Cobaltosic oxide, preparation method thereof and positive electrode material
By controlling the flow rate and pH of cobalt salt, aluminum salt and ammonium bicarbonate solutions, cobalt tetroxide with pores and high crystallinity surfaces was prepared, which solved the cracking problem caused by doping Al and improved the fast charging and cycling performance of the material.
Patent Information
- Application Number
- CN202510679228.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-26
- Publication Date
- 2025-08-26
AI Technical Summary
In the prior art, Al-doped cobalt tetroxide is difficult to meet the needs of fast charging and cycling performance, and is prone to cracking due to difficulty in releasing internal stress.
By controlling the flow rate and pH of cobalt salt, aluminum salt and ammonium bicarbonate solutions, cobalt tetroxide with pores and high crystallinity surfaces were prepared, and the pores were used as stress buffer structures to avoid cracking and improve crystallinity to enhance performance.
The internal pore structure and high crystallinity surface of cobalt tetroxide are realized, improving the rate performance and circulation performance of its corresponding lithium cobalt oxide material, and avoiding cracking.
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Figure CN120535019A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery materials and relates to cobalt tetroxide, a preparation method thereof and a positive electrode material. Background Art
[0002] With the rapid development of the 3C industry, the capacity requirements for lithium cobalt oxide batteries are getting higher and higher. Among them, in order to increase the capacity, a common method is to stabilize the structure through doping, thereby increasing the voltage window. Aluminum (Al) is a common doping element for lithium cobalt oxide modification in industry. After a large number of scientific research tests, it was found that doping Al has the following advantages:
[0003] 1) Aluminum has no electrochemical activity within the electrochemical window of lithium cobalt oxide and is a stable doping element that can effectively improve the thermal stability and cycle performance of the cathode material;
[0004] 2)Al 3+ The radius is 53.5pm, Co 3+ The radius of Al is 54.5 pm, which is close to that of Al. Therefore, Al can be incorporated into the unit cell of lithium cobalt oxide without affecting the structure of lithium cobalt oxide.
[0005] 3) As the third most abundant element in the earth's crust, Al is abundant and inexpensive;
[0006] 4) The Al-O bond strength is higher than the Co-O bond strength. During the charge and discharge process of lithium cobalt oxide, the lattice size of the material becomes smaller, thereby increasing the operating voltage of the battery.
[0007] However, as a precursor of lithium cobalt oxide, conventional single-morphology aluminum-doped cobalt tetroxide is difficult to meet the market demand for fast charging and cycling; therefore, it is necessary to develop a cobalt tetroxide with a new morphology, its preparation method and positive electrode material. Summary of the Invention
[0008] In view of the shortcomings of the existing technology, the object of the present invention is to provide a cobalt tetroxide, a preparation method thereof and a positive electrode material. The cobalt tetroxide prepared by the preparation method can avoid cracking caused by the difficulty in releasing internal stress due to Al doping, and can also use pores as a stress buffer structure to improve the rate performance and cycle performance of the cobalt tetroxide corresponding to the lithium cobalt oxide material.
[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:
[0010] In a first aspect, the present invention provides a method for preparing cobalt trioxide, comprising the following steps:
[0011] (1) providing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution;
[0012] (2) introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution into the base liquid in parallel to perform a first nucleation to a first particle size;
[0013] (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and a second nucleation is performed to a second particle size;
[0014] (4) After the second nucleation is completed, the introduction of the cobalt salt solution and the aluminum salt solution is stopped, and ammonium bicarbonate solution is introduced to adjust the pH value to 7-8;
[0015] (5) introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel at a first temperature to grow the particles to a third particle size; then raising the temperature to a second temperature, adjusting the flow rates of the cobalt salt solution and the ammonium bicarbonate solution to lower the pH value of the solution to 5 to 7, and growing the particles to a stop particle size; washing and drying to obtain aluminum-doped cobalt carbonate;
[0016] (6) calcining the aluminum-doped cobalt carbonate described in step (5) to obtain the cobalt trioxide.
[0017] The preparation method provided by the present invention can prepare cobalt tetroxide with internal pores and a surface having a high degree of crystallinity. In the second nucleation stage, the introduction of ammonium bicarbonate solution is stopped, and the flow rates of cobalt salt solution and aluminum salt solution in the first nucleation stage are maintained to make the local Co concentration too high, thereby causing the primary particles generated in the first nucleation stage to agglomerate and obtain a desired agglomerated structure. Then, the introduction of cobalt salt solution and aluminum salt solution is stopped to prevent further agglomeration. Then, the growth of cobalt carbonate is carried out. In the present invention, by setting the first temperature lower than the second temperature and coordinating different pH value ranges, internal pores can be formed while also increasing the degree of crystallinity on the surface, so that Al exists in the more stable form of AlOOH. Simultaneously, the control of pH value during the growth process can also prevent cracking caused by nucleation explosion during the growth process.
[0018] Preferably, the cobalt concentration in the cobalt salt solution in step (1) is 80 g / L to 160 g / L, for example, 80 g / L, 100 g / L, 120 g / L, 150 g / L or 160 g / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0019] Preferably, the cobalt salt in the cobalt salt solution includes any one or a combination of at least two of cobalt sulfate, cobalt chloride or cobalt nitrate. Typical but non-limiting combinations include a combination of cobalt sulfate and cobalt chloride, a combination of cobalt sulfate and cobalt nitrate, a combination of cobalt chloride and cobalt nitrate, or a combination of cobalt sulfate, cobalt chloride and cobalt nitrate.
[0020] Preferably, the aluminum concentration in the aluminum salt solution is 1 g / L to 9 g / L, for example, 1 g / L, 3 g / L, 5 g / L, 6 g / L, 8 g / L or 9 g / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0021] Preferably, the aluminum salt in the aluminum salt solution includes any one or a combination of at least two of aluminum sulfate, aluminum chloride or aluminum nitrate. Typical but non-limiting combinations include a combination of aluminum sulfate and aluminum chloride, a combination of aluminum sulfate and aluminum nitrate, a combination of aluminum chloride and aluminum nitrate, or a combination of aluminum sulfate, aluminum chloride and aluminum nitrate.
[0022] Preferably, the concentration of the ammonium bicarbonate solution is 210 g / L to 260 g / L, for example, 210 g / L, 220 g / L, 240 g / L, 250 g / L or 260 g / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0023] Preferably, during the first nucleation in step (2), the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3 to 1:3.5, for example, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4 or 1:3.5, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0024] Preferably, during the first nucleation in step (2), the flow rates of the cobalt salt solution and the aluminum salt solution are controlled so that the mass ratio of cobalt to aluminum is 72:1 to 72:2, for example, 72:1, 72:1.2, 72:1.5, 72:1.8 or 72:2, but is not limited to the listed values, and the remaining values within the numerical range not listed are also applicable.
[0025] In the present invention, the cobalt-aluminum mass ratio refers to the mass ratio of cobalt to aluminum in the cobalt salt solution and the aluminum salt solution introduced per unit time.
[0026] Preferably, the temperature of the first nucleation in step (2) is 35°C to 50°C, for example, it can be 35°C, 36°C, 40°C, 42°C, 45°C, 48°C or 50°C, but is not limited to the listed values, and the remaining values within the numerical range not listed are also applicable.
[0027] Preferably, the pH value of the first nucleation in step (2) is 7 to 9, for example, 7, 7.5, 8, 8.5 or 9, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0028] Preferably, the first nucleation in step (2) is carried out under stirring conditions at a rotation speed of 200 rpm to 300 rpm, for example, it can be 200 rpm, 220 rpm, 250 rpm, 280 rpm or 300 rpm, but is not limited to the listed values, and the remaining values not listed within the numerical range are also applicable.
[0029] Preferably, the first particle size D50 reaches 0.5μm to 2μm, for example, it can be 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm or 2μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0030] Preferably, the temperature of the second nucleation in step (3) is 35°C to 50°C, for example, 35°C, 36°C, 40°C, 42°C, 45°C, 48°C or 50°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0031] Preferably, the pH value of the second nucleation in step (3) is 5 to 7, for example, 5, 5.5, 6, 6.5 or 7, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0032] Preferably, the second nucleation in step (3) is carried out under stirring conditions at a rotation speed of 200 rpm to 300 rpm, for example, it can be 200 rpm, 220 rpm, 250 rpm, 280 rpm or 300 rpm, but is not limited to the listed values, and the remaining values not listed within the numerical range are also applicable.
[0033] Preferably, in step (3), the second particle size D50 reaches 3 μm to 7 μm, for example, it can be 3 μm, 4 μm, 5 μm, 6 μm or 7 μm, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.
[0034] As a preferred technical solution, in step (5), during the process of growing to the stopping particle size, the aluminum salt solution is fed through a spiral nozzle to avoid Al segregation.
[0035] Preferably, the first temperature in step (5) is 30°C to 50°C, for example, 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0036] Preferably, the third particle size D50 in step (5) reaches 12 μm to 16 μm, for example, it can be 12 μm, 13 μm, 14 μm, 15 μm or 16 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0037] Preferably, the second temperature in step (5) is 50°C to 70°C, for example, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0038] Preferably, the stopping particle size D50 in step (5) reaches 20 μm to 22 μm, for example, it can be 20 μm, 20.5 μm, 21 μm, 21.5 μm or 22 μm, but is not limited to the listed values, and the remaining values not listed within the numerical range are also applicable.
[0039] Preferably, the washing temperature is 50°C to 80°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0040] Preferably, the drying temperature is 50°C to 120°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or 120°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0041] Preferably, the calcination in step (6) comprises performing a first calcination at a first oxygen concentration and then performing a second calcination at a second oxygen concentration;
[0042] The first oxygen concentration is lower than the second oxygen concentration.
[0043] Preferably, the first oxygen concentration is 8 vol% to 12 vol%, for example, 8 vol%, 9 vol%, 10 vol%, 11 vol% or 12 vol%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0044] Preferably, the second oxygen concentration is 18 vol% to 22 vol%, for example, 18 vol%, 19 vol%, 20 vol%, 21 vol% or 22 vol%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0045] In the present invention, the balance gas for adjusting the first oxygen concentration and the second oxygen concentration includes nitrogen.
[0046] Preferably, the first calcination comprises: heating to 450° C. to 600° C. at a heating rate of 5° C. / min to 20° C. / min, and keeping the temperature for 30 min to 120 min.
[0047] The heating rate of the first calcination is 5°C / min to 20°C / min, for example, it can be 5°C / min, 8°C / min, 10°C / min, 12°C / min, 15°C / min, 18°C / min or 20°C / min, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.
[0048] The temperature of the first calcination is 450°C to 600°C, for example, 450°C, 480°C, 500°C, 540°C, 550°C, 580°C or 600°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0049] The holding time of the first calcination is 30 min to 120 min, for example, 30 min, 50 min, 60 min, 80 min, 100 min or 120 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0050] Preferably, the second calcination comprises: heating to 650° C. to 850° C. at a heating rate of 2° C. / min to 10° C. / min, and keeping the temperature for 30 min to 180 min.
[0051] The heating rate of the second calcination is 2°C / min to 10°C / min, for example, 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min or 10°C / min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0052] The temperature of the second calcination is 650°C to 850°C, for example, 650°C, 680°C, 720°C, 750°C, 780°C, 800°C, 820°C or 850°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.
[0053] The holding time of the second calcination is 30 min to 180 min, for example, 30 min, 50 min, 60 min, 80 min, 100 min, 120 min, 150 min, 160 min or 180 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0054] As a preferred technical solution of the preparation method described in the first aspect of the present invention, the preparation method comprises the following steps:
[0055] (1) providing a cobalt salt solution with a cobalt concentration of 80 g / L to 160 g / L, an aluminum salt solution with an aluminum concentration of 1 g / L to 9 g / L, and an ammonium bicarbonate solution with a concentration of 210 g / L to 260 g / L;
[0056] (2) adding pure water and ammonium bicarbonate solution into the reactor to prepare a base solution with a pH value of 7 to 9; flowing cobalt salt solution, aluminum salt solution and ammonium bicarbonate solution into the base solution in parallel to perform the first nucleation until the particle size D50 reaches 0.5 μm to 2 μm;
[0057] During the first nucleation, the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3 to 1:3.5;
[0058] During the first nucleation, the flow rates of the cobalt salt solution and the aluminum salt solution are controlled so that the mass ratio of cobalt to aluminum is 72:1 to 72:2;
[0059] The temperature of the first nucleation is 35°C to 50°C, the pH value is 7 to 9, and the stirring speed is 200 rpm to 300 rpm;
[0060] (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and the second nucleation is carried out until the particle size D50 reaches 3 μm to 7 μm;
[0061] The temperature of the second nucleation is 35°C to 50°C, the pH value is 5 to 7, and the stirring speed is 200 rpm to 300 rpm;
[0062] (4) After the second nucleation is completed, the introduction of the cobalt salt solution and the aluminum salt solution is stopped, and ammonium bicarbonate solution is introduced to adjust the pH value to 7-8;
[0063] (5) at a first temperature of 30°C to 50°C, introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel to grow the particles until their particle size D50 reaches 12 μm to 16 μm; then raising the temperature to a second temperature of 50°C to 70°C, adjusting the flow rates of the cobalt salt solution and the ammonium bicarbonate solution to lower the pH value of the solution to 5 to 7, and growing the particles until their particle size D50 reaches 20 μm to 22 μm; washing the particles at a temperature of 50°C to 80°C, and drying the particles at a temperature of 50°C to 120°C to obtain aluminum-doped cobalt carbonate;
[0064] (6) performing a first calcination at a first oxygen concentration of 8 vol% to 12 vol%, and then performing a second calcination at a second oxygen concentration of 18 vol% to 22 vol% to obtain the cobalt trioxide;
[0065] The first calcination comprises: heating to 450°C to 600°C at a heating rate of 5°C / min to 20°C / min, and keeping the temperature for 30min to 120min;
[0066] The second calcination comprises: heating the temperature to 650° C. to 850° C. at a heating rate of 2° C. / min to 10° C. / min, and keeping the temperature for 30 minutes to 180 minutes.
[0067] In a second aspect, the present invention provides cobalt trioxide, which is prepared by the preparation method described in the first aspect.
[0068] In a third aspect, the present invention provides a positive electrode material, which is prepared from the cobalt trioxide described in the second aspect.
[0069] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.
[0070] Compared with the prior art, the present invention has the following beneficial effects:
[0071] The preparation method provided by the present invention can prepare cobalt tetroxide with internal pores and a surface having a high degree of crystallinity. In the second nucleation stage, the introduction of ammonium bicarbonate solution is stopped, and the flow rates of cobalt salt solution and aluminum salt solution in the first nucleation stage are maintained to make the local Co concentration too high, thereby causing the primary particles generated in the first nucleation stage to agglomerate and obtain a desired agglomerated structure. Then, the introduction of cobalt salt solution and aluminum salt solution is stopped to prevent further agglomeration. Then, the growth of cobalt carbonate is carried out. In the present invention, by setting the first temperature lower than the second temperature and coordinating different pH value ranges, internal pores can be formed while also increasing the degree of crystallinity on the surface, so that Al exists in the more stable form of AlOOH. Simultaneously, the control of pH value during the growth process can also prevent cracking caused by nucleation explosion during the growth process. BRIEF DESCRIPTION OF THE DRAWINGS
[0072] Figure 1 This is a SEM image of the material in the slurry obtained after the second nucleation is completed in Example 1, after the pH value is adjusted by passing ammonium bicarbonate solution;
[0073] Figure 2 This is a cross-sectional view of the cobalt trioxide obtained in Example 1. DETAILED DESCRIPTION
[0074] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.
[0075] Example 1
[0076] This embodiment provides a method for preparing cobalt tetroxide, which comprises the following steps:
[0077] (1) providing a cobalt sulfate solution with a cobalt concentration of 120 g / L, an aluminum sulfate solution with an aluminum concentration of 5 g / L, and an ammonium bicarbonate solution with a concentration of 240 g / L;
[0078] (2) Pure water and ammonium bicarbonate solution were added to the reactor to prepare a base solution with a pH value of 8; a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution were introduced into the base solution in parallel to perform the first nucleation until the particle size D50 reached 1 μm;
[0079] During the first nucleation, the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3.2;
[0080] During the first nucleation, the flow rates of the cobalt salt solution and the aluminum salt solution are controlled so that the mass ratio of cobalt to aluminum is 72:1.5;
[0081] The temperature of the first nucleation was 40°C, the pH value was 8, and the stirring speed was 250 rpm;
[0082] (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and the second nucleation is carried out until the particle size D50 reaches 5 μm;
[0083] The temperature of the second nucleation was 40°C, the pH value was 6, and the stirring speed was 250 rpm;
[0084] (4) After the second nucleation, the introduction of the cobalt salt solution and the aluminum salt solution was stopped, and the ammonium bicarbonate solution was introduced to adjust the pH value to 7.5. The SEM image of the material in the obtained slurry is as follows: Figure 1 As shown;
[0085] (5) at a first temperature of 40° C., introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel to grow the particles until their particle size D50 reaches 14 μm; then raising the temperature to a second temperature of 60° C., adjusting the flow rates of the cobalt salt solution and the ammonium bicarbonate solution to lower the pH value of the solution to 6, and growing the particles until their particle size D50 reaches 21 μm; washing the particles at 60° C. and drying the particles at 80° C. to obtain aluminum-doped cobalt carbonate;
[0086] (6) performing a first calcination at a first oxygen concentration (10 vol%), and then performing a second calcination at a second oxygen concentration (20 vol%) to obtain the cobalt trioxide;
[0087] The first calcination is as follows: heating to 500°C at a heating rate of 10°C / min and keeping the temperature for 80 minutes;
[0088] The second calcination is as follows: heating to 750° C. at a heating rate of 6° C. / min and keeping the temperature for 100 minutes.
[0089] The cross-sectional view of the cobalt trioxide obtained in this embodiment is as follows Figure 2 shown.
[0090] Example 2
[0091] This embodiment provides a method for preparing cobalt tetroxide, which comprises the following steps:
[0092] (1) providing a cobalt sulfate solution with a cobalt concentration of 80 g / L, an aluminum sulfate solution with an aluminum concentration of 1 g / L, and an ammonium bicarbonate solution with a concentration of 210 g / L;
[0093] (2) adding pure water and ammonium bicarbonate solution into the reactor to prepare a base solution with a pH value of 8; flowing cobalt salt solution, aluminum salt solution and ammonium bicarbonate solution into the base solution in parallel to perform the first nucleation until the particle size D50 reaches 0.5 μm;
[0094] During the first nucleation, the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3;
[0095] During the first nucleation, the flow rates of the cobalt salt solution and the aluminum salt solution are controlled so that the mass ratio of cobalt to aluminum is 72:1;
[0096] The temperature of the first nucleation was 35°C, the pH value was 7, and the stirring speed was 200 rpm;
[0097] (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and the second nucleation is carried out until the particle size D50 reaches 3 μm;
[0098] The temperature of the second nucleation was 35°C, the pH value was 5, and the stirring speed was 200 rpm;
[0099] (4) After the second nucleation is completed, the introduction of the cobalt salt solution and the aluminum salt solution is stopped, and ammonium bicarbonate solution is introduced to adjust the pH value to 7;
[0100] (5) at a first temperature of 30° C., introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel to grow the particles until their particle size D50 reaches 12 μm; then raising the temperature to a second temperature of 50° C., adjusting the flow rates of the cobalt salt solution and the ammonium bicarbonate solution to lower the pH value of the solution to 5, and growing the particles until their particle size D50 reaches 20 μm; washing the particles at 50° C. and drying the particles at 50° C. to obtain aluminum-doped cobalt carbonate;
[0101] (6) performing a first calcination at a first oxygen concentration (8 vol%), and then performing a second calcination at a second oxygen concentration (18 vol%) to obtain the cobalt trioxide;
[0102] The first calcination is as follows: heating to 450°C at a heating rate of 5°C / min and keeping the temperature for 120 minutes;
[0103] The second calcination is as follows: heating to 650° C. at a heating rate of 2° C. / min and keeping the temperature for 180 min.
[0104] Example 3
[0105] This embodiment provides a method for preparing cobalt tetroxide, which comprises the following steps:
[0106] (1) providing a cobalt sulfate solution with a cobalt concentration of 160 g / L, an aluminum sulfate solution with an aluminum concentration of 9 g / L, and an ammonium bicarbonate solution with a concentration of 260 g / L;
[0107] (2) adding pure water and ammonium bicarbonate solution into the reactor to prepare a base solution with a pH value of 8; flowing cobalt salt solution, aluminum salt solution and ammonium bicarbonate solution into the base solution in parallel to perform the first nucleation until the particle size D50 reaches 2 μm;
[0108] During the first nucleation, the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3.5;
[0109] During the first nucleation, the flow rates of the cobalt salt solution and the aluminum salt solution are controlled so that the mass ratio of cobalt to aluminum is 72:2;
[0110] The temperature of the first nucleation was 50°C, the pH value was 9, and the stirring speed was 300 rpm;
[0111] (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and the second nucleation is carried out until the particle size D50 reaches 7 μm;
[0112] The temperature of the second nucleation was 50°C, the pH value was 7, and the stirring speed was 300 rpm;
[0113] (4) After the second nucleation is completed, the introduction of the cobalt salt solution and the aluminum salt solution is stopped, and ammonium bicarbonate solution is introduced to adjust the pH value to 8;
[0114] (5) at a first temperature of 50° C., introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel to grow the particles until their particle size D50 reaches 16 μm; then raising the temperature to a second temperature of 70° C., adjusting the flow rates of the cobalt salt solution and the ammonium bicarbonate solution to lower the pH value of the solution to 7, and growing the particles until their particle size D50 reaches 22 μm; washing the particles at 80° C. and drying the particles at 120° C. to obtain aluminum-doped cobalt carbonate;
[0115] (6) performing a first calcination at a first oxygen concentration (12 vol%), and then performing a second calcination at a second oxygen concentration (22 vol%) to obtain the cobalt trioxide;
[0116] The first calcination is as follows: heating to 600°C at a heating rate of 20°C / min and keeping the temperature for 30 minutes;
[0117] The second calcination is as follows: heating to 850° C. at a heating rate of 10° C. / min and keeping the temperature for 30 minutes.
[0118] Example 4
[0119] This embodiment provides a method for preparing cobalt trioxide, which is the same as that of Example 1 except that the first temperature in step (5) is 20°C.
[0120] Example 5
[0121] This embodiment provides a method for preparing cobalt trioxide, which is the same as that of Example 1 except that the second temperature in step (5) is 80°C.
[0122] Comparative Example 1
[0123] This comparative example provides a method for preparing cobalt trioxide, which is the same as Example 1 except that the second nucleation is not performed and the particle size D50 is directly adjusted to 5 μm under the conditions of the first nucleation.
[0124] Comparative Example 2
[0125] This comparative example provides a method for preparing cobalt trioxide, which is the same as Example 1 except that the pH value is not adjusted after the second nucleation.
[0126] Comparative Example 3
[0127] This comparative example provides a method for preparing cobalt trioxide, which is the same as Example 1 except that step (5) is different from Example 1.
[0128] Step (5) in this comparative example comprises:
[0129] At a first temperature of 40°C, a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution are introduced in parallel to grow the particles until their particle size D50 reaches 14 μm. Then, at a second temperature of 40°C, the flow rates of the cobalt salt solution and the ammonium bicarbonate solution are adjusted to lower the pH value of the solution to 6, and the particles are grown until their particle size D50 reaches 21 μm. The particles are then washed at 60°C and dried at 80°C to obtain aluminum-doped cobalt carbonate.
[0130] Comparative Example 4
[0131] This comparative example provides a method for preparing cobalt trioxide, which is the same as Example 1 except that step (5) is different from Example 1.
[0132] Step (5) in this comparative example comprises:
[0133] At a first temperature of 60°C, a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution are introduced in parallel to grow the particles until their particle size D50 reaches 14 μm. Then, at a second temperature of 60°C, the flow rates of the cobalt salt solution and the ammonium bicarbonate solution are adjusted to lower the pH value of the solution to 6, and the particles are grown until their particle size D50 reaches 21 μm. The particles are then washed at 60°C and dried at 80°C to obtain aluminum-doped cobalt carbonate.
[0134] Comparative Example 5
[0135] This comparative example provides a method for preparing cobalt trioxide, which is the same as Example 1 except that step (5) is different from Example 1.
[0136] Step (5) in this comparative example comprises:
[0137] At a first temperature of 60° C., a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution are introduced in parallel to grow the particles until the particle size D50 reaches 21 μm; the particles are washed at 60° C. and dried at 80° C. to obtain aluminum-doped cobalt carbonate.
[0138] Performance Characterization
[0139] The cobalt trioxide prepared in the above examples and comparative examples was used as a precursor material. The precursor material and lithium carbonate were weighed and mixed at a lithium-cobalt molar ratio (Li / Co) of 1.025. The mixture was then sintered at 980°C in an air atmosphere for 20 hours. After sintering, the product was crushed, deironed, and sieved to obtain a lithium cobalt oxide positive electrode material.
[0140] Lithium cobalt oxide positive electrode material is used as the positive electrode active material. 80wt% of the positive electrode active material, 10wt% of Super-P and 10wt% of polyvinylidene fluoride are dispersed in N-methylpyrrolidone to prepare an electrode slurry, which is then coated on an aluminum foil current collector and dried to obtain a positive electrode.
[0141] The lithium sheet serves as the negative electrode;
[0142] The diaphragm is PP microporous membrane (Celgard2400);
[0143] LiPF6 is dissolved in a mixed solvent to obtain an electrolyte with a LiPF6 concentration of 1 mol / L. The mixed solvent is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1.
[0144] The positive electrode, negative electrode, separator and electrolyte were assembled to obtain a button battery. The discharge capacity, cycle performance and rate performance of the button battery were tested. The results are shown in Table 1.
[0145] The test method for discharge specific capacity is: test in the electrochemical window of 2.5V ~ 4.55V;
[0146] The test method for cycle performance is: in the electrochemical window of 2.5V to 4.55V, the cycle test is carried out at 0.2C / 0.5C to obtain the capacity retention rate after 100 cycles;
[0147] The test method for rate performance is: charge at a constant current density of 0.2C in the electrochemical window of 2.5V~4.55V, discharge at 0.5C, 1C, 2C, and 3C for 5 cycles respectively, then return to 0.2C discharge, and calculate the capacity retention rate.
[0148] Table 1
[0149]
[0150]
[0151] As can be seen from Table 1 of the present invention, when the first temperature is too low (Example 4), the resulting cobalt trioxide will have too many pores, thereby affecting its electrochemical performance. Similarly, when the second temperature is too high (Example 5), the electrochemical performance of the resulting cobalt trioxide will also decrease.
[0152] From the comparison between Comparative Example 1 and Example 1, it can be seen that when the second nucleation is not performed, the specific capacity, cycle performance and rate performance of the lithium cobalt oxide material corresponding to the obtained cobalt trioxide are significantly reduced.
[0153] From the comparison between Comparative Example 2 and Example 1, it can be seen that when the pH value is not adjusted after the second nucleation is completed, the specific capacity, cycle performance and rate performance of the lithium cobalt oxide material corresponding to the obtained cobalt trioxide are also significantly reduced.
[0154] From the comparison of Comparative Examples 3, 4, and 5 with Example 1, it can be seen that the first temperature and the second temperature in the growth stage are more important for the smooth realization of the technical effect of the present invention. It is necessary to strictly control the first temperature to 30°C to 50°C, and strictly control the second temperature to 50°C to 70°C.
[0155] In summary, the preparation method provided by the present invention can prepare cobalt tetroxide with internal pores and a high crystallinity surface. The introduction of ammonium bicarbonate solution is stopped in the second nucleation stage, and the flow rate of cobalt salt solution and aluminum salt solution in the first nucleation stage is maintained to make the local Co concentration too high, so that the primary particles produced in the first nucleation stage agglomerate to obtain the desired agglomerated structure, and then the introduction of cobalt salt solution and aluminum salt solution is stopped to avoid further agglomeration; and then the growth of cobalt carbonate is carried out. The present invention forms internal pores while also improving the degree of surface crystallinity by setting the first temperature lower than the second temperature and coordinating different pH value ranges, so that Al exists in the more stable form of AlOOH. At the same time, the control of pH value during the growth process can also prevent cracking caused by nucleation during the growth process.
[0156] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.
Claims
1. A method for preparing cobalt trioxide, characterized in that: The preparation method comprises the following steps: (1) providing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution; (2) introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution into the base liquid in parallel to perform a first nucleation to a first particle size; (3) After the first nucleation is completed, the introduction of ammonium bicarbonate solution is stopped and a second nucleation is performed to a second particle size; (4) After the second nucleation is completed, the introduction of the cobalt salt solution and the aluminum salt solution is stopped, and ammonium bicarbonate solution is introduced to adjust the pH value to 7-8; (5) introducing a cobalt salt solution, an aluminum salt solution, and an ammonium bicarbonate solution in parallel at a first temperature to grow the particles to a third size; Then, the temperature is raised to a second temperature, the flow rates of the cobalt salt solution and the ammonium bicarbonate solution are adjusted to reduce the pH value of the solution to 5-7, and the particles are grown to a stopping size; washing and drying are performed to obtain aluminum-doped cobalt carbonate; (6) calcining the aluminum-doped cobalt carbonate described in step (5) to obtain the cobalt trioxide.
2. The preparation method according to claim 1, characterized in that The cobalt concentration in the cobalt solution in step (1) is 80 g / L to 160 g / L; and / or, the aluminum concentration in the aluminum salt solution is 1 g / L to 9 g / L; And / or, the concentration of the ammonium bicarbonate solution is 210 g / L to 260 g / L.
3. The preparation method according to claim 1, characterized in that During the first nucleation in step (2), the flow ratio of the cobalt salt solution to the ammonium bicarbonate solution is 1:3 to 1:3.5; and / or, during the first nucleation in step (2), controlling the flow rates of the cobalt salt solution and the aluminum salt solution so that the mass ratio of cobalt to aluminum is 72:1 to 72:2; and / or, the temperature of the first nucleation in step (2) is 35° C. to 50° C.; and / or, the pH value of the first nucleation in step (2) is 7 to 9; and / or, the first nucleation in step (2) is carried out under stirring conditions at a rotation speed of 200 rpm to 300 rpm; And / or, the first particle size D50 reaches 0.5 μm to 2 μm.
4. The preparation method according to claim 1, characterized in that Step (3) the temperature of the second nucleation is 35°C to 50°C; and / or, the pH value of the second nucleation in step (3) is 5 to 7; and / or, the second nucleation in step (3) is carried out under stirring conditions at a rotation speed of 200 rpm to 300 rpm; And / or, in step (3), the second particle size D50 reaches 3 μm to 7 μm.
5. The preparation method according to claim 1, characterized in that Step (5) wherein the first temperature is 30° C. to 50° C.; And / or, the third particle size D50 in step (5) reaches 12 μm to 16 μm.
6. The preparation method according to claim 1, characterized in that Step (5) the second temperature is 50° C. to 70° C.; And / or, the stopping particle size D50 in step (5) reaches 20 μm to 22 μm.
7. The preparation method according to claim 1, characterized in that The washing temperature is 50°C to 80°C; And / or, the drying temperature is 50°C to 120°C.
8. The preparation method according to claim 1, characterized in that The calcination in step (6) includes performing a first calcination at a first oxygen concentration and then performing a second calcination at a second oxygen concentration; The first oxygen concentration is lower than the second oxygen concentration; and / or, the first oxygen concentration is 8 vol% to 12 vol%; and / or, the second oxygen concentration is 18 vol% to 22 vol%; And / or, the first calcination comprises: heating to 450°C to 600°C at a heating rate of 5°C / min to 20°C / min, and keeping the temperature for 30min to 120min; And / or, the second calcination comprises: heating to 650° C. to 850° C. at a heating rate of 2° C. / min to 10° C. / min, and keeping the temperature for 30 min to 180 min.
9. A cobalt trioxide, characterized in that: The cobalt trioxide is prepared by the preparation method according to any one of claims 1 to 8.
10. A positive electrode material, characterized in that The positive electrode material is prepared from the cobalt trioxide described in claim 9.