Preparation method of single crystal lamellar aluminum-doped cobalt carbonate

Abstract

The invention provides a preparation method of single-crystal lamellar aluminum-doped cobalt carbonate, which comprises the following steps: preparing lamellar aluminum-doped cobalt carbonate particles by using cobalt salt, ammonium bicarbonate and a dopant as raw materials through a liquid phase precipitation method, and sequentially comprises a low-temperature high-pH-value nucleation stage, a high-temperature high-pH-value nucleation stage, a high-temperature high-pH-value nucleation stage, a high-temperature high-pH-value nucleation stage and a high-temperature high-pH-value nucleation stage, the aluminum-doped cobalt carbonate is prepared in the high-temperature large-flow crystal nucleus growth and aging stage, the aluminum-doped cobalt carbonate is a flaky primary particle aggregate, primary particles are compact and uniform in size, the material structure is beneficial to impurity element desorption and dehydration performance improvement in the washing stage, the product drying efficiency is improved, and the product quality is improved. And drying and crushing to obtain the single crystal lamellar aluminum-doped cobalt carbonate. The method disclosed by the invention has the advantages of simplicity in operation, high production efficiency, no need of a dispersing agent, high washing efficiency and the like, the prepared single-crystal lamellar aluminum-doped cobalt carbonate takes the doped aluminum element as an inducer to realize high selectivity and accuracy of a material deposition crystal face, cobalt and the aluminum element form a solid solution, the aluminum is uniformly dispersed in cobalt carbonate precipitate, and the crystal surface of the single-crystal lamellar aluminum-doped cobalt carbonate is prepared. The particle size is nanoscale, the surface is smooth, flat and compact, the thickness is uniform, and the application potential of the cobalt carbonate nano material is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery material preparation, and in particular to a method for preparing single crystal crystalline aluminum-doped cobalt carbonate. Background Art

[0002] As the world's demand for new energy continues to increase, lithium-ion batteries (LIBs) have also been widely studied and used due to their excellent performance (high energy density, high power density, long cycle life, excellent safety performance, etc.), especially in the fields of mobile phones, tablets, drones, electric vehicles and fixed energy storage. At the same time, there is an urgent need to develop (LIBs) with higher energy density and longer cycle life. By increasing the charging cut-off voltage of lithium-ion battery materials (LIBs), more lithium ions are allowed to participate in charging and discharging to increase the specific capacity. With the increase of the high charging cut-off voltage (4.5V or above), the amount of lithium removed from the battery material increases, and more active Li + Participating in the deintercalation process significantly improves the actual gram capacity of the material. However, at the same time, high operating voltage will cause irreversible phase transitions in the material structure and increase the number of interface side reactions, leading to reduced material performance and battery capacity attenuation. In order to solve the above problems, researchers have proposed various modification strategies, mainly including surface coating, intracrystalline doping and crystal morphology control.

[0003] At present, the industry often uses thin-flaked cobalt hydroxide as a coating agent for positive electrode materials of lithium-ion batteries. However, in the preparation process of flaky cobalt hydroxide materials, there are problems such as particle agglomeration, high impurity elements, and material oxidation. On the one hand, when the particle size D50 of cobalt hydroxide reaches below 1μm, the particle surface energy is high and unstable, and it is easy to spontaneously agglomerate. The impurity removal efficiency is low during washing, a large amount of wastewater is generated, and the energy consumption is high and the production efficiency is low; in addition, the one-step precipitation method is adopted without adding any additives. In addition to the inability to effectively control the particle size and morphology of the crystals, the particles are irregular, and the product is very easy to oxidize and deteriorate during the drying, crushing, screening and other processing procedures, resulting in impure product purity and the presence of impurities in the phase analysis, which is difficult to meet the actual application of the material in the battery industry.

[0004] Therefore, how to safely and economically prepare coating materials with large specific surface area, good fluidity, strong dispersibility and excellent processing performance has become an urgent problem that needs to be solved. Solving this problem will help further improve the performance of lithium-ion batteries and promote their application and development in the field of new energy. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a monocrystalline aluminum-doped cobalt carbonate. The monocrystalline aluminum-doped cobalt carbonate prepared by the method realizes the formation of a solid solution between cobalt and aluminum elements, and aluminum is uniformly dispersed in the cobalt carbonate precipitate. The particle size is nanometer-level, the surface is smooth, flat and dense, and the thickness is uniform. The particle can be embedded in the surface defects of the positive electrode material, is not easy to fall off after coating, and the coating is stable. After coating, the rate performance of the material can be improved, and the electrolyte is prevented from passing through the surface defects and generating side reactions with the positive electrode material. At the same time, the utilization efficiency of the precipitant is improved through the control of the reaction process, the pH value of the reaction system is stabilized, the metal oxidation in the reaction process is prevented, and the difficulty of wastewater treatment is reduced.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention uses aluminum doping as an inducing agent and staged process dynamic adjustment to achieve high selectivity and accuracy of the material deposition crystal surface, realizes the formation of a solid solution of cobalt and aluminum elements, and aluminum is evenly dispersed in the cobalt carbonate precipitate. The particles are single crystal nanosheets with a smooth, flat and dense surface and uniform thickness. Specifically, the following steps are included: (1) Raw material preparation: preparing a first cobalt salt solution containing aluminum ions and cobalt ions, wherein the concentration of cobalt ions is 120-160 g / L and the concentration of aluminum ions is 0.33-1.76 g / L; preparing a second cobalt salt solution containing aluminum ions and cobalt ions, wherein the concentration of cobalt ions is 80-140 g / L and the concentration of aluminum ions is 0.22-1.55 g / L; preparing a first ammonium bicarbonate solution with a concentration of 150-220 g / L and a second ammonium bicarbonate solution with a concentration of 200-280 g / L; The cobalt salt is at least one of cobalt sulfate, cobalt acetate, cobalt nitrate and cobalt chloride; the first cobalt salt solution and the second cobalt salt solution contain M Co / M Al consistent; the mass concentration of cobalt in the first cobalt salt solution is greater than the mass concentration of cobalt in the second cobalt salt solution.

[0007] (2) Nucleation stage: Add the second ammonium bicarbonate solution as the base liquid into the reactor, heat the base liquid and start stirring the reactor, add the first cobalt salt solution into the base liquid until nucleation is completed; the temperature of the reaction system is controlled at 30-40°C, and the pH value is controlled at 7.8-8.6; the stirring speed is 800-1000 r / min; when the pH value of the reaction system is ≤7.8, the nucleation stage is completed and the crystal nucleus growth stage is entered.

[0008] The volume of the bottom liquid is 15-40% of the volume of the reactor; the first cobalt salt solution is added separately, and the rate of adding the cobalt salt solution per hour is 2%-8% of the volume of the reactor.

[0009] (3) Crystal nucleus growth stage: the second cobalt salt solution and the first ammonium bicarbonate solution are added to the reaction system of step (2) at the same time, and CO2 gas is introduced in this stage until the crystal nucleus growth is completed; the temperature of the reaction system is controlled at 40-65°C, the pH value is controlled at 7.1-7.8, and the stirring speed is 600-800 r / min; when the particle size D50 of the flaky aluminum-doped cobalt carbonate in the reaction system reaches 2.0-4.0 μm, the crystal nucleus growth stage ends and enters the aging stage; The first ammonium bicarbonate solution and the second cobalt salt solution are added simultaneously, the flow rate of the ammonium bicarbonate solution is adjusted according to the synthetic pH value, the second cobalt salt solution is added at a rate of 10%-20% of the volume of the reactor per hour, and the CO2 gas introduction rate in the reactor is 1L / h-60L / h.

[0010] (4) Aging stage: stop adding liquid to the reaction system in step (3), increase the temperature of the reaction system, and reduce the stirring speed to promote the densification of the aluminum-doped cobalt carbonate particles; the temperature of the reaction system is controlled at 55-75° C., the stirring speed is 200-400 r / min, and the aging time is 30 min-60 min.

[0011] (5) Post-processing stage: The slurry of step (4) is washed, dried and crushed to obtain single crystal crystalline aluminum-doped cobalt carbonate.

[0012] The washing equipment is a centrifuge, the filter cloth specification is 8000 mesh filter cloth, the washing liquid is deionized water with a temperature of 60~90℃, and the moisture content of the cobalt carbonate filter cake after washing is ≤12%.

[0013] The drying equipment is at least one of a blast drying oven or a flash dryer, the drying temperature is 100-280°C, and the moisture content of the material after drying is ≤1.0%.

[0014] The crushing equipment is air flow crushing, and the crushing gas pressure is 0.8~1.2MPa.

[0015] The obtained single crystal aluminum-doped cobalt carbonate has the following indexes: D50<1μm, D99<2.5μm, 20nm≤d 片层厚度 ≤80nm, the mass fraction of aluminum in cobalt carbonate is 0.13~0.54%, BET≥15m 2 / g.

[0016] The present invention has the following advantages and beneficial effects: 1. The present invention uses doped aluminum as an inducing agent, maintains a relatively low temperature of 30° C. to 40° C. in the nucleation stage, maintains a pH value of 7.8 to 8.6, and simultaneously adds a high-concentration cobalt salt solution of 120 to 160 g / L. Homogeneous nucleation occurs at a relatively high supersaturation, forming a large number of nuclei, slowing down the precipitation rate of aluminum, and allowing aluminum to be doped in the cobalt carbonate in the form of amorphous aluminum carbonate, which not only promotes the growth of cobalt carbonate crystals, but also changes its growth habit, thereby reducing the surface energy of the (110) crystal plane. In this way, the driving force required for the newly generated (110) plane of the same area is smaller than that for the (001) plane, thereby causing the expansion rate of the (110) crystal plane to be significantly faster, achieving epitaxial growth of the dominant crystal plane, and aluminum-doped cobalt carbonate particles tend to form regular lamellar particles, and the lamellar thickness does not increase during the crystal growth process, and the particles grow into lamellar primary particle agglomerates, and the primary particles are dense and uniform in size.

[0017] 2. During the crystal nucleus growth stage, CO2 gas is introduced into the reactor until the crystal nucleus growth is completed. From the chemical formula, it can be seen that the introduction of CO2 at this stage is conducive to the negative reaction of formula (2), while promoting the positive reaction of formula (1), improving the utilization efficiency of the precipitant, and stabilizing the pH value of the reaction system. 2+ It complexes with NH3 to form soluble [Co(NH3) n ] 2+ Complex ion, [Co(NH3) n ] 2+ It is easily oxidized to [Co(NH3) n ] 3+ The dissociation equilibrium constant of the trivalent cobalt ammine complex is 10 -35.2 , it is extremely stable. The introduction of CO2 can effectively prevent the oxidation of cobalt in the cobalt-ammine complex during the reaction process. Since the dissociation equilibrium constant of the divalent cobalt-ammine complex is 10 -5.11 , which is beneficial to the reaction process Co 2+ The cobalt is decomplexed and released slowly, which improves the precipitation efficiency of cobalt. The cobalt content in the mother liquor is less than 0.04g / L, which reduces the difficulty of wastewater treatment and saves the cost of wastewater treatment.

[0018] 3. The aluminum-doped cobalt carbonate prepared in the synthesis stage is a flaky primary particle agglomerate. The primary particles are dense and uniform in size. The particle size D50 is in the range of 2.0~4.0μm, which is much larger than the particle size of conventional nanomaterials. At this time, the material structure is conducive to the desorption of impurity elements and the improvement of dehydration performance in the washing stage. The moisture content of the cobalt carbonate filter cake after washing is ≤12%, and the efficiency of the drying process is improved.

[0019] 4. The prepared single-crystal aluminum-doped cobalt carbonate realizes the formation of a solid solution between cobalt and aluminum elements. Aluminum is evenly dispersed in the cobalt carbonate precipitate. The particle size is nanometer-scale, the surface is smooth, flat and dense, and the thickness is uniform. It can be embedded in the surface defects of the positive electrode material. It is not easy to fall off after coating and the coating is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope (SEM) image of the cobalt-doped aluminum carbonate after drying during the process of preparing the single crystal crystalline cobalt-doped aluminum carbonate in Example 1.

[0021] Figure 2 This is a particle size distribution diagram of the aluminum-doped cobalt carbonate after aging in the process of preparing the single crystal aluminum-doped cobalt carbonate in Example 1.

[0022] Figure 3 This is a scanning electron microscope (SEM) image of the single crystal crystalline cobalt doped with aluminum carbonate prepared in Example 1.

[0023] Figure 4 This is the diffraction pattern of the single crystal crystalline aluminum-doped cobalt carbonate obtained in Example 2.

[0024] Figure 5 This is the particle size distribution diagram of the single crystal aluminum-doped cobalt carbonate prepared in Example 2.

[0025] Figure 6 This is a scanning electron microscope (SEM) image of cobalt carbonate after aging during the process of preparing single-crystal aluminum-doped cobalt carbonate in Comparative Example 1. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present invention, the present invention is described more comprehensively below in conjunction with the examples and the accompanying drawings. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. After reading the relevant contents of the present invention, various modifications of equivalent forms applied by researchers related to the field all belong to the scope defined by the appended claims of this application, and the illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1 A cobalt chloride solution with a cobalt ion concentration of 120 g / L was prepared, aluminum sulfate was added, and the aluminum content was adjusted to 0.33 g / L to obtain a first cobalt salt solution; a cobalt chloride solution with a cobalt ion concentration of 80 g / L was prepared, aluminum sulfate was added, and the aluminum content was adjusted to 0.22 g / L to obtain a second cobalt salt solution. A first ammonium bicarbonate solution with a concentration of 220 g / L and a second ammonium bicarbonate solution with a concentration of 280 g / L were prepared as auxiliary materials.

[0028] Add the prepared second ammonium bicarbonate solution as the bottom liquid to the reactor, the amount of the bottom liquid added is 15% of the volume of the reactor, heat the bottom liquid, start the reactor stirring, the stirring speed is 1000r / min, when the bottom liquid temperature reaches 40°C, add the prepared first cobalt salt solution to the reactor, the rate of adding cobalt salt solution per hour is 8% of the volume of the reactor and remains stable, when the pH of the reaction system is reduced to 7.8, the nucleation stage is completed, and the crystal nucleus growth stage is entered, the stirring speed is adjusted to 800r / min, and the reaction temperature is 65°C , add the first ammonium bicarbonate solution and the second cobalt salt solution into the reactor in parallel, the second cobalt salt solution is added at a rate of 20% of the volume of the reactor per hour, CO2 gas is introduced into the reactor at a rate of 60L / h, the pH value is stabilized at 7.2±0.1, the flow rate of ammonium bicarbonate solution is adjusted according to the synthetic pH value, when the particle size D50 of aluminum-doped cobalt carbonate reaches 2.0~4.0μm, the crystal nucleus growth stage ends, the temperature of the reaction system rises to 75℃ in the aging stage, the stirring speed is 400r / min, and the aging time is 30min.

[0029] The aluminum-doped cobalt carbonate slurry was put into a centrifuge for filtration and washing. The filter cloth of the centrifuge was 8000 mesh. The temperature of the deionized water for washing was 90°C. The moisture content of the washed cobalt carbonate filter cake was ≤12%. The washed aluminum-doped cobalt carbonate wet residue was placed in a blast drying oven for drying. The drying temperature was 100°C. The drying was completed when the moisture content of the material was ≤1.0%. The dried aluminum-doped cobalt carbonate was crushed in an air flow crusher with a crushing pressure of 1.2 MPa. Finally, single-crystal aluminum-doped cobalt carbonate was obtained. The specific surface area of ​​the single-crystal aluminum-doped cobalt carbonate was 22.3 m 2 / g, particle size D50: 0.880μm, D99: 1.364μm, 20nm≤d 片层厚度 ≤80nm.

[0030] Figure 1 This is a scanning electron microscope (SEM) image of the aluminum-doped cobalt carbonate after drying in the process of preparing the single-crystal aluminum-doped cobalt carbonate in Example 1. It can be seen from the image that the aluminum-doped cobalt carbonate has good morphology uniformity and no fine powder exists. The particles are flaky agglomerates, and the primary particles are dense and smooth. Figure 2 The particle size distribution diagram of the aluminum-doped cobalt carbonate after aging in the process of preparing the single-crystal aluminum-doped cobalt carbonate in Example 1. It can be seen from the figure that the aluminum-doped cobalt carbonate at this stage has a larger particle size and better particle size distribution consistency, wherein the particle size D50: 2.862μm, D99: 4.769μm, and the particle size distribution of the aluminum-doped cobalt carbonate at this stage effectively reduces the difficulty of washing and drying processes. Figure 3 This is a scanning electron microscope (SEM) image of the single-crystal aluminum-doped cobalt carbonate prepared in Example 1. It can be seen from the image that the aluminum-doped cobalt carbonate particles have a single-crystal morphology and a large specific surface area.

[0031] Example 2 A cobalt chloride solution with a cobalt ion concentration of 160 g / L was prepared, and aluminum sulfate was added to adjust the aluminum content to 1.76 g / L to obtain a first cobalt salt solution; a cobalt chloride solution with a cobalt ion concentration of 140 g / L was prepared, and aluminum sulfate was added to adjust the aluminum content to 1.55 g / L to obtain a second cobalt salt solution. A first ammonium bicarbonate solution with a concentration of 150 g / L and a second ammonium bicarbonate solution with a concentration of 200 g / L were prepared as auxiliary materials.

[0032] Add the prepared second ammonium bicarbonate solution as the bottom liquid to the reactor, the amount of the bottom liquid added is 40% of the volume of the reactor, heat the bottom liquid, start the reactor stirring, the stirring speed is 800r / min, when the bottom liquid temperature reaches 30°C, add the prepared first cobalt salt solution to the reactor, the rate of adding the cobalt salt solution per hour is 2% of the volume of the reactor and remains stable, when the pH of the reaction system is reduced to 7.8, the nucleation stage is completed, and the crystal nucleus growth stage is entered, the stirring speed is adjusted to 600r / min, the reaction temperature is 4 0℃, add the first ammonium bicarbonate solution and the second cobalt salt solution into the reactor in parallel, the second cobalt salt solution is added at a rate of 10% of the volume of the reactor per hour, CO2 gas is introduced into the reactor at a rate of 1L / h, the pH value is stabilized at 7.7±0.1, the flow rate of ammonium bicarbonate solution is adjusted according to the synthetic pH value, when the particle size D50 of aluminum-doped cobalt carbonate reaches 2.0~4.0μm, the crystal nucleus growth stage ends, the temperature of the reaction system rises to 55℃, the stirring speed is 400r / min, and the aging time is 60min.

[0033] The aluminum-doped cobalt carbonate slurry was put into a centrifuge for filtration and washing. The filter cloth of the centrifuge was 8000 mesh. The temperature of the deionized water for washing was 60°C. The moisture content of the aluminum-doped cobalt carbonate filter cake after washing was ≤12%. The washed aluminum-doped cobalt carbonate wet residue was placed in a blast drying oven for drying at a drying temperature of 280°C. The drying was completed when the moisture content of the material was ≤1.0%. The dried aluminum-doped cobalt carbonate was crushed in an air flow crusher at a crushing pressure of 0.8 MPa. Finally, a single crystal aluminum-doped cobalt carbonate was obtained. The specific surface area of ​​the single crystal aluminum-doped cobalt carbonate was 24.6 m 2 / g, particle size D50: 0.892μm, D99: 1.727μm, 20nm≤d 片层厚度 ≤80nm.

[0034] Figure 4 This is the diffraction pattern of the single crystal aluminum-doped cobalt carbonate prepared in Example 2. From the XRD pattern, it can be seen that there is no obvious change in the peak intensity and the peak position, indicating that all aluminum ions have entered the cobalt carbonate lattice without changing its crystal structure or agglomerating to form a new phase. Figure 5 This is a particle size distribution diagram of the single crystal crystalline aluminum-doped cobalt carbonate prepared in Example 2. It can be seen from the figure that the single crystal crystalline aluminum-doped cobalt carbonate is evenly distributed, has a small particle size span, and has good controllability.

[0035] Comparative Example 1 The first cobalt salt solution was prepared with a cobalt ion concentration of 120 g / L; the second cobalt salt solution was prepared with a cobalt ion concentration of 80 g / L, and aluminum ions were not added to the first and second cobalt salt solutions. A first ammonium bicarbonate solution with a concentration of 220 g / L and a second ammonium bicarbonate solution with a concentration of 280 g / L were prepared as auxiliary materials.

[0036] Add the prepared second ammonium bicarbonate solution as the bottom liquid to the reactor, the amount of the bottom liquid added is 15% of the volume of the reactor, heat the bottom liquid, start the reactor stirring, the stirring speed is 1000r / min, when the bottom liquid temperature reaches 40°C, add the prepared first cobalt salt solution to the reactor, the rate of adding the cobalt salt solution per hour is 8% of the volume of the reactor and remains stable, when the pH of the reaction system is reduced to 7.8, the nucleation stage is completed, and the crystal nucleus growth stage is entered, the stirring speed is adjusted to 800r / min, and the reaction temperature is 40°C, add the first ammonium bicarbonate solution and the second cobalt salt solution into the reactor in parallel, the second cobalt salt solution is added at a rate of 8% of the volume of the reactor per hour, CO2 gas is introduced into the reactor at a rate of 60L / h, the pH value is stabilized at 7.2±0.1, the flow rate of ammonium bicarbonate solution is adjusted according to the synthetic pH value, when the cobalt carbonate particle size D50 reaches 2.0~4.0μm, the crystal nucleus growth stage ends, the temperature of the reaction system is raised to 75°C, the stirring speed is 400r / min, and the aging time is 30min.

[0037] The cobalt carbonate slurry was filtered and washed in a centrifuge. The filter cloth of the centrifuge was 8000 mesh. The temperature of the deionized water for washing was 90°C. The moisture content of the cobalt carbonate filter cake after washing was ≤12%. The wet cobalt carbonate residue after washing was placed in a blast drying oven for drying at a temperature of 100°C. The drying was completed when the moisture content of the material was ≤1.0%. The dried cobalt carbonate was crushed in an air flow crusher at a crushing pressure of 1.2MPa. Finally, cobalt carbonate was obtained. The specific surface area of ​​cobalt carbonate was 9.3 m 2 / g, particle size D50: 3.011μm, D99: 4.728μm, the particles are spherical agglomerates. Figure 6 This is a scanning electron microscope (SEM) image of cobalt carbonate after aging in the process of preparing cobalt carbonate in Comparative Example 1. It can be seen from the image that the cobalt carbonate particles are spherical agglomerates, the surface of the particles is blocky and fine accumulation, the accumulation is tight, and the pores are small.

[0038] In summary, the present invention uses cobalt salt, ammonium bicarbonate and dopant as raw materials to prepare flaky aluminum-doped cobalt carbonate particles by liquid phase precipitation method. The steps of preparing flaky aluminum-doped cobalt carbonate particles by liquid phase precipitation method include low temperature and high pH value nucleation stage, high temperature and large flow rate crystal nucleus growth and aging stage to prepare aluminum-doped cobalt carbonate. The aluminum-doped cobalt carbonate is a flaky primary particle agglomerate, the primary particles are dense and uniform in size, and the material structure is conducive to the desorption of impurity elements and the improvement of dehydration performance in the washing stage, which improves the drying efficiency of the product, and then the single-crystal aluminum-doped cobalt carbonate is obtained by drying and crushing. The method of the present invention has the advantages of simple operation, high production efficiency, no need for dispersant, high washing efficiency, etc. The prepared single-crystal aluminum-doped cobalt carbonate uses aluminum doping as an inducing agent to achieve high selectivity and accuracy of the material deposition crystal surface, realizes the formation of solid solution between cobalt and aluminum elements, and aluminum is evenly dispersed in the cobalt carbonate precipitate. The particle size is nanometer-level, the surface is smooth, flat and dense, and the thickness is uniform, which expands the application potential of cobalt carbonate nanomaterials.

Claims

1. A method for preparing a single crystal crystalline aluminum-doped cobalt carbonate, characterized in that: The following steps are involved: (1) Raw material preparation: preparing a first cobalt salt solution containing aluminum ions and cobalt ions, wherein the concentration of cobalt ions is 120-160 g / L and the concentration of aluminum ions is 0.33-1.76 g / L; preparing a second cobalt salt solution containing aluminum ions and cobalt ions, wherein the concentration of cobalt ions is 80-140 g / L and the concentration of aluminum ions is 0.22-1.55 g / L; preparing a first ammonium bicarbonate solution with a concentration of 150-220 g / L and a second ammonium bicarbonate solution with a concentration of 200-280 g / L; (2) Nucleation stage: add the second ammonium bicarbonate solution as the base liquid to the reactor, heat the base liquid and start stirring the reactor, add the first cobalt salt solution to the base liquid until nucleation is completed; the temperature of the reaction system is controlled at 30-40°C, and the pH value is controlled at 7.8-8.6; the stirring speed is 800-1000 r / min; when the pH value of the reaction system is ≤7.8, the nucleation stage is completed and the crystal nucleus growth stage is entered; (3) Crystal nucleus growth stage: the second cobalt salt solution and the first ammonium bicarbonate solution are added to the reaction system of step (2) at the same time, and CO2 gas is introduced in this stage until the crystal nucleus growth is completed; the temperature of the reaction system is controlled at 40-65°C, the pH value is controlled at 7.1-7.8, and the stirring speed is 600-800 r / min; when the particle size D50 of the flaky aluminum-doped cobalt carbonate in the reaction system reaches 2.0-4.0 μm, the crystal nucleus growth stage ends and enters the aging stage; (4) Aging stage: stop adding liquid to the reaction system in step (3), increase the temperature of the reaction system, and reduce the stirring speed to promote the densification of the aluminum-doped cobalt carbonate particles; the temperature of the reaction system is controlled at 55-75°C, the stirring speed is 200-400 r / min, and the aging time is 30 min-60 min; (5) Post-processing stage: The slurry of step (4) is washed, dried and crushed to obtain single crystal crystalline aluminum-doped cobalt carbonate.

2. The method for preparing the single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (1), the cobalt salt is at least one of cobalt sulfate, cobalt acetate, cobalt nitrate and cobalt chloride; the first cobalt salt solution and the second cobalt salt solution are Co / M Al consistent; the mass concentration of cobalt in the first cobalt salt solution is greater than the mass concentration of cobalt in the second cobalt salt solution.

3. The method for preparing the single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (2), the volume of the bottom liquid is 15-40% of the volume of the reactor; the first cobalt salt solution is added at a rate of 2%-8% of the volume of the reactor per hour.

4. The method for preparing the single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (3), the second cobalt salt solution is added at a rate of 10%-20% of the volume of the reactor per hour, the flow rate of the ammonium bicarbonate solution is adjusted according to the synthetic pH value, and the amount of CO2 gas introduced into the reactor is 1L / h-60L / h.

5. The method for preparing the single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (5), the washing equipment is a centrifuge, the filter cloth specification is 8000 mesh filter cloth, the washing liquid is deionized water at a temperature of 60-90° C., and the moisture content of the cobalt carbonate filter cake after washing is ≤12%.

6. The method for preparing the single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (5), the drying equipment is at least one of a blast drying oven or a flash dryer, the drying temperature is 100-280°C, and the moisture content of the material after drying is ≤1.0%.

7. The method for preparing single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (5), in said step (5), the crushing equipment is air flow crushing, and the crushing gas pressure is 0.8~1.2MPa.

8. The method for preparing single crystal crystalline aluminum-doped cobalt carbonate according to claim 1, characterized in that: In step (5), the single crystal crystalline aluminum-doped cobalt carbonate is obtained with the following indexes: D50<1μm, D99<2.5μm, 20nm≤d 片层厚度 ≤80nm, the mass fraction of aluminum in cobalt carbonate is 0.13~0.54%, BET≥15m 2 / g.

9. A single crystal crystalline aluminum-doped cobalt carbonate, characterized in that: A single crystal crystalline aluminum-doped cobalt carbonate prepared by the method described in any one of claims 1 to 9.

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