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

Abstract

The present invention discloses a method for preparing cobalt tetroxide by combining static nucleation and dynamic growth. The method comprises stirring and mixing a cobalt salt solution and a precipitant solution to obtain a reaction system, then stopping stirring to perform static nucleation; after the static nucleation is completed, continuously feeding the cobalt salt solution and the precipitant solution, and performing dynamic growth under stirring, collecting the intermediate product until the particle size reaches a preset value to obtain cobalt carbonate; and heat-treating the cobalt carbonate to obtain cobalt tetroxide. The present invention does not require controlling the pH of the reaction process of the cobalt salt solution and the precipitant solution, nor does it require adding any chelating agent or structure-adjusting agent. By simply controlling the initial feeding of the cobalt salt solution and the precipitant solution and the subsequent continuous feeding, and using a combination of static nucleation and dynamic growth, cobalt tetroxide with uniform morphology, almost no agglomeration, and 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 highly sought after for their high voltage, high energy density, long cycle life, and minimal environmental impact. Lithium cobalt oxide (LCO) is currently one of the most mature cathode materials for lithium-ion batteries and is widely used in batteries for high-capacity 3C electronic products such as mobile phones, laptops, and digital cameras. LCO is typically prepared by compacting cobalt trioxide with lithium carbonate or lithium hydroxide and then sintering them. With the advancement of new electronic products, the demand for LCO capacity is increasing.

[0003] As an important precursor material for lithium cobalt oxide, factors such as the composition, morphology, and particle size of cobalt trioxide have a significant impact on the physical and chemical indicators of lithium cobalt oxide. In 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 trioxide. This is prone to severe local reactions and excessive particle growth, resulting in different morphologies and poor stability of the prepared cobalt trioxide. There are also some methods that ensure the uniformity of cobalt carbonate growth by strictly controlling the reaction pH and stirring speed, which makes it easier to prepare cobalt trioxide with stable performance. For example, CN108147473A discloses a method for preparing semi-continuous spherical cobalt carbonate, ammonium bicarbonate solution and cobalt salt solution are added simultaneously to the reactor containing ammonium bicarbonate bottom solution, reaction temperature and stirring speed are adjusted, the addition rate of constant cobalt salt solution, while controlling pH value to be 7.3-7.6 and 7.1-7.4 in nucleation reaction 1h and after 12h, respectively, 22-24h is reacted, ammonium bicarbonate solution and cobalt salt solution are 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, cobalt carbonate is grown to a preset size, reaction is terminated, and water is added for centrifugal washing. This method can prepare the approximately spherical cobalt carbonate of particle size being relatively uniform. However, the pH of reaction needs to be strictly controlled during the process, and a higher rotating 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 that combines 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 to grow the crystal nuclei subsequently, ensuring that cobalt carbonate is highly dispersed in the seed stage and reducing 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:

[0007] The cobalt salt solution and the precipitant solution are stirred to obtain a reaction system, and then the stirring is stopped to perform static nucleation;

[0008] After static nucleation is completed, a cobalt salt solution and a precipitant solution are continuously introduced by a continuous feeding method, and dynamic growth is carried out under stirring. When the intermediate particle size reaches a preset value, cobalt carbonate is collected;

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

[0010] Furthermore, the cobalt salt concentration in the cobalt salt solution is 90-160 g / L;

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

[0012] 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.

[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 stirring speed during the stirring and mixing to obtain the reaction system is 400-700 rpm;

[0015] The static nucleation is continued at a temperature of 35-65° C. for 4-8 hours.

[0016] 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.

[0017] Furthermore, the dynamic growth is carried out at a temperature of 35-65° C. and a stirring speed of 150-240 rpm.

[0018] Furthermore, the collection is carried out by filter pressing and washing;

[0019] The filter press washing reduces the conductivity of the washing liquid for washing the cobalt carbonate to less than 20 μS / m.

[0020] Furthermore, the heat treatment is carried out in stages, specifically including:

[0021] 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.

[0022] 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.

[0023] The present invention also provides the application of the above-mentioned cobalt tetroxide in energy storage materials

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention does not require controlling the pH of the reaction process between the cobalt salt solution and the precipitant solution, nor does it require adding any chelating agent or structure-adjusting agent. By simply controlling the initial feeding and subsequent continuous feeding of the cobalt salt solution and the precipitant solution, and adopting a combination of static nucleation and dynamic growth, cobalt trioxide with uniform morphology, almost no agglomeration, and a perfect spherical structure can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 A flow chart showing the method for preparing cobalt trioxide by combining static nucleation and dynamic growth of the present invention is shown;

[0028] Figure 2 shows a scanning electron microscope image of the seed crystal obtained by static nucleation in Example 1;

[0029] Figure 3 shows a scanning electron microscope image of the cobalt carbonate obtained after dynamic growth in Example 1;

[0030] Figure 4 The scanning electron microscope image of the cobaltous oxide prepared in Example 1 is shown;

[0031] Figure 5The scanning electron microscope image of the cobalt trioxide prepared in Comparative Example 1 is shown. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] Example 1

[0035] A method for preparing cobalt tetroxide by combining static nucleation and dynamic growth, such as Figure 1 As shown, it includes the following steps,

[0036] (1) Solution preparation: Prepare 130 g / L cobalt chloride solution with cobalt chloride hexahydrate and water; prepare 220 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0037] (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. Then, stirring was stopped and the mixture was kept at 50 °C for 6 h to obtain a seed crystal mixture.

[0038] (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 ammonium bicarbonate solution were simultaneously introduced into the continuously stirred seed mixture at flow rates of 100 L / h and 220 L / h, respectively. 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 chloride solution and ammonium bicarbonate solution were stopped.

[0039] (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;

[0040] (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.

[0041] Example 2

[0042] A method for preparing cobalt trioxide by combining static nucleation and dynamic growth comprises the following steps:

[0043] (1) Solution preparation: Prepare 90 g / L cobalt chloride solution with cobalt chloride hexahydrate and water; prepare 180 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0044] (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. Then, stirring was stopped and the mixture was kept at 60 °C for 6 h to obtain a seed crystal mixture.

[0045] (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 ammonium bicarbonate solution were simultaneously introduced into the continuously stirred seed mixture at flow rates of 120 L / h and 260 L / h. The particle size of the formed cobalt carbonate was tested by sampling every 4 h. When the particle size of the cobalt carbonate reached the required size, the stirring and the introduction of the cobalt chloride solution and ammonium bicarbonate solution were stopped.

[0046] (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;

[0047] (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.

[0048] Example 3

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

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

[0051] (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. Then, stirring was stopped and the mixture was kept at 40 °C for 6 h to obtain a seed crystal mixture.

[0052] (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 ammonium bicarbonate solution were simultaneously introduced into the continuously stirred seed mixture at flow rates of 80 L / h and 180 L / h, respectively. 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 chloride solution and ammonium bicarbonate solution were stopped.

[0053] (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;

[0054] (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.

[0055] Comparative Example 1

[0056] A method for preparing cobalt tetroxide, using continuous feeding in all stages, comprises the following steps:

[0057] (1) Solution preparation: Prepare 160 g / L cobalt chloride solution with cobalt chloride crystals and pure water; prepare 260 g / L ammonium bicarbonate solution with ammonium bicarbonate and water;

[0058] (2) Seed crystal stage: Cobalt chloride 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 6.0-7.0 μm to obtain seed crystals.

[0059] (3) Growth stage: The seed crystals were mixed with 30 L of ammonium bicarbonate solution to obtain a seed mixture, the temperature was maintained at 50 ° C, the stirring speed was 180 rpm / min, and the cobalt chloride solution and 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 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 chloride solution and ammonium bicarbonate solution were stopped.

[0060] (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;

[0061] (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.

[0062] Test Case

[0063] The micromorphologies of the seeds obtained by static nucleation, the cobalt carbonate obtained by dynamic growth, and the final cobalt oxide in the process of preparing cobalt oxide in Example 1 were observed using a scanning electron microscope. The results are as follows: Figure 2-Figure 4 As shown. Figure 2 It can be seen that by controlling the concentrations of the cobalt solution and the soluble bicarbonate solution and their volume ratio in the present invention, after mixing and stirring, the static nucleation of the cobalt carbonate crystal nuclei with good dispersion and uniform particle size of about 5-6 μm can be obtained. Figure 3 It can be seen that the cobalt carbonate nuclei continue to grow to the target particle size of 11-12 μm and a 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 presents a perfect spherical shape. Figure 4 It can be seen that the particle size and spherical structure of cobalt trioxide obtained by calcining cobalt carbonate are retained, and a loose pore structure appears on the surface. This is due to the thermal decomposition of carbonate ions, but the thermal decomposition does not destroy the good dispersibility and relatively perfect spherical structure of cobalt trioxide.

[0064] 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, which shows that it is difficult to prepare cobalt trioxide with uniform morphology using the continuous feeding method.

[0065] The morphologies of Examples 2 and 3 were also observed and were similar to those of Example 1. These results demonstrate that there is no need to control the pH of the reaction between the cobalt salt solution and the precipitant solution, nor is there any need to add any chelating agents or structure-adjusting agents. By simply controlling the initial and subsequent continuous feeding of the cobalt salt solution and the precipitant solution, and employing a combination of static nucleation and dynamic growth, cobalt trioxide with a uniform morphology, virtually no agglomeration, and a perfectly spherical structure can be prepared. Furthermore, the present invention has low requirements for stirring speed and temperature during preparation, significantly saving energy during continuous production and being highly suitable for industrial production.

[0066] 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 static nucleation and dynamic growth, characterized in that: include, The cobalt salt solution and the precipitant solution are stirred to obtain a reaction system, and then the stirring is stopped to perform static nucleation; After static nucleation is completed, a cobalt salt solution and a precipitant solution are continuously introduced by a continuous feeding method, and dynamic growth is carried out under stirring. When the intermediate particle size reaches a preset value, cobalt carbonate is collected; Heat-treating cobalt carbonate to obtain cobalt tetroxide; 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; The stirring speed when stirring and mixing to obtain the reaction system is 400-700 rpm; The static nucleation is continued for 4-8 hours at a temperature of 35-65°C; When continuous feeding is used, the flow rates of the cobalt salt solution and the precipitant solution are 80-120 L / h and 180-260 L / h, respectively; The dynamic growth is carried out at a temperature of 35-65° C. and a stirring speed of 150-240 rpm.

2. The method for preparing cobalt trioxide 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 for washing the cobalt carbonate to less than 20 μS / m.

3. The method for preparing cobalt trioxide 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℃ and keep it for 3-8h, and finally increase the temperature to 650-800℃ and keep it for 8-12h.

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