Method for preparing large-particle spherical aluminum-doped cobalt-tetroxide by hydrogen peroxide assisted oxidation

Abstract

The application provides a method for preparing large-particle spherical aluminum-doped cobalt trioxide by hydrogen peroxide assisted oxidation, comprising the following steps: preparing a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, a complexing agent solution and a reaction bottom solution; adding the cobalt-aluminum mixed solution containing hydrogen peroxide, the precipitant solution and the complexing agent solution into the reaction bottom solution in parallel flow, and simultaneously introducing air to perform a co-precipitation reaction; after the target particle size is reached, performing solid-liquid separation, drying and calcination to obtain large-particle high-aluminum-doped spherical cobalt oxyhydroxide. The application cooperatively controls the oxidation rate of cobalt ions and the precipitation and crystallization process through oxygen and hydrogen peroxide assisted oxidation, effectively improves the compactness of the surface of the cobalt oxyhydroxide precursor, and the obtained cobalt trioxide particles are uniform, high in sphericity, high in tap density, narrow in particle size distribution and uniform in aluminum element doping.

Description

Technical Field

[0001] This invention relates to the field of cathode materials technology for new energy lithium batteries, specifically to a method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation. Background Technology

[0002] As lithium-ion batteries develop towards higher energy densities, the demand for lithium cobalt oxide (LiCoO2) as a cathode material continues to grow, and its performance is highly dependent on the quality of the precursor cobalt tetroxide (Co3O4). Currently, for lithium cobalt oxide with operating voltages of 4.55V and above, cobalt tetroxide with aluminum doping of 8000ppm or higher is used as the precursor. The mainstream cobalt tetroxide synthesis process in the market adopts a carbonate system, prepared by calcining cobalt carbonate. Although this process is mature and widely used, it has inherent defects: during the doping modification process, firstly, due to the poor fluidity of cobalt carbonate particles and the tendency to crack during calcination, the distribution of doping elements (such as aluminum and magnesium) is uneven; secondly, the higher the content of doping elements, the easier it is for element segregation to occur, leading to uneven element distribution, which in turn affects the structural stability and electrochemical performance of the final lithium cobalt oxide material.

[0003] To address the shortcomings of carbonate systems, hydroxyl-based systems (using cobalt hydroxyoxide as an intermediate) have been proposed as an alternative. Studies have shown that in the wet co-precipitation stage, the +2 valence cobalt ions in the hydroxyl-based system are oxidized to +3 valence cobalt ions. The ionic radius of these hydroxyl-based ions is similar to that of dopant elements such as aluminum, nickel, and manganese, allowing the dopant elements to partially replace the +3 valence cobalt ions. This enables atomic-scale doping and effectively avoids the uneven distribution problems caused by solid-phase mixing. Furthermore, the cobalt oxide synthesized using the hydroxyl-based system supports multi-element doping with relatively uniform distribution, laying the foundation for the preparation of high-performance doped cobalt tetroxide. However, traditional preparation processes for hydroxyl-based cobalt oxide still suffer from problems such as small particle size, severe agglomeration, wide particle size distribution, and inhomogeneous morphology. This makes it difficult to achieve controllable preparation of large-particle, spherical precursors, failing to meet the requirements of high-voltage lithium cobalt oxide for high tap density and good flowability of the precursor.

[0004] Therefore, effectively controlling the growth process of cobalt hydroxyl oxide precursor particles and achieving the preparation of cobalt tetroxide with large particles, high sphericity, and narrow particle size distribution is of great significance for improving the performance of high-voltage lithium cobalt oxide cathode materials. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, aiming to solve the technical problems of low tap density, wide particle size distribution, uneven morphology and low sphericity in the preparation of large-particle cobalt tetroxide by existing hydroxyl system.

[0006] In a first aspect, the present invention provides a method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, comprising the following steps: Prepare a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, a complexing agent solution, and a reaction base solution; A co-precipitation reaction was carried out by adding a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, and a complexing agent solution in parallel to the reaction base liquid, while simultaneously introducing air. After the target particle size was reached, large-particle, highly aluminum-doped spherical cobalt hydroxyoxide was obtained by solid-liquid separation, drying, and calcination. The mass fraction of hydrogen peroxide in the cobalt-aluminum mixed solution containing hydrogen peroxide is 0.06%~0.08%. The flow rate of the cobalt-aluminum mixture containing hydrogen peroxide is 130~320 L / h, the flow rate of the precipitant solution is 60~160 L / h, and the flow rate of the complexing agent solution is 0.5~1.2 L / h.

[0007] Preferably, the concentration of cobalt ions in the cobalt-aluminum mixed solution containing hydrogen peroxide is 120~140 g / L, and the concentration of aluminum ions is 1.7~1.9 g / L.

[0008] Preferably, the precipitant solution is a 30wt%~40wt% sodium hydroxide solution.

[0009] Preferably, the concentration of the complexing agent in the complexing agent solution is 0.1~0.5 g / L; the complexing agent includes at least one of sodium citrate, EDTA, sodium pyrophosphate, and oxalic acid.

[0010] Preferably, the reaction substrate is an aqueous solution; the pH of the reaction substrate is 10.1~10.7.

[0011] Preferably, during the coprecipitation reaction, the pH of the reaction system is controlled at 10.1~10.7, and the reaction temperature is controlled at 65℃~75℃.

[0012] Preferably, the target particle size is ≥10μm.

[0013] Preferably, the drying temperature is 150~200℃, the drying time is 2~4h, and the moisture content of the dried product is ≤1%.

[0014] Preferably, the calcination temperature is 600~660℃ and the calcination time is 6~8h.

[0015] In a second aspect, the present invention provides a large-particle spherical aluminum-doped cobalt tetroxide, which is prepared by the method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation as described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing large-particle spherical aluminum-doped cobalt tetroxide using hydrogen peroxide-assisted oxidation. Air is used as the primary oxidant, and hydrogen peroxide as the secondary oxidant. This method synergistically regulates oxidation kinetics and crystal growth processes, significantly improving the density and sphericity of the precursor particles. The resulting aluminum-doped cobalt tetroxide product exhibits high sphericity, narrow particle size distribution, and excellent tap density, while also demonstrating good uniformity of aluminum doping.

[0017] This invention employs a continuous overflow method, allowing finished materials to be fed in and discharged simultaneously. This enables rapid production of finished materials, reduces waiting time for subsequent processes, improves production efficiency, reduces losses caused by reactor shutdowns due to unforeseen circumstances, and achieves efficient continuous operation, effectively lowering production costs. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the method for preparing large-particle cobalt tetroxide using hydrogen peroxide-assisted oxidation provided by the present invention. Figure 2 This is a SEM image of cobalt hydroxyoxide synthesized in Example 1 of the present invention; Figure 3 This is a SEM image of cobalt hydroxyoxide synthesized in Example 2 of the present invention; Figure 4 This is a SEM image of cobalt hydroxyoxide synthesized in Example 3 of the present invention; Figure 5 This is a SEM image of cobalt tetroxide synthesized in Example 1 of the present invention; Figure 6 This is a SEM image of cobalt tetroxide synthesized in Example 2 of the present invention; Figure 7 This is a SEM image of cobalt tetroxide synthesized in Example 3 of the present invention; Figure 8 This is a cross-sectional SEM image of cobalt tetroxide synthesized in Example 1 of the present invention; Figure 9 This is a cross-sectional EDS image of cobalt tetroxide synthesized in Example 1 of the present invention; Figure 10 This is a SEM image of cobalt tetroxide synthesized in Comparative Example 1 of this invention; Figure 11 This is a SEM image of cobalt tetroxide synthesized in Comparative Example 2 of this invention; Figure 12 This is a SEM image of cobalt tetroxide synthesized in Comparative Example 3 of this invention. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0020] To address the technical problems of low tap density, wide particle size distribution, uneven morphology, and poor sphericity in the preparation of large-particle cobalt tetroxide using existing hydroxyl-based systems, this invention provides a method for preparing large-particle spherical aluminum-doped cobalt tetroxide using hydrogen peroxide-assisted oxidation. This method effectively improves the surface density of the hydroxyl-cobalt oxide precursor by synergistically controlling the oxidation rate and precipitation crystallization process of cobalt ions through oxygen introduction and hydrogen peroxide-assisted oxidation. The resulting cobalt tetroxide particles are uniform, have high sphericity, high tap density, narrow particle size distribution, and uniform aluminum doping.

[0021] Please see Figure 1 In a first aspect, embodiments of the present invention provide a method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, comprising the following steps: Prepare a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, a complexing agent solution, and a reaction base solution; A co-precipitation reaction was carried out by adding a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, and a complexing agent solution in parallel to the reaction base liquid, while simultaneously introducing air. After the target particle size was reached, large-particle, highly aluminum-doped spherical cobalt hydroxyoxide was obtained by solid-liquid separation, drying, and calcination. The mass fraction of hydrogen peroxide in the cobalt-aluminum mixed solution containing hydrogen peroxide is 0.06%~0.08%. The flow rate of the cobalt-aluminum mixture containing hydrogen peroxide is 130~320 L / h, the flow rate of the precipitant solution is 60~160 L / h, and the flow rate of the complexing agent solution is 0.5~1.2 L / h.

[0022] In the technical solution of this invention embodiment, the present invention utilizes the synergistic oxidation effect of hydrogen peroxide and air to ultimately obtain large-particle spherical cobalt tetroxide powder with tightly stacked, lamellar surfaces, fine pores, and excellent overall density. Air slowly oxidizes the co-precipitated cobalt hydroxide precursor, inducing the aggregation of primary nanosheets to form a regular spherical secondary particle framework. Hydrogen peroxide plays a crucial surface modification role, rapidly oxidizing free cobalt ions in the liquid phase on the surface of the spherical particles and in the interlayer spaces, generating nanoparticles in situ to fill the gaps between the layers, effectively reducing internal porosity and enhancing the overall mechanical strength of the particles. This dual oxidation mechanism not only regulates crystal growth kinetics but also significantly improves the sphericity and surface density of the precursor particles, thereby inhibiting particle breakage and aggregation during subsequent calcination, resulting in a cobalt tetroxide product with a complete structure and uniform morphology. The concentration of hydrogen peroxide is controlled within the range of 0.06% to 0.08%, ensuring sufficient oxidation capacity for surface modification while avoiding excessive concentration that could lead to localized violent reactions and damage to the particle morphology.

[0023] Furthermore, in some embodiments, the concentration of cobalt ions in the cobalt-aluminum mixed solution containing hydrogen peroxide is 120~140 g / L, and the concentration of aluminum ions is 1.7~1.9 g / L.

[0024] This invention does not limit the types of cobalt and aluminum sources in the cobalt-aluminum mixed solution; those skilled in the art can select them according to the actual situation. In some specific embodiments of this invention, the cobalt source includes cobalt chloride hexahydrate and / or cobalt sulfate, and the aluminum source includes anhydrous aluminum chloride and / or aluminum sulfate.

[0025] Furthermore, in some embodiments, the precipitant solution is a 30wt%~40wt% sodium hydroxide solution.

[0026] Furthermore, in some embodiments, the concentration of the complexing agent in the complexing agent solution is 0.1~0.5 g / L; the complexing agent includes at least one of sodium citrate, EDTA, sodium pyrophosphate, and oxalic acid.

[0027] Furthermore, in some embodiments, the reaction substrate is an aqueous solution; the pH of the reaction substrate is 10.1 to 10.7.

[0028] In the technical solution of this invention embodiment, no seed crystals are added to the reaction base liquid, which makes the distribution of dopant elements more uniform inside and outside, and prevents enrichment on the seed crystal surface, thereby avoiding phase separation or structural defects caused by excessively high local concentrations.

[0029] Furthermore, in some embodiments, during the coprecipitation reaction, the pH of the reaction system is controlled to be 10.1~10.7, and the reaction temperature is 65℃~75℃.

[0030] Furthermore, in some embodiments, the target particle size is ≥10μm.

[0031] Furthermore, in some embodiments, solid-liquid separation includes filtration and washing.

[0032] Furthermore, in some embodiments, washing is performed until the chloride ion concentration in the washing solution is ≤20ppm.

[0033] Furthermore, in some embodiments, the drying temperature is 150~200℃, the drying time is 2~4h, and the moisture content of the dried product is ≤1%.

[0034] Furthermore, in some embodiments, the calcination temperature is 600~660℃, and the calcination time is 6~8h.

[0035] Secondly, embodiments of the present invention provide a large-particle spherical aluminum-doped cobalt tetroxide, which is prepared by the method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation as described in the first aspect.

[0036] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0037] Example 1 A method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, the specific steps of which are as follows: (1) Solution preparation Cobalt chloride hexahydrate and anhydrous aluminum chloride were mixed with water to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 130 g / L and an aluminum concentration of 1.8 g / L. Hydrogen peroxide with a mass fraction of 0.072% was then added to the cobalt-aluminum mixed solution. Sodium citrate was dissolved in water to prepare a complexing agent solution with a concentration of 0.4 g / L; Sodium hydroxide was dissolved in water to prepare a precipitant solution with a mass fraction of 35%.

[0038] (2) Wet synthesis Pure water was added to the reactor as the reaction base solution. Sodium hydroxide solution was added to adjust the pH of the base solution to 10.60. The stirring speed was controlled at 220 r / h. The prepared cobalt-aluminum mixed solution containing hydrogen peroxide, the precipitant solution, and the complexing agent solution were continuously added to the reactor in a co-current flow. The flow rate of the cobalt-aluminum mixed solution was 280 L / h, the flow rate of the precipitant solution was 140 L / h, and the flow rate of the complexing agent solution was 1.0 L / h. Simultaneously, air was used as the main oxidant and injected into the reactor along with the cobalt-aluminum mixed solution through an injector at a flow rate of 20 m³ / h. 3 The system maintains a pH of 10.5-10.7 and a reaction temperature of 72℃ during the reaction process. The slurry generated by the reaction is continuously discharged from the overflow port. When the particle size reaches 10μm, the valve can be switched to the finished product tank to achieve continuous production without thickening process.

[0039] (3) Washing, drying and calcining After the material in the finished product tank is demagnetized through circulation until the content of magnetic impurities meets the standard, it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is lower than 20ppm. Then, air is blown to obtain a semi-dry material with a moisture content of 0.7%. The semi-dry material is placed into saggers, 12 kg per sagger, and dried in a pusher kiln at 160℃ for 4 hours to obtain the finished cobalt hydroxyl oxide. Cobalt hydroxyl oxide is calcined at 650°C for 6 hours in a calcining furnace to obtain cobalt tetroxide.

[0040] Example 2 A method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, the specific steps of which are as follows: (1) Solution preparation Cobalt chloride hexahydrate and anhydrous aluminum chloride were mixed with water to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 120 g / L and an aluminum concentration of 1.7 g / L. Hydrogen peroxide with a mass fraction of 0.061% was then added to the cobalt-aluminum mixed solution. Sodium pyrophosphate was dissolved in water to prepare a complexing agent solution with a concentration of 0.5 g / L; Sodium hydroxide was dissolved in water to prepare a precipitant solution with a mass fraction of 35%.

[0041] (2) Wet synthesis Pure water was added to the reactor as the reaction base solution, and the pH of the base solution was adjusted to 10.5 with sodium hydroxide solution. The stirring speed was set to 200 r / h. The above cobalt-aluminum mixed solution (containing hydrogen peroxide), precipitant solution, and complexing agent solution were continuously pumped into the reactor in a parallel flow manner, with the flow rate of the cobalt-aluminum mixed solution being 160 L / h, the flow rate of the precipitant solution being 60 L / h, and the flow rate of the complexing agent solution being 0.6 L / h. Simultaneously, air was used as the main oxidizing gas and injected into the reactor along with the cobalt-aluminum mixed solution through an injector, with the air flow rate controlled at 18 m³ / h. 3 / h; During the reaction, the pH of the system is maintained at 10.4~10.6 and the reaction temperature is 65℃; The slurry generated by the reaction is continuously discharged from the overflow port. When the particle size reaches 10μm, the valve can be switched to the finished product tank to realize continuous production without thickening process.

[0042] (3) Washing, drying and calcining After the material in the finished product tank is demagnetized through circulation until the content of magnetic impurities meets the standard, it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is lower than 20ppm. Then, air is blown to obtain a semi-dry material with a moisture content of 0.6%. The semi-dry material is placed into saggers, 8 kg per sagger, and dried in a pusher kiln at 150℃ for 5 hours to obtain the finished cobalt hydroxyl oxide product. Cobalt hydroxyoxide is calcined at 620°C for 6 hours in a calcining furnace to obtain cobalt tetroxide.

[0043] Example 3 A method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, the specific steps of which are as follows: (1) Solution preparation Cobalt chloride hexahydrate and anhydrous aluminum chloride were mixed with water to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 140 g / L and an aluminum concentration of 1.9 g / L. Hydrogen peroxide with a mass fraction of 0.08% was then added to the cobalt-aluminum mixed solution. Prepare a complexing agent solution with a concentration of 0.4 g / L by adding EDTA to water; Sodium hydroxide was dissolved in water to prepare a precipitant solution with a mass fraction of 35%.

[0044] (2) Wet synthesis Pure water was added to the reactor as the reaction base solution, and sodium hydroxide solution was added to adjust the pH of the base solution to 10.6. The stirring speed was set to 220 r / h. The above cobalt-aluminum mixed solution (containing hydrogen peroxide), precipitant solution, and complexing agent solution were continuously pumped into the reactor in a parallel flow manner, with the flow rate of the cobalt-aluminum mixed solution being 300 L / h, the flow rate of the precipitant solution being 150 L / h, and the flow rate of the complexing agent solution being 1.2 L / h. Simultaneously, air was used as the main oxidizing gas and injected into the reactor along with the cobalt-aluminum mixed solution through an injector, with the air flow rate controlled at 22 m³ / h.3 / h; During the reaction, the pH of the system is maintained at 10.5~10.7 and the reaction temperature is 75℃; The slurry generated by the reaction is continuously discharged from the overflow port. When the particle size reaches 10μm, the valve can be switched to the finished product tank to realize continuous production without thickening process.

[0045] (3) Washing, drying and calcining After the material in the finished product tank is demagnetized through circulation until the content of magnetic impurities meets the standard, it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is lower than 20ppm. Then, air is blown to obtain a semi-dry material with a moisture content of 0.5%. The semi-dry material is placed into saggers, 15 kg per sagger, and dried in a pusher kiln at 180°C for 3 hours to obtain the finished cobalt hydroxyl oxide product. Cobalt hydroxyl oxide is calcined at 650°C for 6 hours in a calcining furnace to obtain cobalt tetroxide.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that hydrogen peroxide was not added to the cobalt-aluminum mixture; all other components and process parameters are the same as in Example 1. The specific steps are as follows: (1) Solution preparation Cobalt chloride hexahydrate and anhydrous aluminum chloride were mixed with water to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 130 g / L and an aluminum concentration of 1.8 g / L. Sodium citrate was dissolved in water to prepare a complexing agent solution with a concentration of 0.4 g / L; Sodium hydroxide was dissolved in water to prepare a precipitant solution with a mass fraction of 35%.

[0047] (2) Wet synthesis Pure water was added to the reactor as the reaction base solution. Sodium hydroxide solution was added to adjust the pH of the base solution to 10.60. The stirring speed was controlled at 220 r / h. The prepared cobalt-aluminum mixed solution containing hydrogen peroxide, the precipitant solution, and the complexing agent solution were continuously added to the reactor in a co-current flow. The flow rate of the cobalt-aluminum mixed solution was 280 L / h, the flow rate of the precipitant solution was 140 L / h, and the flow rate of the complexing agent solution was 1.0 L / h. Simultaneously, air was used as the main oxidant and injected into the reactor along with the cobalt-aluminum mixed solution through an injector at a flow rate of 20 m³ / h. 3 The system maintains a pH of 10.5-10.7 and a reaction temperature of 72℃ during the reaction process. The slurry generated by the reaction is continuously discharged from the overflow port. When the particle size reaches 10μm, the valve can be switched to the finished product tank to achieve continuous production without thickening process.

[0048] (3) Washing, drying and calcining After the material in the finished product tank is demagnetized through circulation until the content of magnetic impurities meets the standard, it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is lower than 20ppm. Then, air is blown to obtain a semi-dry material with a moisture content of 0.7%. The semi-dry material is placed into saggers, 12 kg per sagger, and dried in a pusher kiln at 160℃ for 4 hours to obtain the finished cobalt hydroxyl oxide. Cobalt hydroxyl oxide is calcined at 650°C for 6 hours in a calcining furnace to obtain cobalt tetroxide.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that air was not used as an oxidant; oxidation was carried out solely using hydrogen peroxide. The specific steps are as follows: (1) Solution preparation Cobalt chloride hexahydrate and anhydrous aluminum chloride were mixed with water to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 130 g / L and an aluminum concentration of 1.8 g / L. Hydrogen peroxide with a mass fraction of 0.072% was then added to the cobalt-aluminum mixed solution. Sodium citrate was dissolved in water to prepare a complexing agent solution with a concentration of 0.4 g / L; Sodium hydroxide was dissolved in water to prepare a precipitant solution with a mass fraction of 35%.

[0050] (2) Wet synthesis Pure water is added to the reactor as the reaction base liquid. Sodium hydroxide solution is added to adjust the pH of the base liquid to 10.60. The stirring speed is controlled at 220 r / h. The prepared cobalt-aluminum mixed solution (containing hydrogen peroxide), precipitant solution, and complexing agent solution are continuously added to the reactor in a parallel flow. The flow rate of the cobalt-aluminum mixed solution is 280 L / h, the flow rate of the precipitant solution is 140 L / h, and the flow rate of the complexing agent solution is 1.0 L / h. No additional air or other gaseous oxidants are introduced during the reaction. Oxidation is carried out solely by the active oxygen generated by the decomposition of hydrogen peroxide. The pH of the system is maintained at 10.5~10.7, and the reaction temperature is 72℃. The slurry generated by the reaction is continuously discharged from the overflow port. When the particle size reaches 10 μm, the valve can be switched to the finished product tank to achieve continuous production without thickening process.

[0051] (3) Washing, drying and calcining After the material in the finished product tank is demagnetized through circulation until the content of magnetic impurities meets the standard, it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is lower than 20ppm. Then, air is blown to obtain a semi-dry material with a moisture content of 0.7%. The semi-dry material was packed into saggers, 12 kg per sagger, and dried in a pusher kiln at 160°C for 4 hours to obtain cobalt hydroxyl oxide product. Cobalt hydroxyl oxide is calcined at 650°C for 6 hours in a calcining furnace to obtain cobalt tetroxide.

[0052] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass fraction of hydrogen peroxide is 0.3%.

[0053] Performance testing The cobalt hydroxyl oxide and cobalt tetroxide prepared in the above examples and comparative examples were characterized and tested. The test results are shown in Table 1.

[0054] Table 1

[0055] Combining Table 1 and Figures 2-11 The characterization results show that the aluminum-doped cobalt hydroxyl oxide and cobalt tetroxide prepared in the embodiments of the present invention have the characteristics of narrow particle size distribution, high sphericity, high tap density, and uniform elemental distribution. This indicates that the synergistic oxidation of hydrogen peroxide and air effectively promotes the densification growth of particles and improves sphericity. Hydrogen peroxide-assisted oxidation has unique advantages in regulating crystallization kinetics and surface modification. From the SEM images of the products, it can be observed that the products obtained by the synergistic oxidation of hydrogen peroxide and air have high sphericity and high density. In addition to exhibiting plate-like stacking, fine particles can also be observed adhering to the plate-like grains on the surface. These small particles further fill the pores, making the overall particles more dense, and ultimately obtaining a product with higher tap density. In contrast, Comparative Example 1, which did not add hydrogen peroxide, had a slower particle growth rate and could not stably prepare large particle products of the target particle size. The resulting particle surface density was not high, and the sphericity decreased. The product of Comparative Example 2, which relied solely on hydrogen peroxide oxidation, had a significantly loose surface and was difficult to form a particle structure with high sphericity and high density. The hydrogen peroxide content added in Comparative Example 3 was too high, making it difficult to grow large particles. Furthermore, the particle distribution width increased, and the tap density was significantly lower than that of the Example.

[0056] This invention employs hydrogen peroxide-assisted air oxidation, which ensures sufficient oxidation efficiency and, through in-situ oxidation of hydrogen peroxide, regulates grain growth rate and surface modification, thereby achieving continuous and stable production of large-particle cobalt tetroxide.

[0057] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation, characterized in that, Includes the following steps: Prepare a cobalt-aluminum mixed solution containing hydrogen peroxide, a precipitant solution, a complexing agent solution, and a reaction base solution; The cobalt-aluminum mixed solution containing hydrogen peroxide, the precipitant solution, and the complexing agent solution are added concurrently to the reaction base liquid, while air is introduced to carry out a co-precipitation reaction. After the target particle size is reached, large-particle, highly aluminum-doped spherical cobalt hydroxyoxide is obtained by solid-liquid separation, drying, and calcination. The hydrogen peroxide in the cobalt-aluminum mixed solution contains 0.06% to 0.08% by mass; the air flow rate is 18 to 22 m³ / s. 3 The flow rate of the cobalt-aluminum mixture containing hydrogen peroxide is 130~320 L / h, the flow rate of the precipitant solution is 60~160 L / h, and the flow rate of the complexing agent solution is 0.5~1.2 L / h.

2. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The concentration of cobalt ions in the hydrogen peroxide-containing cobalt-aluminum mixed solution is 120~140 g / L, and the concentration of aluminum ions is 1.7~1.9 g / L.

3. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The precipitant solution is a 30wt%~40wt% sodium hydroxide solution.

4. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The concentration of the complexing agent in the complexing agent solution is 0.1~0.5 g / L; the complexing agent includes at least one of sodium citrate, EDTA, sodium pyrophosphate, and oxalic acid.

5. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The reaction substrate is an aqueous solution; the pH of the reaction substrate is 10.1~10.

7.

6. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, During the coprecipitation reaction, the pH of the reaction system is controlled at 10.1~10.7, and the reaction temperature is controlled at 65℃~75℃.

7. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The target particle size is ≥10μm.

8. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The drying temperature is 150~200℃, the drying time is 2~4h, and the moisture content of the dried product is ≤1%.

9. The method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation according to claim 1, characterized in that, The calcination temperature is 600~660℃, and the calcination time is 6~8h.

10. A large-particle spherical aluminum-doped cobalt tetroxide, characterized in that, It is prepared by the method for preparing large-particle spherical aluminum-doped cobalt tetroxide by hydrogen peroxide-assisted oxidation as described in any one of claims 1 to 9.

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