Preparation method of cobaltosic oxide with combination of dynamic nucleation and static growth

Abstract

The invention discloses a preparation method of cobaltosic oxide combining dynamic nucleation and static growth. The preparation method comprises the following steps: diluting a precipitant solution to obtain a base solution; continuously introducing the cobalt salt solution and the precipitant solution into the continuously stirred base solution, and carrying out dynamic nucleation to obtain a seed crystal system; adding the cobalt salt solution and the precipitant solution into the seed crystal system, stirring and mixing, stopping stirring, carrying out static growth until the crystal reaches the target particle size, and collecting to obtain cobalt carbonate; and carrying out heat treatment on the cobalt carbonate to obtain the cobaltosic oxide. According to the method, the problems of tedious preparation process, long time consumption, high cost and the like of a traditional continuous production system are solved, static growth without stirring and charging is adopted in the crystal grain growth stage of cobalt carbonate, and on the premise that energy consumption caused by charging and stirring is avoided, the yield of cobalt carbonate is increased. And cobaltosic oxide with uniform morphology and proper particle size can 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 positive electrode material have the characteristics of light weight, large capacity, high specific energy, high operating voltage, stable discharge, suitable for large current discharge, good cycle performance, long life, etc. They are mainly used in the 3C digital field. With the development of science and technology and the growing demand, lithium cobalt oxide is developing in the direction of high voltage, high compaction and high cycle performance.

[0003] As the performance requirements for lithium cobalt oxide increase, the requirements for the raw material cobalt oxide are also getting higher and higher. At present, the traditional method for preparing cobalt oxide in the carbonate system usually adopts continuous feeding to synthesize seeds, and then continuously feeds the seeds 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: The precipitant solution is diluted to obtain a base solution; The cobalt salt solution and the precipitant solution are continuously introduced into the constantly 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 cobalt carbonate is collected; Cobalt carbonate is heat treated to obtain cobalt tetroxide.

[0006] Further, 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.

[0007] In the present invention, the types of cobalt salt and soluble bicarbonate salt need not be strictly limited. For example, the cobalt salt can be at least one of cobalt sulfate, cobalt chloride, cobalt nitrate, etc.; the soluble bicarbonate salt can be at least one of potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, etc. The solvents of the cobalt salt solution and the precipitant solution do not need to be strictly limited, and are general solvents, such as at least one of water, ethanol, acetone, etc., preferably water.

[0008] Furthermore, the cobalt salt solution and the precipitant solution are continuously introduced into the base liquid stirred at a stirring speed of 400-700 rpm at flow rates of 80-120 L / h and 180-260 L / h respectively, and dynamic nucleation is performed until the average particle size of the seeds in the seed system is 2-3 μm.

[0009] 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.

[0010] Furthermore, the stirring and mixing is continued for 1-2 hours at a stirring speed of 150-220 rpm.

[0011] Furthermore, the static growth is continued at a temperature of 35-60° C. for 4-10 hours.

[0012] 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.

[0013] 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.

[0014] The present invention also provides cobalt tetroxide, which is obtained by the cobalt tetroxide preparation method combining dynamic nucleation and static growth.

[0015] The present invention also provides the application of the above-mentioned cobalt tetroxide in energy storage materials.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention overcomes the problems of complicated preparation process, long time consumption and high cost in the traditional continuous production system. In the grain growth stage of cobalt carbonate, static growth without stirring and feeding is adopted, and on the premise of avoiding the energy consumption caused by feeding and stirring, cobalt tetraoxide with uniform morphology and appropriate particle size can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0018] Figure 1 A flow chart showing the method for preparing cobalt tetroxide by combining dynamic nucleation and static growth of the present invention is shown; Figure 2 The scanning electron microscope image of the seed crystal obtained by dynamic nucleation in Example 3 is shown; Figure 3 shows a scanning electron microscope image of cobalt carbonate obtained after static growth in Example 3; Figure 4 The scanning electron microscope image of the cobalt tetroxide prepared in Example 3 is shown; Figure 5 The scanning electron microscope image of the cobalt tetroxide prepared in Comparative Example 1 is shown. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in the present invention 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 endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0020] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0021] Example 1 A method for preparing cobalt tetroxide by combining dynamic nucleation and static growth, such as Figure 1 As shown, it includes the following steps: (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; (2) Dilution to obtain a base liquid: add 50 L of ammonium bicarbonate solution and 450 L of water into an 8000 L reactor, dilute the ammonium bicarbonate solution to obtain a base liquid, heat the base liquid to 40° C. and stir at a stirring speed of 400 rpm; (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, and a seed crystal system was obtained. The average particle size of the seeds in the seed crystal system was 2 μm. (4) The reactor was siphoned to reduce the volume of the seed system to 50% of the original volume, and cobalt sulfate solution and ammonium bicarbonate solution were added at a volume ratio of 1:1 to restore the original volume. The stirring was stopped after stirring at a speed of 150 rpm for 1 h. The reactor was sealed and the temperature in the reactor was controlled at 40 °C for static growth for 6 h. (5) Filter pressing and washing: After the static growth is completed, the insoluble matter is collected and pumped into a filter press for filter pressing and 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; (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 at 230°C for 3 h, then heated to 460°C for 5 h, and finally heated to 750°C for 9 h. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0022] Example 2 A method for preparing cobalt tetroxide by combining dynamic nucleation and static growth, such as Figure 1 As shown, it includes the following steps: (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; (2) Dilution to obtain a base liquid: add 50 L of ammonium bicarbonate solution and 600 L of water into an 8000 L reactor, dilute the ammonium bicarbonate solution to obtain a base liquid, heat the base liquid to 50° C. and maintain stirring at a stirring speed of 600 rpm; (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. (4) The reactor was siphoned to reduce the volume of the seed system to 60% of the original volume, and cobalt sulfate solution and ammonium bicarbonate solution were added at a volume ratio of 1:2 to restore the original volume. The stirring was stopped after stirring at a speed of 150 rpm for 1 h. The reactor was sealed and the temperature in the reactor was controlled at 50 °C for static growth for 6 h. (5) Filter pressing and washing: After the static growth is completed, the insoluble matter is collected and pumped into a filter press for filter pressing and 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; (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 at 230°C for 3 h, then heated to 460°C for 5 h, and finally heated to 750°C for 9 h. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0023] Example 3 A method for preparing cobalt tetroxide by combining dynamic nucleation and static growth comprises the following steps: (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; (2) Dilution to obtain a base liquid: add 50 L of ammonium bicarbonate solution and 750 L of water into 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; (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. (4) The reactor was siphoned to reduce the volume of the seed system to 60% of the original volume, and cobalt sulfate solution and ammonium bicarbonate solution were added at a volume ratio of 1:3 to restore the original volume. The stirring was stopped after stirring at a speed of 150 rpm for 1 h. The reactor was sealed and the temperature in the reactor was controlled at 60 °C for static growth for 6 h. (5) Filter pressing and washing: After the static growth is completed, the insoluble matter is collected and pumped into a filter press for filter pressing and 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; (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 at 230°C for 3 h, then heated to 460°C for 5 h, and finally heated to 750°C for 9 h. Finally, it is naturally cooled to room temperature to obtain cobalt tetroxide.

[0024] Comparative Example 1 A method for preparing cobalt tetroxide, using continuous feeding in all stages, comprises the following steps: (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; (2) Seed stage: Cobalt sulfate solution and ammonium bicarbonate solution were directly added to the reactor at flow rates of 300 L / h and 500 L / h respectively, the temperature was maintained at 50 °C, the stirring speed was 210 rpm / min, and the reaction was stopped when D50 was about 3 μm to obtain a seed system; (3) Growth stage: The seed system and 30 L of ammonium bicarbonate solution were mixed to obtain a seed mixture, the temperature was maintained at 50° C., the stirring speed was 180 rpm / min, and the cobalt sulfate solution and the ammonium bicarbonate solution were simultaneously introduced into the continuously stirred seed mixture at flow rates of 150 L / h and 225 L / h, respectively. The particle size of the formed cobalt carbonate was tested by sampling every 4 hours. When the particle size of the cobalt carbonate reached the required size, the stirring was stopped and the introduction of the cobalt sulfate solution and the ammonium bicarbonate solution was stopped; (4) Filter pressing and washing: collect the insoluble matter and put it into the filter press for filter pressing and 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; (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, kept at 220°C for 3 hours, then heated to 450°C for 5 hours, and finally heated to 720°C for 9 hours, and finally naturally cooled to room temperature to obtain cobalt tetroxide.

[0025] Test Case The microscopic morphologies of the seeds obtained by dynamic nucleation, the cobalt carbonate obtained by static growth, and the cobalt oxide obtained by static growth during the preparation process of Example 3 were observed by scanning electron microscopy. The results are as follows: Figure 2-Figure 4 As shown. Figure 2 It can be seen that the original seed crystals are not uniform in size, agglomerated, and irregularly spherical, with an average particle size of 3 μm. 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 decreased, the particle size became more uniform and spherical, and the average particle size was 7 μm; Figure 4 It can be seen that after calcination, the decomposition of cobalt carbonate makes cobalt tetroxide 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.

[0026] 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.

[0027] In general, the present invention overcomes the problems of complicated preparation process, long time consumption and high cost in the traditional continuous production system. In the grain growth stage of cobalt carbonate, static growth without stirring and feeding is adopted. On the premise of avoiding the energy consumption caused by feeding and stirring, cobalt tetroxide with uniform morphology and suitable particle size can be obtained.

[0028] 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, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to 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 protection scope of the present invention.

Claims

1. A method for preparing cobalt tetroxide 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 constantly 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 cobalt carbonate is collected; Cobalt carbonate is heat treated to obtain cobalt tetroxide.

2. The method for preparing cobalt tetroxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: 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.

3. The method for preparing cobalt tetroxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: The cobalt salt solution and the precipitant solution are continuously introduced into the base liquid stirred at a stirring speed of 400-700 rpm at flow rates of 80-120 L / h and 180-260 L / h respectively, and dynamic nucleation is performed until the average particle size of the seeds in the seed system is 2-3 μm.

4. The method for preparing cobalt tetroxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: 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.

5. The method for preparing cobalt tetroxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: The stirring and mixing is continued for 1-2 hours at a stirring speed of 150-220 rpm.

6. The method for preparing cobalt tetroxide by combining dynamic nucleation and static growth according to claim 1, characterized in that: The static growth is continued at a temperature of 35-60°C for 4-10 hours.

7. The method for preparing cobalt tetroxide 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 washes the conductivity of the washing liquid for washing the cobalt carbonate to less than 20 μS / m.

8. The method for preparing cobalt tetroxide 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.

9. A cobalt trioxide, characterized in that: The cobalt trioxide is obtained by the preparation method of the dynamic nucleation and static growth combined as described in any one of claims 1 to 8.

10. Use of the cobalt tetroxide as claimed in claim 9 in energy storage materials.

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