Method for producing a positive electrode active material precursor

Abstract

The method for producing a cathode active material precursor according to the present invention includes a first step of generating nuclei of the precursor and a second step of growing the nuclei generated in the first step, wherein in the first and second steps, a flow rate of the transition metal compound solution introduced into a batch reactor is 15 mL / min to 55 mL / min, the stirring speed in the reactor in the first step is 200 rpm to 875 rpm, and the stirring speed in the reactor in the second step is 475 rpm or less.

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 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 and co-precipitating them, while 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 precursor 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) or air jet mill to collect 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 had problems with increased costs and overall process time due to additional processes / equipment, which can lead to poor line of balance (LOB) efficiency and reduced production of cathode active material precursors. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing a precursor having a uniform particle size distribution by minimizing the formation of precursor fine particles during the precursor nucleus growth step by controlling the co-precipitation reaction conditions without any additional process. [Means for solving the problem]

[0008] A method for producing a cathode active material precursor according to one aspect of the present invention includes a first step of generating nuclei of the precursor and a second step of growing the nuclei generated in the first step, wherein in the first and second steps, a flow rate of the transition metal compound solution introduced into a batch reactor is 15 mL / min to 55 mL / min, the stirring speed in the reactor in the first step is 200 rpm to 875 rpm, and the stirring speed in the reactor in the second step is 475 rpm or less.

[0009] 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.

[0010] 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.

[0011] According to one aspect of the present invention, the reaction solution in the batch reactor in the first step may have a pH of 10.5 to 13.5.

[0012] According to one aspect of the present invention, the reaction solution in the batch reactor in the second step may have a pH of 10.5 to 13.5.

[0013] According to one aspect of the present invention, the reaction solution in the batch reactor in the second step may have an ammonia concentration of 3,000 ppm to 7,000 ppm.

[0014] According to one aspect of the present invention, the flow rate of the nitrogen-containing compound solution in the first and second steps may be 1.0 mL / min to 10.0 mL / min.

[0015] According to one aspect of the present invention, the basic compound solution may be introduced at a flow rate of 8.0 mL / min to 32.0 mL / min in the first and second steps.

[0016] According to one aspect of the present invention, the positive electrode active material precursor produced through the first and second steps may have a span value of 0.55 or less according to the following Equation 1:

[0017] [Formula 1]

[0018] Span = (particle diameter D 90 - Particle size D 10 ) / average particle size D50

[0019] According to one aspect of the present invention, the method may further include a third step of washing and drying the positive electrode active material precursor produced through the first and second steps. [Effects of the Invention]

[0020] According to the present invention, by controlling the flow rates of the components introduced into the reactor during the co-precipitation reaction and the stirring speed during the precursor nucleation and growth stages at constant levels, it is possible to minimize the formation of fine particles in the reaction solution during the nucleation and growth stage and shorten the co-precipitation reaction time required to produce the precursor, thereby enabling the rapid production of a cathode active material precursor having a desired particle size and uniform particle size distribution.

[0021] In addition, the present invention minimizes the formation of fine particles during precursor nuclei growth and does not require a separate process for removing the fine particles, thereby significantly reducing the overall process time and process costs, thereby improving line organization efficiency and increasing the production yield of the cathode active material precursor. [Brief explanation of the drawings]

[0022] [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 the co-precipitation reaction was carried out for 48 hours according to Example 1 of the present invention and then dried. [Figure 3] FIG. 3 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 34 hours according to Example 2 of the present invention and then dried. [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 55 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 co-precipitation for 55 hours according to Comparative Example 2 of the present invention and drying the extracted positive electrode active material precursor. DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In the present disclosure, the phrase "A and / or B" means either A, or B, or A and B.

[0029] 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.

[0030] The method for producing a cathode active material precursor according to the present invention includes a first step of generating precursor nuclei and a second step of growing the nuclei generated in the first step, wherein the flow rate of the transition metal compound solution introduced into a batch reactor in the first and second steps is 15 mL / min to 55 mL / min, the stirring speed in the reactor in the first step is 200 rpm to 875 rpm, and the stirring speed in the reactor in the second step is 475 rpm or less.

[0031] FIG. 1 is an exemplary diagram of 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 producing a reaction slurry containing a cathode active material precursor. According to the present invention, by controlling the input flow rates of each component during the co-precipitation reaction and the stirring speed during the precursor nucleation and growth stages to consistent levels, the formation of precursor microparticles during the nucleation and growth stage is minimized, thereby producing a cathode active material precursor with a targeted particle size and uniform particle size distribution. As a result, the targeted physical properties of the cathode active material, such as tap density and specific surface area, can be achieved, thereby improving the charge / discharge capacity performance of the battery.

[0032] According to the present invention, before the transition metal-containing solution, the basic aqueous solution, and the ammonium ion-containing solution are added to the batch reactor, deionized water is added to the batch reactor and nitrogen (N) gas is purged 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.

[0033] 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.

[0034] 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.

[0035] Each step of the precursor preparation method according to the present invention will now be described in more detail.

[0036] Nucleation stage (stage 1)

[0037] The first step is to generate nuclei of the positive electrode 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, thereby generating precursor particle nuclei in the form of transition metal hydroxide. At this time, the precursor particle nuclei have an average particle size D 50 The particle diameter is 1.2 μm to 6 μm, specifically 1.5 μm to 5.5 μm.

[0038] The stirring speed in the reactor in the first stage can be 200 rpm to 875 rpm, preferably 300 rpm to 850 rpm, and more preferably 500 rpm to 800 rpm. If the stirring speed in the first stage is less than 200 rpm, the input components are not stirred sufficiently, resulting in a delay in particle formation and a decrease in yield. If the stirring speed in the first stage is more than 875 rpm, aggregation between fine particles is difficult to occur, resulting in insufficient precursor nucleation.

[0039] The pH of the reaction solution in the first stage can be 10.5 to 13.5, preferably 10.8 to 13.0, and more preferably 11.0 to 12.8. When the pH of the reaction solution in the first stage 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.

[0040] The co-precipitation reaction in the first step may be carried out for 0.5 hours or more, preferably 0.5 to 10 hours, and more preferably 0.5 to 7 hours. When the co-precipitation reaction time in the first step 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.

[0041] The coprecipitation reaction in the first stage can be carried out in an inert atmosphere such as nitrogen or argon at a temperature of 40° C. to 60° C. When this temperature range is satisfied, the rate of the coprecipitation reaction can be controlled.

[0042] 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.

[0043] A 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, the capacity and energy density per unit volume of the battery are high, which has the effect of increasing the driving distance of an electric vehicle.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] 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 NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3. 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, which is effective in suppressing the generation of fine particles.

[0049] 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 produced 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% by weight to 50% by weight, preferably 10% by weight to 45% by weight, which makes it easy to adjust the pH.

[0050] Nucleus growth stage (stage 2)

[0051] The second stage is a stage in which the nuclei generated in the first stage grow. Specifically, in the second stage, according to Ostwald ripening, the relatively small particles among the nuclei generated in the first stage disappear, while the average diameter of the relatively large particles increases.

[0052] According to the present invention, the average particle size D of the precursor nuclei produced in the first stage 50 When the particle size reaches 1.2 μm to 6.0 μm, the second stage can be carried out. The second stage is characterized in 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 are maintained the same as in the first stage, but the stirring speed and pH are changed from those in the first stage.

[0053] According to the precursor production method of the present invention, the average particle size D of the precursor particles is 50 can grow by 0.5 μm to 1.5 μm every 5 hours, and in the latter part of the second stage, the average particle size of the precursor particles, D 50 can grow by 0.1μm~0.3μm every 5 hours. In the latter stage of the second stage, as the particle size distribution of the precursor in the reaction solution becomes more uniform, the Span value of the precursor particles can become smaller and smaller.

[0054] The stirring speed in the reactor in the second stage can be 475 rpm or less, preferably 100 rpm to 475 rpm, more preferably 200 rpm to 450 rpm. If the stirring speed in the second stage exceeds 475 rpm, a large number of precursor particles are generated in the nucleus growth stage due to the dominant side reaction rather than the nucleus growth reaction, resulting in an uneven particle size distribution of the precursor or an increase in the average particle size D of the precursor. 50 However, there is a problem in that the coprecipitation reaction time required for the particle size to reach 5 μm to 25 μm increases.

[0055] In the second step, the pH of the reaction solution 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 the second step 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, and / or basic compound solution.

[0056] The ammonia concentration in the reaction solution in the second step 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, new nucleation occurs, resulting in the generation of fine particles in the reaction solution. If the ammonia concentration is more than 7,000 ppm, nickel forms a new complex with ammonia, resulting in the generation of fine particles in the reaction solution. The ammonia concentration in the reaction solution can be adjusted by adjusting the flow rate of the nitrogen-containing compound solution.

[0057] The coprecipitation reaction in the second step may be carried out for 12 hours or more, preferably 15 to 70 hours, and more preferably 18 to 60 hours. When the coprecipitation reaction time in the second step falls within the above range, it is possible to produce a positive electrode active material precursor having a certain particle size distribution and a sufficient target average particle size.

[0058] The coprecipitation reaction in the second step can be carried out in an inert atmosphere such as nitrogen or argon at a temperature of 40° C. to 60° C. When this temperature range is satisfied, the rate of the coprecipitation reaction can be controlled.

[0059] Meanwhile, the flow rate at which the transition metal compound solution is introduced into the batch reactor in the first and second stages may be 15 mL / min to 55 mL / min, preferably 16 mL / min to 50 mL / min, and more preferably 18 mL / min to 45 mL / min. If the flow rate at which the transition metal compound solution is introduced in the first and second stages is less than 15 mL / min, productivity may deteriorate, while if it exceeds 55 mL / min, side reactions may occur.

[0060] The flow rate of the nitrogen-containing compound solution in the first and second steps 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. When this range is satisfied, nucleation can be controlled while maintaining an appropriate ammonia concentration in the reaction solution.

[0061] The flow rate of the basic compound solution in the first and second steps may be 8.0 mL / min to 32.0 mL / min, preferably 9.0 mL / min to 29.0 mL / min, and more preferably 10.0 mL / min to 26.0 mL / min. When the flow rate is within this range, the transition metal compound solution can be coprecipitated while maintaining the pH of the reaction solution at an appropriate value.

[0062] When the batch reactor is filled with the reaction solution during the coprecipitation reaction in steps 1 and 2, the addition of each component and the rotation of the agitator are stopped, and the reactor is left for one hour to allow precipitation to proceed. The cathode active material precursor particles and the supernatant liquid are then separated. The speed and volume of the supernatant liquid discharged can be adjusted so that the top of the agitator is submerged at a depth of at least 2 cm below the surface of the reaction solution to prevent the agitator from causing friction on the surface of the reaction solution during future re-agitation, resulting in the formation of fine particles.

[0063] In the case of the positive electrode active material precursor produced through the first and second steps, the span value according to the following Equation 1 may be 0.55 or less, preferably 0.50 or less, and more preferably 0.20 to 0.50.

[0064] [Formula 1]

[0065] Span = (particle diameter D 90 - Particle size D 10 ) / average particle size D 50

[0066] 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.

[0067] Meanwhile, the method for preparing a precursor according to the present invention may further include a water washing and drying step (a third step) after the first and second steps.

[0068] Washing and drying stage (stage 3)

[0069] The third step is to wash and dry the positive electrode active material precursor produced through the first and second steps, in order to separate the positive electrode active material precursor from the reaction solution and obtain the positive electrode active material precursor.

[0070] Average particle size D of the precursor generated through the first and second stages50 When the particle size reaches 5 μm to 25 μm, specifically 6 μm to 22 μm, and more specifically 7 μm to 20 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 in which the reaction solution is forced into a sealed filtration chamber and washed while separating the cake and liquid filtrate through a filter material. Next, once the water-washing of the separated precursor particles is complete, the supernatant and washing liquid can be dehydrated by supplying nitrogen, argon, oxygen, compressed air, etc. at a pressure of 0.4 MPa.

[0071] 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.

[0072] 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.

[0073] Although the present invention may be embodied in many different forms, it is not intended to be limited to the embodiments set forth herein, and the present invention is not limited to the embodiments set forth herein.

[0074] Examples and Comparative Examples

[0075] Example 1

[0076] (1) Nucleation stage (first stage)

[0077] 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 88:5.0:7.0.

[0078] 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 from 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 37.50 mL / min, a 25 wt% NaOH solution at a flow rate of 21.82 mL / min, and a 9 wt% NH4OH solution at a flow rate of 3.41 mL / min.

[0079] 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.

[0080] The coprecipitation reaction in the nucleation stage lasted for 1 h.

[0081] (2) Nucleus growth stage (stage 2)

[0082] After the first stage was completed, a 1N sulfuric acid solution was added to the batch reactor so that the pH of the reaction solution became 11.2, and the impeller stirring speed was changed to 400 rpm.

[0083] Every 5 hours, 100 mL of the reaction solution was extracted, and ammonia titration was carried out. When the ammonia concentration in the reaction solution decreased, additional NH4OH solution was added to maintain the ammonia concentration at 4,000 ppm.

[0084] Meanwhile, during the first and second steps, 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 (25°C). After measuring the pH of the extracted reaction solution, it was reintroduced into the reactor. In addition, it was confirmed through an electrode installed in the reactor whether the pH of the reaction solution was maintained at 10.75 at 50°C.

[0085] When the coprecipitation reaction was carried out in steps 1 and 2, once the 30L reactor was filled with liquid, the addition of each component and the rotation of the impeller were stopped and the reactor was left for 1 hour to allow precipitation to proceed, after which the NCM precursor and the supernatant were separated. The supernatant was discharged in an amount of 10-12L, and the discharge rate and amount were controlled so that the top of the impeller was immersed at a depth of 2cm or more below the surface of the coprecipitation reaction solution to prevent friction between the impeller and the surface of the reaction solution.

[0086] (3) Washing and drying stage (third stage)

[0087] The average particle size of the precursor D 50 When the particle size reached 5 μm to 25 μm, 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 filtration material while undergoing 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 liquid.

[0088] 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.

[0089] Example 2

[0090] A cathode active material precursor was prepared in the same manner as in Example 1, except that a 2.4 M transition metal compound solution was added at a flow rate of 18.03 mL / min, a 25 wt % NaOH solution was added at a flow rate of 11.33 mL / min, and a 9 wt % NH OH solution was added at a flow rate of 1.86 mL / min.

[0091] Comparative Example 1

[0092] A cathode active material precursor was prepared in the same manner as in Example 1, except that the stirring speed in the first stage was 750 rpm, and the stirring speed in the second stage was 625 rpm for the first 15 hours and then 500 rpm until the end.

[0093] Comparative Example 2

[0094] A positive electrode active material precursor was prepared in the same manner as in Example 1, except that a 2.4 M transition metal compound solution was introduced at a flow rate of 18.03 mL / min, a 25 wt % NaOH solution was introduced at a flow rate of 11.33 mL / min, and a 9 wt % NH4OH solution was introduced at a flow rate of 1.86 mL / min, and the stirring speed in the first stage was 625 rpm, and the stirring speed in the second stage was 625 rpm.

[0095] Experimental Example 1: SEM image analysis of precursor

[0096] During the first and second stages of Examples 1 and 2 and Comparative Examples 1 and 2, 50 ml of the reaction solution was extracted and dried every 5 hours, and then SEM images of the precursor were taken.

[0097] FIG. 2 is an SEM image of the extracted positive electrode active material precursor after co-precipitation for 48 hours according to Example 1 of the present invention and drying the extracted positive electrode active material precursor.

[0098] FIG. 3 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 34 hours according to Example 2 of the present invention and then dried.

[0099] FIG. 4 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 55 hours according to Comparative Example 1 of the present invention and then dried.

[0100] FIG. 5 is an SEM image of the extracted positive electrode active material precursor after the co-precipitation reaction was carried out for 55 hours according to Comparative Example 2 of the present invention and then dried.

[0101] 2 to 5, in Examples 1 and 2, in which the stirring speed in the first stage is 200 rpm to 875 rpm and the stirring speed in the second stage is 475 rpm or less, it can be seen that the number of fine particles observed in the SEM images is significantly smaller than in Comparative Examples 1 and 2, in which the stirring speed in the second stage is outside the above range.

[0102] Experimental Example 2: Analysis of precursor particle size and composition

[0103] During the first and second stages of Examples 1 and 2 and Comparative Examples 1 and 2, 50 ml of the reaction solution was extracted every 5 hours, and the particle size and composition of the precursor were analyzed.

[0104] Specifically, particle size analysis was performed under wet conditions using a Malvern Mastersizer 2000 instrument.

[0105] Composition analysis was carried out using an Agilent 5900 ICP-OES instrument under inductively coupled plasma conditions.

[0106] The particle size and composition of the precursors in the reaction solutions extracted in Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed, and the results are shown in Table 1 below.

[0107] [Table 1]

[0108] From Table 1, it can be seen that in Examples 1 and 2, where the stirring speed in the first stage was 200 rpm to 875 rpm and the stirring speed in the second stage was 475 rpm or less, the Span value was lower or the co-precipitation reaction time was shorter than in Comparative Examples 1 and 2, where the stirring speed in the second stage was outside this range. From this, it can be seen that the particle size distribution of the precursors prepared in Examples 1 and 2 was more uniform than in Comparative Example 1, and the co-precipitation reaction time required to prepare the precursor was significantly shorter in Examples 1 and 2 than in Comparative Example 2.

[0109] 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, a first step of nucleating said precursor; and a second step of growing the nuclei produced by the first step; The flow rate of the transition metal compound solution introduced into the batch reactor in the first and second steps is 15 mL / min to 55 mL / min; The stirring speed in the reactor in the first stage is 200 rpm to 875 rpm; The method for producing the present invention, wherein the stirring speed in the reactor in the second stage is 475 rpm or less.

2. The method according to claim 1 , wherein the transition metal compound solution contains at least one element selected from the group consisting of nickel, cobalt, and manganese.

3. The transition metal compound solution 60 mol% to 96 mol% nickel; 0 mol % to 20 mol % cobalt; and The method according to claim 1, wherein the manganese content is 4 mol% to 40 mol%.

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

5.

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

5.

6. 2. The method according to claim 1, wherein the reaction solution in the batch reactor in the second step has an ammonia concentration of 3,000 ppm to 7,000 ppm.

7. 2. The method according to claim 1, wherein the flow rate of the nitrogen-containing compound solution in the first and second steps is 1.0 mL / min to 10.0 mL / min.

8. The method according to claim 1, wherein the basic compound solution is introduced at a flow rate of 8.0 mL / min to 32.0 mL / min in the first and second steps.

9. 2. The method of claim 1, wherein the positive electrode active material precursor produced through the first and second steps has a span value of 0.55 or less according to Equation 1: [Formula 1] Span = (particle diameter D ９０ - Particle diameter D １０ ) / average particle size D of particles ５０

10. The method of claim 1 , further comprising a third step of washing and drying the positive electrode active material precursor produced through the first and second steps.

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