 to 9.

11. The precursor for the positive electrode active material according to claim 10, wherein, The precursor for the positive electrode active material has a 10 μm 2 / g to 20 m 2 / g of Brueer-Emmett-Teller (BET) specific surface area.

12. The precursor for the positive electrode active material according to claim 10, wherein, The precursor for a positive electrode active material has a composition represented by [Formula 1] or [Formula 2], [Formula 1] [Ni a What b Mn c M 1 d ](OH)2 [Formula 2] [Ni a Co b Mr c M 1 d ]O·OH wherein, in Formula 1 and Formula 2, M 1 It is selected from at least one of Al, W, Mo, Cr, Zr, Ti, Mg, Ta, and Nb. 0.8 ≤ a < 1, 0 < b < 0.2, 0 < c < 0.2, and 0 ≤ d < 0.1.

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