A preparation method of cobalt tetroxide combining dynamic nucleation and static growth

Abstract

The present invention discloses a method for preparing cobalt tetroxide by combining dynamic nucleation and static growth. The method comprises the following steps: diluting a precipitant solution to obtain a base liquid; continuously introducing a cobalt salt solution and a precipitant solution into the continuously stirred base liquid to perform dynamic nucleation to obtain a seed crystal system; adding the cobalt salt solution and the precipitant solution to the seed crystal system, stirring and mixing, and then stopping stirring, performing static growth until the crystals reach a target particle size, and collecting cobalt carbonate; and heat-treating the cobalt carbonate to obtain cobalt tetroxide. The present invention overcomes the problems of the traditional continuous production system, such as the complicated preparation process, long time consumption, and high cost. In the grain growth stage of the cobalt carbonate, static growth without stirring and feeding is adopted. While avoiding the energy consumption caused by feeding and stirring, cobalt tetroxide with uniform morphology and suitable particle size can also be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of cobalt tetroxide preparation, and in particular to a method for preparing cobalt tetroxide by combining dynamic nucleation and static growth. Background Art

[0002] Lithium-ion batteries made with lithium cobalt oxide as the cathode material feature light weight, high capacity, high specific energy, high operating voltage, stable discharge, suitability for high current discharge, excellent cycle performance, and long life. They are primarily used in the 3C digital industry. With technological advancements and growing demand, lithium cobalt oxide is developing towards higher voltages, higher compaction rates, and improved cycle performance.

[0003] As the performance requirements for lithium cobalt oxide increase, the requirements for the raw material cobalt oxide are also getting higher. Currently, the traditional method for preparing cobalt oxide in a carbonate system usually uses a continuous feeding method to synthesize seed crystals, and then continuously feed the seed crystals to grow to the required particle size. However, this method has problems such as cumbersome preparation process, long time consumption and high cost. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention adopts a method that combines dynamic nucleation and static growth, that is, a continuous feeding method is adopted in the seed nucleation stage, and a static growth method is adopted in the subsequent crystal nucleus growth, thereby simplifying the entire wet synthesis process, eliminating the need to strictly control the pH of the reaction process, and reducing the energy consumption cost caused by long-term stirring.

[0005] In order to achieve the above object, the present invention provides a method for preparing cobalt tetroxide by combining dynamic nucleation and static growth, comprising:

[0006] The precipitant solution is diluted to obtain a base solution;

[0007] The cobalt salt solution and the precipitant solution are continuously introduced into the continuously stirred bottom liquid to perform dynamic nucleation to obtain a seed crystal system;

[0008] The cobalt salt solution and the precipitant solution are added to the seed crystal system, stirred and mixed, and then the stirring is stopped to perform static growth until the crystals reach the target particle size, and the cobalt carbonate is collected;

[0009] Cobalt carbonate is heat treated to obtain cobalt tetroxide.

[0010] Further, the precipitant solution is diluted at a volume ratio of 1:5-15 to obtain 400-750 L of base solution;

[0011] The precipitant solution is a soluble bicarbonate solution of 180-260 g / L;

[0012] The cobalt salt concentration in the cobalt salt solution is 90-160 g / L.

[0013] In the present invention, the types of the cobalt salt and the soluble bicarbonate salt are not strictly limited. For example, the cobalt salt can be at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate; and the soluble bicarbonate salt can be at least one of potassium bicarbonate, sodium bicarbonate, and ammonium bicarbonate. The solvents for the cobalt salt solution and the precipitant solution are not strictly limited and can be common solvents such as at least one of water, ethanol, and acetone, preferably water.

[0014] Furthermore, the cobalt salt solution and the precipitant solution are continuously introduced into the bottom liquid stirred at a stirring speed of 400-700 rpm at flow rates of 80-120 L / h and 180-260 L / h, respectively, to perform dynamic nucleation until the average particle size of the seeds in the seed system is 2-3 μm.

[0015] Furthermore, after the volume of the seed crystal system is reduced to 40%-60% of the original volume, the cobalt salt solution and the precipitant solution are added in a volume ratio of 1:1-3 and replenished to the original volume.

[0016] Furthermore, the stirring and mixing is continued for 1-2 hours at a stirring speed of 150-220 rpm.

[0017] Furthermore, the static growth is continued at a temperature of 35-60° C. for 4-10 hours.

[0018] Furthermore, the collection is performed by filter pressing and washing, and the filter pressing and washing reduces the conductivity of the washing liquid for washing the cobalt carbonate to less than 20 μS / m.

[0019] Furthermore, the heat treatment is carried out at 150-250° C. for 2-5 hours, then the temperature is raised to 350-480° C. for 3-8 hours, and finally the temperature is raised to 650-800° C. for 8-12 hours.

[0020] The present invention also provides cobalt tetroxide, which is obtained by the above-mentioned method for preparing cobalt tetroxide combining dynamic nucleation and static growth.

[0021] The present invention also provides the use of the above-mentioned cobalt tetroxide in energy storage materials.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention overcomes the problems of complicated preparation process, long time consumption and high cost in traditional continuous production systems. In the grain growth stage of cobalt carbonate, static growth without stirring and feeding is adopted. While avoiding the energy consumption caused by feeding and stirring, cobalt tetroxide with uniform morphology and suitable particle size can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A flow chart showing the method for preparing cobalt trioxide by combining dynamic nucleation and static growth of the present invention is shown;

[0026] Figure 2 The scanning electron microscope image of the seed crystal obtained by dynamic nucleation in Example 3 is shown;

[0027] Figure 3 shows a scanning electron microscope image of cobalt carbonate obtained after static growth in Example 3;

[0028] Figure 4 The scanning electron microscope image of the cobaltous oxide prepared in Example 3 is shown;

[0029] Figure 5 The scanning electron microscope image of the cobalt trioxide prepared in Comparative Example 1 is shown. DETAILED DESCRIPTION

[0030] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing cobalt trioxide by combining dynamic nucleation and static growth, such as Figure 1 As shown, it includes the following steps,

[0034] (1) Solution preparation: Prepare 90 g / L cobalt sulfate solution with cobalt sulfate and water; prepare 180 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0035] (2) Dilution to obtain a base liquid: Add 50 L of ammonium bicarbonate solution and 450 L of water to an 8000 L reactor, dilute the ammonium bicarbonate solution to obtain a base liquid, heat the base liquid to 40 ° C and maintain a stirring speed of 400 rpm;

[0036] (3) Dynamic nucleation: Cobalt sulfate solution and ammonium bicarbonate solution were continuously fed into the bottom liquid which was stirred at a stirring speed of 400 rpm. The flow rate of cobalt sulfate solution was 80 L / h and the flow rate of ammonium bicarbonate solution was 180 L / h. During the process, samples were taken every 1 h to test the particle size to obtain a seed crystal system. The average particle size of the seeds in the seed crystal system was 2 μm.

[0037] (4) Siphon the reactor to reduce the volume of the seed system to 50% of the original volume, add cobalt sulfate solution and ammonium bicarbonate solution at a volume ratio of 1:1 to restore the original volume, and stir at a stirring speed of 150 rpm for 1 hour, then stop stirring, seal the reactor, control the temperature in the reactor at 40°C, and perform static growth for 6 hours;

[0038] (5) Filter press washing: After the static growth is completed, the insoluble matter is collected and put into the filter press for filter press washing. The conductivity of the washing liquid for washing the cobalt carbonate is washed to less than 20 μS / m to obtain a wet material;

[0039] (6) Calcination in stages: The wet material is placed on a ceramic tray at a rate of 16 kg / tray, and then placed in a roller kiln for calcination. The temperature is kept at 230 ° C for 3 hours, then the temperature is raised to 460 ° C for 5 hours, and finally the temperature is raised to 750 ° C for 9 hours. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0040] Example 2

[0041] A method for preparing cobalt trioxide by combining dynamic nucleation and static growth, such as Figure 1 As shown, it includes the following steps,

[0042] (1) Solution preparation: Prepare 130 g / L cobalt sulfate solution with cobalt sulfate and water; prepare 220 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0043] (2) Dilution to obtain a base liquid: Add 50 L of ammonium bicarbonate solution and 600 L of water to an 8000 L reactor, dilute the ammonium bicarbonate solution to obtain a base liquid, heat the base liquid to 50 ° C and maintain a stirring speed of 600 rpm;

[0044] (3) Dynamic nucleation: Cobalt sulfate solution and ammonium bicarbonate solution were continuously fed into the bottom liquid which was stirred at a stirring speed of 600 rpm. The flow rate of cobalt sulfate solution was 120 L / h, and the flow rate of ammonium bicarbonate solution was 260 L / h. During the process, samples were taken every 1 h to test the particle size, and a seed crystal system was obtained. The average particle size of the seeds in the seed crystal system was 2.5 μm.

[0045] (4) Siphon the reactor to reduce the volume of the seed system to 60% of the original volume, add cobalt sulfate solution and ammonium bicarbonate solution at a volume ratio of 1:2 to restore the original volume, and stir at a stirring speed of 150 rpm for 1 hour, then stop stirring, seal the reactor, control the temperature in the reactor at 50 ° C, and perform static growth for 6 hours;

[0046] (5) Filter press washing: After the static growth is completed, the insoluble matter is collected and put into the filter press for filter press washing. The conductivity of the washing liquid for washing the cobalt carbonate is washed to less than 20 μS / m to obtain a wet material;

[0047] (6) Calcination in stages: The wet material is placed on a ceramic tray at a rate of 16 kg / tray, and then placed in a roller kiln for calcination. The temperature is kept at 230 ° C for 3 hours, then the temperature is raised to 460 ° C for 5 hours, and finally the temperature is raised to 750 ° C for 9 hours. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0048] Example 3

[0049] A method for preparing cobalt trioxide by combining dynamic nucleation and static growth comprises the following steps:

[0050] (1) Solution preparation: Prepare 160 g / L cobalt sulfate solution with cobalt sulfate and water; prepare 260 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0051] (2) Dilution to obtain a base liquid: Add 50 L of ammonium bicarbonate solution and 750 L of water to an 8000 L reactor, dilute the ammonium bicarbonate solution to obtain a base liquid, heat the base liquid to 60 ° C and maintain a stirring speed of 700 rpm;

[0052] (3) Dynamic nucleation: Cobalt sulfate solution and ammonium bicarbonate solution were continuously fed into the bottom liquid which was stirred at a stirring speed of 700 rpm. The flow rate of cobalt sulfate solution was 120 L / h, and the flow rate of ammonium bicarbonate solution was 260 L / h. During the process, samples were taken every 1 h to test the particle size, and a seed crystal system was obtained. The average particle size of the seeds in the seed crystal system was 3 μm.

[0053] (4) Siphon the reactor to reduce the volume of the seed system to 60% of the original volume, add cobalt sulfate solution and ammonium bicarbonate solution at a volume ratio of 1:3 to restore the original volume, and stir at a stirring speed of 150 rpm for 1 hour, then stop stirring, seal the reactor, control the temperature in the reactor at 60°C, and perform static growth for 6 hours;

[0054] (5) Filter press washing: After the static growth is completed, the insoluble matter is collected and put into the filter press for filter press washing. The conductivity of the washing liquid for washing the cobalt carbonate is washed to less than 20 μS / m to obtain a wet material;

[0055] (6) Calcination in stages: The wet material is placed on a ceramic tray at a rate of 16 kg / tray, and then placed in a roller kiln for calcination. The temperature is kept at 230 ° C for 3 hours, then the temperature is raised to 460 ° C for 5 hours, and finally the temperature is raised to 750 ° C for 9 hours. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0056] Comparative Example 1

[0057] A method for preparing cobalt tetroxide, using continuous feeding in all stages, comprises the following steps:

[0058] (1) Solution preparation: Prepare 160 g / L cobalt sulfate solution with cobalt sulfate and pure water; prepare 260 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0059] (2) Seed stage: Cobalt sulfate solution and ammonium bicarbonate solution were added directly to the reactor at flow rates of 300 L / h and 500 L / h, respectively. The temperature was maintained at 50°C and the stirring speed was 210 rpm / min. The reaction was stopped when D50 was about 3 μm to obtain a seed system.

[0060] (3) Growth stage: The seed crystal system and 30 L of ammonium bicarbonate solution were mixed to obtain a seed crystal mixture, the temperature was maintained at 50 ° C, the stirring speed was 180 rpm / min, and the cobalt sulfate solution and ammonium bicarbonate solution were simultaneously introduced into the continuously stirred seed crystal mixture at flow rates of 150 L / h and 225 L / h. The particle size of the formed cobalt carbonate was sampled and tested every 4 h. When the particle size of the cobalt carbonate reached the required size, the stirring and the introduction of the cobalt sulfate solution and ammonium bicarbonate solution were stopped;

[0061] (4) Filter press washing: collect the insoluble matter and put it into the filter press for filter press washing. Wash the cobalt carbonate with a washing liquid with a conductivity lower than 20 μS / m to obtain a wet material.

[0062] (5) Calcination in stages: The wet material is placed on a ceramic tray at a rate of 18 kg / tray, and then placed in a roller kiln for calcination. The temperature is kept at 220 ° C for 3 hours, then the temperature is raised to 450 ° C for 5 hours, and finally the temperature is raised to 720 ° C for 9 hours. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0063] Test Case

[0064] The micromorphologies of the seeds obtained by dynamic nucleation, the cobalt carbonate obtained by static growth, and the cobalt trioxide obtained by static growth during the preparation process of Example 3 were observed using a scanning electron microscope. The results were as follows: Figure 2-Figure 4 As shown. Figure 2 It can be seen that the original seed crystal particle size is not uniform, there are agglomerations, and the shape is irregular and spherical, with an average particle size of 3μm; Figure 3 It can be seen that after a one-time addition of cobalt solution and soluble bicarbonate solution for 6 hours of dynamic growth, the agglomeration phenomenon is reduced, the particle size becomes more uniform and the spherical shape is more obvious, with an average particle size of 7 μm; Figure 4 It can be seen that after calcination, the decomposition of cobalt carbonate makes cobalt trioxide have a rough surface while retaining good dispersibility. The appearance is closer to spherical, the average particle size is 7μm, and there is almost no agglomeration phenomenon.

[0065] The microscopic morphology of Comparative Example 1 is as follows Figure 5 As shown, it can be seen that the particle size distribution is uneven and there is obvious agglomeration, which shows that it is difficult to prepare cobalt tetroxide with uniform morphology and good dispersion using the continuous feeding method.

[0066] Overall, the present invention overcomes the problems of complicated preparation process, long time consumption and high cost in traditional continuous production systems. In the grain growth stage of cobalt carbonate, static growth without stirring and feeding is adopted. While avoiding the energy consumption caused by feeding and stirring, cobalt tetroxide with uniform morphology and suitable particle size can be obtained.

[0067] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing cobalt trioxide by combining dynamic nucleation and static growth, characterized in that: include, The precipitant solution is diluted to obtain a base solution; The cobalt salt solution and the precipitant solution are continuously introduced into the continuously stirred bottom liquid to perform dynamic nucleation to obtain a seed crystal system; The cobalt salt solution and the precipitant solution are added to the seed crystal system, stirred and mixed, and then the stirring is stopped to perform static growth until the crystals reach the target particle size, and the cobalt carbonate is collected; Heat-treating cobalt carbonate to obtain cobalt tetroxide; The precipitant solution is diluted at a volume ratio of 1:5-15 to obtain 400-750 L of base solution; The precipitant solution is a soluble bicarbonate solution of 180-260 g / L; The cobalt salt concentration in the cobalt salt solution is 90-160 g / L; The cobalt salt solution and the precipitant solution are continuously introduced into the base liquid which is continuously stirred at a stirring speed of 400-700 rpm at flow rates of 80-120 L / h and 180-260 L / h, respectively, to perform dynamic nucleation until the average particle size of the seed crystals in the seed crystal system is 2-3 μm; After reducing the volume of the seed system to 40%-60% of the original volume, the cobalt salt solution and the precipitant solution are added at a volume ratio of 1:1-3 and replenished to the original volume; The stirring and mixing is continued for 1-2 hours at a stirring speed of 150-220 rpm; The static growth is continued at a temperature of 35-60°C for 4-10 hours.

2. The method for preparing cobalt trioxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: The collection is performed by filter pressing and washing, and the filter pressing and washing reduces the conductivity of the washing liquid for washing the cobalt carbonate to less than 20 μS / m.

3. The method for preparing cobalt trioxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: The heat treatment is carried out at 150-250° C. for 2-5 hours, then the temperature is raised to 350-480° C. for 3-8 hours, and finally the temperature is raised to 650-800° C. for 8-12 hours.

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