Preparation method of micro-powder-free cobalt hydroxide

Abstract

The invention provides a preparation method of micro-powder-free cobalt hydroxide, belongs to the technical field of lithium ion battery material preparation, and solves the problems that the content of micro powder is high and the synthesis process is difficult to control when the cobalt hydroxide is prepared in the prior art. The method comprises the following operation steps: preparing a solution, carrying out a synthetic reaction, aging, washing, drying and the like, and synthesizing a crimson beta-type cobalt hydroxide product with a product index D0 greater than or equal to 3 microns and regular morphology by controlling the temperature of a synthetic raw material solution at-5 to + 5 DEG C and controlling proper synthesis conditions. The cobalt hydroxide prepared by the method is regular in microstructure, does not contain fine micro-powder particles, and can be used for preparing cobaltosic oxide required by high-voltage lithium cobalt oxide.

Description

A method for preparing cobalt hydroxide without micron powder Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation technology, specifically relating to a method for preparing micron-free cobalt hydroxide. Background Technology

[0002] Lithium cobalt oxide is the earliest commercially available cathode material for lithium-ion batteries. It has advantages such as high operating voltage, stable discharge, high specific energy, and good cycle performance. It is mainly used to manufacture cathode materials for lithium-ion batteries in mobile phones, laptops, and other portable electronic devices.

[0003] Currently, the lithium-ion battery industry is developing rapidly, which has also driven the development of cobalt-based cathode materials such as lithium cobalt oxide. Therefore, the demand for cobalt-based cathode materials for lithium-ion batteries has increased significantly. Cobalt tetroxide, as the main raw material for lithium cobalt oxide, a cathode material in lithium-ion batteries, has physicochemical properties, chemical purity, and physical properties that directly affect the performance of the resulting lithium cobalt oxide. Currently, the main methods for preparing cobalt tetroxide include chemical precipitation, spray pyrolysis, thermal decomposition, and oxidation. At present, most cobalt tetroxide manufacturers use the chemical precipitation-calcination method for large-scale production of cobalt tetroxide products.

[0004] Currently, cobalt tetroxide is mainly prepared by high-temperature calcination of cobalt carbonate or cobalt hydroxide. However, due to the rapid reaction rate of cobalt hydroxide synthesis, problems such as high micropowder content and difficulty in controlling the synthesis process often arise during its preparation. Consequently, fewer and fewer manufacturers are using cobalt hydroxide to prepare cobalt tetroxide. Furthermore, existing manufacturers of hydroxide-based cobalt tetroxide primarily remove micropowder from the product through physical removal during the post-processing classification stage. The classified micropowder is then recycled into cobalt raw materials. This process reduces the direct yield of the product and increases production costs. Therefore, developing a micropowder-free cobalt hydroxide preparation process has become an important task for manufacturers of hydroxide-based cobalt tetroxide. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing cobalt hydroxide without micron powder, so as to solve the problems that the existing technology for preparing cobalt hydroxide often has high micron powder content and the synthesis process is not easy to control.

[0006] The technical solution of this invention is: a method for preparing cobalt hydroxide without micronized powder, comprising the following steps: Step 1: using cobalt nitrate as raw material, prepare a cobalt solution with a cobalt concentration of 100-120 g / L as solution A, a sodium hydroxide solution with a concentration of 280-320 g / L as solution B, and an ammonia solution with a concentration of 40-50 g / L as solution C. Cool the prepared solutions A, B, and C, controlling their temperatures between -5 and +5°C; Step 2: Perform a synthesis reaction on solutions A, B, and C. At the start of the synthesis reaction, add solutions A, B, and C... Three solutions (A, B, and C) are added to the reactor in parallel flow and the synthesis reaction is carried out under stirring. During the reaction, the flow rates of the three solutions (A, B, and C), the reaction pH, the reaction temperature, the stirring intensity, and the reaction time are controlled, and the temperature of the three solutions (A, B, and C) before addition is kept between -5 and +5℃. After the synthesis is completed, the slurry is a deep red β-type cobalt hydroxide slurry. Step 3: After the synthesis reaction is completed, the addition of solutions is stopped and aging begins. Step 4: After aging, the prepared material is washed, and the washed material is deep red. Step 5: The washed material is dried to obtain a powder-free cobalt hydroxide product.

[0007] As a further improvement of the present invention, in step two, the flow rate of solution A is controlled at 800 L / h, the flow rate of solution B is adjusted according to the synthesis pH value, the flow rate of solution C is 60-80 L / h, the ammonia concentration in the slurry solution in the reactor is controlled at 2.5-3.0 g / L, the reaction pH value is controlled at 8.4-8.8, the reaction temperature is 72-76℃, the stirring intensity of the reactor is 100-120 rpm, the blade tip linear velocity is 7.0-8.0 m / s, and the reaction time is 8-10 h.

[0008] As a further improvement of the present invention, in step three, the aging time is 30-60 min, the aging temperature is 72-76℃, and the stirring intensity during aging is 100-120 rpm.

[0009] As a further improvement of the present invention, in step four, the washing equipment is a centrifuge, the filter cloth is a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature ≥90℃, and the Na content in the cobalt hydroxide after washing is ≤0.005%.

[0010] As a further improvement of the present invention, in step five, the drying equipment is a flash evaporator, the drying temperature is 200-240℃, and the moisture content of the material after drying is ≤0.5%.

[0011] As a further improvement of the present invention, in step five, the micron-free cobalt hydroxide product has the following specifications: D0≥3μm, Na%≤0.005%, microstructure is a blocky accumulation, and color is dark red.

[0012] The beneficial effects of this invention are as follows: In the traditional synthesis process of powder-free cobalt hydroxide, due to the high synthesis temperature, large liquid flow rate, and short synthesis time, fine powder particles are easily produced in the cobalt hydroxide product. This invention relates to a new method for preparing powder-free cobalt hydroxide materials, and in particular, a method for preparing powder-free cobalt hydroxide by simply controlling the temperature of the raw material solution. In the synthesis process of powder-free cobalt hydroxide materials, the inventors discovered and confirmed that there is a relationship between the temperature of the raw material solution and the content of cobalt hydroxide powder. When the temperature of the raw material solution is between -5℃ and +5℃, powder-free cobalt hydroxide products can be synthesized.

[0013] This invention slows down the initial reaction rate of cobalt ions with the precipitant and complexing agent from a crystallization kinetic perspective by cooling the solutions of raw materials A, B, and C to -5 to +5°C. This avoids the rapid and massive generation of crystal nuclei caused by excessively high raw material temperatures in traditional processes, thus inhibiting the formation of microparticles at the source. This temperature range prevents reaction stagnation due to excessively low temperatures and local concentration imbalances due to excessively high temperatures, laying the foundation for subsequent orderly crystal growth and serving as a key prerequisite for achieving "microparticle-free" crystal production.

[0014] This invention precisely controls parameters such as pH (8.4-8.8), ammonia concentration (2.5-3.0 g / L), and stirring intensity (100-120 rpm) during the synthesis process, creating a synergistic effect with the low-temperature raw materials. Ammonia water acts as a complexing agent; its appropriate concentration stabilizes the cobalt ion concentration in the solution, preventing localized supersaturation that could lead to fine crystal precipitation. A specific pH range promotes the directional growth of β-type cobalt hydroxide crystals. Reasonable stirring intensity and impeller linear velocity ensure uniform mixing of the three solutions, eliminating localized differences in reaction conditions, further preventing the formation of micro-powder, and simultaneously promoting crystal agglomeration into regular blocky aggregates.

[0015] After synthesis, the crystals are aged at 72-76℃ and 100-120 rpm for 30-60 minutes, maintaining consistency with the synthesis temperature and stirring intensity, to achieve a "maturation" process. This step dissolves a small amount of metastable fine crystals in the system, allowing the solute to redeposit on the surface of larger crystal grains. This improves crystal integrity, further reduces potential microparticles, and enhances the morphological characteristics of the bulk accumulation, thereby increasing the product's bulk density.

[0016] This invention employs a centrifuge with 6000-mesh filter cloth and washing with deionized water at ≥90℃. The high-mesh filter cloth effectively traps fine impurities, while the high-temperature deionized water improves sodium ion desorption efficiency, ensuring that the product's Na content is ≤0.005%, meeting high purity requirements. Flash drying at 200-240℃ quickly removes moisture, avoiding particle agglomeration or crystal damage caused by prolonged drying, thus preserving the product's original blocky morphology and powder-free characteristics.

[0017] This invention directly obtains a powder-free product through front-end process parameter control, eliminating the need for subsequent grading and impurity removal steps. This avoids raw material losses caused by powder recycling, increases the direct product recovery rate, and reduces equipment and operating costs for grading and recycling. At the same time, the product's physicochemical properties are compatible with the preparation requirements of cobalt tetroxide for high-voltage lithium cobalt oxide, demonstrating clear industrial application value. Attached Figure Description

[0018] Figure 1 shows the microstructure of the cobalt hydroxide without micropowder prepared in Example 1; Figure 2 shows the microstructure of the cobalt hydroxide without micropowder prepared in Example 2; Figure 3 shows the microstructure of the cobalt hydroxide without micropowder prepared in Example 3; Figure 4 shows the microstructure of the cobalt hydroxide prepared in Comparative Example 1; Figure 5 shows the microstructure of the cobalt hydroxide prepared in Comparative Example 2. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1, Step 1: Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 100 g / L (solution A), a sodium hydroxide solution with a concentration of 280 g / L (solution B), and an ammonia solution with a concentration of 40 g / L (solution C). Cool the prepared solutions A, B, and C to -5°C. Step 2: Perform a synthesis reaction on solutions A, B, and C. At the start of the reaction, add solutions A, B, and C concurrently to the reactor. The synthesis reaction is carried out under stirring. During the reaction, control the flow rate of solution A at 800 L / h, the flow rate of solution B according to the synthesis pH, and the flow rate of solution C at 60 L / h. Control the ammonia concentration in the slurry solution in the reactor to 2.5 g / L, the reaction pH to 8.4, the reaction temperature to 72°C, the stirring intensity in the reactor to 100 rpm, and the impeller tip linear velocity to 7.0 m / s. The reaction time is 8 hours, and the temperature of solutions A, B, and C is kept at -5℃ before addition. After synthesis, the slurry is a deep red β-type cobalt hydroxide slurry. Step 3: After the synthesis reaction, the addition of liquid is stopped, and aging begins. The aging time is 30 minutes, the aging temperature is 72℃, and the stirring intensity during aging is 100 rpm. Step 4: After aging, the prepared material is washed using a centrifuge with a 6000-mesh filter cloth and deionized water at 90℃. After washing, the Na content in the cobalt hydroxide is ≤0.005%, and the washed material is deep red. Step 5: The washed material is dried using a flash evaporator at 200℃. After drying, the moisture content of the material is ≤0.5%, resulting in a powder-free cobalt hydroxide product with the following specifications: D0≥3μm, Na%≤0.005%, and a blocky aggregate morphology with a deep red color.

[0021] Example 2, Step 1: Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 110 g / L (solution A), a sodium hydroxide solution with a concentration of 300 g / L (solution B), and an ammonia solution with a concentration of 45 g / L (solution C). Cool the prepared solutions A, B, and C to 0°C. Step 2: Perform a synthesis reaction on solutions A, B, and C. At the start of the reaction, add solutions A, B, and C concurrently to the reactor. The synthesis reaction is carried out under stirring. During the reaction, control the flow rate of solution A at 800 L / h, the flow rate of solution B according to the pH value, and the flow rate of solution C at 70 L / h. Control the ammonia concentration in the slurry solution in the reactor to 2.7 g / L, the reaction pH to 8.6, the reaction temperature to 74°C, the stirring intensity in the reactor to 110 rpm, and the impeller tip linear velocity to 7.5 m / s. The reaction time is 9 hours, and the temperature of solutions A, B, and C is kept at 0℃ before addition. After synthesis, the slurry is a deep red β-type cobalt hydroxide slurry. Step 3: After the synthesis reaction is completed, the addition of liquid is stopped and aging begins. The aging time is 45 minutes, the aging temperature is 74℃, and the stirring intensity during aging is 110 rpm. Step 4: After aging, the prepared material is washed using a centrifuge with a 6000-mesh filter cloth and deionized water at 91℃. After washing, the Na content in the cobalt hydroxide is ≤0.005%, and the washed material is deep red. Step 5: The washed material is dried using a flash evaporator at 220℃. After drying, the moisture content of the material is ≤0.5%, resulting in a powder-free cobalt hydroxide product with the following specifications: D0≥3μm, Na%≤0.005%, and a blocky aggregate morphology with a deep red color.

[0022] Example 3, Step 1: Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 120 g / L (solution A), a sodium hydroxide solution with a concentration of 320 g / L (solution B), and an ammonia solution with a concentration of 50 g / L (solution C). Cool the prepared solutions A, B, and C, controlling their temperatures at +5°C. Step 2: Perform a synthesis reaction on solutions A, B, and C. At the start of the reaction, add solutions A, B, and C concurrently to the reactor. The synthesis reaction is carried out under stirring. During the reaction, control the flow rate of solution A at 800 L / h, the flow rate of solution B according to the synthesis pH, and the flow rate of solution C at 80 L / h. Control the ammonia concentration in the slurry solution in the reactor to 3.0 g / L, the reaction pH to 8.8, the reaction temperature to 76°C, the stirring intensity in the reactor to 120 rpm, and the impeller tip linear velocity to 8.0 m / s. The reaction time is 10 hours, and the temperature of solutions A, B, and C is kept at +5℃ before addition. After synthesis, the slurry is a deep red β-type cobalt hydroxide slurry. Step 3: After the synthesis reaction is completed, the addition of solutions is stopped, and aging begins. The aging time is 60 minutes, the aging temperature is 76℃, and the stirring intensity during aging is 120 rpm. Step 4: After aging, the prepared material is washed using a centrifuge with a 6000-mesh filter cloth and deionized water at 92℃. After washing, the Na content in the cobalt hydroxide is ≤0.005%, and the washed material is deep red. Step 5: The washed material is dried using a flash evaporator at 240℃. After drying, the moisture content of the material is ≤0.5%, resulting in a powder-free cobalt hydroxide product with the following specifications: D0≥3μm, Na%≤0.005%, and a blocky aggregate morphology with a deep red color.

[0023] Comparative Example 1: The production process steps and parameters of Comparative Example 1 are the same as those of Example 1, except that the temperature of the raw material solution is controlled at 30℃-40℃.

[0024] Comparative Example 2 and Comparative Example 2 have the same production process steps and parameters as Example 3, except that the temperature of the raw material solution is controlled at 50℃-60℃.

[0025] The physicochemical properties of the powder-free cobalt hydroxide prepared in Examples 1-3 and Comparative Examples 1 and 2 are shown in Table 1 below. The microstructures of the powder-free cobalt hydroxide prepared in Examples 1-3 and Comparative Examples 1 and 2 are shown in Figures 1-5 respectively.

[0026] Based on the experimental data in Table 1 and the microstructure diagrams in Figures 1-5 of Examples 1-3 and Comparative Examples 1-2, it can be concluded that when the temperature of the raw material solution in Examples 1-3 is controlled between -5 and +5℃, and the synthesis, aging, washing, and drying parameters specified in this invention are used, a deep red β-type cobalt hydroxide product with D0 ≥ 3μm, Na% ≤ 0.005%, and a blocky aggregate microstructure can be stably prepared, and the product has no fine powder particles. However, in Comparative Examples 1-2, only the temperature of the raw material solution was increased to 30-60℃, while the other parameters remained unchanged. The product D0 was only 0.53μm, and obvious fine powder appeared in the microstructure, which confirms the decisive role of low temperature control of the raw material in inhibiting the formation of fine powder.

[0027] The cobalt hydroxide product prepared by this invention exhibits excellent performance in key indicators such as particle size distribution, purity, and morphology. It effectively solves the problems of high cobalt hydroxide micro powder content and difficult synthesis process control in the prior art, providing a high-quality raw material for the preparation of cobalt tetroxide for high-voltage lithium cobalt oxide. It has strong process stability, good economic efficiency, and is suitable for industrial production.

Claims

1. A method for preparing cobalt hydroxide without micronized powder, characterized in that: The process includes the following steps: Step 1: Using cobalt nitrate as a raw material, prepare a cobalt solution (solution A) with a cobalt concentration of 100-120 g / L, a sodium hydroxide solution (solution B) with a concentration of 280-320 g / L, and an ammonia solution (solution C) with a concentration of 40-50 g / L. Cool the prepared solutions A, B, and C, controlling their temperatures between -5 and +5°C. Step 2: Perform a synthesis reaction on solutions A, B, and C. At the start of the synthesis reaction, add solutions A, B, and C concurrently into the reaction vessel. The synthesis reaction was carried out under stirring. During the reaction, the flow rates of solutions A, B, and C, the reaction pH, the reaction temperature, the stirring intensity, and the reaction time were controlled. The temperature of solutions A, B, and C before addition was kept between -5 and +5℃. After the synthesis was completed, the slurry was a deep red β-type cobalt hydroxide slurry. Step 3: After the synthesis reaction was completed, the addition of solutions was stopped, and aging began. Step 4: After aging, the prepared material was washed. The washed material was a deep red color. Step 5: The washed material was dried to obtain a powder-free cobalt hydroxide product.

2. The method for preparing powderless cobalt hydroxide according to claim 1, characterized in that: In step two, during the synthesis reaction, the flow rate of solution A is controlled at 800 L / h, the flow rate of solution B is adjusted according to the synthesis pH value, the flow rate of solution C is 60-80 L / h, the ammonia concentration in the slurry solution in the reactor is controlled at 2.5-3.0 g / L, the reaction pH value is controlled at 8.4-8.8, the reaction temperature is 72-76℃, the stirring intensity of the reactor is 100-120 rpm, the blade tip linear velocity is 7.0-8.0 m / s, and the reaction time is 8-10 h.

3. The method for preparing powderless cobalt hydroxide according to claim 1, characterized in that: In step three, the aging time is 30-60 minutes, the aging temperature is 72-76℃, and the stirring intensity during aging is 100-120 rpm.

4. The method for preparing powder-free cobalt hydroxide according to claim 1, characterized in that: In step four, the washing equipment is a centrifuge, the filter cloth is 6000 mesh, the washing solution is deionized water at a temperature ≥90℃, and the Na content in the cobalt hydroxide after washing is ≤0.005%.

5. The method for preparing powderless cobalt hydroxide according to claim 1, characterized in that: In step five, the drying equipment is a flash evaporator, the drying temperature is 200-240℃, and the moisture content of the dried material is ≤0.5%.

6. The method for preparing powderless cobalt hydroxide according to claim 1, characterized in that: In step five, the micron-free cobalt hydroxide product obtained has the following specifications: D0≥3μm, Na%≤0.005%, microstructure is a blocky accumulation, and color is dark red.

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