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

Abstract

The invention discloses a static nucleation and dynamic growth combined cobaltosic oxide preparation method which comprises the following steps: stirring and mixing a cobalt salt solution and a precipitator solution to obtain a reaction system, and then stopping stirring for static nucleation; after static nucleation is completed, continuously introducing a cobalt salt solution and a precipitant solution in a continuous feeding manner, carrying out dynamic growth under stirring, and collecting cobalt carbonate when the particle size of an intermediate reaches a preset value; and carrying out heat treatment on the cobalt carbonate to obtain the cobaltosic oxide. The method does not need to control the pH value of the reaction process of the cobalt salt solution and the precipitant solution, does not need to add any chelating agent or structure adjusting reagent, only controls the initial feeding and subsequent continuous feeding of the cobalt salt solution and the precipitant solution, and adopts a means of combining static nucleation and dynamic growth, so that the cobalt salt solution and the precipitant solution can be synthesized. The cobaltosic oxide which is uniform in morphology, almost free of agglomeration and of a perfect spherical structure can be prepared.

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 static nucleation and dynamic growth. Background Art

[0002] Lithium-ion batteries are favored for their high voltage, high energy density, long cycle life, and low environmental pollution. At the same time, lithium cobalt oxide is one of the most mature positive electrode materials for lithium-ion batteries, and is widely used in batteries for 3C electronic products such as large-capacity mobile phones, laptops, and digital cameras. The conventional preparation method of lithium cobalt oxide is to compact and sinter cobalt oxide and lithium carbonate or lithium hydroxide. With the upgrading of electronic products, higher requirements are placed on the capacity of lithium cobalt oxide.

[0003] As an important precursor material for lithium cobalt oxide, the composition, morphology and particle size of cobalt oxide have an important impact on the physical and chemical indicators of lithium cobalt oxide. For the current mature industrial production, cobalt carbonate is prepared by reacting a cobalt salt solution with a bicarbonate solution and then calcined to prepare cobalt oxide. It is easy to have violent local reactions and too fast particle growth, resulting in different morphologies and poor stability of the prepared cobalt oxide. There are also some methods that ensure the uniformity of cobalt carbonate growth by strictly controlling the pH and stirring speed of the reaction, which makes it easy to prepare cobalt oxide with stable performance. For example, CN108147473A discloses a method for preparing semi-continuous spherical cobalt carbonate, wherein ammonium bicarbonate solution and cobalt salt solution are simultaneously added to a reactor containing ammonium bicarbonate bottom solution, reaction temperature and stirring speed are adjusted, the addition rate of constant cobalt salt solution, and pH value is controlled to be 7.3-7.6 and 7.1-7.4 respectively in nucleation reaction 1h and after 12h, reaction 22-24h, ammonium bicarbonate solution and cobalt salt solution are continuously added simultaneously, reaction temperature and stirring speed are adjusted, the addition rate of cobalt salt solution is increased, and the pH value of crystallization reaction is controlled to be constant to 7.1-7.4 by adjusting the addition rate of ammonium bicarbonate solution, reaction is performed until cobalt carbonate grows to a preset size, reaction is terminated, and water is added for centrifugal washing. This method can prepare cobalt carbonate with a relatively uniform particle size and a spherical shape. However, the pH of the reaction needs to be strictly controlled in the process, and a higher rotation speed is also used for reaction, which improves energy consumption and increases the workload of operators.

[0004] It is necessary to improve the current mass production process of cobalt carbonate to prepare more uniform cobalt carbonate without excessive control of reaction parameters, so as to prepare cobalt tetroxide with more stable performance. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention adopts a method combining static nucleation and dynamic growth, that is, static precipitation is used to obtain crystal nuclei in the seed nucleation stage, and dynamic feeding is used for subsequent crystal nucleus growth, so as to ensure that cobalt carbonate is highly dispersed in the seed stage and reduce agglomeration, so as to prepare uniform and stable cobalt tetroxide.

[0006] In order to achieve the above object, the present invention provides a method for preparing cobalt tetroxide by combining static nucleation and dynamic growth, comprising: The cobalt salt solution and the precipitant solution are stirred and mixed to obtain a reaction system, and then the stirring is stopped to perform static nucleation; After the static nucleation is completed, the cobalt salt solution and the precipitant solution are continuously introduced by continuous feeding, and dynamic growth is carried out under stirring. When the particle size of the intermediate reaches a preset value, cobalt carbonate is collected; Cobalt carbonate is heat treated to obtain cobalt tetroxide.

[0007] Further, the cobalt salt concentration in the cobalt salt solution is 90-160 g / L; The precipitant solution is a soluble bicarbonate solution of 180-260 g / L; The volume of the reaction system is 5000-10000 L, wherein the volume ratio of the cobalt salt solution to the precipitant solution is 1:1-2.5.

[0008] 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.

[0009] Further, the stirring speed when stirring and mixing to obtain the reaction system is 400-700 rpm; The static nucleation lasts for 4-8 hours at a temperature of 35-65°C.

[0010] Furthermore, when continuous feeding is adopted, the flow rates of the cobalt salt solution and the precipitant solution are 80-120 L / h and 180-260 L / h respectively.

[0011] Furthermore, the dynamic growth is carried out at a temperature of 35-65° C. and a stirring speed of 150-240 rpm.

[0012] Furthermore, the collection is carried out by filter pressing and washing; The filter press washing reduces the conductivity of the washing liquid used to wash the cobalt carbonate to less than 20 μS / m.

[0013] Furthermore, the heat treatment is carried out in stages, specifically including: Keep the temperature at 150-250℃ for 2-5h, then increase the temperature to 350-480℃ and keep it for 3-8h, and finally increase the temperature to 650-800℃ and keep it for 8-12h.

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

[0015] The present invention also provides the use of the above-mentioned cobalt tetraoxide in energy storage materials Compared with the prior art, the present invention has the following beneficial effects: The present invention does not need to control the pH of the reaction process of the cobalt salt solution and the precipitant solution, nor does it need to add any chelating agent or structure adjustment agent. Only by controlling the initial feeding of the cobalt salt solution and the precipitant solution and the subsequent continuous feeding, a method combining static nucleation and dynamic growth is adopted to prepare cobalt tetraoxide with uniform morphology, almost no agglomeration and a perfect spherical structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 A flow chart showing the preparation method of cobalt tetroxide combining static nucleation and dynamic growth of the present invention; Figure 2 The scanning electron microscope image of the seed crystal obtained by static nucleation in Example 1 is shown; Figure 3 The scanning electron microscope image of the cobalt carbonate obtained after dynamic growth in Example 1 is shown; Figure 4 The scanning electron microscope image of the cobalt tetroxide prepared in Example 1 is shown; Figure 5 The scanning electron microscope image of the cobalt tetroxide prepared in Comparative Example 1 is shown. DETAILED DESCRIPTION

[0018] 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.

[0019] 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.

[0020] Example 1 A method for preparing cobalt tetroxide by combining static nucleation and dynamic growth, such as Figure 1 As shown, the following steps are included: (1) Solution preparation: Prepare a 130 g / L cobalt chloride solution with cobalt chloride hexahydrate and water; prepare a 220 g / L ammonium bicarbonate solution with ammonium bicarbonate and water; (2) Static nucleation: 2500 L of cobalt chloride solution and 5000 L of ammonium bicarbonate solution were directly mixed and stirred at a stirring speed of 600 rpm to obtain a reaction system, and then the stirring was stopped and maintained at 50 ° C for 6 h to obtain a seed mixture; (3) Dynamic growth: The seed mixture was kept at a temperature of 50°C and a stirring rate of 200 rpm, and the cobalt chloride solution and the ammonium bicarbonate solution were simultaneously introduced into the seed mixture at flow rates of 100 L / h and 220 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 chloride 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.

[0021] Example 2 A method for preparing cobalt tetroxide by combining static nucleation and dynamic growth comprises the following steps: (1) Solution preparation: Prepare a 90 g / L cobalt chloride solution with cobalt chloride hexahydrate and water; prepare a 180 g / L ammonium bicarbonate solution with ammonium bicarbonate and water; (2) Static nucleation: 3000 L of cobalt chloride solution and 3000 L of ammonium bicarbonate solution were directly mixed and stirred at a stirring speed of 700 rpm to obtain a reaction system, and then the stirring was stopped and maintained at 60 ° C for 6 h to obtain a seed mixture; (3) Dynamic growth: The seed mixture was kept at a temperature of 60°C and a stirring rate of 240 rpm, and the cobalt chloride solution and the ammonium bicarbonate solution were simultaneously introduced into the seed mixture at flow rates of 120 L / h and 260 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 chloride 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.

[0022] Example 3 A method for preparing cobalt tetroxide by combining static nucleation and dynamic growth comprises the following steps: (1) Solution preparation: Prepare a 160 g / L cobalt chloride solution with cobalt chloride hexahydrate and water; prepare a 260 g / L ammonium bicarbonate solution with ammonium bicarbonate and water; (2) Static nucleation: 3000 L of cobalt chloride solution and 6000 L of ammonium bicarbonate solution were directly mixed and stirred at a stirring speed of 400 rpm to obtain a reaction system, and then the stirring was stopped and maintained at 40 ° C for 6 h to obtain a seed mixture; (3) Dynamic growth: The seed mixture was kept at a temperature of 40°C and a stirring rate of 150 rpm, and the cobalt chloride solution and the ammonium bicarbonate solution were simultaneously introduced into the seed mixture at flow rates of 80 L / h and 180 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 chloride 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.

[0023] Comparative Example 1 A method for preparing cobalt tetroxide, using continuous feeding in all stages, comprises the following steps: (1) Solution preparation: Prepare a 160 g / L cobalt chloride solution using cobalt chloride crystals and pure water; prepare a 260 g / L ammonium bicarbonate solution using ammonium bicarbonate and water; (2) Seed stage: cobalt chloride 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 6.0-7.0 μm to obtain seed crystals; (3) Growth stage: the seed crystals 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 chloride solution and the ammonium bicarbonate solution were simultaneously introduced into the seed crystal mixture at flow rates of 150 L / h and 225 L / h, respectively. The particle size of the formed cobalt carbonate was sampled and tested 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 chloride 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.

[0024] Test Case The microscopic morphologies of the seeds obtained by static nucleation, the cobalt carbonate obtained by dynamic growth, and the final cobalt tetroxide in the process of preparing cobalt tetroxide in Example 1 were observed by scanning electron microscopy. The results are as follows: Figure 2-Figure 4 As shown. Figure 2 It can be seen that by controlling the concentration of the cobalt solution and the soluble bicarbonate solution and their volume ratio in the present invention, after mixing and stirring, the static nucleation can be carried out by heating, and cobalt carbonate crystal nuclei with good dispersion, uniform particle size and a size of about 5-6 μm can be obtained. Figure 3It can be seen that the cobalt carbonate nuclei can keep growing to the target particle size of 11-12 μm and smooth surface under the continuous feeding of cobalt solution and soluble bicarbonate solution, which shows that under the conditions of the present invention, the growth of the nuclei is well controlled, the morphology is very uniform, and almost perfectly spherical. Figure 4 It can be seen that the particle size and spherical structure of cobalt tetroxide obtained by calcining cobalt carbonate are retained, and a loose pore structure appears on the surface, which is derived from the pyrolysis of carbonate ions, but the pyrolysis does not destroy the good dispersibility and relatively perfect spherical structure of cobalt tetroxide.

[0025] The microscopic morphology of Comparative Example 1 is as follows Figure 5 As shown, it can be seen that the particle size distribution is not uniform, which indicates that it is difficult to prepare cobalt tetroxide with uniform morphology using the continuous feeding method.

[0026] The morphologies of Examples 2 and 3 were also observed, which were similar to those of Example 1. These results show that it is not necessary to control the pH of the reaction process of the cobalt salt solution and the precipitant solution, nor is it necessary to add any chelating agent or structure adjustment agent. Only by controlling the initial feeding of the cobalt salt solution and the precipitant solution and the subsequent continuous feeding, a method combining static nucleation and dynamic growth can be used to prepare cobalt tetraoxide with uniform morphology, almost no agglomeration, and a perfect spherical structure. At the same time, the present invention has low requirements for the stirring speed and temperature of the preparation, can save a lot of energy during continuous production, and is very suitable for industrial production.

[0027] 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 static nucleation and dynamic growth, characterized in that: include, The cobalt salt solution and the precipitant solution are stirred and mixed to obtain a reaction system, and then the stirring is stopped to perform static nucleation; After the static nucleation is completed, the cobalt salt solution and the precipitant solution are continuously introduced by continuous feeding, and dynamic growth is carried out under stirring. When the particle size of the intermediate reaches a preset value, cobalt carbonate is collected; Cobalt carbonate is heat treated to obtain cobalt tetroxide.

2. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: The cobalt salt concentration in the cobalt salt solution is 90-160 g / L; The precipitant solution is a soluble bicarbonate solution of 180-260 g / L; The volume of the reaction system is 5000-10000 L, wherein the volume ratio of the cobalt salt solution to the precipitant solution is 1:1-2.

5.

3. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: The stirring speed when stirring and mixing to obtain the reaction system is 400-700 rpm; The static nucleation lasts for 4-8 hours at a temperature of 35-65°C.

4. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: When continuous feeding is adopted, the flow rates of the cobalt salt solution and the precipitant solution are 80-120 L / h and 180-260 L / h respectively.

5. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: The dynamic growth is carried out at a temperature of 35-65° C. and a stirring speed of 150-240 rpm.

6. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: The collection is carried out by filter pressing and washing; The filter press washing reduces the conductivity of the washing liquid used to wash the cobalt carbonate to less than 20 μS / m.

7. The method for preparing cobalt tetroxide by combining static nucleation and dynamic growth according to claim 1, characterized in that: The heat treatment is carried out in stages, specifically including: Keep the temperature at 150-250℃ for 2-5h, then increase the temperature to 350-480℃ for 3-8h, and finally increase the temperature to 650-800℃ for 8-12h.

8. A cobalt trioxide, characterized in that: The cobalt trioxide is obtained by the preparation method of the static nucleation and dynamic growth combined as described in any one of claims 1 to 7.

9. Use of the cobalt tetroxide according to claim 8 in energy storage materials.

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