A method for preparing sheet-like nanoscale cobalt hydroxide

Abstract

This invention discloses a method for preparing sheet-like nano-sized cobalt hydroxide. The method includes the following steps: using cobalt nitrate as the cobalt source and sodium hydroxide solution as the precipitant, a co-precipitation reaction is carried out. The cobalt nitrate solution and sodium hydroxide solution are added together to a reaction vessel. By controlling the synthesis pH and temperature, the synthesized cobalt hydroxide slurry is washed with hot pure water, dried, and crushed using an air jet mill to obtain sheet-like nano-sized pink cobalt hydroxide with low sodium content. Specifically, the key to preparing sheet-like nano-sized cobalt hydroxide is to prevent oxidation and particle agglomeration during the synthesis process. This invention uses a low-temperature (40-60℃), low-pH (8.0-9.0) cobalt hydroxide synthesis process with a small amount of antioxidant added to prepare sheet-like micron-sized cobalt hydroxide that is not easily oxidized or agglomerated. In addition, at the low pH, the sodium content is low, making the subsequent filtration and washing steps easier to operate.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation technology, specifically relating to a method for preparing sheet-like nanoscale 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] During the preparation of lithium cobalt oxide, it was found that the surface of lithium cobalt oxide contained excess lithium after the solid-state reaction. Therefore, it was necessary to coat the surface of lithium cobalt oxide with ultrafine cobalt hydroxide with small particle size to consume the excess lithium. Coating the surface of lithium cobalt oxide is an effective method to ensure its stability at voltage platforms of 4.5V and above. After coating, a protective layer is formed on the surface of lithium cobalt oxide. This protective layer can effectively delay the structural collapse of lithium cobalt oxide and reduce cobalt dissolution, as well as inhibit O2 precipitation and reduce internal short circuits, thereby improving the thermal stability of lithium cobalt oxide.

[0004] Currently, the preparation of nano-sized cobalt hydroxide typically employs a low-temperature, high-pH synthesis process with the addition of a large amount of antioxidant, or involves staged adjustment of pH and reaction temperature. Chinese invention patent application CN 114835172 A discloses cobalt hydroxide particles, their preparation method, and applications. The preparation method includes the following steps: cobalt salt solution, alkaline solution, and antioxidant solution are mixed into a base solution for a co-precipitation reaction; the pH of the co-precipitation reaction is maintained at 5-8 for the first 0.3-0.6 hours, and then maintained at 12.5-13.0; after the co-precipitation reaction, aging and post-treatment are performed to obtain the cobalt hydroxide particles. However, this method requires staged pH adjustment, necessitates a large amount of antioxidant under nitrogen protection, and is complex to operate; furthermore, when the reaction pH is above 12, subsequent washing to remove Na is difficult.

[0005] In addition, the synthesis of nano-sized cobalt hydroxide also faces the following difficulties: (1) Nano-sized cobalt hydroxide itself has a small particle size, large specific surface area and high activity. It is easy to spontaneously agglomerate and stick together in the wet synthesis stage, resulting in a larger particle size; (2) Nano-sized cobalt hydroxide is easily oxidized to cobalt hydroxide during the synthesis, aging and washing process, which affects the purity of the product. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of complex operation, easy agglomeration and adhesion, and low product purity in the existing synthesis process of nano-sized cobalt hydroxide, and to provide a method for preparing sheet-like nano-sized cobalt hydroxide.

[0007] To achieve its purpose, the present invention adopts the following technical solution: The present invention provides a method for preparing sheet-like nano-sized cobalt hydroxide, comprising the following steps: (1) Preparation of cobalt solution: Using cobalt nitrate as raw material, prepare a cobalt solution with a cobalt concentration of 100-120 g / L; (2) Preparation of sodium hydroxide solution: Dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 80-160 g / L; (3) Synthesis process: Heat the reactor to 40-60℃, turn on the stirrer, and then add the cobalt solution and sodium hydroxide solution from steps (1) and (2), and add an antioxidant at the same time; during the reaction, control the flow rate of the cobalt solution to 3L / h, control the flow rate of the sodium hydroxide solution to make the reaction pH 8.0-9.0, and react for 0.5-1.5h to obtain cobalt hydroxide slurry; (4) After aging, the cobalt hydroxide slurry is washed, dried at low temperature, and then crushed by airflow to obtain a non-agglomerated flake-shaped nano-sized cobalt hydroxide product.

[0008] As a further preferred embodiment of the technical solution of the present invention, in step (3), the stirring intensity of the reactor is 200-400 r / min, and the antioxidant accounts for 0.02-0.05% of the total mass of Co.

[0009] Furthermore, in step (3), the antioxidant is one or more of sodium borohydride, acetone oxime, hydrazine hydrate, and carbazide.

[0010] Furthermore, in step (4), the aging time is 0.5 to 1.5 hours, the aging temperature is 40 to 60 degrees Celsius, and the stirring intensity during aging is 200 to 400 r / min.

[0011] Furthermore, in step (4), the washing equipment is a filter press, the washing water is deionized water at a temperature of 60°C, and the Na content in the cobalt hydroxide after washing is ≤0.008%.

[0012] Furthermore, in step (4), the drying equipment is a vacuum drying oven, the drying temperature is 60-80℃, and the moisture content of the material after drying is <1.0%.

[0013] Furthermore, in step (4), the crushing equipment is an air jet mill with a crushing pressure of 0.4 to 0.8 MPa.

[0014] Furthermore, in step (4), the nano-sized cobalt hydroxide has the following properties: D50≤1.0μm, Na%≤0.008%, and its microstructure is lamellar.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The key to preparing sheet-like nanoscale cobalt hydroxide is to prevent oxidation and particle agglomeration during the synthesis process. This process uses a low-temperature (40-60℃), low-pH (8.0-9.0) cobalt hydroxide synthesis process with a small amount of antioxidant added. Under these conditions, sheet-like micron-sized cobalt hydroxide can be prepared, which is not easily oxidized or agglomerated. In addition, the low pH results in low sodium content, making subsequent filtration and washing steps easier to operate. Attached Figure Description

[0016] Figure 1 Photograph of a sheet-like, nano-sized, pink cobalt hydroxide sample; Figure 2 The microstructure of cobalt hydroxide prepared in Example 1 is shown. Figure 3 The microstructure of cobalt hydroxide prepared in Example 2 is shown. Figure 4 The microstructure of cobalt hydroxide prepared in Example 3 is shown below. Figure 5 To compare the microstructure of cobalt hydroxide prepared in Example 1; Figure 6 To compare the microstructure of cobalt hydroxide prepared in Example 2; Figure 7 The microstructure of cobalt hydroxide prepared in Comparative Example 3 is shown. Detailed Implementation

[0017] The process and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 100 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 80 g / L; 2. Heat the reactor to 40°C, start stirring, and simultaneously add the cobalt solution from step 1 at a flow rate of 3 L / h and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate, which accounts for 0.02% of the total mass of Co. Control the amount of sodium hydroxide solution added to make the pH of the reaction system 8.5, and set the stirring intensity of the reactor to 200 r / min. React for 1.0 h to obtain cobalt hydroxide slurry.

[0019] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 40℃, and stirring intensity 200r / min during aging.

[0020] 4. After aging, the slurry is fed into a filter press and washed with deionized water at 60°C. After washing, the product is dried at 40°C and crushed using an air jet mill at a pressure of 0.4 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0021] The cobalt hydroxide slurry prepared in this embodiment is light pink ( Figure 1 The sodium content was 0.0098% by using an air jet mill to crush the nano-sized, pink cobalt hydroxide in flake form. The final product, cobalt hydroxide, contained 0.0098% sodium. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure showing microstructure]. Figure 2 .

[0022] Example 2 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 110 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100 g / L.

[0023] 2. Heat the reactor to 50°C, start stirring, and simultaneously add the cobalt solution from step 1 (flow rate 3 L / H) and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate (0.03% of the total Co mass). Control the amount of sodium hydroxide solution added to maintain the pH of the reaction system at 8.5, and maintain the stirring intensity of the reactor at 300 r / min. React for 1.5 h to obtain cobalt hydroxide slurry.

[0024] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 50℃, and stirring intensity 300r / min during aging.

[0025] 4. After aging, the slurry is fed into a filter press and washed with deionized water at 60°C. After washing, the product is dried at 40°C and crushed using an air jet mill at a pressure of 0.5 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0026] The cobalt hydroxide slurry prepared in this embodiment is pink, and the sodium content in the final cobalt hydroxide product is 0.0076%. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure 1]. Figure 3 .

[0027] Example 3 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 120 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 160 g / L. 2. Heat the reactor to 60°C, start stirring, and simultaneously add the cobalt solution from step 1 at a flow rate of 3 L / H and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate, which accounts for 0.05% of the total mass of Co. Control the amount of sodium hydroxide solution added to make the pH of the reaction system 8.5. The stirring intensity of the reactor is 400 r / min, and the reaction is carried out for 2.0 h to obtain cobalt hydroxide slurry.

[0028] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 60℃, and stirring intensity 400r / min during aging.

[0029] 4. After aging, the slurry is fed into a filter press and washed with deionized water at 60°C. After washing, the product is dried at 40°C and crushed using an air jet mill at a pressure of 0.6 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0030] 5. The cobalt hydroxide slurry prepared in this embodiment is pink, and the sodium content in the final cobalt hydroxide product is 0.0046%. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure 1]. Figure 4 .

[0031] Comparative Example 1 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 110 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100 g / L. 2. Heat the reactor to 40°C, start stirring, and simultaneously add the cobalt solution from step 1 (flow rate of 3 L / H) and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate (2% of the total Co mass). Control the amount of sodium hydroxide solution added to maintain the pH of the reaction system at 9.0. Set the stirring intensity of the reactor to 200 r / min and react for 1.0 h to obtain the cobalt hydroxide slurry.

[0032] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 50℃, and stirring intensity 300r / min during aging.

[0033] 4. After aging, the slurry is fed into a filter press and washed with deionized water at 60°C. After washing, the product is dried at 40°C and crushed using an air jet mill at a pressure of 0.5 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0034] The cobalt hydroxide slurry prepared in this comparative example is pink, and the sodium content in the final product, cobalt hydroxide, is 0.012%. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure 1]. Figure 5 .

[0035] Comparative Example 2 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 110 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100 g / L. 2. Heat the reactor to 40°C, start stirring, and simultaneously add the cobalt solution from step 1 at a flow rate of 3 L / H and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate, which accounts for 2% of the total mass of Co. Control the amount of sodium hydroxide solution added to keep the pH of the reaction system above 12, and set the stirring intensity of the reactor to 200 r / min. React for 1.0 h to obtain cobalt hydroxide slurry.

[0036] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 50℃, and stirring intensity 300r / min during aging.

[0037] 4. After aging, the slurry is fed into a centrifuge and washed with deionized water at 60°C. After washing, the product is dried at 40°C and crushed using an air jet mill at a pressure of 0.5 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0038] The cobalt hydroxide slurry prepared in this comparative example changed from blue-green to pink. The Na content in the cobalt hydroxide was 0.23%. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure 1]. Figure 6 .

[0039] Comparative Example 3 1. Using cobalt nitrate as raw material, prepare a cobalt solution with a concentration of 110 g / L at room temperature; dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100 g / L. 2. Heat the reactor to 80°C, start stirring, and simultaneously add the cobalt solution from step 1 at a flow rate of 3 L / H and the sodium hydroxide solution from step 2, along with the antioxidant hydrazine hydrate, which accounts for 2% of the total mass of Co. Control the amount of sodium hydroxide solution added to make the pH of the reaction system 12, and set the stirring intensity of the reactor to 200 r / min. React for 1.0 h to obtain cobalt hydroxide slurry.

[0040] 3. Aging cobalt hydroxide slurry: aging time 0.5h, aging temperature 50℃, and stirring intensity 300r / min during aging.

[0041] 4. After aging, the slurry is fed into a filter press and washed. The washing water is deionized water at 60°C. When the sodium content in cobalt hydroxide is less than 0.17%, the washing is completed. The product is dried at 40°C and crushed using an air jet mill at a crushing pressure of 0.5 MPa to obtain agglomerated nano-sized cobalt hydroxide product.

[0042] The cobalt hydroxide slurry prepared in this comparative example changed from blue-green to pink, and finally to brownish-red. The Na content in the cobalt hydroxide was 0.21%. The microstructure of the prepared nano-cobalt hydroxide is shown in [Figure 1]. Figure 7 .

[0043] The above description is a preferred embodiment of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing sheet-like nanoscale cobalt hydroxide, characterized in that, Includes the following steps: (1) Preparation of cobalt solution: Using cobalt nitrate as raw material, prepare a cobalt solution with a cobalt concentration of 100-120 g / L; (2) Preparation of sodium hydroxide solution: Dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 80-160 g / L; (3) Synthesis process: Heat the reactor to 40-60℃, turn on the stirrer, and then add the cobalt solution and sodium hydroxide solution from steps (1) and (2), and add an antioxidant at the same time. During the reaction, control the flow rate of the cobalt solution to 3L / h and control the flow rate of the sodium hydroxide solution to make the pH value of the synthesis reaction 8.0-9.

0. The reaction is carried out for 0.5-1.5h to obtain cobalt hydroxide slurry. (4) After aging, the cobalt hydroxide slurry is washed, dried at low temperature, and then crushed by airflow to obtain a non-agglomerated flake-shaped nano-sized cobalt hydroxide product.

2. The method for preparing nano-sized cobalt hydroxide according to claim 1, characterized in that, In step (3), the stirring intensity of the reactor is 200-400 r / min, and the antioxidant accounts for 0.02-0.05% of the total mass of Co.

3. The method for preparing sheet-like nanoscale cobalt hydroxide according to claim 1, characterized in that, In step (3), the antioxidant is one or more of sodium borohydride, acetone oxime, hydrazine hydrate, and carbazide.

4. The method for preparing sheet-like nanoscale cobalt hydroxide according to claim 1, characterized in that, In step (4), the aging time is 0.5 to 1.5 hours, the aging temperature is 40 to 60 degrees Celsius, and the stirring intensity during aging is 200 to 400 r / min.

5. The method for preparing sheet-like nanoscale cobalt hydroxide according to claim 1, characterized in that: In step (4), the washing equipment is a filter press, the washing water is deionized water at a temperature of 60°C, and the Na content in cobalt hydroxide after washing is ≤0.008%.

6. The method for preparing sheet-like nanoscale cobalt hydroxide according to claim 1, characterized in that, In step (4), the drying equipment is a vacuum drying oven, the drying temperature is 60-80℃, and the moisture content of the material after drying is <1.0%.

7. The method for preparing sheet-like nanoscale cobalt hydroxide according to claim 1, characterized in that, In step (4), the crushing equipment is an air jet mill with a crushing pressure of 0.4 to 0.8 MPa.

8. A method for preparing sheet-like nanoscale cobalt hydroxide according to any one of claims 1-7, characterized in that, In step (4), the nano-sized cobalt hydroxide has the following properties: D50≤1.0μm, Na%≤0.008%, and its microstructure is lamellar.

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