Method for producing a positive electrode active material precursor

Abstract

The method for producing a cathode active material precursor using a batch reactor according to the present invention includes: (S1) generating nuclei of the precursor; (S2) growing the nuclei generated in step S1; (S3) further growing the precursor particles grown in step S2; and (S4) further growing the precursor particles grown in step S3. The stirring speed in the batch reactor is 200 rpm to 900 rpm in step S2, 800 rpm or less in step S3, and 700 rpm or less in step S4. When the batch reactor is full, the reaction solution is allowed to overflow.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a cathode active material precursor, and more particularly to a method for producing a cathode active material precursor using an overflow method in a batch reactor. [Background technology]

[0002] Recently, the demand for secondary batteries has been increasing due to the expansion of the battery electric vehicle (BEV) market. A secondary battery generally includes a positive electrode, a negative electrode, an electrolyte, and a separator, and the positive electrode and the negative electrode include active materials capable of intercalating and deintercalating lithium ions, for example.

[0003] Representative methods for producing a cathode active material precursor include a method for producing a cathode active material precursor using a continuous stirred-tank reactor (CSTR) and a method for producing a cathode active material precursor using a batch reactor. The continuous reactor method involves adding raw materials, co-precipitating them, and simultaneously discharging the precursor particles. The batch reactor method involves adding raw materials to the reactor in accordance with the reactor volume for a certain period of time, reacting them, and discharging the precursor after the reaction is complete.

[0004] In a batch reactor, precursor particles are formed as the co-precipitation reaction time passes. In order to form precursor particles of a certain size or larger, the precursor particles formed through the initial nucleation reaction must continuously grow.

[0005] However, during the reaction for growing the precursor particles, new nucleation reactions continuously occur, resulting in the continuous generation of small precursor particles, which results in a smaller average particle size and a less uniform particle size distribution at the end of the co-precipitation reaction time, which can lead to problems such as the tap density and specific surface area of ​​the cathode active material not meeting target values ​​and adversely affecting the charge / discharge capacity performance of the battery.

[0006] To address this issue, conventional techniques have used an air classifier mill (ACM), air jet mill, etc. to capture the fine particles through a separate bag filter during the grinding process, or have transferred the precursor-containing reaction solution from the reactor to a cyclone facility and centrifuged to remove the fine particles. However, these conventional techniques have the drawback of increasing costs and time required for the entire process due to additional processes / equipment, thereby worsening line of balance (LOB) efficiency and reducing the production volume of cathode active materials.

[0007] Meanwhile, as the average particle size of precursor particles increases during the precursor preparation process, cracks may occur on the particle surface due to collisions between particles, which is problematic. When cracks occur on the precursor particle surface, the press density decreases, which can lead to additional cracks during the electrode rolling process during the preparation of the cathode active material. This can lead to side reactions with the electrolyte, resulting in reduced battery performance. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for preparing a precursor that can minimize the formation of precursor fine particles during the precursor nucleus growth step, thereby achieving a uniform particle size distribution and preventing the problem of cracks occurring on the precursor particle surface. [Means for solving the problem]

[0009] According to one aspect of the present invention, a method for preparing a cathode active material precursor using a batch reactor includes: (S1) generating nuclei of the precursor; (S2) growing the nuclei generated in step S1; (S3) further growing the precursor particles grown in step S2; and (S4) further growing the precursor particles grown in step S3. The stirring speed in the batch reactor is 200 rpm to 900 rpm in step S2, 800 rpm or less in step S3, and 700 rpm or less in step S4. When the batch reactor is full, the reaction solution is allowed to overflow.

[0010] According to one aspect of the present invention, the co-precipitation reaction in step S2 may be carried out for 1 hour to 20 hours.

[0011] According to one aspect of the present invention, the average particle size D of the precursor after the S3 step is completed 50 can be 6.5 μm to 13.0 μm.

[0012] According to one aspect of the present invention, in step S1, the stirring speed in the batch reactor may be 250 rpm to 1,000 rpm.

[0013] According to one aspect of the present invention, the flow rate of the transition metal compound solution introduced into the batch reactor may be 5 mL / min to 40 mL / min in steps S2 and S3, and 2 mL / min to 30 mL / min in step S4.

[0014] According to one aspect of the present invention, the transition metal compound solution may contain at least one element selected from the group consisting of nickel, cobalt, and manganese.

[0015] According to one aspect of the present invention, the transition metal compound solution may contain 60 mol % to 96 mol % of nickel, 0 mol % to 20 mol % of cobalt, and 4 mol % to 40 mol % of manganese.

[0016] According to one aspect of the present invention, the input flow rate of the nitrogen-containing compound solution may be 1.0 mL / min to 10.0 mL / min in the steps S2 and S3, and 1.2 mL / min to 8.0 mL / min in the step S4.

[0017] According to one aspect of the present invention, the flow rate of the basic compound solution may be 3 mL / min to 35 mL / min in the steps S2 and S3, and 2 mL / min to 30 mL / min in the step S4.

[0018] According to one aspect of the present invention, the reaction solution in the batch reactor in step S1 may have a pH of 10.5 to 13.5.

[0019] According to one aspect of the present invention, in steps S2, S3, and S4, the reaction solution in the batch reactor may have a pH of 10.5 to 13.0.

[0020] According to one aspect of the present invention, in steps S2, S3, and S4, the ammonia concentration in the reaction solution inside the batch reactor may be 3,000 ppm to 7,000 ppm.

[0021] According to one aspect of the present invention, in steps S2, S3, and S4, the concentration of residual nickel in the reaction solution inside the batch reactor may be 250 ppm or less.

[0022] According to one aspect of the present invention, the positive electrode active material precursor produced through steps S1 to S4 may have a span value of 0.38 or less according to the following Equation 1:

[0023] [Formula 1]

[0024] Span = (particle diameter D 90 - Particle size D 10 ) / average particle size D 50

[0025] According to one aspect of the present invention, the method may further include (S5) washing and drying the positive electrode active material precursor produced through steps S1 to S4. [Effects of the Invention]

[0026] In the present invention, when the batch reactor becomes full with the reaction solution during the precursor coprecipitation reaction, the reaction solution is overflowed through a discharge line. As a result, the ratio of precursors in the reactor is controlled to induce uniform growth of the precursors, thereby preventing the problem of cracks occurring on the precursor particle surface. In addition, when the overflow method is used, the solid density inside the reactor can be controlled by adjusting the amount of reaction solution input and output, so that even in the limited space inside the reactor, the particle size distribution becomes uniform and the average particle size D 50 However, it is possible to produce large precursor particles with a size of 7 μm to 30 μm.

[0027] In addition, the present invention can reduce the average particle size D by controlling the stirring speed in each of the precursor nucleus growth stages (S2 to S4) to a specific range. 50 This prevents cracks on the particle surface that may occur due to collisions between particles when preparing large precursor particles with particle sizes of 7 μm to 30 μm. As a result, it is possible to prevent cracks on the active material particle surface during the rolling process in the process of preparing a cathode active material from the precursor.

[0028] According to the precursor preparation method of the present invention, the formation of fine particles in the reaction solution is minimized during the nucleus growth steps (S2 to S4). As a result, a cathode active material precursor having a target particle size and uniform particle size distribution can be produced. Furthermore, because a separate process for removing fine particles is not required, the total process time and process costs can be significantly reduced, thereby improving production line efficiency and increasing the production yield of cathode active material. [Brief explanation of the drawings]

[0029] [Figure 1]FIG. 1 is a diagram illustrating a method for producing a positive electrode active material precursor according to the present invention. [Figure 2] FIG. 2 is an SEM image of the extracted positive electrode active material precursor after co-precipitation for 50 hours according to Example 1 of the present invention and drying the extracted positive electrode active material precursor. [Figure 3] FIG. 3 is an SEM image of the extracted positive electrode active material precursor after co-precipitation for 50 hours according to Example 2 of the present invention and drying the extracted positive electrode active material precursor. [Figure 4] FIG. 4 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 110 hours according to Comparative Example 1 of the present invention and then dried. [Figure 5] FIG. 5 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 110 hours according to Comparative Example 1 of the present invention and then dried. [Figure 6] FIG. 6 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 110 hours according to Comparative Example 1 of the present invention and then dried. [Figure 7] FIG. 7 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 110 hours according to Comparative Example 1 of the present invention and then dried. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, specific details for implementing the present disclosure will be described in detail with reference to the accompanying drawings. However, in the following description, detailed descriptions of well-known functions and configurations will be omitted if they may unnecessarily obscure the gist of the present disclosure.

[0031] In the accompanying drawings, identical or corresponding components are denoted by the same reference numerals. In addition, in the following description of the embodiments, duplicated descriptions of identical or corresponding components may be omitted. However, omission of a description of a component does not mean that such a component is not included in a certain embodiment.

[0032] The terms used in this disclosure will be briefly explained, and the disclosed embodiments will be described in detail. The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present disclosure. However, these terms may change depending on the intentions of engineers in the relevant field, legal precedents, the emergence of new technologies, etc. In addition, in certain cases, the applicant may arbitrarily select terms, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this disclosure should be defined based on the meanings of the terms and the overall content of the present disclosure, rather than simply by the names of the terms.

[0033] In this disclosure, the singular includes the plural unless the context clearly dictates otherwise, and the plural includes the singular unless the context clearly dictates otherwise.

[0034] In this disclosure, when a part includes certain elements, this means that it may further include other elements, but not excluding other elements, unless otherwise specified to the contrary.

[0035] In the present disclosure, the phrase "A and / or B" means either A, or B, or A and B.

[0036] The advantages and features of the disclosed embodiments, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments taken in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, and may be embodied in various different forms. The embodiments are provided solely for the purpose of ensuring completeness of the disclosure and fully conveying the scope of the invention to those skilled in the art.

[0037] The method for preparing a cathode active material precursor using a batch reactor according to the present invention includes: (S1) generating nuclei of the precursor; (S2) growing the nuclei generated in step S1; (S3) further growing the nuclei grown in step S2; and (S4) further growing the nuclei grown in step S3. The stirring speed in the batch reactor is 200 rpm to 900 rpm in step S2, 800 rpm or less in step S3, and 700 rpm or less in step S4. When the batch reactor is full, the reaction solution is allowed to overflow.

[0038] 1 is a diagram illustrating a method for preparing a cathode active material precursor according to the present invention. As shown in FIG. 1, a transition metal-containing solution, a basic aqueous solution, and an ammonium ion-containing solution are introduced into a batch reactor and stirred to cause a co-precipitation reaction, thereby preparing a reaction slurry containing a cathode active material precursor.

[0039] According to the present invention, before the transition metal-containing solution, the basic aqueous solution, and the ammonium ion-containing solution are introduced into the batch reactor, deionized water is introduced into the batch reactor and purged with an inert gas (e.g., nitrogen and / or argon) to remove dissolved oxygen in the water, thereby creating a non-oxidizing atmosphere within the reactor. This non-oxidizing atmosphere within the reactor can be maintained until the end of the coprecipitation reaction.

[0040] The transition metal-containing solution, the basic aqueous solution, and the ammonium ion-containing solution may be continuously supplied to the batch reactor through an inlet provided in the batch reactor. The transition metal-containing solution, the basic aqueous solution, and the ammonium ion-containing solution may be mixed in the batch reactor to form a reaction solution, and positive electrode active material precursor particles may be formed through a co-precipitation reaction of the reaction solution.

[0041] A batch reactor may be provided with an agitator as shown in Figure 1. The agitator may be, but is not limited to, an impeller. In the present invention, when a three-stage impeller is used as the agitator, it has the advantage of being able to uniformly agitate the reaction slurry from the lower to the upper stage.

[0042] Each step of the precursor preparation method according to the present invention will now be described in more detail.

[0043] Nucleation stage (S1 stage)

[0044] Step S1 is a step of generating nuclei of a cathode active material precursor. Specifically, by adding a transition metal compound solution, a nitrogen-containing compound solution, and a basic compound solution to a batch reactor and stirring them, the transition metal in the transition metal compound solution is co-precipitated, generating precursor particle nuclei in the form of transition metal hydroxide. At this time, the precursor particle nuclei have an average particle diameter D 50 It means particles having a particle size of 1.2 μm to 6.0 μm, specifically 1.5 μm to 5.5 μm.

[0045] The stirring speed in the reactor in the S1 step may be 250 rpm to 1,000 rpm, preferably 350 rpm to 900 rpm, and more preferably 450 rpm to 850 rpm. When the stirring speed in the S1 step satisfies the above range, it is effective in inducing uniform nucleation.

[0046] The pH of the reaction solution in step S1 may be 10.5 to 13.5, preferably 10.7 to 13.3, and more preferably 10.8 to 13.0. When the pH of the reaction solution in step S1 is within this range, it is possible to control the formation of primary particles. The pH of the reaction solution can be adjusted by adjusting the flow rates of the transition metal compound solution, nitrogen-containing compound solution, and / or basic compound solution.

[0047] The co-precipitation reaction in step S1 may be carried out in an inert atmosphere such as nitrogen and / or argon at a temperature of 40° C. to 60° C. When the temperature range is satisfied, the rate of the co-precipitation reaction can be controlled.

[0048] The flow rate of the transition metal compound solution introduced into the batch reactor in step S1 may be 2 mL / min to 35 mL / min, preferably 3 mL / min to 30 mL / min, and more preferably 4 mL / min to 25 mL / min. When the flow rate is within this range, the solid density in the reactor can be controlled to be advantageous for the nucleus growth reaction.

[0049] The transition metal compound solution may contain at least one element selected from the group consisting of nickel, cobalt, and manganese. For example, the transition metal compound solution may contain a nickel-cobalt-manganese compound.

[0050] The transition metal compound solution according to one embodiment of the present invention may contain nickel in an amount of 60 mol% to 96 mol%, preferably 80 mol% to 96 mol%, cobalt in an amount of 0 mol% to 20 mol%, preferably 0 mol% to 10 mol%, and manganese in an amount of 4 mol% to 40 mol%, preferably 4 mol% to 20 mol%. When the contents of nickel, cobalt, and manganese in the transition metal compound solution satisfy the above numerical ranges, it has the effect of increasing the energy density during battery production.

[0051] The transition metal compound solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water. From the viewpoint of productivity, the concentration of the transition metal compound solution can be 1.80 M to 2.65 M, preferably 2.00 M to 2.55 M. The amount of each transition metal-containing raw material added can be determined in consideration of the molar ratio between the transition metals in the final cathode active material to be prepared.

[0052] The transition metal-containing source material may include, but is not limited to, acetates, carbonates, nitrates, sulfates, halites, sulfides, oxides, hydrates, hydroxides, and / or oxyhydroxides of the transition metal. Preferably, the transition metal-containing source material may include a hydrate of the transition metal, which has the advantage of being easy to store and use.

[0053] The transition metal compound solution can be prepared by dissolving a nickel-containing source material, a cobalt-containing source material, and a manganese-containing source material in water. The nickel-containing source material can be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, a fatty acid nickel salt, a nickel halide, or a combination thereof. The cobalt-containing source material can be CoSO4, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4·7H2O, Co(SO4)2·7H2O, or a combination thereof. The manganese-containing source material can be manganese oxides such as Mn2O3, MnO2, and Mn3O4, MnCO3, Mn(NO3)2, MnSO4, MnSO4·H2O, manganese salts such as manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid salt, oxyhydroxide, manganese chloride, or a combination thereof. For example, NiSO4·6H2O can be used as the nickel-containing source material, CoSO4·7H2O can be used as the cobalt-containing source material, and MnSO4·H2O can be used as the manganese-containing source material.

[0054] When the positive electrode active material precursor further contains a metal element (M) other than nickel (Ni), manganese (Mn), and cobalt (Co), a raw material containing the metal element (M) may be optionally added during preparation of the transition metal compound solution. The metal element (M) may include one or more elements selected from the group consisting of W, Y, Ba, Ca, Mo, Cr, Al, Zr, Ti, Mg, Ta, and Nb. The raw material containing the metal element (M) may include, but is not limited to, acetate, carbonate, nitrate, sulfate, halite, sulfide, hydroxide, oxyhydroxide, and / or oxide of the metal element (M).

[0055] In step S1, the flow rate of the nitrogen-containing compound solution may be 1.0 mL / min to 10 mL / min, preferably 1.2 mL / min to 8.0 mL / min, and more preferably 1.5 mL / min to 5.0 mL / min. When the flow rate is within this range, nucleation can be controlled while maintaining an appropriate ammonia concentration in the reaction solution.

[0056] The nitrogen-containing compound solution can act as a complexing agent to promote the coprecipitation reaction between the transition metals in the transition metal compound solution.

[0057] The nitrogen-containing compound solution may contain an ammonium cation complexing agent. The ammonium cation complexing agent may contain at least one compound selected from the group consisting of NHOH, (NH)SO, NHNO, NHCl, CHCOONH, and NHCO. For example, the nitrogen-containing compound solution may be prepared by dissolving the ammonium cation complexing agent in a solvent. In this case, the solvent may be water or a mixture of water and an organic solvent (e.g., alcohol). The concentration of the nitrogen-containing compound solution may be 1% by weight to 50% by weight, preferably 5% by weight to 25% by weight. In this case, the ammonia concentration in the reactor may be appropriately controlled.

[0058] In step S1, the basic compound solution may be introduced at a flow rate of 2.0 mL / min to 30.0 mL / min, preferably 2.5 mL / min to 25.0 mL / min, and more preferably 2.8 mL / min to 20.0 mL / min. When the flow rate is within this range, the pH of the reaction solution can be maintained at an appropriate value, and constant nucleation can be induced.

[0059] The basic aqueous solution may contain at least one selected from the group consisting of alkali metal hydrates, alkali metal hydroxides, alkaline earth metal hydrates, and alkaline earth metal hydroxides. For example, the basic aqueous solution may be prepared by dissolving at least one selected from the group consisting of NaOH, KOH, and Ca(OH)2 in a solvent. The concentration of the basic aqueous solution may be 5% to 50% by weight, preferably 10% to 45% by weight, which makes it easy to maintain the reaction solution at an appropriate pH.

[0060] The co-precipitation reaction in step S1 may be carried out for 0.5 hours or more, preferably 0.5 to 10 hours, and more preferably 0.5 to 8 hours. That is, step S1 may be completed when the co-precipitation reaction time has elapsed. When the co-precipitation reaction time in step S1 falls within the above range, precursor nuclei of a consistent composition are sufficiently formed, thereby increasing the yield of the positive electrode active material precursor.

[0061] Nucleus growth stage (stages S2 to S4)

[0062] Steps S2 to S4 are steps for growing the nuclei generated in step S1. Specifically, step S2 is a step for growing the nuclei generated in step S1, step S3 is a step for further growing the precursor particles grown in step S2, and step S4 is a step for further growing the precursor particles grown in step S3.

[0063] The stages S2 to S4 follow the Ostwald ripening process, where relatively small particles among the nuclei generated in the S1 stage disappear, and the relatively large particles increase in average diameter. In the early stages S2 to S4, the average diameter D of the precursor particles increases. 50 can grow by 0.5 μm to 1.5 μm every 5 hours, and the average particle size of the precursor particles D 50may grow by 0.1 μm to 0.3 μm every 5 hours. In the later stages of S2 to S4, as the particle size distribution of the precursor in the reaction solution becomes more uniform, the Span value of the precursor particles may become smaller and smaller.

[0064] The pH of the reaction solution in steps S2 to S4 may be 10.5 to 13.0, preferably 10.8 to 12.5, and more preferably 11.0 to 12.2. When the pH of the reaction solution in steps S2 to S4 is within this range, the nucleus growth reaction is more dominant than the nucleation reaction. The pH of the reaction solution can be adjusted by adjusting the flow rates of the transition metal compound solution, nitrogen-containing compound solution, basic compound solution, and / or acidic compound solution.

[0065] The ammonia concentration in the reaction solution in steps S2 to S4 can be 3,000 ppm to 7,000 ppm, preferably 3,200 ppm to 6,500 ppm, and more preferably 3,400 ppm to 6,000 ppm. If the ammonia concentration is less than 3,000 ppm, the formation of transition metal hydrates takes precedence over the coprecipitation reaction, resulting in the generation of new fine particles in the reaction solution. If the ammonia concentration is more than 7,000 ppm, the residual nickel in the reaction solution forms a new complex with ammonia, resulting in the generation of new fine particles in the reaction solution. The ammonia concentration in the reaction solution can be adjusted by adjusting the input flow rate of the nitrogen-containing compound solution.

[0066] When the ammonia concentration in the reaction solution is maintained at 3,000 ppm to 7,000 ppm in steps S2 to S4, the concentration of residual nickel in the solution may gradually increase as the coprecipitation reaction time increases. In this case, the concentration of residual nickel in the reaction solution inside the batch reactor in steps S2 to S4 may be 250 ppm or less, preferably 0 ppm to 225 ppm, and more preferably 0 ppm to 200 ppm. Here, the concentration of residual nickel refers to the concentration of nickel in the solution that remains unreacted during the conversion of the transition metal compound solution into a cathode active material precursor. When the concentration of residual nickel in the reaction solution is within this range, the formation of new fine particles in the reaction solution may be suppressed according to Le Chatelier's principle. The concentration of residual nickel in the reaction solution may be adjusted by adjusting the input flow rate of the transition metal compound solution.

[0067] The coprecipitation reaction in steps S2 to S4 can be carried out in an inert atmosphere such as nitrogen or argon at a temperature of 40 to 60° C. When this temperature range is satisfied, the rate of the coprecipitation reaction can be controlled.

[0068] When the batch reactor is filled with the reaction solution during the coprecipitation reaction in steps S2 to S4, the reaction solution is allowed to overflow through the discharge line. As a result, the solid density in the reactor is adjusted, preventing the problem of cracks on the particle surface. In addition, when the overflow method is used, the solid density inside the reactor can be controlled by adjusting the amount of reaction solution fed in and discharged, so that a uniform particle size distribution and an average particle size D can be obtained in a short time even in the limited space inside the reactor. 50 However, it is possible to produce large precursor particles with a size of 7 μm to 30 μm.

[0069] Each sub-stage of the nucleus growth stage will be described in detail below.

[0070] (1) S2 stage

[0071] The average diameter of the precursor nuclei generated in the S1 stage, D 50When the particle size reaches 1.2 μm to 6.0 μm, step S2 can be carried out. Step S2 is characterized by different feeding rates of the transition metal compound solution, nitrogen-containing compound solution, and basic compound solution into the batch reactor, different stirring speed, and different pH compared to step S1.

[0072] The stirring speed in the reactor in step S2 can be 200 rpm to 900 rpm, preferably 225 rpm to 850 rpm, and more preferably 250 rpm to 800 rpm. If the stirring speed in step S2 exceeds 900 rpm, side reactions will prevail over the nucleus growth reaction, resulting in the generation of a large number of precursor microparticles during the nucleus growth stage, resulting in a non-uniform particle size distribution of the precursor. If the stirring speed in step S2 is less than 200 rpm, the aspect ratio of the precursor produced will be low, resulting in a low specific gravity of the precursor per unit volume during battery production, resulting in a reduced battery capacity.

[0073] In step S2, the flow rate of the transition metal compound solution introduced into the batch reactor may be 5 mL / min to 40 mL / min, preferably 7 mL / min to 35 mL / min, and more preferably 10 mL / min to 30 mL / min. When the flow rate is within the above range, the growth reaction rate of the generated nuclei can be appropriately controlled.

[0074] The flow rate of the nitrogen-containing compound solution in step S2 may be the same as that in step S1. For example, the flow rate of the nitrogen-containing compound solution in step S2 may be 1.0 mL / min to 10.0 mL / min, preferably 1.2 mL / min to 8.0 mL / min, and more preferably 1.5 mL / min to 5.0 mL / min.

[0075] In step S2, the flow rate of the basic compound solution may be 3 mL / min to 35 mL / min, preferably 5 mL / min to 30 mL / min, and more preferably 8 mL / min to 25 mL / min. When the flow rate is within the above range, the pH of the reaction solution can be maintained within an appropriate range.

[0076] The co-precipitation reaction in step S2 may be carried out for 1 hour or more, preferably 1.5 to 20 hours, and more preferably 2 to 15 hours. That is, step S2 may be completed when the co-precipitation reaction time has elapsed. When the co-precipitation reaction time in step S2 falls within the above range, the aspect ratio of the precursor increases, thereby increasing the energy density of the battery and controlling fine particles.

[0077] (2) S3 stage

[0078] After the step S2 is completed, the step S3 can be carried out, which is characterized by a different stirring speed compared to the step S2.

[0079] The stirring speed in the reactor in the S3 stage may be slower than that in the S2 stage. Specifically, the stirring speed in the reactor in the S3 stage may be 800 rpm or less, preferably 175 rpm to 750 rpm, and more preferably 200 rpm to 700 rpm. If the stirring speed in the S3 stage exceeds 800 rpm, there is a problem that the Span value becomes high.

[0080] The flow rate at which the transition metal compound solution is introduced into the batch reactor in step S3 may be the same as that in step S2. For example, the flow rate at which the transition metal compound solution is introduced in step S3 may be 5 mL / min to 40 mL / min, preferably 7 mL / min to 35 mL / min, and more preferably 10 mL / min to 30 mL / min.

[0081] The flow rate of the nitrogen-containing compound solution in step S3 may be the same as that in step S2. For example, the flow rate of the nitrogen-containing compound solution in step S3 may be 1.0 mL / min to 10.0 mL / min, preferably 1.2 mL / min to 8.0 mL / min, and more preferably 1.5 mL / min to 5 mL / min.

[0082] The flow rate of the basic compound solution introduced in step S3 may be the same as that in step S2. For example, the flow rate of the basic compound solution introduced in step S3 may be 3 mL / min to 35 mL / min, preferably 5 mL / min to 30 mL / min, and more preferably 8 mL / min to 25 mL / min.

[0083] The co-precipitation reaction in the step S3 may be carried out for, for example, 5 hours or more, preferably 7 to 35 hours. When the co-precipitation reaction time in the step S3 is within the above range, the average particle size D 50 However, the average particle size D of the precursor particles can reach 6.5 μm to 13.0 μm. 50 If the particle size does not reach 6.5 μm to 13.0 μm, the coprecipitation reaction in the S3 stage can be continued under the same conditions until the particle size reaches this size.

[0084] After the completion of the S3 step, the average particle size D 50 After the completion of the S3 step, the average particle size D of the precursor particles may be 6.5 μm to 13.0 μm, preferably 7.5 μm to 12.5 μm, and more preferably 8.0 μm to 12.0 μm. 50 If the average particle size is less than 6.5 μm, the target average particle size D 50 After the S3 step is completed, the average particle size D of the precursor particles is 50 If the average particle diameter D of the precursor particles exceeds 13.0 μm, the number of collisions between particles increases during the coprecipitation reaction due to stirring, which may cause cracks on the particle surface. 50 When the particle size reaches 6.5 μm to 13.0 μm, the S3 stage is completed and the S4 stage can be carried out.

[0085] (3) S4 stage

[0086] The average diameter of the precursor nuclei generated in the S3 stage, D 50 When the particle size reaches 6.5 μm to 13.0 μm, step S3 is completed and step S4 can be carried out. Step S4 is characterized by the fact that the flow rates of the transition metal compound solution, the nitrogen-containing compound solution, and the basic compound solution introduced into the batch reactor and the stirring speed are different from those of step S3.

[0087] The stirring speed in the reactor in the S4 stage may be slower than that in the S2 and S3 stages. Specifically, the stirring speed in the reactor in the S4 stage may be 700 rpm or less, preferably 150 rpm to 650 rpm, more preferably 175 rpm to 600 rpm. When the stirring speed in the S4 stage is more than 700 rpm, the average particle size D 50 The number of collisions between large precursor particles increases, which causes cracks on the particle surface.

[0088] The flow rate of the transition metal compound solution introduced into the batch reactor in step S4 may be 2 mL / min to 30 mL / min, preferably 3 mL / min to 25 mL / min, and more preferably 5 mL / min to 20 mL / min. When the flow rate satisfies the above range, the average particle diameter D 50 The present invention uses an overflow method during precursor preparation, which prevents the problem of a decrease in the growth rate of precursor particles even if the input flow rate of the transition metal compound solution is reduced in step S4 compared to steps S2 and S3.

[0089] Considering the flow rate of the transition metal compound solution introduced in step S4, the flow rate of the nitrogen-containing compound solution introduced in step S4 may be 1.0 mL / min to 10.0 mL / min, preferably 1.2 mL / min to 8.0 mL / min, and more preferably 1.5 mL / min to 5.0 mL / min.

[0090] Considering the flow rate of the transition metal compound solution introduced in step S4, the flow rate of the basic compound solution introduced in step S4 may be 2 mL / min to 30 mL / min, preferably 3 mL / min to 25 mL / min, and more preferably 4 mL / min to 20 mL / min.

[0091] Meanwhile, in the case of the positive electrode active material precursor produced through steps S1 to S4, the Span value according to the following Equation 1 may be 0.38 or less, preferably 0.35 or less, and more preferably 0.25 to 0.33.

[0092] [Formula 1]

[0093] Span = (particle diameter D 90 - Particle size D 10 ) / average particle size D 50

[0094] When the span value of the produced precursor satisfies the above range, the particle size deviation of the precursor particles is small, and the target physical properties such as the tap density and specific surface area of ​​the precursor can be achieved, and the charge / discharge capacity of the positive electrode active material can also be improved.

[0095] Meanwhile, the method for preparing a precursor according to the present invention may further include a water washing and drying step (step S5) after steps S1 to S4.

[0096] Washing and drying step (S5 step)

[0097] Step S5 is a step of washing and drying the positive electrode active material precursor produced through steps S1 to S4, in order to separate the positive electrode active material precursor from the reaction solution and obtain the positive electrode active material precursor.

[0098] Average particle size D of the precursor generated through the S4 stage 50 When the particle size reaches 7 μm to 30 μm, specifically 8 μm to 27 μm, and more specifically 9 μm to 25 μm, a water-washing step of the precursor can be performed. At this time, the reaction solution can be transferred to equipment used for a filter press process to wash the precursor. The filter press process can refer to a process of forcing the reaction solution into a sealed filtration chamber and separating the cake and liquid filtrate through a filter material while washing the precursor. Next, once the water-washing of the separated precursor particles is complete, nitrogen gas can be purged to prevent oxidation of the cathode active material precursor.

[0099] After the water washing treatment of the precursor is completed, a step of drying the precursor may be performed to remove moisture from the cathode active material precursor. The drying treatment of the precursor may be performed so that the moisture content in the precursor is 1.0 wt % or less, preferably 0.8 wt % or less, based on the total weight of the precursor. When the moisture content satisfies this range, the productivity and product quality of subsequent processes are favorable.

[0100] Furthermore, in the precursor production method according to the present invention, a pulverization step and / or a classification step may be additionally carried out as necessary.

[0101] Although 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.

[0102] Examples and Comparative Examples

[0103] Example 1

[0104] (1) Nucleation stage (S1 stage)

[0105] A transition metal compound solution with a concentration of 2.4 M was prepared by mixing NiSO4·6H2O hydrate, CoSO4·7H2O hydrate, and MnSO4·H2O hydrate in deionized water in amounts such that the molar ratio of nickel:cobalt:manganese was 91:4.5:4.5.

[0106] A 30 L batch reactor was charged with 15 L of deionized water and purged with nitrogen (N2) gas at a flow rate of 5 mL / min to remove dissolved oxygen in the water and create a non-oxidizing atmosphere inside the reactor. Then, while purging nitrogen gas into the reactor at a flow rate of 5 mL / min, the transition metal compound solution was charged at a flow rate of 4.51 mL / min, a 25 wt% NaOH solution at a flow rate of 2.84 mL / min, and a 9 wt% NH4OH solution at a flow rate of 3.00 mL / min.

[0107] At this time, the temperature of the batch reactor was adjusted to 50°C, the pH of the reaction solution was adjusted to 11.8, and the stirring speed by the impeller was adjusted to 750 rpm.

[0108] The coprecipitation reaction in the nucleation stage (S1) produces precursor particle nuclei with an average particle size D 50 It continued for 0.5 hours until the particle size reached 1.2μm to 6.0μm.

[0109] (2) Nucleus growth stage (S2 stage to S4 stage)

[0110] After completion of the S1 stage, a 1N sulfuric acid solution was added to the batch reactor so that the pH of the reaction solution became 11.2.

[0111] After the completion of the S1 stage, the flow rates of the components were changed in the S2 stage. Specifically, the 2.4 M transition metal compound solution was added at a flow rate of 18.03 mL / min, the 25 wt% NaOH solution at a flow rate of 11.33 mL / min, and the 9 wt% NH4OH solution at a flow rate of 3.00 mL / min. The impeller stirring speed in the S2 stage was changed to 400 rpm. The coprecipitation reaction in the S2 stage continued for 4.5 hours.

[0112] After the completion of the S2 stage, in the S3 stage, the input flow rates of each component were maintained as in the S2 stage, but the impeller stirring speed was changed to 300 rpm. The coprecipitation reaction in the S3 stage was continued for 15 hours. At this time, the average particle size D of the precursor particles was 50 If the particle size did not reach 6.5 μm to 13.0 μm, the coprecipitation reaction was continued under the same conditions until it reached this size.

[0113] After completion of stage S3, the flow rates of the components were changed in stage S4. Specifically, the 2.4 M transition metal compound solution was added at a flow rate of 9.02 mL / min, the 25 wt % NaOH solution at a flow rate of 5.67 mL / min, and the 9 wt % NH4OH solution at a flow rate of 2.10 mL / min. The impeller stirring speed in stage S4 was changed to 200 rpm. The coprecipitation reaction in stage S4 continued for 30 hours.

[0114] When steps S2 to S4 were carried out, if the inside of the batch reactor became full, the reaction liquid was allowed to overflow through a discharge line.

[0115] When carrying out steps S2 to S4, 100 mL of the reaction solution was extracted every 5 hours, and then ammonia titration was performed. When the ammonia concentration in the reaction solution decreased, additional NH4OH solution was added to maintain the ammonia concentration at 4,000 ppm.

[0116] During steps S2 to S4, 50 ml of the reaction solution was extracted every hour, and it was confirmed whether the pH of the reaction solution was maintained at 11.2 at room temperature of 25° C. After measuring the pH of the extracted reaction solution, it was re-introduced into the reactor.

[0117] (3) Washing and drying step (S5 step)

[0118] After the coprecipitation reaction was carried out for a total of 50 hours through steps S1 to S4, the reaction solution was transferred to the filter press process. In the filter press process, the reaction solution was forced into a sealed filtration chamber, and the solid (cake) and liquid (filtrate) were separated through the filter material, followed by a water washing process. Next, after the water washing process of the separated precursor particles was completed, nitrogen, argon, oxygen, compressed air, etc. were supplied at a pressure of 0.4 MPa to dehydrate the supernatant and washing solution.

[0119] After the filter press and water washing steps, the positive electrode active material precursor was dried at 150° C. for 8 hours so that the water content in the positive electrode active material precursor was 0.5 wt % or less.

[0120] Example 2

[0121] A positive electrode active material precursor was prepared in the same manner as in Example 1, except that the stirring speed of the impeller in step S1 was adjusted to 650 rpm.

[0122] Comparative Example 1

[0123] In steps S2 to S4, when the batch reactor was filled to capacity, the introduction of each component and the rotation of the impeller were stopped, and the reactor was left for 1 hour to allow precipitation to proceed. The supernatant was then discharged in an amount of 10 L to 12 L to separate the NCM precursor from the supernatant, and a cathode active material precursor was prepared in the same manner as in Example 1.

[0124] At this time, the coprecipitation reaction in the S1 stage is carried out with the average particle size of the precursor particles D 50 It continued for 0.5 hours until the particle size reached 1.2μm to 6.0μm.

[0125] The coprecipitation reaction in the S2 stage lasted for 4.5 h.

[0126] The coprecipitation reaction in the S3 stage produces precursor particles with an average particle size D 50 It continued for 15 hours until the particle size reached 6.5μm to 13.0μm.

[0127] The coprecipitation reaction in the S4 stage produces precursor particles with an average particle size D 50 It continued for 90 hours until the particle size changed from 7.0 μm to 30.0 μm.

[0128] Experimental Example 1: SEM image analysis of precursor

[0129] During the progress of steps S2 to S4 in Examples 1 and 2 and Comparative Example 1, 50 ml of the reaction solution was extracted and dried every 5 hours, and then SEM images of the precursor were taken.

[0130] FIG. 2 is an SEM image of the extracted positive electrode active material precursor after co-precipitation for 50 hours according to Example 1 of the present invention and drying the extracted positive electrode active material precursor.

[0131] FIG. 3 is an SEM image of the extracted positive electrode active material precursor after co-precipitation for 50 hours according to Example 2 of the present invention and drying the extracted positive electrode active material precursor.

[0132] 4, 5, 6, and 7 are SEM images taken of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 110 hours according to Comparative Example 1 of the present invention and then dried.

[0133] 2 to 7, in Examples 1 and 2 where the stirring speed was 200 to 900 rpm in step S2, 800 rpm or less in step S3, and 700 rpm or less in step S4, and overflow was performed when the reactor was full, the number of fine particles observed in the SEM images was significantly smaller than in Comparative Example 1 where precipitation separation was performed when the reactor was full with the reaction solution, confirming that no surface cracks were generated in the precursor particles.

[0134] Experimental Example 2: Analysis of precursor particle size and composition

[0135] During the progress of steps S2 to S4 in Examples 1 and 2 and Comparative Example 1, 50 ml of the reaction solution was extracted every 5 hours, and the particle size and composition of the precursor were analyzed.

[0136] Specifically, particle size analysis was performed under wet conditions using a Malvern Mastersizer 2000 instrument.

[0137] Composition analysis was carried out using an Agilent 5900 ICP-OES instrument under inductively coupled plasma conditions.

[0138] The particle size and composition of the precursors extracted from the reaction solutions in Examples 1 and 2 and Comparative Example 1 were analyzed, and the results are shown in Table 1 below.

[0139] [Table 1]

[0140] According to Table 1, in Examples 1 and 2, where the stirring speed was 200-900 rpm in step S2, 800 rpm or less in step S3, and 700 rpm or less in step S4, and where overflow was performed when the reactor was full, the Span value was lower and the co-precipitation reaction time was shorter than in Comparative Example 1, in which precipitation separation was performed when the reactor was full. This confirms that the particle size distribution of the precursors prepared in Examples 1 and 2 was more uniform than in Comparative Example 1, and that the co-precipitation reaction time required to prepare the precursor was significantly shorter in Examples 1 and 2 than in Comparative Example 1.

[0141] Although the present invention has been described herein with reference to certain embodiments, it should be understood that various modifications and changes may be made thereto without departing from the spirit and scope of the present invention, as would be understood by one of ordinary skill in the art to which the present invention pertains, and such modifications and changes should be considered to fall within the scope of the claims appended hereto.

Claims

1. A method for producing a positive electrode active material precursor using a batch reactor, comprising: (S1) generating nuclei of the precursor; (S2) growing the nuclei generated in step S1; (S3) further growing the precursor particles grown in step S2; and (S4) further growing the precursor particles grown in step S3; The stirring speed in the batch reactor is The S2 stage is 200 rpm to 900 rpm, The S3 stage is 800 rpm or less, The S4 stage is 700 rpm or less, The method for producing a batch reactor comprises overflowing the reaction solution when the inside of the batch reactor is full.

2. The method of claim 1, wherein the co-precipitation reaction in step S2 is carried out for 1 to 20 hours.

3. The average particle size D of the precursor after the completion of the S3 step ５０ The manufacturing method according to claim 1, wherein the thickness is 6.5 μm to 13.0 μm.

4. 2. The method of claim 1, wherein the stirring speed in the batch reactor in step S1 is 250 rpm to 1,000 rpm.

5. The flow rate of the transition metal compound solution introduced into the batch reactor is: The S2 stage and the S3 stage are 5 mL / min to 40 mL / min; The method according to claim 1, wherein the flow rate in the S4 step is 2 mL / min to 30 mL / min.

6. The method according to claim 5 , wherein the transition metal compound solution contains at least one element selected from the group consisting of nickel, cobalt, and manganese.

7. The transition metal compound solution 60 mol% to 96 mol% nickel; 0 mol % to 20 mol % cobalt; and The method according to claim 5, wherein the manganese content is 4 mol% to 40 mol%.

8. The input flow rate of the nitrogen-containing compound solution is The S2 stage and the S3 stage are 1.0 mL / min to 10.0 mL / min; The method of claim 1, wherein the flow rate in the S4 step is 1.2 mL / min to 8.0 mL / min.

9. The input flow rate of the basic compound solution is The S2 stage and the S3 stage are 3 mL / min to 35 mL / min, The method according to claim 1, wherein the flow rate in the S4 step is 2 mL / min to 30 mL / min.

10. 2. The method of claim 1, wherein the reaction solution in the batch reactor in step S1 has a pH of 10.5 to 13.

5.

11. 2. The method of claim 1, wherein the reaction solution in the batch reactor has a pH of 10.5 to 13.0 in steps S2, S3, and S4.

12. 2. The method of claim 1, wherein the ammonia concentration in the reaction solution in the batch reactor is 3,000 ppm to 7,000 ppm in steps S2, S3, and S4.

13. 2. The method of claim 1, wherein the concentration of residual nickel in the reaction solution in the batch reactor is 250 ppm or less in steps S2, S3, and S4.

14. 2. The method of claim 1, wherein the cathode active material precursor produced through steps S1 to S4 has a span value of 0.38 or less according to Equation 1: [Formula 1] Span = (particle diameter D ９０ - Particle diameter D １０ ) / average particle size D of particles ５０

15. The method of claim 1, further comprising: (S5) washing and drying the cathode active material precursor produced through steps S1 to S4.

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