Method for manufacturing a positive electrode active material precursor for a lithium secondary battery and positive electrode active material precursor for a lithium secondary battery manufactured by the same

Abstract

The present invention relates to a method for producing a positive electrode active material precursor for a lithium secondary battery, the method comprising: a first coprecipitation step of charging a first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution into a first reactor to form a first reaction solution, and carrying out a coprecipitation reaction at a first stirring speed; and a second coprecipitation step of transferring the first reaction solution to a second reactor, charging a second transition metal-containing solution, a second complexing agent-containing solution, and a second pH adjuster-containing solution to form a second reaction solution, and carrying out a coprecipitation reaction at a second stirring speed to form a positive electrode active material precursor, wherein the second stirring speed is slower than the first stirring speed.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a positive electrode active material precursor for a lithium secondary battery, and to a positive electrode active material precursor for a lithium secondary battery produced thereby. [Background technology]

[0002] As technological development and demand for mobile devices increases, the demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0003] Lithium-transition metal composite oxides are used as the positive electrode active material for lithium secondary batteries, and among these, lithium-cobalt composite metal oxides such as LiCoO2 are mainly used because of their high working voltage and excellent capacity characteristics. However, LiCoO2 has very poor thermal properties due to the instability of its crystal structure caused by delithiation, and is expensive, so there are limitations to its mass use as a power source in fields such as electric vehicles.

[0004] Lithium manganese composite metal oxides (e.g., LiMnO2 or LiMn2O4), lithium iron phosphate compounds (e.g., LiFePO4), and lithium nickel composite metal oxides (e.g., LiNiO2) have been developed as alternatives to LiCoO2. Among these, lithium nickel composite metal oxides, which have a high reversible capacity of approximately 200 mAh / g and facilitate the realization of high-capacity batteries, have been the subject of active research and development. However, LiNiO2 has inferior thermal stability compared to LiCoO2. If an internal short circuit occurs during charging due to external pressure, the positive electrode active material itself can decompose, resulting in battery explosion and fire. Therefore, lithium nickel cobalt metal oxides, in which a portion of the Ni is replaced with Co and a metal element M (where M is at least one of Mn and Al), have been developed as a way to improve the low thermal stability of LiNiO2 while maintaining its excellent reversible capacity.

[0005] A typical method for producing such a cathode active material precursor is to use a batch reactor. However, when using a conventional batch reactor, the co-precipitation reaction continues, and the reaction ends when the reactor is filled with the reaction solution, requiring a cleaning process and time to establish the initial reaction conditions. Another drawback is that the reactor size cannot be increased due to issues such as motor overload and vibration during high-speed stirring. This significantly reduces the productivity of the cathode active material precursor. Furthermore, the continuous high-speed stirring co-precipitation can cause cracks, fragmentation, or wear in the precursor. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, one object of the present invention is to provide a method for producing a positive electrode active material precursor that can significantly improve the productivity of the positive electrode active material precursor and significantly reduce cracks (particle cracking), defects, or wear.

[0007] Another object of the present invention is to provide a positive electrode active material precursor produced by the above-mentioned production method. [Means for solving the problem]

[0008] One embodiment of the present invention provides a method for producing a cathode active material precursor for a lithium secondary battery, the method comprising: a first co-precipitation step of introducing a first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution into a first reactor to form a first reaction solution, and conducting a co-precipitation reaction at a first stirring speed; and a second co-precipitation step of transferring the first reaction solution to a second reactor, introducing a second transition metal-containing solution, a second complexing agent-containing solution, and a second pH adjuster-containing solution to form a second reaction solution, and conducting a co-precipitation reaction at a second stirring speed to form a cathode active material precursor, wherein the second stirring speed is slower than the first stirring speed.

[0009] The volume of the second reactor may be greater than the volume of the first reactor.

[0010] The second reactor may be plural.

[0011] The number of the second reactors may be two to four.

[0012] The first stirring speed may be between 100 and 170 rpm.

[0013] The first agitation speed may be adjusted to include a region of decreased agitation speed.

[0014] The second stirring speed may be between 30 and 100 rpm.

[0015] The first co-precipitation step may be carried out under a first pH condition, and the second co-precipitation step may be carried out under a second pH condition, and the second pH may be adjusted between a maximum and minimum value of the first pH.

[0016] The first pH may be adjusted to 11-13 and the second pH may be adjusted to 10-12.

[0017] The first pH may be adjusted to include a pH decreasing region, a first pH region, and a second pH region, and the pH values ​​of the first pH region and the second pH region may be lower than the starting pH value of the first pH.

[0018] In the first co-precipitation step, the supply rate of the first transition metal-containing solution may be adjusted to sequentially include a primary supply rate region and a secondary supply rate region, and the secondary supply rate may be higher than the primary supply rate.

[0019] The primary feed rate may be between 250 and 350 kg / h and the secondary feed rate may be between 1900 and 2100 kg / h.

[0020] In the second co-precipitation step, the supply rate of the second transition metal-containing solution may be 1900 to 2100 kg / h.

[0021] The supply rate of the first complexing agent-containing solution in the first co-precipitation step may be greater than the supply rate of the second complexing agent-containing solution in the second co-precipitation step.

[0022] The supply rate of the first complexing agent-containing solution may be 1.3 to 1.7 kg / h, and the supply rate of the second complexing agent-containing solution may be 0.4 to 0.8 kg / h.

[0023] In the first co-precipitation step, the ammonia concentration of the first reaction solution may be adjusted to 0.40 to 1.60 wt %, and the ammonia concentration of the first reaction solution may be adjusted to include a concentration increasing region, and in the second co-precipitation step, the ammonia concentration of the second reaction solution may be adjusted between the maximum and minimum values ​​of the ammonia concentration of the first reaction solution.

[0024] In the second co-precipitation step, the ammonia concentration of the second reaction solution may be adjusted to include a decreasing concentration region and a constant concentration region, and the ammonia concentration in the constant concentration region may be adjusted to 0.80 to 1.00 wt %.

[0025] In the second co-precipitation step, a portion of the second reaction solution may be discharged through an outlet attached to one side of the second reactor, and only the liquid may be selectively discharged through a CCSVR (Continuous Concentrate Single Vessel Reactor) concentration in the outlet.

[0026] Another embodiment of the present invention provides a positive electrode active material precursor for a lithium secondary battery prepared by the above-described method. [Effects of the Invention]

[0027] In a method for preparing a positive electrode active material precursor for a lithium secondary battery according to one embodiment of the present invention, the coprecipitation reaction is carried out in a first reactor in which a coprecipitation reaction occurs with high-speed stirring and a second reactor in which a coprecipitation reaction occurs with low-speed stirring. This significantly increases the volume of the entire reactors, thereby significantly improving precursor productivity and significantly reducing the occurrence of cracks, cracks, or wear of the precursor.

[0028] In addition, such a co-precipitation reaction system has industrial advantages such as simple equipment, low process costs, easy control of co-precipitation reaction conditions, and the ability to produce precursors with diverse specifications. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram of a method for producing a positive electrode active material precursor for a lithium secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 shows pH profiles during the production of the positive electrode active material precursors for lithium secondary batteries according to Example 1 and Comparative Example 1. [Figure 3] FIG. 3 shows the stirring speed profiles during the production of the positive electrode active material precursor for lithium secondary batteries according to Example 1 and Comparative Example 1. [Figure 4] FIG. 4 shows the supply rate profiles of the transition metal-containing solution during the production of the positive electrode active material precursor for lithium secondary batteries according to Example 1 and Comparative Example 1. [Figure 5] FIG. 5 shows profiles of the supply rate of the complexing agent-containing solution during the production of the positive electrode active material precursor for lithium secondary batteries according to Example 1 and Comparative Example 1. [Figure 6] FIG. 6 shows ammonia concentration profiles in the reaction solution during the production of the positive electrode active material precursor for lithium secondary batteries according to Example 1 and Comparative Example 1. [Figure 7] FIG. 7 is an SEM image of the positive electrode active material precursor prepared in Example 1. [Figure 8] FIG. 8 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1. [Figure 9]FIG. 9 is an SEM image of the positive electrode active material precursor prepared in Example 1. [Figure 10] FIG. 10 is an SEM image of the positive electrode active material precursor prepared in Example 1. [Figure 11] FIG. 11 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1. [Figure 12] FIG. 12 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may also be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0031] The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular form includes the plural form unless the context clearly dictates otherwise. As used in the specification, the meaning of "comprising" embodies certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0032] When we say that a part is "on" another part, it may be directly on top of the other part, or there may be other parts in between. In contrast, when we say that a part is "directly on top of" another part, there are no other parts in between.

[0033] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless otherwise defined.

[0034] Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0035] In this specification, the term "combination (etc.)" used in a maxi-format expression means a mixture or combination of one or more elements selected from the group of elements described in the maxi-format expression, and means including any one or more elements selected from the group of elements.

[0036] While the present invention may be embodied in many different forms, it is to be understood that the invention is not limited to the embodiments set forth herein.

[0037] Conventional coprecipitation reactors for producing cathode active material precursors typically use batch-type coprecipitation reactors. However, precursor productivity during coprecipitation reactions is generally proportional to the volume of the coprecipitation reactor. However, batch-type coprecipitation reactors have limitations on reactor volume due to issues such as motor overload and vibration during high-speed stirring, resulting in reduced precursor productivity. Furthermore, when high-speed stirring coprecipitation reactions are performed for long periods of time, cracks (particle cracking) occur in the precursor, increasing friction and wear.

[0038] Therefore, the present inventors have developed a coprecipitation reaction system in which the coprecipitation reaction is carried out in two separate reactors, a first reactor with high-speed stirring and a second reactor with low-speed stirring, thereby significantly increasing the volume of the coprecipitation reactors and reducing the occurrence of cracks in the precursor. The present invention will be described in more detail below.

[0039] FIG. 1 is a schematic diagram of a method for producing a positive electrode active material precursor for a lithium secondary battery according to one embodiment of the present invention.

[0040] Referring to FIG. 1 , one embodiment of the present invention provides a method for producing a cathode active material precursor for a lithium secondary battery, the method comprising: a first co-precipitation step of introducing a first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution into a first reactor 10 to form a first reaction solution and conducting a co-precipitation reaction at a first stirring speed; and a second co-precipitation step of transferring the first reaction solution to a second reactor 20, introducing a second transition metal-containing solution, a second complexing agent-containing solution, and a second pH adjuster-containing solution to form a second reaction solution and conducting a co-precipitation reaction at a second stirring speed to form a cathode active material precursor, wherein the second stirring speed is slower than the first stirring speed.

[0041] First, the precursor production system of the present invention will be described in general.

[0042] A method for producing a positive electrode active material precursor according to one embodiment of the present invention includes a first co-precipitation step which is a low-speed stirring co-precipitation step and a second co-precipitation step which is a high-speed stirring co-precipitation step.

[0043] The first co-precipitation step is carried out in a first reactor 10, in which a first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution are introduced to form a first reaction solution, and the co-precipitation reaction is carried out at a first stirring speed.

[0044] The second co-precipitation step is carried out in a second reactor 20. The first reaction solution, which has undergone some co-precipitation, is transferred to the second reactor 20, and a second transition metal-containing solution, a second complexing agent-containing solution, and a second pH adjuster-containing solution are further added to form a second reaction solution, which is then co-precipitated at a second stirring speed, thereby obtaining a final cathode active material precursor.

[0045] In this case, the second stirring speed is lower than the first stirring speed. By including the low-speed stirring coprecipitation reaction, the occurrence of cracks, cracks, or wear of the precursor can be significantly reduced.

[0046] Furthermore, in the second reactor, coprecipitation is performed at a low second agitation speed, significantly reducing motor overload and vibration issues compared to the first reactor, and the volume of the second reactor can be made larger than that of the first reactor. As mentioned above, an increase in the volume of the coprecipitation reactor leads to an increase in precursor productivity, maximizing the effect of improving precursor productivity. For example, the first coprecipitation reactor is approximately 10 m 3 and the second coprecipitation reactor can have a volume of about 30 m 3 However, the present invention is not limited to this and may be embodied in various sizes depending on the purpose of the process.

[0047] The second reactor may be multiple, more specifically, two to four. By using multiple second reactors, the coprecipitation reactor volume increases, maximizing precursor productivity. However, if the number of second reactors is too large, the overall reaction time and the concentration of the solution may change significantly, which is why the upper limit is set as above.

[0048] The stirring speed conditions in the precursor production method of the present invention will be explained in more detail below.

[0049] In the first co-precipitation step, the first stirring speed may be adjusted to a range of 100 to 170 rpm or 100 to 160 rpm.

[0050] More specifically, the first stirring speed may be adjusted to include a stirring speed reduction region, which may occur throughout the first co-precipitation step or only during a portion of the first co-precipitation step.

[0051] The second stirring speed may be 30 to 100 rpm, more specifically 40 to 100 rpm.

[0052] More specifically, the second stirring speed may be adjusted to include a region of decreased stirring speed at the beginning of the second co-precipitation step and a region of constant stirring speed thereafter, although slight fluctuations in the stirring speed may occur in the region of constant stirring speed during actual implementation of the process.

[0053] As described above, by implementing the ranges and profiles of the first and second stirring speeds, the reaction is induced in a direction that reduces the zeta potential of the particles, and the inhibition of new reactions and particle collisions are reduced, thereby favorably realizing the effects of preventing precursor cracking, differentiation, and wear.

[0054] Meanwhile, when forming the second reaction solution in the second co-precipitation step, water may be added, which allows the stirring speed to be easily reduced and makes it easier to realize the second stirring speed range and profile.

[0055] The pH conditions for the precursor production method of the present invention will be explained in more detail below.

[0056] The first co-precipitation step may be carried out under a first pH condition, and the second co-precipitation step may be carried out under a second pH condition, and the second pH may be adjusted between a maximum and minimum value of the first pH.

[0057] In this case, the first pH may be adjusted to 11 to 13, and the second pH may be adjusted to 10 to 12.

[0058] Specifically, the maximum value of the first pH may be 12.5 to 13, and the minimum value of the first pH may be 11 to 11.6. The final pH value of the first pH may be smaller than the initial pH value.

[0059] More specifically, the first pH may be adjusted to include a pH decreasing region, a first pH region, and a second pH region, and the pH values ​​of the first pH region and the second pH region may be lower than the starting pH value of the first pH.

[0060] The magnitude relationship between the pH value of the first pH region and the pH value of the second pH region is not particularly limited. For example, the pH value of the second pH region may be smaller than, equal to, or larger than the pH value of the first pH region. In this case, the pH value of the second pH region may be 11 to 12.

[0061] At this time, the first pH region and the second pH region may appear to be maintained constant, but may vary slightly when the actual process is implemented.

[0062] More specifically, the second pH may be adjusted to 10 to 12 or 11 to 12, and may be maintained at a constant pH, but may vary slightly during actual implementation of the process.

[0063] As described above, by implementing the first and second pH ranges and profiles, an appropriate amount of seeds can be initially generated, and then a relatively low pH can be maintained to improve the particle aggregation and orientation of the precursor. The improved particle aggregation and orientation of the precursor can improve the capacity and output characteristics of the battery.

[0064] The conditions for the supply rate of the transition metal-containing solution in the precursor production method of the present invention will be explained in more detail below.

[0065] In the first co-precipitation step, the supply rate of the first transition metal-containing solution may be adjusted to sequentially include a primary supply rate region and a secondary supply rate region, and the secondary supply rate may be higher than the primary supply rate.

[0066] More specifically, the primary supply rate may be 250 to 350 kg / h or 280 to 320 kg / h, and may be maintained constant, but may vary slightly when the process is actually implemented.

[0067] The secondary supply rate may be 1900 to 2100 kg / h or 1950 to 2050 kg / h, and may be maintained constant, but may vary slightly when the process is actually implemented.

[0068] In the second coprecipitation step, the supply rate of the second transition metal-containing solution may be 1900 to 2100 kg / h or 1950 to 2050 kg / h, and may appear to be maintained constant, but of course there may be slight variations when the process is actually implemented.

[0069] As described above, by implementing the range and profile of the supply rate of the first transition metal-containing solution and the supply rate of the second transition metal-containing solution, it is possible to control the reaction time and produce a high-density precursor.

[0070] The supply rate conditions for the complexing agent-containing solution in the precursor production method of the present invention will be explained in more detail below.

[0071] The supply rate of the first complexing agent-containing solution in the first co-precipitation step may be greater than the supply rate of the second complexing agent-containing solution in the second co-precipitation step.

[0072] In this case, the supply rate of the first complexing agent-containing solution may be 1.3 to 1.7 kg / h or 1.4 to 1.6 kg / h, and the supply rate of the second complexing agent-containing solution may be 0.4 to 0.8 kg / h or 0.5 to 0.7 kg / h.

[0073] The supply rate of the first complexing agent-containing solution and the supply rate of the second complexing agent-containing solution may appear to be maintained constant, but of course, there may be slight variations when the process is actually implemented.

[0074] As described above, by realizing the range and profile of the supply rate of the first complexing agent-containing solution and the supply rate of the second complexing agent-containing solution, it is possible to easily control the shape and density of the primary particles.

[0075] The ammonia concentration conditions of the reaction solution in the precursor production method of the present invention will be explained in more detail below.

[0076] In the first co-precipitation step, the ammonia concentration of the first reaction solution may be adjusted to 0.40 to 1.60 wt %, and the ammonia concentration of the first reaction solution may be adjusted to include a concentration increasing region. In the second co-precipitation step, the ammonia concentration of the second reaction solution may be adjusted between the maximum and minimum values ​​of the ammonia concentration of the first reaction solution. More specifically, in the first co-precipitation step, the minimum value of the ammonia concentration of the first reaction solution may be 0.40 to 0.50 wt %, and the maximum value of the ammonia concentration of the first reaction solution may be 1.40 to 1.60 wt %. Also, in the first co-precipitation step, the final concentration of the first reaction solution may be greater than the initial concentration.

[0077] In the second coprecipitation step, the ammonia concentration of the second reaction solution is adjusted to include a decreasing concentration region and a constant concentration region, and the ammonia concentration in the constant concentration region may be adjusted to 0.80 to 1.00 wt % or 0.85 to 0.95 wt %. Of course, the constant concentration region may vary slightly during actual implementation of the process.

[0078] As described above, the range and profile of the ammonia concentration of the first reaction solution and the ammonia concentration of the second reaction solution are realized, thereby enabling the production of uniform seeds.

[0079] Meanwhile, in the second co-precipitation step, a portion of the second reaction solution is discharged through an outlet 30 attached to one side of the second reactor, and only the liquid phase can be selectively discharged through a CCSVR (Continuous Concentrate Single Vessel Reactor) concentration in the outlet.

[0080] More specifically, when the second reaction solution reaches 50 to 90% or more of the volume of the second reactor in the second co-precipitation step, only the liquid portion of the second reaction solution can be selectively discharged through the outlet.

[0081] As used herein, CCSVR (Continuous Concentrate Single Vessel Reactor) concentration refers to a process in which, when the coprecipitation reaction solution reaches a certain size or larger, a multi-layer sieve installed in an outlet attached to one side of the coprecipitation reactor filters the solid precursor from the reaction solution so that it remains in the reactor, and only the liquid precursor from the reaction solution is discharged, thereby enabling the reaction to continue beyond the reactor volume.

[0082] This allows only the liquid portion of the second reaction solution to be selectively discharged, while the solid precursor remains in the reactor, securing additional reaction solution volume and increasing the solid-liquid ratio, thereby improving the co-precipitation reaction efficiency and maximizing productivity. In particular, the CCSVR concentration performed within the outlet of the second reactor eliminates the need for a separate concentrator vessel, resulting in high space efficiency and low equipment costs, which is advantageous in implementing process economy.

[0083] The first and second transition metal-containing solutions, the first and second complexing agent-containing solutions, and the first and second pH adjuster-containing solutions used in the precursor production method of the present invention will be described in more detail below.

[0084] The first and second transition metal-containing solutions may be prepared by adding a nickel source material and, optionally, a cobalt source material or a manganese source material to a solvent, specifically, a mixed solvent of water or an organic solvent (e.g., alcohol) that is uniformly miscible with water, or by mixing an aqueous solution of a nickel source material and, optionally, an aqueous solution of a cobalt source material or an aqueous solution of a manganese source material.

[0085] Meanwhile, the first and second transition metal-containing solutions may contain nickel in an amount of 60 to 99 atm%, 70 to 99 atm%, 80 to 99 atm%, 85 to 99 atm%, 90 to 99 atm%, or 90 to 95 atm% of the total transition metals.

[0086] The first and second transition metal-containing solutions may contain cobalt in an amount of 0 to 30 atm %, 1 to 20 atm %, 1 to 10 atm %, 2 to 8 atm %, or 2 to 6 atm % of the total transition metals.

[0087] In addition, the first and second transition metal-containing solutions may contain manganese in an amount of 0 to 30 atm %, 1 to 20 atm %, 1 to 10 atm %, 2 to 8 atm %, or 2 to 6 atm % of the total transition metals.

[0088] The first and second complexing agent-containing solutions function to form complexes and may contain, as a complexing agent, for example, but not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof. Meanwhile, the complexing agent-containing solutions may be used in the form of an aqueous solution, and the solvent may be water or a mixture of water and an organic solvent (e.g., alcohol) that is uniformly miscible with water.

[0089] The first and second pH adjuster-containing solutions function as precipitants or pH adjusters and may contain alkali compounds such as hydroxides of alkali metals or alkaline earth metals, hydrates thereof, or combinations thereof, such as NaOH, KOH, or Ca(OH)2. Meanwhile, the pH adjuster-containing solutions may also be used in the form of aqueous solutions, and in this case, the solvent may be water or a mixture of water and an organic solvent (e.g., alcohol) that is uniformly miscible with water.

[0090] Alternatively, the co-precipitation reaction may be carried out under an inert atmosphere such as nitrogen or argon.

[0091] Another embodiment of the present invention provides a positive electrode active material precursor for a lithium secondary battery prepared by the above-described method.

[0092] The cathode active material precursor prepared by this process exhibits significantly reduced cracks, defects, and wear, and significantly improved sphericity, aggregation, and orientation. The morphology of the active material precursor can be confirmed through SEM (Scanning Electron Microscope) images.

[0093] The positive electrode active material precursor may be a hydroxide containing nickel and optionally further containing cobalt or manganese, and more specifically, may be represented by the following Chemical Formula 1:

[0094] [Chemical formula 1] Ni x1 Co y1 Mn z1 (OH)2

[0095] In the above Chemical Formula 1, 0.6≦x1≦0.99, 0≦y1≦0.3, and 0≦z1≦0.3. [Example]

[0096] Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are merely preferred examples of the present invention and are not intended to limit the scope of the present invention.

[0097] Example 1: Two-step co-precipitation through first and second reactors (Preparation of raw materials) A first transition metal-containing solution and a second transition metal-containing solution were prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.88:0.05:0.07. The transition metal element concentration of the transition metal-containing solution was adjusted to 2.5 M. Then, an ammonia aqueous solution with a concentration of 28 wt% was prepared as a first complexing agent-containing solution and a second complexing agent-containing solution. In addition, a sodium hydroxide aqueous solution with a concentration of 25 wt% was prepared as a first pH adjuster-containing solution and a second pH adjuster-containing solution.

[0098] (First co-precipitation step) Volume is 10m 3 A first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution were charged into a first reactor to form a first reaction solution, nitrogen gas was supplied to the reactor to remove dissolved oxygen, and the coprecipitation reaction was carried out with stirring while maintaining the temperature of the reactor at 50° C. Here, the initial pH of the first coprecipitation step was 12.5, the initial stirring speed was 150 rpm, the initial first transition metal-containing solution feed rate was 300 rpm, the initial first complexing agent-containing solution feed rate was 1.5 kg / h, and the initial ammonia concentration of the first reaction solution was 0.45 wt %.

[0099] (Second co-precipitation step) After about 7 to 10 hours of the first coprecipitation reaction, the first reaction solution was diluted to an individual volume of 30 ml 3 The resulting mixture was transferred to three second reactors, and a second transition metal-containing solution, a second complexing agent-containing solution, a second pH adjuster-containing solution, and water were further added to form second reaction solutions. Nitrogen gas was supplied to the reactors to remove dissolved oxygen, and the reactors were stirred while maintaining the temperature at 50°C to carry out a coprecipitation reaction.

[0100] The pH in the coprecipitation reaction region, the stirring speed, the supply rate of the transition metal-containing solution, the supply rate of the complexing agent-containing solution, and the ammonia concentration profile of the reaction solution during the first and second coprecipitation steps are shown in Figures 2 to 6. The total coprecipitation reaction time was approximately 50 to 60 hours.

[0101] The composition of the produced positive electrode active material precursor was Ni 0.88 Co 0.05 Mn 0.07 (OH)2.

[0102] Comparative Example 1: One-step coprecipitation through a single reactor A transition metal-containing solution, a complexing agent-containing solution, and a pH adjuster-containing solution, each having the same composition as in Example 1, were prepared and introduced into a single coprecipitation reactor to carry out a coprecipitation reaction. The initial pH was 11.7, the initial stirring speed was 150 rpm, the initial transition metal-containing solution was supplied at a rate of 1900 kg / h, the initial complexing agent-containing solution was supplied at a rate of 0.7 kg / h, and the initial ammonia concentration of the reaction solution was 0.90 wt %. A positive electrode active material precursor was prepared in the same manner as in Example 1, except that a one-step coprecipitation reaction process was used in which these initial process conditions were maintained constant throughout the coprecipitation reaction. The process condition profiles are shown in Figures 2 through 6, respectively. The total coprecipitation reaction time was approximately 50 to 60 hours. The composition of the resulting positive electrode active material precursor was the same as in Example 1.

[0103] Experimental Example 1: Comparison of production yield of positive electrode active material precursor The yield of the positive electrode active material precursor prepared in Example 1 and Comparative Example 1 was measured, and the results are shown in Table 1 below.

[0104] [Table 1]

[0105] Referring to Table 1, it was confirmed that the productivity of the precursor was significantly improved by about three times as a result of applying the two-step co-precipitation reaction of the present invention.

[0106] Experimental Example 2: Evaluation of precursor cracks, differential cracks, and wear occurrence SEM images of the positive electrode active material precursors prepared in Example 1 and Comparative Example 1 were observed, and the results are shown in FIG. 7 (Example 1) and FIG. 8 (Comparative Example 1).

[0107] 7 and 8, it was confirmed that the positive electrode active material precursor of Example 1 was prepared using a two-step process with high and low stirring speed profiles, and thus the occurrence of cracks, defects, or wear was significantly reduced compared to Comparative Example 1.

[0108] Experimental Example 3: Evaluation of precursor orientation and sphericity SEM images of the positive electrode active material precursors prepared in Example 1 and Comparative Example 1 were observed, and the results are shown in FIGS. 9 and 10 (Example 1) and FIGS. 11 and 12 (Comparative Example 1).

[0109] 9 to 12, it was confirmed that the cathode active material precursor of Example 1 was prepared using a two-step pH profile process, which resulted in better overall sphericity of the secondary particle precursor particles and significantly improved orientation of the primary particles within the secondary particles compared to Comparative Example 1. This is expected to contribute to the capacity and output characteristics of the battery.

[0110] In summary, the technical gist of the present invention is that the reactor volume can be significantly increased through two-stage co-precipitation steps using high-speed and low-speed co-precipitation reactors, which not only significantly improves precursor productivity but also significantly reduces the occurrence of cracks, defects, or wear, thereby improving the physical properties of the precursor.

[0111] In addition, the sphericity and orientation of the precursor can be improved by controlling other process condition factors such as pH.

[0112] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention.

[0113] Therefore, the true scope of the present invention is defined by the appended claims and their equivalents. [Explanation of symbols]

[0114] 10: First reactor 20: Second reactor 30: Outlet

Claims

1. a first coprecipitation step of charging a first transition metal-containing solution, a first complexing agent-containing solution, and a first pH adjuster-containing solution into a first reactor to form a first reaction solution, and carrying out a coprecipitation reaction at a first stirring speed; and a second co-precipitation step of transferring the first reaction solution to a second reactor, adding a second transition metal-containing solution, a second complexing agent-containing solution, and a second pH adjuster-containing solution to form a second reaction solution, and performing a co-precipitation reaction at a second stirring speed to form a positive electrode active material precursor; The second stirring speed is less than the first stirring speed. A method for producing a positive electrode active material precursor for a lithium secondary battery.

2. The method for producing a positive electrode active material precursor for a lithium secondary battery according to claim 1 , wherein the second reactor has a volume larger than the volume of the first reactor.

3. The method of claim 1 , wherein the second reactor is a plurality of reactors.

4. The method of claim 3, wherein the number of the second reactors is two to four.

5. 2. The method of claim 1, wherein the first stirring speed is 100 to 170 rpm.

6. The method of claim 5 , wherein the first stirring speed is adjusted to include a stirring speed decreasing region.

7. 2. The method of claim 1, wherein the second stirring speed is 30 to 100 rpm.

8. 2. The method for producing a positive electrode active material precursor for a lithium secondary battery according to claim 1, wherein the first co-precipitation step is performed under a first pH condition, the second co-precipitation step is performed under a second pH condition, and the second pH is adjusted between a maximum value and a minimum value of the first pH.

9. 9. The method of claim 8, wherein the first pH is adjusted to 11 to 13, and the second pH is adjusted to 10 to 12.

10. 2. The method of claim 1, wherein the first pH is adjusted to sequentially include a pH decreasing region, a first pH region, and a second pH region, and the pH values ​​of the first pH region and the second pH region are lower than an initial pH value of the first pH.

11. 2. The method of claim 1, wherein in the first co-precipitation step, a supply rate of the first transition metal-containing solution is sequentially adjusted to include a primary supply rate region and a secondary supply rate region, and the secondary supply rate is higher than the primary supply rate.

12. 12. The method of claim 11, wherein the primary supply rate is 250 to 350 kg / h, and the secondary supply rate is 1900 to 2100 kg / h.

13. 2. The method of claim 1, wherein the second co-precipitation step supplies the second transition metal-containing solution at a supply rate of 1900 to 2100 kg / h.

14. 2. The method for producing a positive electrode active material precursor for a lithium secondary battery according to claim 1, wherein a supply rate of the first complexing agent-containing solution in the first co-precipitation step is higher than a supply rate of the second complexing agent-containing solution in the second co-precipitation step.

15. 15. The method of claim 14, wherein the supply rate of the first complexing agent-containing solution is 1.3 to 1.7 kg / h, and the supply rate of the second complexing agent-containing solution is 0.4 to 0.8 kg / h.

16. In the first co-precipitation step, the ammonia concentration of the first reaction solution is adjusted to 0.40 to 1.60 wt %, and the ammonia concentration of the first reaction solution is adjusted to include a concentration increasing region; 2. The method of claim 1, wherein in the second co-precipitation step, the ammonia concentration of the second reaction solution is adjusted to be between the maximum and minimum values ​​of the ammonia concentration of the first reaction solution.

17. 2. The method of claim 1, wherein, in the second co-precipitation, the ammonia concentration of the second reaction solution is adjusted to include a concentration decreasing region and a constant concentration region, and the ammonia concentration in the constant concentration region is adjusted to 0.80 to 1.00 wt %.

18. 2. The method of claim 1, wherein in the second co-precipitation, a portion of the second reaction solution is discharged through an outlet attached to one side of the second reactor, and only a liquid phase is selectively discharged through continuous concentrate single vessel reactor (CCSVR) concentration in the outlet.

19. A positive electrode active material precursor for a lithium secondary battery, produced by the production method according to any one of claims 1 to 18.

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