Preparation method of aluminum-doped small-particle-size cobalt carbonate
By controlling the reaction conditions and stirring speed in stages, the problem of uneven aluminum distribution in aluminum-doped cobalt carbonate with small particle size was solved, achieving uniform growth and improved stability of aluminum-doped cobalt carbonate particles, forming a dense nanosheet structure, and solving the problems of aluminum segregation and morphology control in the existing technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JINCHUAN GROUP NICKEL COBALT CO LTD
- Filing Date
- 2026-02-12
- Publication Date
- 2026-05-01
AI Technical Summary
Existing technologies make it difficult to achieve a uniform distribution of aluminum in small-particle cobalt carbonate doped with aluminum, which leads to difficulties in controlling particle morphology and makes it impossible to form an effective core-shell or uniform doped structure, affecting the stability and batch consistency of the material.
By precisely controlling the reaction conditions in stages, including controlling the temperature, stirring speed and pH value in the reactor, the uniform growth of aluminum-doped cobalt carbonate crystals is ensured. By adjusting the pH value and stirring speed multiple times, the aluminum-doped cobalt carbonate crystals are able to stack in an orderly manner and optimize their crystal form under a low shear force environment, forming a uniform and dense nanosheet structure.
This process improved the uniformity and stability of aluminum-doped cobalt carbonate particles, prevented the recrystallization and precipitation of aluminum, ensured improved product performance and batch consistency, and formed a regular, thin-film crystal structure, thus enhancing the material's performance.
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Abstract
Description
A method for preparing aluminum-doped small-particle cobalt carbonate Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method for preparing aluminum-doped small-particle cobalt carbonate. Background Technology
[0002] Lithium cobalt oxide cathode materials have long held an important position in the 3C consumer electronics field due to their excellent high energy density characteristics. However, traditional lithium cobalt oxide materials have gradually revealed inherent shortcomings such as limited cycle life and insufficient thermal stability. Currently, researchers generally use the introduction of aluminum to enhance the crystal structure stability of lithium cobalt oxide and significantly improve its electrochemical performance. However, in actual production, with the increase of aluminum doping, aluminum-doped cobalt carbonate has poor tolerance during post-processing such as washing and drying, and aluminum segregation easily occurs on the surface of cobalt carbonate particles. This phenomenon directly leads to uneven material structure and performance fluctuations, seriously affecting the batch consistency of products.
[0003] Currently, for large-particle cobalt carbonate products, the industry typically employs core-shell structure designs to effectively coat and immobilize aluminum, thereby preventing its segregation on the surface. However, due to the short synthesis time of aluminum-doped small-particle cobalt carbonate products, the nucleation and growth processes are difficult to precisely control. Consequently, aluminum cannot achieve uniform distribution in the reaction system, leading to difficulties in controlling particle morphology and the inability to form an effective core-shell or uniformly doped structure. Therefore, preparing aluminum-doped small-particle cobalt carbonate with excellent stability is extremely challenging. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing aluminum-doped small-particle cobalt carbonate, so as to solve the problems of easy recrystallization and precipitation of aluminum element and difficulty in controlling particle morphology in existing aluminum-doped small-particle cobalt carbonate.
[0005] The technical solution of this invention is: a method for preparing aluminum-doped small-particle cobalt carbonate, characterized by comprising the following steps: A. Mixing a cobalt salt solution and a soluble aluminum salt solution evenly to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 100-140 g / L, wherein the aluminum to cobalt ratio in the cobalt-aluminum mixed solution is 0.0055-0.0181 wt%; B. Adding an NH4HCO3 solution with a concentration of 40 g / L-150 g / L to a reaction vessel as a base solution, and turning on the reaction vessel for heating to raise the temperature of the NH4HCO3 solution to 3°C. At temperatures ranging from 5℃ to 40℃, the stirring speed of the reactor is set to 350 r / min to 400 r / min. A cobalt-aluminum mixed solution is added to the reactor at a rate of 3% to 4% of the reactor volume per hour to initiate the reaction. Next, an NH4HCO3 solution with a concentration of 200 g / L to 260 g / L is added to the reactor to adjust the pH of the solution to 7.2 to 7.4. The addition continues until the D50 particle size of the aluminum-doped cobalt carbonate reaches 3.7 μm to 3.8 μm. At this point, the addition of the cobalt-aluminum mixed solution and the NH4HCO3 solution is stopped. The synthesis temperature was increased to 45℃-50℃ within 30-60 minutes, and stirring was continued after heating. D. After stirring, an NH4HCO3 solution with a concentration of 200g / L-260g / L was added to the reactor to adjust the pH of the solution to 7.6-7.8. During the reaction, a cobalt-aluminum mixed solution was added to the reactor at a rate of 4%-5% of the reactor volume per hour, while the stirring speed was reduced to 250-300 rpm until the particle size D50 of the aluminum-doped cobalt carbonate reached 4.0μm-4.5μm. E. Reduce the stirring speed to 200 r / min to 250 r / min, reduce the flow rate of the cobalt-aluminum mixed solution into the reactor to 2% / h to 3% / h, and reduce the synthesis temperature to 42℃ to 47℃ within 30 min to 60 min. Maintain the pH value of the solution in the reactor and continue the reaction until the particle size D50 of the aluminum-doped cobalt carbonate reaches 4.0 μm to 5.0 μm. Then, stop the reaction and obtain the aluminum-doped cobalt carbonate slurry. F. Extract the prepared aluminum-doped cobalt carbonate slurry from the reactor, wash and dry it to obtain aluminum-doped small-particle cobalt carbonate.
[0006] As a further improvement of the present invention, in step A, the cobalt salt is at least one of CoSO4, Co(CH3COO)2, Co(NO3)2 and CoCl2, and the soluble aluminum salt is at least one of Al2(SO4)3, Al(NO3)3 and AlCl3.
[0007] As a further improvement of the present invention, in step B, the volume of the bottom liquid NH4HCO3 solution accounts for 30% to 50% of the volume of the reaction vessel.
[0008] As a further improvement of the present invention, in step C, the particle size growth rate is controlled at 0.04 μm / h to 0.06 μm / h.
[0009] As a further improvement of the present invention, in step C, the mixture is continuously stirred for 1 to 2 hours after heating.
[0010] As a further improvement of the present invention, in step D, the particle size growth rate is controlled at 0.05 μm / h to 0.08 μm / h.
[0011] As a further improvement of the present invention, in step E, the particle size growth rate is controlled at 0.01 μm / h to 0.02 μm / h.
[0012] The beneficial effects of this invention are: 1. By precisely controlling the reaction conditions in stages, this invention ensures the uniform growth of aluminum-doped cobalt carbonate crystals, effectively improves the uniformity and stability of aluminum-doped cobalt carbonate particles, and results in a narrower particle size distribution. This avoids the precipitation of aluminum elements in small-particle aluminum-doped cobalt carbonate due to recrystallization, thus effectively improving product performance and ensuring the effectiveness of using small-particle aluminum-doped cobalt carbonate.
[0013] 2. This invention employs a method of repeatedly adjusting the pH value and stirring speed to enable the aluminum-doped cobalt carbonate crystals to undergo ordered stacking and crystal form optimization under a lower shear force environment. This promotes the directional alignment of the aluminum-doped cobalt carbonate crystal faces and the formation of dense and regular thin sheets. The thin sheet-like aluminum-doped cobalt carbonate crystals gradually expand two-dimensionally along the axial direction to form a uniform and dense nanosheet structure. This promotes the uniform growth and structural densification of the crystals and protects the aluminum element in the small-particle cobalt carbonate from loss and segregation in subsequent processes.
[0014] 3. The present invention also stops feeding in the reactor and increases the reaction temperature within a set heating time to fully mature the aluminum-doped cobalt carbonate grains. High-speed stirring in the reactor further densifies the structure of the aluminum-doped cobalt carbonate grains, thereby eliminating possible concentration gradients and interfacial tensions in the system and ensuring the stability of the aluminum-doped cobalt carbonate grains.
[0015] 4. This invention is easy to operate and has a stable reaction. It achieves precise matching of the entire process from crystal nucleation and growth to structural control, ensuring the synergistic control of the uniformity of aluminum element distribution and structural integrity of aluminum-doped cobalt carbonate particles within a small particle size range. It avoids the problem of aluminum element enrichment and performance degradation on the surface of small aluminum-doped cobalt carbonate particles as the amount of aluminum doping increases, and has strong practicality. Attached Figure Description
[0016] Figure 1 is a scanning electron microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate seed crystals prepared in step C of Example 1 of the present invention; Figure 2 is a scanning electron microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate prepared in step D of Example 1 of the present invention; Figure 3 is a microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate prepared in Example 1 of the present invention; Figure 4 is a distribution diagram of Al in the aluminum-doped small-particle cobalt carbonate prepared in Example 2 of the present invention; Figure 5 is a microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate prepared in Comparative Example 1 of the present invention. Detailed Implementation
[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0018] Example 1: A method for preparing aluminum-doped small-particle cobalt carbonate. CoCl2 is prepared into a CoCl2 solution with a cobalt ion concentration of 100 g / L. Al2(SO4)3·18H2O crystals are added to the CoCl2 solution and stirred until homogeneous to prepare a cobalt-aluminum mixed solution. The aluminum to cobalt ratio in the cobalt-aluminum mixed solution is 0.0097 wt%. 30% of a 40 g / L NH4HCO3 solution is added to a reactor as the base solution. The reactor is heated, and the stirring speed is set to 350 r / min to allow the NH4HCO3 solution to dissolve. The CO3 solution was heated to 35°C. The prepared cobalt-aluminum mixed solution was added to the reactor at a rate of 3% / h of the reactor volume. NH4HCO3 solution with a concentration of 200 g / L was also added to the reactor to bring the pH of the solution to 7.2. The particle size growth rate was controlled at 0.04 μm / h until the D50 of the aluminum-doped cobalt carbonate particles reached a minimum of 3.7 μm and a maximum of 3.8 μm. At this point, the addition of the cobalt-aluminum mixed solution and NH4HCO3 solution was stopped, and the synthesis temperature was increased to 45°C over 30 min. High-speed stirring was then continued for 1 h after the temperature increase.
[0019] After stirring, a 200 g / L NH4HCO3 solution was added to the reactor to bring the pH of the solution to 7.6. The stirring speed was reduced to 250 r / min, and a cobalt-aluminum mixed solution was added to the reactor at a rate of 4% / h of the reactor volume to allow the reaction to continue. The particle size increase rate was controlled at 0.05 μm / h until the D50 of the aluminum-doped cobalt carbonate reached a minimum of 4.0 μm and a maximum of 4.5 μm. At this point, the stirring speed was reduced to 200 r / min, the flow rate of the cobalt-aluminum mixed solution into the reactor was reduced to 2% / h, and the synthesis temperature was lowered to 42℃ over 30 minutes. This was achieved by adjusting the NH4HCO3 concentration. The flow rate of O3 solution was maintained at a pH of 7.6 within the reactor, and the particle size growth rate was controlled at 0.01 μm / h to further optimize the thermodynamic and kinetic environment for the growth of aluminum-doped cobalt carbonate crystals. This prevented the formation of fine particles and allowed the thin-film aluminum-doped cobalt carbonate particles to gradually expand two-dimensionally along the axial direction, forming a uniform and dense nanosheet structure. This promoted uniform crystal growth and structural densification. The reaction continued until the particle size D50 of the aluminum-doped cobalt carbonate reached a minimum of 4.0 μm and a maximum of 5.0 μm. The reaction was then terminated, yielding an aluminum-doped cobalt carbonate slurry. The prepared aluminum-doped cobalt carbonate slurry was extracted from the reactor, washed, and dried to obtain aluminum-doped small-particle cobalt carbonate.
[0020] As shown in Figures 1-3, the tap density of the aluminum-doped small-particle cobalt carbonate obtained in Example 1 is 1.87 g / cm³. 3 Figure 1 is a scanning electron microscope (SEM) image of the aluminum-doped cobalt carbonate seed crystals prepared in step C of Example 1. It can be seen from the figure that the cobalt carbonate particles have good sphericity, and the particle surface is a blocky accumulation of small particles. The accumulation is tight, the surface is round and dense, the pores are small, and there is no micro powder present. Figure 2 is a scanning electron microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate prepared in step D of Example 1. It can be seen from the figure that dense and regular thin-plate-like primary particles are uniformly attached to the surface of the aluminum-doped small-particle cobalt carbonate matrix, forming a surface modification structure. Figure 3 is a scanning electron microscope (SEM) image of the aluminum-doped small-particle cobalt carbonate prepared in Example 1. It can be observed from the figure that the primary particles of the final product have a relatively regular thin-plate-like structure, and are evenly and densely distributed. The overall particles are spherical, with a smooth surface, high crystallinity, and stable structure, showing excellent morphology control effect.
[0021] Example 2: A method for preparing aluminum-doped small-particle cobalt carbonate. CoCl2 is prepared into a CoCl2 solution with a cobalt ion concentration of 140 g / L. Al2(SO4)3·18H2O crystals are added to the CoCl2 solution and stirred until homogeneous to prepare a cobalt-aluminum mixed solution. The aluminum to cobalt ratio in the cobalt-aluminum mixed solution is 0.0139 wt%. 50% of a 150 g / L NH4HCO3 solution is added to a reactor as the base solution. The reactor is heated, and the stirring speed is set to 400 r / min to allow the NH4HCO3 in the base solution to dissolve. The HCO3 solution was heated to 40℃. The prepared cobalt-aluminum mixed solution was added to the reactor at a rate of 4% / h of the reactor volume. NH4HCO3 solution with a concentration of 260 g / L was also added to the reactor to bring the pH of the solution to 7.4. The particle size growth rate was controlled at 0.06 μm / h until the D50 of the aluminum-doped cobalt carbonate particles reached a minimum of 3.7 μm and a maximum of 3.8 μm. At this point, the addition of the cobalt-aluminum mixed solution and NH4HCO3 solution was stopped, and the synthesis temperature was increased to 50℃ over 60 min. After heating, the mixture was continuously stirred at high speed for 2 h.
[0022] After stirring, a 260 g / L NH4HCO3 solution was added to the reactor to bring the pH of the solution to 7.8. The stirring speed was reduced to 300 r / min, and a cobalt-aluminum mixed solution was added to the reactor at a rate of 4% of the reactor volume per hour to allow the reaction to continue. The particle size increase rate was controlled at 0.08 μm / h until the D50 of the aluminum-doped cobalt carbonate reached a minimum of 4.0 μm and a maximum of 4.5 μm. At this point, the stirring speed was reduced to 250 r / min, the flow rate of the cobalt-aluminum mixed solution into the reactor was reduced to 2% / h, and the synthesis temperature was lowered to 45℃ over 60 minutes. This was achieved by adjusting the NH4HCO3 concentration. The flow rate of O3 solution was maintained at a pH of 7.8 in the reactor, and the particle size growth rate was controlled at 0.02 μm / h to further optimize the thermodynamic and kinetic environment for the growth of aluminum-doped cobalt carbonate crystals. This prevented the formation of fine particles and allowed the thin-film aluminum-doped cobalt carbonate particles to gradually expand two-dimensionally along the axial direction, forming a uniform and dense nanosheet structure. This promoted the uniform growth and densification of the crystals. The reaction continued until the particle size D50 of the aluminum-doped cobalt carbonate reached a minimum of 4.0 μm and a maximum of 5.0 μm. The reaction was then terminated to obtain an aluminum-doped cobalt carbonate slurry. The aluminum-doped cobalt carbonate slurry prepared in the reactor was extracted, washed, and dried to obtain aluminum-doped small-particle cobalt carbonate.
[0023] As shown in Figure 4, the tap density of aluminum-doped small-particle cobalt carbonate is 1.92 g / cm³. 3 Figure 4 shows the distribution of Al in the aluminum-doped small-particle cobalt carbonate prepared in Example 2. It can be seen from the figure that the Al element is evenly distributed and there is no obvious enrichment phenomenon, indicating that the aluminum element can stably enter the cobalt carbonate lattice during the synthesis process, achieving a good doping effect.
[0024] Comparative Example 1: A CoCl2 solution with a cobalt ion concentration of 140 g / L was prepared. Al2(SO4)3·18H2O crystals were added to the CoCl2 solution and stirred until homogeneous to prepare a cobalt-aluminum mixed solution with an aluminum to cobalt ratio of 0.0139 wt%. A 50% solution of NH4HCO3 with a concentration of 170 g / L was added to the reactor as the base solution. The reactor was heated, and the stirring speed was set to 400 r / m. The bottom solution of NH4HCO3 was heated to 40℃. The prepared cobalt-aluminum mixed solution was added to the reactor at a rate of 4% / h of the reactor volume. NH4HCO3 solution with a concentration of 260 g / L was also added to the reactor to make the pH of the solution in the reactor 7.4. The particle size growth rate was controlled at 0.06 μm / h until the particle size D50 of the aluminum-doped cobalt carbonate reached a minimum of 4.0 μm and a maximum of 5.0 μm. At this point, the reaction was stopped, and small-particle aluminum-doped cobalt carbonate was obtained.
[0025] As shown in Figure 5, the tap density of aluminum-doped small-particle cobalt carbonate is 1.74 g / cm³. 3 Figure 5 shows a microscopic (SEM) image of the aluminum-doped cobalt carbonate prepared in Comparative Example 1. It can be seen from the figure that aluminum elements on the surface of cobalt carbonate particles undergo hydrolysis and recrystallization, precipitating in an irregular sheet-like structure with obvious enrichment, resulting in poor aluminum doping effect and affecting the cycling performance of aluminum-doped cobalt carbonate.
Claims
1. A method for preparing aluminum-doped small-particle cobalt carbonate, characterized in that, The process includes the following steps: A. Mixing cobalt salt solution and soluble aluminum salt solution evenly to prepare a cobalt-aluminum mixed solution with a cobalt ion concentration of 100-140 g / L, wherein the aluminum to cobalt ratio in the cobalt-aluminum mixed solution is 0.0055-0.0181 wt%; B. Adding an NH4HCO3 solution with a concentration of 40 g / L-150 g / L to the reactor as the base liquid, turning on the reactor heating to raise the temperature of the base liquid NH4HCO3 solution to 35℃-40℃, setting the stirring speed of the reactor to 350 r / min-400 r / min, and adding the cobalt-aluminum mixed solution to the reactor at a rate of 3%-4% of the reactor volume per hour per hour to allow the reaction to proceed. C. Add an NH4HCO3 solution with a concentration of 200 g / L to 260 g / L to the reactor in step B, so that the pH value of the solution in the reactor is 7.2 to 7.4, until the particle size D50 of aluminum-doped cobalt carbonate is 3.7 μm to 3.8 μm. Then stop adding the cobalt-aluminum mixed solution and NH4HCO3 solution, and raise the synthesis temperature to 45℃ to 50℃ within 30 min to 60 min, and continue stirring after raising the temperature. D. After stirring, add an NH4HCO3 solution with a concentration of 200 g / L to 260 g / L to the reactor in step C, and adjust the pH value of the solution in the reactor in step C to 7.6 to 7.8; E. Add a cobalt-aluminum mixed solution to the reactor in step D at a rate of 4% to 5% of the reactor volume per hour, and simultaneously add an NH4HCO3 solution with a concentration of 200 g / L to 260 g / L, keeping the pH value of the solution in the reactor stable at 7.6 to 7.8, and reduce the stirring speed of the reactor to 250 r / min to 300 r / min until the particle size D50 of the aluminum-doped cobalt carbonate is 4.0 μm to 4.5 μm; F. Reduce the stirring speed to 200 r / min to 250 r / min, reduce the flow rate of the cobalt-aluminum mixed solution into the reactor to 2% / h to 3% / h, and reduce the synthesis temperature to 42℃ to 47℃ within 30 min to 60 min. Keep the pH value of the solution in the reactor stable at 7.6 to 7.8, and continue the reaction until the particle size D50 of the aluminum-doped cobalt carbonate is 4.0 μm to 5.0 μm. Then, stop the reaction and obtain the aluminum-doped cobalt carbonate slurry. G. Extract the aluminum-doped cobalt carbonate slurry prepared in the reactor, wash and dry it to obtain aluminum-doped small-particle cobalt carbonate.
2. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 1, characterized in that: In step A, the cobalt salt is one or more of CoSO4, Co(CH3COO)2, Co(NO3)2 and CoCl2, and the soluble aluminum salt is one or more of Al2(SO4)3, Al(NO3)3 and AlCl3.
3. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 1, characterized in that: In step B, the volume of the bottom liquid NH4HCO3 solution accounts for 30% to 50% of the volume of the reactor.
4. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 1, characterized in that: In step C, the growth rate of aluminum-doped cobalt carbonate particles is controlled at 0.04 μm / h to 0.06 μm / h.
5. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 4, characterized in that: In step C, the stirring time after heating is 1 to 2 hours.
6. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 1, characterized in that: In step D, the particle size growth rate is controlled between 0.05 μm / h and 0.08 μm / h.
7. The method for preparing aluminum-doped small-particle cobalt carbonate according to claim 1, characterized in that: In step E, the growth rate of aluminum-doped cobalt carbonate particles is controlled at 0.01 μm / h to 0.02 μm / h.