Aluminum-doped cobaltite and preparation method and application thereof
By controlling reaction conditions and using specific surfactants and complexing agents to prepare aluminum-doped cobalt tetroxide, the problems of small particle size, low density, and few pores have been solved, enabling efficient wastewater treatment and high-performance lithium cobalt oxide cathode material applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GEM JIANGSU COBALT IND CO LTD
- Filing Date
- 2023-12-27
- Publication Date
- 2026-06-16
AI Technical Summary
In existing technologies, aluminum-doped cobalt tetroxide has small particle size, low tap density, poor primary crystal form, and few pore structures. Furthermore, the use of EDTA as a complexing agent during production results in high cobalt content in the supernatant, increasing the difficulty of wastewater treatment.
Aluminum-doped cobalt tetroxide was prepared by reacting a mixture of cobalt salt, aluminum salt, and water with hexadecyltrimethylammonium bromide, ammonia, and hydroxide solution at a specific temperature and then calcining the mixture. Hexadecyltrimethylammonium bromide was used as a surfactant, and ammonia was used as a complexing agent. The reaction conditions were controlled to obtain cobalt tetroxide with large particle size, high density, and porous structure.
The prepared aluminum-doped cobalt tetroxide has large particle size, multiple pore structures, high tap density, and good primary crystal form, which reduces the difficulty of wastewater treatment and improves the efficiency of wastewater treatment. It is suitable for high-voltage lithium cobalt oxide cathode materials.
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Figure CN117776279B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of cobalt tetroxide material preparation technology, specifically relating to an aluminum-doped cobalt tetroxide, its preparation method, and its application. Background Technology
[0002] Large-particle aluminum-doped cobalt tetroxide can be used in the synthesis of high-voltage (4.5V) lithium cobalt oxide cathode materials. Aluminum-doped cobalt tetroxide is a functional material with unique structure and properties. Due to its high voltage and high density, the market demand for large-particle aluminum-doped cobalt tetroxide is gradually becoming apparent, and its preparation has become a hot topic. Currently, the method of preparing cobalt carbonate first using a carbonate system and then sintering it to obtain large-particle aluminum-doped cobalt tetroxide is more common. Methods using a hydroxyl system to prepare cobalt tetroxide are less common. Cobalt tetroxide prepared using the hydroxyl system has small particle size, low tap density, poor primary crystal form, and fewer pore structures, which is not conducive to the entry of lithium cobalt oxide in subsequent synthesis. Furthermore, ethylenediaminetetraacetic acid (EDTA) as a complexing agent easily complexes with various metal ions in water, resulting in a high cobalt content in the supernatant during production, increasing the difficulty of wastewater treatment. Summary of the Invention
[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects of cobalt tetroxide prepared by the prior art, such as small particle size, low tap density, poor primary crystal form, few pore structures, and high cobalt content in the supernatant of EDTA as a complexing agent during the production process, which increases the difficulty of wastewater treatment. Thus, the present invention provides an aluminum-doped cobalt tetroxide, its preparation method and application.
[0004] This invention provides a method for preparing aluminum-doped cobalt tetroxide, comprising the following steps:
[0005] 1) Mix cobalt salt, aluminum salt and water to obtain a cobalt salt-aluminum salt mixed solution;
[0006] 2) Mix hexadecyltrimethylammonium bromide, ammonia and water, then add the cobalt and aluminum salt mixed solution obtained in step 1) and the hydroxide solution, and react at a reaction temperature of 69-71℃. After the reaction is completed, calcine to obtain the aluminum-doped cobalt tetroxide.
[0007] Preferably, the reaction speed in step 2) is 220-240 r / min and the reaction time is 450-500 h.
[0008] Preferably, the cobalt salt in step 1) is selected from at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate;
[0009] The aluminum salt is selected from at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate;
[0010] The bottom water mentioned in step 2) is selected from water;
[0011] The hydroxide solution mentioned in step 2) is selected from at least one of sodium hydroxide solution and potassium hydroxide solution.
[0012] The mass concentration of cobalt salt in the cobalt-aluminum salt mixed solution described in step 1) is 120-180 g / L;
[0013] The mass concentration of aluminum salt in the cobalt-aluminum salt mixed solution is 1-2 g / L.
[0014] Preferably, the mass ratio of hexadecyltrimethylammonium bromide to water in step 2) is (0.1-0.5): 4160;
[0015] The ammonia concentration in the ammonia solution is 0.5-1 g / L.
[0016] The volume ratio of ammonia to water is (1-2):4.16.
[0017] Preferably, the flow rate of the cobalt-aluminum salt mixed solution in step 2) is 220-240 kg / h;
[0018] The mass concentration of hydroxide in the hydroxide solution is 401.6-449.6 g / L;
[0019] In step 2), the pH of the reaction solution is controlled to be 9.8-10.3 by adjusting the amount of hydroxide solution added.
[0020] Optionally, the reaction atmosphere during the reaction is air, and the flow rate of the reaction atmosphere is 9-12 m³ / s. 3 / h.
[0021] Preferably, the calcination temperature in step 2) is 120-680℃ and the calcination time is 280-1240 min;
[0022] Step 2) includes washing and demagnetizing steps before the calcination step.
[0023] Optionally, the washing process uses alkaline water.
[0024] Optionally, sodium can be removed by alkaline washing until the conductivity at the reactor outlet is acceptable (below 20 S / m).
[0025] Optionally, a magnetic separator can be used for demagnetization.
[0026] In the preparation process, the pH, reaction speed, flow rate of the cobalt and aluminum salt mixed solution, flow rate of sodium hydroxide solution, and amount of ammonia added can be adjusted in a timely manner to ensure the synthesis time and the particle size of the reaction product.
[0027] Preferably, the calcination in step 2) is carried out in a roller kiln device, which includes a heating zone and a heat preservation zone;
[0028] Optionally, the length of the roller conveyor in the roller kiln device is 40-60m;
[0029] Optionally, the temperature range of the heating zone is 120-680℃, the temperature difference between adjacent zones in the heating zone is 40-80℃, and the time for the calcined material to pass through the heating zone is 560-700 min.
[0030] The temperature of the heat preservation zone is 600-780℃, and the time for the calcined material to pass through the heat preservation zone is 280-540 minutes.
[0031] When the calcined material passes through the heating zone, it passes through from low temperature to high temperature in sequence according to the temperature gradient.
[0032] This invention provides an aluminum-doped cobalt tetroxide, which is prepared by the above-described method for preparing aluminum-doped cobalt tetroxide;
[0033] The median particle size D50 of the aluminum-doped cobalt tetroxide is 10-12 μm, and the tap density is 2.40-2.60 g / cm³. 3 It has a porous structure;
[0034] The aluminum doping content in the aluminum-doped cobalt tetroxide is 6000-6600 ppm.
[0035] This invention provides an application of the above-mentioned aluminum-doped cobalt tetroxide in the preparation of lithium cobalt oxide cathode materials.
[0036] The technical solution of this invention has the following advantages:
[0037] 1. The method for preparing aluminum-doped cobalt tetroxide provided by the present invention includes the following steps: 1) mixing cobalt salt, aluminum salt, and water to obtain a cobalt-aluminum salt mixed solution; 2) mixing hexadecyltrimethylammonium bromide, ammonia, and bottom water, then adding the cobalt-aluminum salt mixed solution obtained in step 1) and a hydroxide solution, and reacting at a reaction temperature of 69-71℃. After the reaction is completed, calcining is performed to obtain the aluminum-doped cobalt tetroxide. The present invention uses hexadecyltrimethylammonium bromide (CTAB) as a surfactant and ammonia as a complexing agent to overcome the disadvantage that ethylenediaminetetraacetic acid (EDTA) easily complexes with various metal ions in water, resulting in a high cobalt content in the supernatant during the production process, increasing the difficulty of wastewater treatment. Furthermore, the supernatant has a low cobalt content during the synthesis reaction, making it easy to precipitate and reducing the difficulty of wastewater treatment. The ammonia in the supernatant can be removed through a deammoniation tower and recycled. Meanwhile, this invention uses hexadecyltrimethylammonium bromide (CTAB) as a surfactant and ammonia as a complexing agent to prepare aluminum-doped cobalt tetroxide through a hydroxyl system at a specific temperature. The cobalt tetroxide synthesized by the preparation method of this invention has large particle size, multiple pore structures, high tap density, good primary crystal form, and uniform aluminum doping.
[0038] 2. The method for preparing aluminum-doped cobalt tetroxide provided by the present invention results in a high tap density of the prepared aluminum-doped cobalt tetroxide, which, when used as a positive electrode material in a battery, results in a high specific capacity of the battery. Attached Figure Description
[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0040] Figure 1 Electron probe X-ray microscopy (EPMA) image of aluminum-doped cobalt tetroxide prepared in Example 1 of this invention;
[0041] Figure 2 Scanning electron microscope image of aluminum-doped cobalt tetroxide prepared in Example 1 of this invention;
[0042] Figure 3 Scanning electron microscope image of the cross-section of aluminum-doped cobalt tetroxide prepared in Example 1 of this invention. Detailed Implementation
[0043] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0044] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0045] Example 1
[0046] This embodiment provides a method for preparing aluminum-doped cobalt tetroxide, comprising the following steps:
[0047] 1) Prepare a cobalt-aluminum salt mixed solution in a mixing tank, wherein the mass concentration of cobalt salt in the mixed solution is 130 g / L and the mass concentration of aluminum salt in the mixed solution is 1 g / L, and then transfer it to a high-level tank for storage.
[0048] 2) First, add 4160L of water to the reactor as base water, then add 320g of cetyltrimethylammonium bromide surfactant and 1000L of ammonia complexing agent (ammonia concentration in the ammonia solution is 0.5g / L). Mix the mixture, then introduce the cobalt and aluminum salt mixed solution obtained in step 1) through a skid-mounted device at a flow rate of 220kg / h. Maintain the pH of the reaction solution at 10.3 by introducing a sodium hydroxide solution with a mass concentration of 417.2g / L. Perform granulation at a reactor rotation speed of 220r / min and a reactor temperature of 70℃. Maintain an air flow rate of 10m³ / h during the reaction. 3 The reaction is carried out for 500 hours to ensure that the particle size D50 reaches 12±0.3μm. After the reaction, the product is washed with alkaline water to remove sodium until the conductivity at the outlet of the reactor is qualified (the conductivity is below 20S / m). The product is then demagnetized using an iron remover. A heating zone and a heat preservation zone are set in a 40m roller kiln. The calcined product passes through the heating zone and the heat preservation zone of the roller kiln in sequence. The heating zone has an increasing temperature of 120℃, 180℃, 240℃, 300℃, 360℃, 420℃, 480℃, 540℃, 600℃ and 660℃. The calcined product passes through the heating zone from low temperature to high temperature in sequence according to the temperature increasing gradient, and the passage time is 630min. Then it enters the heat preservation zone at 680℃ and the passage time in the heat preservation zone is 360min, thus obtaining the aluminum-doped cobalt tetroxide.
[0049] Example 2
[0050] This embodiment provides a method for preparing aluminum-doped cobalt tetroxide, comprising the following steps:
[0051] 1) Prepare a cobalt-aluminum salt mixed solution in a mixing tank, wherein the mass concentration of cobalt salt in the mixed solution is 120 g / L and the mass concentration of aluminum salt in the mixed solution is 2 g / L, and then transfer it to a high-level tank for storage.
[0052] 2) First, add 4160L of water to the reactor as base water, then add 320g of cetyltrimethylammonium bromide surfactant and 1000L of ammonia complexing agent (ammonia concentration in the ammonia solution is 1g / L). Mix the mixture, then introduce the cobalt and aluminum salt mixed solution obtained in step 1) through a skid-mounted device at a flow rate of 220kg / h. Maintain the pH of the reaction solution at 10.1 by introducing a sodium hydroxide solution with a mass concentration of 401.6g / L. Perform granulation at a reactor rotation speed of 200r / min and a reactor temperature of 71℃. Maintain an air flow rate of 9m³ / h during the reaction. 3 The reaction was carried out for 450 hours to ensure that the particle size D50 reached 12±0.3μm. After the reaction, the mixture was washed with alkaline water to remove sodium until the conductivity of the reactor outlet was qualified (the conductivity was below 20S / m). The mixture was then demagnetized with an iron remover and calcined at 600℃ for 800 minutes to obtain the aluminum-doped cobalt tetroxide.
[0053] Example 3
[0054] This embodiment provides a method for preparing aluminum-doped cobalt tetroxide, comprising the following steps:
[0055] 1) Prepare a cobalt-aluminum salt mixed solution in a mixing tank, wherein the mass concentration of cobalt salt in the mixed solution is 120 g / L and the mass concentration of aluminum salt in the mixed solution is 1.5 g / L, and then transfer it to a high-level tank for storage.
[0056] 2) First, add 4160L of water to the reactor as a base water, then add 320g of cetyltrimethylammonium bromide surfactant and 1000L of ammonia complexing agent (ammonia concentration in the ammonia solution is 0.5g / L). Mix the mixture, then introduce the cobalt and aluminum salt mixed solution obtained in step 1) through a skid-mounted device at a flow rate of 220kg / h. Maintain the pH of the reaction solution at 9.8 by introducing a sodium hydroxide solution with a mass concentration of 449.6g / L. Perform granulation at a reactor rotation speed of 250r / min and a reactor temperature of 70℃ for 500h. During the reaction, maintain an air flow rate of 12m³ / h. 3The reaction is carried out for 500 hours to ensure that the particle size D50 reaches 12±0.3μm. After the reaction, the product is washed with alkaline water to remove sodium until the conductivity at the outlet of the reactor is qualified (the conductivity is below 20S / m). The product is then demagnetized using an iron remover. A heating zone and a heat preservation zone are set in a 40m roller kiln. The calcined product passes through the heating zone and the heat preservation zone of the roller kiln in sequence. The heating zone has an increasing temperature of 120℃, 180℃, 240℃, 300℃, 360℃, 420℃, 480℃, 540℃, 600℃ and 660℃. The calcined product passes through the heating zone from low temperature to high temperature in sequence according to the temperature increasing gradient, and the passage time is 630min. Then it enters the heat preservation zone at 680℃ and the passage time in the heat preservation zone is 360min, thus obtaining the aluminum-doped cobalt tetroxide.
[0057] Comparative Example 1
[0058] This comparative example provides a method for preparing aluminum-doped cobalt tetroxide. The only difference from Example 1 is that in step 2), 4160L of water is first added to the reactor as a base water, followed by 320g of cetyltrimethylammonium bromide surfactant and 1000L of ammonia complexing agent (ammonia concentration of 0.5g / L). The mixture is then introduced through a skid-mounted device at a flow rate of 220kg / h into the cobalt-aluminum salt mixed solution obtained in step 1). A sodium hydroxide solution with a mass concentration of 417.2g / L is introduced to maintain the pH of the reaction solution at 10.3. Granulation is carried out at a reactor rotation speed of 220r / min and a reactor temperature of 55℃. During the reaction, the air flow rate is maintained at 10L / min. After 500 hours of reaction, the material is washed with alkaline water to remove sodium until the conductivity at the reactor outlet is within acceptable limits (below 20 S / m). It is then demagnetized using an iron remover. A heating zone and a holding zone are then set up in a 40m roller kiln. The calcined material sequentially passes through these zones. The heating zone has increasing temperatures of 120℃, 180℃, 240℃, 300℃, 360℃, 420℃, 480℃, 540℃, 600℃, and 660℃. The calcined material passes through the heating zone sequentially from low to high temperature according to the temperature gradient, with a passage time of 630 minutes. It then enters the holding zone at 680℃, where the passage time is 360 minutes, yielding the aluminum-doped cobalt tetroxide.
[0059] Comparative Example 2
[0060] This comparative example provides a method for preparing aluminum-doped cobalt tetroxide, which differs from Example 1 in that in step 2), 4160L of water is first added to the reactor as a base water, followed by 1000L of ammonia complexing agent (ammonia concentration of 0.5g / L). The mixture is then introduced through a skid-mounted device at a flow rate of 220kg / h to obtain the cobalt-aluminum salt mixed solution from step 1). A sodium hydroxide solution with a mass concentration of 417.2g / L is introduced to maintain the pH of the reaction solution at 10.3. Granulation is carried out at a reactor rotation speed of 220r / min and a reactor temperature of 70℃, with an air flow rate of 10m³ / min maintained during the reaction. 3 The reaction is carried out at a rate of / h for 500h. After the reaction, the product is washed with alkaline water to remove sodium until the conductivity at the outlet of the reactor is qualified (the conductivity is below 20S / m). The product is then demagnetized using an iron remover. A heating zone and a heat preservation zone are set in a 40m roller kiln. The calcined product passes through the heating zone and the heat preservation zone of the roller kiln in sequence. The heating zone has an increasing temperature of 120℃, 180℃, 240℃, 300℃, 360℃, 420℃, 480℃, 540℃, 600℃, and 660℃. The calcined product passes through the heating zone from low temperature to high temperature in sequence according to the temperature increasing gradient, and the passage time is 630min. Then it enters the heat preservation zone at a temperature of 680℃, and the passage time in the heat preservation zone is 360min, thus obtaining the aluminum-doped cobalt tetroxide.
[0061] Comparative Example 3
[0062] This comparative example provides a method for preparing aluminum-doped cobalt tetroxide, which differs from Example 1 in that in step 2), 4160L of water is first added to the reactor as a base water, followed by 320g of cetyltrimethylammonium bromide surfactant. Then, the cobalt-aluminum salt mixed solution obtained in step 1) is introduced through a skid-mounted device at a flow rate of 220kg / h. A sodium hydroxide solution with a mass concentration of 417.2g / L is introduced to maintain the pH of the reaction solution at 10.3. Granulation is carried out at a reactor rotation speed of 220r / min and a reactor temperature of 70℃. Air is introduced at a flow rate of 10L / min during the reaction, and the reaction is carried out for 500h. After the reaction, the mixture is washed with alkaline water. The sodium is washed away until the conductivity at the outlet of the reactor is qualified (below 20 S / m). The material is then demagnetized using an iron remover. A heating zone and a holding zone are then set up in a 40m roller kiln. The calcined material sequentially passes through these zones. The heating zone has increasing temperatures of 120℃, 180℃, 240℃, 300℃, 360℃, 420℃, 480℃, 540℃, 600℃, and 660℃. The calcined material passes through the heating zone sequentially from low to high temperature according to the temperature gradient, with a passage time of 630 minutes. It then enters the holding zone at 680℃, where the passage time is 360 minutes, yielding the aluminum-doped cobalt tetroxide.
[0063] Test case
[0064] The aluminum-doped cobalt tetroxide prepared in Examples 1-3 and Comparative Examples 1-3 were tested: the cobalt content was determined by EDTA titration, and the doping elements aluminum and other elements were tested by ICP. The test results are shown in Table 1. The particle size of the aluminum-doped cobalt tetroxide was measured using a Malvern 3000 particle size analyzer, and the test results are shown in Table 2. 100g of sample was taken into a 100ml standard clean graduated cylinder, and the tap density was measured using a tap density meter with the vibration parameters set as follows: stroke 3mm, vibration frequency 100 times / min, and time 30min. The volume of aluminum-doped cobalt tetroxide in the graduated cylinder after vibration was read, and the tap density was obtained by dividing the powder mass by the volume. The test results are shown in Table 2. The specific surface area (BET) of the aluminum-doped cobalt tetroxide was tested using a specific surface area analyzer. The larger the specific surface area, the more porous the aluminum-doped cobalt tetroxide. The test results are shown in Table 2.
[0065] Table 1. Composition of Aluminum-Doped Cobalt Tetraoxide
[0066] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Co / wt% 72.2 72 72.26 72.28 71.9 72.1 Al / wt% 0.6147 0.6142 0.6145 0.6144 0.614 0.6141 Ni / wt% 0.0003 0.0001 0.0002 0.0005 0.0006 0.0007 Mg / wt% 0.0013 0.0011 0.0016 0.0021 0.0025 0.0019 Fe / wt% 0.0012 0.0018 0.0014 0.0023 0.0017 0.0009 Ca / wt% 0.0054 0.0051 0.0053 0.0058 0.0059 0.005 Na / wt% 0.022 0.0224 0.0226 0.0218 0.0229 0.023 Zn / wt% 0.0003 0.0001 0.0002 0.0004 0.0007 0.0009 Cu / wt% 0.0003 0.0006 0.0007 0.0005 0.0002 0.0004 Mn / wt% 0.0003 0.0004 0.0009 0.0007 0.0002 0.0006 Cr / wt% 0.0003 0.0005 0.0002 0.0004 0.0001 0.0006 Si / wt% 0.0007 0.0009 0.0005 0.0011 0.0006 0.111
[0067] Table 2
[0068]
[0069] The aluminum-doped cobalt tetroxide obtained in Example 1 was characterized and analyzed by electron probe X-ray microscopy (EPMA), and the EPMA images are shown below. Figure 1 As shown in the figure, the uniform aluminum doping in Example 1 is evident. Scanning electron microscopy (SEM) images of aluminum-doped cobalt tetroxide and its cross-section were obtained, as shown below. Figure 2 As shown, the scanning electron microscope cross-sectional image of aluminum-doped cobalt tetroxide is as follows. Figure 3 As shown.
[0070] After XRD diffraction, the full width at half maximum (FWMH) of the aluminum-doped cobalt tetroxide obtained in Example 1 was 1114. FWMH (1114) indicates that the crystallite size of the large particles of the hydroxyl system prepared in Example 1 of the present invention is 1114, which shows that the primary crystal form of the electron probe X-ray microscopy of Example 1 is good.
[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing aluminum-doped cobalt tetroxide, characterized in that, Includes the following steps: 1) Mix cobalt salt, aluminum salt and water to obtain a cobalt salt and aluminum salt mixed solution; 2) Mix hexadecyltrimethylammonium bromide, ammonia and water, then add the cobalt and aluminum salt mixed solution obtained in step 1) and the hydroxide solution and react at a reaction temperature of 69-71℃. After the reaction is completed, calcine to obtain the aluminum-doped cobalt tetroxide. The mass ratio of hexadecyltrimethylammonium bromide to water is (0.1-0.5):4160.
2. The method for preparing aluminum-doped cobalt tetroxide according to claim 1, characterized in that, The reaction speed in step 2) is 220-240 r / min, and the reaction time is 450-500 h.
3. The method for preparing aluminum-doped cobalt tetroxide according to claim 1 or 2, characterized in that, The cobalt salt mentioned in step 1) is selected from at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate; The aluminum salt is selected from at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate; The bottom water mentioned in step 2) is selected from water; The hydroxide solution mentioned in step 2) is selected from at least one of sodium hydroxide solution and potassium hydroxide solution.
4. The method for preparing aluminum-doped cobalt tetroxide according to claim 3, characterized in that, The mass concentration of cobalt salt in the cobalt-aluminum salt mixed solution described in step 1) is 120-180 g / L; The mass concentration of aluminum salt in the cobalt-aluminum salt mixed solution is 1-2 g / L.
5. The method for preparing aluminum-doped cobalt tetroxide according to claim 1, characterized in that, The ammonia concentration in the ammonia solution is 0.5-1 g / L. The volume ratio of ammonia to water is (1-2):4.
16.
6. The method for preparing aluminum-doped cobalt tetroxide according to claim 2, characterized in that, The flow rate of the cobalt-aluminum salt mixed solution in step 2) is 220-240 kg / h; The mass concentration of hydroxide in the hydroxide solution is 401.6-449.6 g / L; In step 2), the pH of the reaction solution is controlled to be 9.8-10.3 by adjusting the amount of hydroxide solution added.
7. The method for preparing aluminum-doped cobalt tetroxide according to claim 6, characterized in that, The calcination temperature in step 2) is 120-680℃, and the calcination time is 280-1240 min; Step 2) includes washing and demagnetizing steps before the calcination step.
8. The method for preparing aluminum-doped cobalt tetroxide according to claim 7, characterized in that, The calcination described in step 2) is carried out in a roller kiln device, which includes a heating zone and a heat preservation zone; The temperature range of the heating zone is 120-680℃, the temperature difference between adjacent zones in the heating zone is 40-80℃, and the time for the calcined material to pass through the heating zone is 560-700 min. The temperature of the heat preservation zone is 600-780℃, and the time for the calcined material to pass through the heat preservation zone is 280-540 minutes.