A method for preparing ultrafine cobalt tetroxide

Abstract

The present invention discloses a method for preparing ultrafine cobalt trioxide, which comprises mixing a cobalt salt, a chelating agent, a regulator and water to prepare a cobalt-containing solution; reacting the cobalt-containing solution with a sodium hydroxide solution, collecting the insoluble matter and calcining to obtain ultrafine cobalt trioxide. The raw materials of the present invention are cheap and easy to obtain, and there is no need to add a special chelating agent and strictly control the feed rate of the cobalt-containing solution and the precipitant solution. Ultrafine cobalt trioxide with uniform particle size and an average particle size of less than 1.5 μm can be obtained by the combined action of the chelating agent and the regulator. Overall, the present invention has the advantages of easy reaction conditions and more uniform and regular product morphology compared to the ultrafine cobalt trioxide currently prepared by the hydrothermal synthesis-calcination method, and has a good prospect for application in industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of cobalt tetroxide, and in particular to a method for preparing ultrafine cobalt tetroxide. Background Art

[0002] The transition metal oxide cobalt tetroxide is widely used as a precursor for lithium cobalt oxide cathode materials. With the rapid development of electronic products and the need for higher and more stable energy storage, the demand for cobalt tetroxide is increasing. It is well known that the morphology of cobalt tetroxide significantly affects its physical and electrochemical properties. The blending of cobalt tetroxide particles of different sizes can increase the compaction density and thus the energy density of lithium cobalt oxide materials. The market demand for smaller particle sizes will continue to decrease.

[0003] At present, medium and large particle cobalt tetroxide is relatively mature in the market, but ultrafine size (<2μm) cobalt tetroxide has not yet been industrialized. In order to meet the development direction of high capacity of lithium cobalt oxide materials, a mature preparation method of ultrafine cobalt tetroxide is particularly important. For example, CN112850803A discloses a method for synthesizing highly tapped ultrafine cobalt tetroxide, in which a cobalt salt solution and an alkaline solution are added to a base liquid containing a complexing agent, and the flow rate of the cobalt salt solution and the alkaline solution is controlled and the pH value is maintained between 10.5-11.5 for stirring and reacting to obtain a cobalt salt precipitate, which is then calcined to obtain cobalt tetroxide. This method can obtain particles with a size concentrated in the range of 1.5-2.5μm and a tap density of 2.1-2.6g / cm 3 However, this method requires strict control of the pH and reactant flow rate of the reaction, which brings difficulties to industrial production and cannot produce cobalt tetroxide with finer particle size.

[0004] There is still a need to provide an effective method for the problems existing in the preparation of ultrafine cobalt tetroxide. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preparing ultrafine cobalt tetroxide, comprising:

[0006] mixing a cobalt salt, a complexing agent, a regulator and water to prepare a cobalt-containing solution;

[0007] The cobalt-containing solution is mixed with an alkaline solution for reaction, and the insoluble matter is collected and calcined to obtain ultrafine cobalt trioxide.

[0008] It should be noted that the type of cobalt salt in the present invention does not need to be strictly limited. For example, it can be at least one of cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt acetate tetrahydrate.

[0009] Furthermore, the complexing agent is 1,2-diaminocyclohexanetetraacetic acid.

[0010] Furthermore, the regulator is hydrogen peroxide with a mass concentration of 27.5%-35%.

[0011] Furthermore, the amounts of cobalt salt, complexing agent and regulator in the cobalt-containing solution are 100-140 g / L, 1-5 g / L and 60-80 mL / L, respectively.

[0012] Furthermore, the calcination is firstly carried out by heating the temperature to 400-500°C at a rate of 3-10°C / min and keeping the temperature for 3-8 hours; then heating the temperature to 650-750°C at a rate of 3-10°C / min and keeping the temperature for 3-8 hours.

[0013] Furthermore, when the cobalt-containing solution and the sodium hydroxide solution are mixed and reacted, the cobalt-containing solution is added to the alkaline solution at a volume ratio of 1:3-10 at a stirring rate of 400-600 rpm.

[0014] Furthermore, the flow rate of adding the cobalt-containing solution is 20-50 L / h, and the reaction is continued for 10-30 minutes after the addition of the cobalt-containing solution is completed.

[0015] Furthermore, the concentration of the alkaline solution is 0.5-1 mol / L.

[0016] The present invention also provides ultrafine cobalt tetroxide, which is obtained by the above-mentioned preparation method.

[0017] The present invention also provides the use of the ultrafine cobalt trioxide in the preparation of lithium cobaltate.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The raw materials of the present invention are inexpensive and readily available, eliminating the need for the addition of special complexing agents and strict control of the feed rates of the cobalt-containing solution and the precipitant solution. Through the combined action of the complexing agent and the regulator, ultrafine cobalt oxide with a uniform particle size and an average particle size of less than 1.5 μm can be obtained. Overall, compared to ultrafine cobalt oxide currently produced through hydrothermal synthesis and calcination methods, the present invention offers advantages such as easier reaction conditions and a more uniform and regular product morphology, demonstrating promising prospects for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1The scanning electron microscope image of the ultrafine cobalt trioxide prepared in Example 1 is shown;

[0022] Figure 2 The scanning electron microscope image of the ultrafine cobalt trioxide prepared in Comparative Example 1 is shown;

[0023] Figure 3 The scanning electron microscope image of the ultrafine cobalt trioxide prepared in Comparative Example 2 is shown;

[0024] Figure 4 The scanning electron microscope image of the ultrafine cobalt trioxide prepared in Comparative Example 3 is shown. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0027] It should be noted that, since 10 mol / L sodium hydroxide is already present in the examples, it is used as the mother liquor and diluted to the desired concentration when used.

[0028] Example 1

[0029] A method for preparing ultrafine cobalt trioxide, comprising the following steps:

[0030] S1. Dissolve 600 g of cobalt chloride hexahydrate in 5 L of water under stirring, then add 10 g of 1,2-diaminocyclohexanetetraacetic acid and stir evenly, then add 350 mL of hydrogen peroxide (30% by mass) and stir evenly to obtain a cobalt-containing solution;

[0031] S2. Add 25 L of water to a 50 L reactor, then set the speed to 600 rpm, start stirring, add 1.6 L of 10 mol / L sodium hydroxide mother liquor, and then pass 5 L of the cobalt-containing solution prepared in step S1 at a flow rate of 30 L / h. After the addition of the cobalt-containing solution, continue stirring and reacting for 20 minutes; after the reaction is completed, filter press, wash, and dry to obtain a precursor;

[0032] S3. The precursor prepared in step S2 is first heated to 450° C. at a rate of 5° C. / min and kept at this temperature for 6 h; then heated to 700° C. at a rate of 5° C. / min and kept at this temperature for 6 h; the calcined product is passed through a 400-mesh sieve to obtain ultrafine cobalt oxide powder.

[0033] Comparative Example 1

[0034] A method for preparing ultrafine cobalt trioxide, comprising the following steps:

[0035] S1. Dissolve 600 g of cobalt chloride hexahydrate in 5 L of water under stirring, then add 10 g of 1,2-diaminocyclohexanetetraacetic acid and stir to obtain a cobalt-containing solution;

[0036] S2. Add 25 L of water to a 50 L reactor, then set the speed to 600 rpm, start stirring, add 1.6 L of 10 mol / L sodium hydroxide mother liquor, and then pass 5 L of the cobalt-containing solution prepared in step S1 at a flow rate of 30 L / h. After the addition of the cobalt-containing solution, continue stirring and reacting for 20 minutes; after the reaction is completed, filter press, wash, and dry to obtain a precursor;

[0037] S3. The precursor prepared in step S2 is first heated to 450° C. at a rate of 5° C. / min and kept at this temperature for 6 h; then heated to 700° C. at a rate of 5° C. / min and kept at this temperature for 6 h; the calcined product is passed through a 400-mesh sieve to obtain ultrafine cobalt oxide powder.

[0038] Comparative Example 2

[0039] S1. Dissolve 600 g of cobalt chloride hexahydrate in 5 L of water under stirring, then add 350 mL of hydrogen peroxide (30% by mass) and stir to obtain a cobalt-containing solution;

[0040] S2. Add 25 L of water to a 50 L reactor, then set the speed to 600 rpm, start stirring, add 1.6 L of 10 mol / L sodium hydroxide mother liquor, and then pass 5 L of the cobalt-containing solution prepared in step S1 at a flow rate of 30 L / h. After the addition of the cobalt-containing solution, continue stirring and reacting for 20 minutes; after the reaction is completed, filter press, wash, and dry to obtain a precursor;

[0041] S3. The precursor prepared in step S2 is first heated to 450° C. at a rate of 5° C. / min and kept at this temperature for 6 h; then heated to 700° C. at a rate of 5° C. / min and kept at this temperature for 6 h; the calcined product is passed through a 400-mesh sieve to obtain ultrafine cobalt oxide powder.

[0042] Comparative Example 3

[0043] S1. Dissolve 600 g of cobalt chloride hexahydrate in 5 L of water under stirring, then add 10 g of 1,2-diaminocyclohexanetetraacetic acid and stir evenly, then add 350 mL of hydrogen peroxide (30% by mass) and stir evenly to obtain a cobalt-containing solution;

[0044] S2. Add 25 L of water to a 50 L reactor, then set the speed to 600 rpm, start stirring, add 1.6 L of 10 mol / L sodium hydroxide mother liquor, and then pass 5 L of the cobalt-containing solution prepared in step S1 at a flow rate of 30 L / h. After the addition of the cobalt-containing solution, continue stirring and reacting for 20 minutes; after the reaction is completed, filter press, wash, and dry to obtain a precursor;

[0045] S3. The precursor prepared in step S2 is heated to 700° C. at a rate of 5° C. / min and kept at this temperature for 12 hours; the calcined product is passed through a 400-mesh sieve to obtain ultrafine cobalt trioxide powder.

[0046] Test Case

[0047] The average particle size of the materials prepared in Example 1 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0048] Table 1 Average particle size of cobalt oxide materials

[0049]

[0050] From the test results in Table 1, it can be seen that Example 1 of the present invention has a finer particle size, with a median particle size D50 of less than 0.2µm and a maximum particle size D100 of less than 2µm. However, compared to Example 1, the cobalt-containing solution of Comparative Example 1 does not contain hydrogen peroxide, and the maximum particle size of the prepared cobalt tetroxide is significantly increased, almost two orders of magnitude lower than the median particle size D50. This may be because the addition of hydrogen peroxide and 1,2-diaminocyclohexane tetraacetic acid work together to adjust the structure of the cobalt species in the early stage of the reaction, enhance the dispersibility and make it less likely to agglomerate into large particles. Compared to Example 1, the cobalt-containing solution of Comparative Example 2 does not contain 1,2-diaminocyclohexane tetraacetic acid, and the maximum particle size D100 of the prepared cobalt tetroxide is also significantly increased. These results illustrate that the addition of hydrogen peroxide and 1,2-diaminocyclohexane tetraacetic acid can work together to reduce the particle size of cobalt tetroxide. Compared with Example 1, Comparative Example 3 did not adopt the method of calcining at a lower temperature of 450°C and then heating to 700°C for further calcination, but was directly calcined at 700°C. The median particle size D50 and the maximum particle size D100 were also significantly improved.

[0051] The materials prepared in Example 1 and Comparative Examples 1-3 were observed using a scanning electron microscope. The results are as follows: Figures 1-4 As shown. Combined Figure 1It can be seen that the cobalt tetroxide prepared in the embodiment of the present invention has a small particle size and is evenly distributed. Figure 1 and Figure 2 It can be seen that the cobalt oxide prepared in Comparative Example 1, in which the cobalt-containing solution does not contain hydrogen peroxide, has uneven particle sizes, with larger particles being evident. Figure 1 and Figure 3 It can be seen that without adding the complexing agent 1,2-diaminocyclohexane tetraacetic acid, small particles will agglomerate and the particle size distribution of cobalt tetroxide will be uneven. Figure 1 and Figure 4 It can be seen that the direct high-temperature calcination of comparative example 3 will lead to the sintering of small particles into cubic structure of cobalt tetroxide, with uneven particle distribution and large morphology differences.

[0052] In summary, the raw materials of the present invention are inexpensive and readily available. There is no need to add special complexing agents or strictly control the feed rates of the cobalt-containing solution and the precipitant solution. By adding the conditioning agent hydrogen peroxide and the complexing agent 1,2-diaminocyclohexanetetraacetic acid, ultrafine cobalt oxide with a uniform particle size and an average particle size of less than 1.5 μm can be obtained. Overall, compared to the ultrafine cobalt oxide currently produced through hydrothermal synthesis and calcination methods, the present invention has the advantages of easier reaction conditions and a more uniform and regular product morphology, showing great prospects for industrial production.

[0053] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine cobalt trioxide, characterized in that: include, mixing a cobalt salt, a complexing agent, a regulator and water to prepare a cobalt-containing solution; The cobalt-containing solution is mixed with an alkaline solution for reaction, and the insoluble matter is collected and calcined to obtain ultrafine cobalt trioxide; The complexing agent is 1,2-diaminocyclohexane tetraacetic acid; The regulator is hydrogen peroxide with a mass concentration of 27.5%-35%; The amounts of cobalt salt, complexing agent, and regulator in the cobalt-containing solution are 100-140 g / L, 1-5 g / L, and 60-80 mL / L, respectively; The calcination is firstly carried out by heating the temperature to 400-500°C at a rate of 3-10°C / min and keeping the temperature for 3-8 hours; then heating the temperature to 650-750°C at a rate of 3-10°C / min and keeping the temperature for 3-8 hours.

2. The method for preparing ultrafine cobalt trioxide according to claim 1, characterized in that: When the cobalt-containing solution and the alkaline solution are mixed for reaction, the cobalt-containing solution is added to the alkaline solution at a volume ratio of 1:3 to 10 at a stirring rate of 400-600 rpm; The alkaline solution includes at least one of a sodium hydroxide solution or a potassium hydroxide solution.

3. The method for preparing ultrafine cobalt trioxide according to claim 2, characterized in that: The cobalt-containing solution is added at a flow rate of 20-50 L / h, and the reaction is continued for 10-30 minutes after the cobalt-containing solution is added.

4. The method for preparing ultrafine cobalt trioxide according to claim 2, wherein: The concentration of the alkaline solution is 0.5-1 mol / L.

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