Preparation method of cobalt hydroxide without ammonia volatilization

Abstract

The invention discloses a method for preparing cobalt hydroxide without ammonia volatilization, which is characterized in that cobalt nitrate and soluble ammonium salt are used as cobalt sources, sodium hydroxide is used as a precipitator, and the cobalt hydroxide is prepared by increasing the synthesis temperature (80 DEG C) and reducing the synthesis pH (potential of hydrogen) value (7.0-7.2). Due to the adoption of a high-temperature and low-pH synthesis process, the complexing dosage (the ammonia concentration is less than or equal to 1g / L) and the free ammonia concentration required by synthesis of the cobalt hydroxide are reduced, so that no ammonia is volatilized into the environment in the preparation process of the cobalt hydroxide, and the ammonia concentration at a kettle opening of a reaction kettle is less than or equal to 0.5 mg / m < 3 >.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery material preparation, and in particular relates to a method for preparing cobalt hydroxide without ammonia volatilization for preparing cobalt tetroxide. Background Art

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

[0003] At present, the lithium-ion battery industry is developing rapidly, which has also driven the development of cobalt-based positive electrode materials such as lithium cobalt oxide. Therefore, the demand for cobalt-based positive electrode materials for lithium-ion batteries has also increased significantly. As the main raw material for lithium cobalt oxide, the positive electrode material of lithium-ion batteries, the physical and chemical properties, chemical purity, and physical properties of cobalt tetroxide are directly related to the relevant properties of the obtained lithium cobalt oxide. The main preparation methods of cobalt tetroxide include chemical precipitation, spray pyrolysis, thermal decomposition, oxidation, etc. At present, various cobalt tetroxide manufacturers generally use chemical precipitation-calcination method to mass-produce cobalt tetroxide products.

[0004] Cobalt tetroxide is mainly prepared by high-temperature calcination of cobalt hydroxide or cobalt carbonate. Manufacturers first use cobalt salt solution and ammonium bicarbonate solution to produce cobalt carbonate or use cobalt salt solution, sodium hydroxide solution and ammonia solution to produce cobalt hydroxide. However, no matter whether cobalt carbonate or cobalt hydroxide is prepared, ammonia gas will evaporate during the preparation process, causing the production workshop to be filled with strong ammonia smell, which is harmful to the health of production personnel. Summary of the invention

[0005] In order to overcome the shortcomings of the existing production process, the purpose of the present invention is to provide a method for preparing cobalt hydroxide without ammonia volatilization, which has a simple production process, is easy to control, and is easy to industrialize.

[0006] To achieve the above object, the present invention adopts the following technical solutions: a. Liquid preparation Use cobalt nitrate and soluble ammonium salt as raw materials, prepare cobalt concentration of 100~120g / L, NH4 + The mixed solution with a concentration of 0.06~~0.1mol / L is solution A; the sodium hydroxide solution with a concentration of 200~240g / L is solution B; b. Synthesis reaction At the beginning of the synthesis reaction, solutions A and B are added to the reactor in parallel and the synthesis reaction is carried out under stirring. During the reaction, the flow rate of solution A, the reaction pH value, the reaction temperature, the stirring intensity and the reaction time are strictly controlled; the flow rate of solution B is dynamically adjusted according to the reaction pH value to ensure that the ammonia concentration at the reactor inlet is ≤0.5mg / m3 ; c. Aging After the synthesis reaction is completed, stop adding liquid and start aging; d. Washing After aging, the prepared material is washed; e. Drying The washed material is dried to obtain a cobalt hydroxide product.

[0007] In step a, the soluble ammonium salt is one of ammonium nitrate, ammonium chloride and ammonium sulfate.

[0008] In step b, the flow rate of solution A is 300 L / h, the flow rate of solution B is adjusted according to the synthetic pH value, the reaction pH value is controlled to be 7.0-7.2, the reaction temperature is 78-82°C, the stirring intensity of the reactor is 45-50 Hz, and the reaction time is 20-24 h.

[0009] In step c, the aging process is as follows: the aging time is 30 to 60 minutes, the aging temperature is 78 to 82° C., and the stirring intensity during aging is 100 to 120 rpm.

[0010] In step d, the washing equipment is a centrifuge, the filter cloth specification is a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature of ≥90° C., and the Na in the cobalt hydroxide after washing is ≤0.002%.

[0011] In step e, the drying equipment is a flash evaporator, the drying temperature is 200-240° C., and the moisture content of the material after drying is ≤0.5%.

[0012] In step e, the cobalt hydroxide index is: D 50 =8~10μm, Na%≤0.002%, TD≥2.0g / cm 3 The microscopic morphology is a blocky accumulation.

[0013] The present invention has the following advantages: Ammonia water is required as a complexing agent in the synthesis process of cobalt hydroxide, so cobalt hydroxide manufacturers generally use ammonia water as a raw material to produce cobalt hydroxide. During the preparation, addition and synthesis of the ammonia solution, due to the high temperature and high pH value, ammonia water will evaporate from the reaction system from the kettle to the environment, making the production environment full of high-concentration ammonia gas, which is harmful to the health of production personnel. The cobalt hydroxide production process of the present invention uses ammonium salt as a raw material to prepare cobalt hydroxide. Before the synthesis reaction is carried out, ammonia is NH4 +In the reaction process, due to the use of high temperature and low synthesis pH value, the required amount of complexing agent is greatly reduced (NH3 concentration in the reaction system ≤ 1g / L), and the NH3 generated by the reaction will not volatilize at this low pH value, but remain in the reaction solution to continue to participate in the reaction, thus ensuring that the ammonia concentration at the reactor outlet is ≤ 0.5mg / m 3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a production process flow chart of the present invention.

[0015] Figure 2 This is a microscopic morphology of the cobalt hydroxide prepared in Example 1.

[0016] Figure 3 This is a microscopic morphology of cobalt hydroxide prepared in Example 2.

[0017] Figure 4 This is a microscopic morphology of cobalt hydroxide prepared in Example 3. DETAILED DESCRIPTION

[0018] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1 Production steps see Figure 1 , which will not be described here. The specific parameters in each step are as follows: Using cobalt nitrate and ammonium nitrate as raw materials, a mixed solution with a cobalt concentration of 100 g / L and an ammonium concentration of 0.06 mol / L was prepared as solution A; a sodium hydroxide solution with a concentration of 240 g / L was prepared as solution B.

[0020] The synthesis reaction was carried out at 15m 3 The reaction was carried out in a reactor. At the beginning of the synthesis reaction, solution A was added to the reactor at a flow rate of 300 L / h and solution B at a flow rate of about 170 L / h, and the synthesis reaction was carried out under stirring. During the reaction, the reaction pH value was strictly controlled to be 7.0~7.1, the reaction temperature was 80~82℃, the stirring intensity was 45Hz, and the reaction time was 24h. During the reaction, the ammonia concentration at the reactor outlet was detected to be ≤0.5mg / m 3 .

[0021] After the synthesis reaction is completed, stop adding liquid and start aging. The aging time is 30 minutes, the aging temperature is 80~82℃, and the stirring intensity during aging is 45Hz.

[0022] After aging, the prepared material is washed using a centrifuge and a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature of ≥90°C, and the Na content in the cobalt hydroxide after washing is ≤0.002%.

[0023] The washed material is dried with a flash evaporator. The drying temperature is 200~240℃, and the moisture content of the material after drying is ≤0.5%.

[0024] The physical and chemical indicators of the prepared micron-free cobalt hydroxide are shown in Table 1 below.

[0025] Table 1 Physical and chemical indicators of cobalt hydroxide prepared in Example 1 The microstructure of the prepared cobalt hydroxide is shown in the attached Figure 2 .

[0026] Example 2 The production steps are the same as above and will not be repeated here. The specific parameters in each step are as follows: Using cobalt nitrate and ammonium chloride as raw materials, a mixed solution with a cobalt concentration of 110 g / L and an ammonium concentration of 0.08 mol / L was prepared as solution A; a sodium hydroxide solution with a concentration of 220 g / L was prepared as solution B.

[0027] The synthesis reaction was carried out at 15m 3 The reaction was carried out in a reactor. At the beginning of the synthesis reaction, solution A was added to the reactor at a flow rate of 300 L / h and solution B was added at a flow rate of about 200 L / h. The synthesis reaction was carried out under stirring. During the reaction, the reaction pH was strictly controlled to be 7.05-7.15, the reaction temperature was 79-81°C, the stirring intensity was 48 Hz, and the reaction time was 22 hours. During the reaction, the ammonia concentration at the reactor outlet was detected to be ≤0.5 mg / m 3 .

[0028] After the synthesis reaction is completed, stop adding liquid and start aging. The aging time is 45 minutes, the aging temperature is 79~81℃, and the stirring intensity during aging is 48Hz.

[0029] After aging, the prepared material is washed using a centrifuge and a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature of ≥90°C, and the Na content in the cobalt hydroxide after washing is ≤0.002%.

[0030] The washed material is dried with a flash evaporator. The drying temperature is 200~240℃, and the moisture content of the material after drying is ≤0.5%.

[0031] The physical and chemical indicators of the prepared micron-free cobalt hydroxide are shown in Table 2 below.

[0032] Table 2 Physical and chemical indicators of cobalt hydroxide prepared in Example 2 The microstructure of the prepared powder-free cobalt hydroxide is shown in the attached figure. Figure 3 .

[0033] Example 3 The production steps are the same as above and will not be repeated here. The specific parameters in each step are as follows: Using cobalt nitrate and ammonium sulfate as raw materials, a mixed solution with a cobalt concentration of 120 g / L and an ammonium concentration of 0.1 mol / L was prepared as solution A; a sodium hydroxide solution with a concentration of 200 g / L was prepared as solution B.

[0034] The synthesis reaction was carried out at 15m 3 The reaction was carried out in a reactor. At the beginning of the synthesis reaction, solution A was added to the reactor at a flow rate of 300 L / h and solution B at a flow rate of about 250 L / h, and the synthesis reaction was carried out under stirring. During the reaction, the reaction pH value was strictly controlled to be 7.1-7.2, the reaction temperature was 78-80°C, the stirring intensity was 50 Hz, and the reaction time was 20 h. During the reaction, the ammonia concentration at the reactor outlet was detected to be ≤0.5 mg / m 3 .

[0035] After the synthesis reaction is completed, stop adding liquid and start aging. The aging time is 60 minutes, the aging temperature is 78~80℃, and the stirring intensity during aging is 50Hz.

[0036] After aging, the prepared material is washed using a centrifuge and a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature of ≥90°C, and the Na content in the cobalt hydroxide after washing is ≤0.002%.

[0037] The washed material is dried with a flash evaporator. The drying temperature is 200~240℃, and the moisture content of the material after drying is ≤0.5%.

[0038] The physical and chemical indicators of the prepared micron-free cobalt hydroxide are shown in Table 3 below.

[0039] Table 3 Physical and chemical indicators of cobalt hydroxide prepared in Example 3 The microstructure of the prepared powder-free cobalt hydroxide is shown in the attached figure. Figure 4 .

Claims

1. A method for preparing cobalt hydroxide without ammonia volatilization, characterized in that: The following steps are involved: a. Liquid preparation Use cobalt nitrate and soluble ammonium salt as raw materials, prepare cobalt concentration of 100~120g / L, NH4 + The mixed solution with a concentration of 0.06~0.1mol / L is solution A; the sodium hydroxide solution with a concentration of 200~240g / L is solution B; b. Synthesis reaction When the synthesis reaction starts, solutions A and B are added to the reactor in parallel, and the synthesis reaction is carried out under stirring.

2. During the reaction, the flow rate of solution A, the reaction pH value, the reaction temperature, the stirring intensity and the reaction time are strictly controlled; the flow rate of solution B is dynamically adjusted according to the reaction pH value to ensure that the ammonia concentration at the reactor outlet is ≤0.5mg / m 3 ; c. Aging After the synthesis reaction is completed, stop adding liquid and start aging; d. Washing After aging, the prepared material is washed; e. Drying The washed material is dried to obtain a cobalt hydroxide product.

3. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step a, the soluble ammonium salt is one of ammonium nitrate, ammonium chloride and ammonium sulfate.

4. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step b, the flow rate of solution A is 300 L / h, the flow rate of solution B is adjusted according to the synthetic pH value, the reaction pH value is controlled to be 7.0-7.2, the reaction temperature is 78-82°C, the stirring intensity of the reactor is 45-50 Hz, and the reaction time is 20-24 h.

5. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step c, the aging process is as follows: the aging time is 30 to 60 minutes, the aging temperature is 78 to 82° C., and the stirring intensity during aging is 100 to 120 rpm.

6. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step d, the washing equipment is a centrifuge, the filter cloth specification is a 6000 mesh filter cloth, the washing liquid is deionized water with a temperature of ≥90° C., and the Na in the cobalt hydroxide after washing is ≤0.002%.

7. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step e, the drying equipment is a flash evaporator, the drying temperature is 200-240° C., and the moisture content of the material after drying is ≤0.5%.

8. A method for preparing cobalt hydroxide without ammonia volatilization as claimed in claim 1, characterized in that: In step e, the cobalt hydroxide index is: D 50 =8~10μm, Na%≤0.002%, TD≥2.0g / cm 3 The microscopic morphology is a blocky accumulation.

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