A method for preparing cobalt hydroxide

Abstract

The invention discloses a method for preparing cobalt hydroxide, comprising the following steps: (1) adding a cobalt salt solution and an ammonia solution to deionized water at 30 to 75°C, controlling the reaction system pH to 6 to 9, and obtaining α-Co(OH)2; (2) adding an antioxidant to the reaction system, continuing to heat to 75 to 100°C, and keeping warm for 4 to 16 hours to obtain β-Co(OH)2; (3) aging, filtering, and taking a filter residue to obtain the cobalt hydroxide. The cobalt hydroxide prepared by the method for preparing cobalt hydroxide of the present invention has the characteristics of narrow particle size distribution range, high sphericity, high purity, and large bulk ratio. The method of the present invention is simple in process and easy to operate. There is no need to add strong alkali sodium hydroxide in the reaction, and there is no need to consume a large amount of water in the washing process caused by adding sodium hydroxide to cause the product to contain more sodium salts. The cobalt hydroxide slurry is easy to wash and has good process safety.

Description

Technical Field

[0001] The invention relates to a method for preparing cobalt hydroxide particles, in particular to a method for preparing micron-sized spherical cobalt hydroxide. Background Art

[0002] With the rapid development of modern electronic technology, energy demand continues to increase, which puts higher requirements on energy storage medium batteries. Batteries with the advantages of high capacity, safety, environmental protection, long charge and discharge cycle life have become a research hotspot, and battery material preparation is particularly important.

[0003] Cobalt hydroxide is a key basic material for battery preparation. It is often used as an additive because it can significantly improve the cycle life of the battery, improve the charging efficiency and the utilization rate of active substances. Chinese patent CN 105329954 B adds a certain concentration of sodium hydroxide solution and cobalt salt solution to a mixed base liquid with ammonia water and hydrazine hydrate as the main components through a parallel feeding method, and obtains cobalt hydroxide after precipitation, washing and drying. The product particle size is 13-40μm, and the loose density is greater than 1.2g / cm 3 Chinese patent CN 101696039 B proposes a method for preparing spherical cobalt hydroxide without a complexing agent. The bulk density of the cobalt hydroxide product is 0.3-0.8 g / cm 3 The particle size of the cobalt hydroxide currently prepared is mainly between 10-60μm. Its particle size is large, the gaps between large particles cannot be filled by small particles, and the particle size distribution range is large, resulting in low bulk density and tap density, which cannot meet the diversified needs of battery preparation materials.

[0004] At present, the method for synthesizing small-particle cobalt hydroxide mainly uses ammonia water as a complexing agent, and the sodium hydroxide solution and the cobalt salt solution directly react to produce cobalt hydroxide precipitate. The pH value of the reaction system is adjusted to between 6 and 10 by controlling the dripping speed of the sodium hydroxide solution and the cobalt salt solution to control the morphology of the cobalt hydroxide, and the cyan α-Co(OH)2 is obtained. Then, an excess of sodium hydroxide is added to adjust the pH value of the solution to between 11 and 13, and the cyan α-Co(OH)2 is converted into pink β-Co(OH)2. The cobalt hydroxide precipitate is washed, filtered, dried and other process steps to obtain the product. The process procedure of this method is simple and easy to operate, but the product contains more sodium salts, so the product needs to consume more water when washing, and the morphology of the cobalt hydroxide is not easy to control, and irregular morphology often occurs and agglomeration is more serious. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing cobalt hydroxide.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing cobalt hydroxide, comprising the following steps:

[0007] (1) Adding a cobalt salt solution and an ammonia solution to deionized water at 30 to 75° C., controlling the pH of the reaction system to 6 to 9, and obtaining α-Co(OH)2;

[0008] (2) adding an antioxidant to the reaction system, continuing to heat to 75-100°C, and keeping the temperature for 4-16 hours to obtain β-Co(OH)2;

[0009] (3) aging, filtering, and taking the filter residue to obtain the cobalt hydroxide.

[0010] The preparation method of cobalt hydroxide of the present invention comprises the following steps: directly reacting a cobalt salt with ammonia water, maintaining the pH value of the reaction system between 6 and 9, obtaining α-Co(OH)2, and promoting the conversion of α-Co(OH)2 into β-Co(OH)2 by heating, thereby obtaining spherical cobalt hydroxide. The cobalt hydroxide prepared by the present invention has the characteristics of narrow particle size distribution range (average particle size 1-3 μm, particle size distribution span Span<1.5 (Span=(D90-D10) / D50)), high sphericity, high purity (cobalt content>62%) and large bulk ratio (0.6-0.8 mg / L). The method of the present invention is simple in process and easy to operate. No strong base sodium hydroxide needs to be added in the reaction, and no large amount of water needs to be consumed in the washing process due to the addition of sodium hydroxide causing the product to contain more sodium salt. The cobalt hydroxide slurry is easy to wash and has good process safety.

[0011] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the cobalt salt solution is a cobalt chloride solution, but is not limited thereto, and may also be a soluble cobalt salt solution such as a cobalt sulfate solution. Based on the value of treating the waste liquid after the reaction and recovering the product, a cobalt chloride solution is preferably used, and the cobalt hydroxide particles prepared from the cobalt chloride solution have the best sphericity and uniformity.

[0012] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the concentration of cobalt ions in the cobalt salt solution is 1 to 4 mol / L. It is difficult to prepare cobalt hydroxide of a suitable size when the concentration of cobalt ions is too high or too low.

[0013] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the mass concentration of the ammonia solution is 7% to 14%. Controlling the ammonia solution to this concentration can better control the morphology of the cobalt hydroxide to be spherical.

[0014] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the addition rate of the cobalt salt solution is 100-500 mL / h. The addition rate of the cobalt salt solution has a great influence on the particle size of α-Co(OH)2. When the above-mentioned dropwise addition rate is adopted, cobalt hydroxide particles with more uniform particle size and good sphericity can be obtained. The addition rate of ammonia water is adjusted to control the pH of the reaction system to 6-9.

[0015] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the antioxidant is at least one of hydrated hydrazine, ascorbic acid and tea polyphenols, but is not limited to the above antioxidant types.

[0016] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, in step (3), the filtering further comprises a step of washing the filter residue, and the end point of the washing is that the conductivity of the washing liquid is less than 200 μs / cm. When the washing end point is reached, the obtained cobalt hydroxide can be used in fields with high requirements for impurity content.

[0017] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, in step (3), after the filtration, the step of drying the filter residue is further included, and the drying conditions are: at a vacuum degree of -0.75 to -0.9 bar and a temperature of 30 to 70°C.

[0018] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, the drying time is 3 to 16 hours.

[0019] As a preferred embodiment of the method for preparing cobalt hydroxide of the present invention, in step (3), after filtering, the filtrate is further treated: the filtrate is evaporated and concentrated at -0.8 to -0.9 bar and 50 to 70°C, and when crystals appear in the filtrate, the concentration is stopped, and the filtrate is placed at room temperature for crystallization, and the process is repeated several times until the ammonia nitrogen content in the filtrate reaches 300 mg / L or less, and the filtrate is discharged to a sewage treatment biochemical system for treatment; the substance obtained by cooling and crystallization after evaporation and concentration is ammonium chloride crystals. The ammonium chloride obtained by treating the generated wastewater can be used as a raw material for producing nitrogen fertilizer.

[0020] The beneficial effects of the present invention are as follows: the present invention provides a method for preparing cobalt hydroxide, and the cobalt hydroxide prepared by the method for preparing cobalt hydroxide of the present invention has the characteristics of narrow particle size distribution range, high sphericity, high purity and large bulk ratio, etc. The method of the present invention has a simple process and is easy to operate, and does not require the addition of strong alkali sodium hydroxide in the reaction, and does not require a large amount of water consumed in the washing process caused by the addition of sodium hydroxide resulting in a large amount of sodium salt in the product, and the cobalt hydroxide slurry is easy to wash, and the process safety is good. The byproduct NH4Cl generated by the reaction is reused industrially, such as producing fertilizers, etc., which is more economical and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of cobalt hydroxide prepared by the preparation method of cobalt hydroxide described in Example 1, with a magnification of 3000 times. DETAILED DESCRIPTION

[0022] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] An embodiment of the method for preparing cobalt hydroxide of the present invention comprises the following steps:

[0025] (1) preparing a 1 mol / L cobalt chloride solution and a 7 wt % ammonia solution;

[0026] (2) Add 1L of deionized water as the base liquid to a 5L reactor, start stirring at a speed of 200r / min, heat to 60°C, dropwise add cobalt chloride solution and ammonia solution, control the addition rate of cobalt chloride solution to 500mL / h, maintain the pH value of the reaction system at 6.5-7.0, and obtain α-Co(OH)2;

[0027] (3) Add 50 mL of 50% hydrated hydrazine solution, heat to 75°C, and keep warm for 9 hours to obtain β-Co(OH)2;

[0028] (4) After aging, the mixture is filtered and washed until the conductivity of the washing liquid is less than 200 μs / cm, and the material is dried in a vacuum oven at a vacuum degree of -0.8 bar, a temperature of 40° C., and a time of 4 hours to obtain the cobalt hydroxide.

[0029] Figure 1 The SEM image of the cobalt hydroxide prepared in this example shows that the cobalt content of the cobalt hydroxide prepared in this example is 62.31%, the bulk density is 0.58 mg / mL, and D 50 The particle size is 1.2μm, and the impurity content meets the industrial cobalt hydroxide HG / T4506-2013 Class I standard.

[0030] Example 2

[0031] An embodiment of the method for preparing cobalt hydroxide of the present invention comprises the following steps:

[0032] (1) preparing a 2 mol / L cobalt chloride solution and a 14 wt % ammonia solution;

[0033] (2) Add 1L of deionized water as the base liquid to a 5L reactor, start stirring, rotate at 400r / min, heat to 60°C, dropwise add cobalt chloride solution and ammonia solution, control the addition rate of cobalt chloride solution to 300mL / h, maintain the pH value of the reaction system at 7.0-7.5, and obtain α-Co(OH)2;

[0034] (3) adding 50 mL of 50% hydrazine solution, heating to 80°C, and keeping warm for 8 h to obtain β-Co(OH)2;

[0035] (4) After aging, the mixture is filtered and washed until the conductivity of the washing liquid is less than 200 μs / cm, and the material is dried in a vacuum oven at a vacuum degree of -0.8 bar, a temperature of 40° C., and a time of 4 hours to obtain the cobalt hydroxide.

[0036] The cobalt content of the cobalt hydroxide prepared in this example is 62.46%, the bulk density is 0.62 mg / mL, and D 50 The particle size is 1.5μm, and the impurity content meets the industrial cobalt hydroxide HG / T4506-2013 Class I standard.

[0037] Example 3

[0038] An embodiment of the method for preparing cobalt hydroxide of the present invention comprises the following steps:

[0039] (1) preparing a 3 mol / L cobalt chloride solution and a 14 wt % ammonia solution;

[0040] (2) Add 1L of deionized water as the base liquid to a 5L reactor, start stirring, rotate at 400r / min, heat to 60°C, dropwise add cobalt chloride solution and ammonia solution, control the addition rate of cobalt chloride solution to 100mL / h, maintain the pH value of the reaction system at 7.5-8.0, and obtain α-Co(OH)2;

[0041] (3) Add 50 mL of 50% hydrated hydrazine solution, heat to 85°C, and keep warm for 10 hours to obtain β-Co(OH)2;

[0042] (4) After aging, the mixture is filtered and washed until the conductivity of the washing liquid is less than 200 μs / cm, and the material is dried in a vacuum oven at a vacuum degree of -0.8 bar, a temperature of 40° C., and a time of 4 hours to obtain the cobalt hydroxide.

[0043] The cobalt content of the cobalt hydroxide prepared in this example is 62.12%, the bulk density is 0.47 mg / mL, and D 50 The particle size is 0.9μm, and the impurity content meets the industrial cobalt hydroxide HG / T4506-2013 Class I standard.

[0044] Example 4

[0045] An embodiment of the method for preparing cobalt hydroxide of the present invention comprises the following steps:

[0046] (1) preparing a 2 mol / L cobalt chloride solution and a 14 wt % ammonia solution;

[0047] (2) Add 1L of deionized water as the base liquid to a 5L reactor, start stirring at a speed of 800r / min, heat to 45°C, dropwise add cobalt chloride solution and ammonia solution, control the addition rate of cobalt chloride solution to 200mL / h, maintain the pH value of the reaction system at 7.0-7.5, and obtain α-Co(OH)2;

[0048] (3) adding 50 mL of 50% hydrazine solution, heating to 85°C, and keeping warm for 8 h to obtain β-Co(OH)2;

[0049] (4) After aging, the mixture is filtered and washed until the conductivity of the washing liquid is less than 200 μs / cm, and the material is dried in a vacuum oven at a vacuum degree of -0.8 bar, a temperature of 40° C., and a time of 4 hours to obtain the cobalt hydroxide.

[0050] The cobalt content of the cobalt hydroxide prepared in this example is 62.23%, the bulk density is 0.65 mg / mL, and D 50 The particle size is 1.3μm, and the impurity content meets the industrial cobalt hydroxide HG / T4506-2013 Class I standard.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing spherical cobalt hydroxide, characterized in that: The following steps are involved: (1) In deionized water at 45-60° C., cobalt salt solution and ammonia solution are added dropwise simultaneously, and the pH of the reaction system is controlled to be 6.5-8 to obtain α-Co(OH)2. The cobalt salt solution is added at a rate of 100-500 mL / h, and the mass concentration of the ammonia solution is 14%; (2) adding an antioxidant to the reaction system, continuing to heat to 75-100°C, and keeping the temperature for 4-16 hours to obtain β-Co(OH)2, wherein the antioxidant is hydrated hydrazine; (3) aging, filtering, and taking the filter residue to obtain the spherical cobalt hydroxide; In the cobalt salt solution, the concentration of cobalt ions is 1-4 mol / L; and the cobalt salt solution is a cobalt chloride solution.

2. The method for preparing spherical cobalt hydroxide according to claim 1, characterized in that: In step (3), after filtering, the filter residue is further washed, and the end point of the washing is that the conductivity of the washing liquid is less than 200 μs / cm.

3. The method for preparing spherical cobalt hydroxide according to claim 1, characterized in that: In step (3), after filtering, the process further includes drying the filter residue, wherein the drying conditions are: a vacuum degree of -0.75 to -0.9 bar and a temperature of 30 to 70°C.

4. The method for preparing spherical cobalt hydroxide according to claim 3, characterized in that: The drying time is 3 to 16 hours.

5. The method for preparing spherical cobalt hydroxide according to claim 1, characterized in that: In step (3), after the filtration, the filtrate is further treated by evaporating and concentrating the filtrate at -0.8 to -0.9 bar and 50 to 70°C. When crystals appear in the filtrate, the concentration is stopped and the filtrate is placed at room temperature for crystallization. This process is repeated multiple times until the ammonia nitrogen content in the filtrate reaches below 300 mg / L, and the filtrate is discharged to a sewage treatment biochemical system for treatment. The substance obtained by evaporation concentration and cooling crystallization is ammonium chloride crystals.

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