Aluminum-doped large-particle spherical cobalt hydroxide as well as preparation method and application thereof

Abstract

The invention provides aluminum-doped large-particle spherical cobalt hydroxide and a preparation method and application thereof, and belongs to the technical field of lithium battery materials, and the preparation method comprises the following steps: dispersing an aluminum salt and a cobalt salt in water to obtain an aluminum-doped cobalt salt solution; adding EDTA-2Na and ascorbic acid into the first sodium hydroxide solution, uniformly stirring, and heating to 68-70 DEG C to obtain a base solution; the aluminum-doped cobalt salt solution, the second sodium hydroxide solution and the ammonia water solution are added into the base solution in a parallel flow mode according to the set feeding flow, and stirring reaction is conducted; and when the particle size D50 of the cobalt hydroxide in the base solution reaches 19-20 microns, stopping feeding, cooling to 30-35 DEG C, preserving heat, aging, filtering, washing, drying and calcining to obtain the aluminum-doped large-particle spherical cobalt hydroxide. The aluminum-doped large-particle spherical cobalt hydroxide prepared by the method is high in lattice stability, compact in structure, large in particle size, good in sphericity degree and high in tap density.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and in particular to aluminum-doped large-particle spherical cobalt hydroxide, a preparation method thereof, and applications thereof. Background Art

[0002] Cobalt hydroxide is an important precursor for lithium cobalt oxide cathode materials, which are mainly used in lithium-ion batteries, supercapacitors, and catalysts. Its structure and morphology have a significant impact on the performance of lithium cobalt oxide. With the development of lithium batteries, people have put forward higher requirements for cobalt hydroxide. Its performance is limited by the following problems: (1) low tap density, which leads to limited electrode coating thickness and insufficient volume energy density; (2) poor structural stability, which is prone to volume expansion and particle pulverization during charging and discharging, resulting in a short cycle life of lithium batteries; (3) impurity phase formation: conventional processes are prone to the formation of CoOOH or Co3O4 impurity phases, which reduces the purity of the material.

[0003] Chinese invention patent CN115849459B discloses a method for preparing cobalt hydroxide and its application, comprising reacting a cobalt solution, an alkaline solution, and an additive; the additives include ascorbic acid and hydrazine hydrate. Chinese invention patent CN118224468A discloses a method for preparing flaky cobalt hydroxide and a flaky cobalt hydroxide product, using a soluble cobalt salt as a cobalt source, sodium hydroxide as a precipitant, and ammonia water as a complexing agent. Flaky β-cobalt hydroxide is prepared by adding a certain amount of hydrazine hydrate solution during a high-speed stirring synthesis process. The cobalt hydroxides produced in the above patents are all flaky and still suffer from low tap density and poor structural stability. Summary of the Invention

[0004] In view of the technical problems existing in the background technology, the present application provides an aluminum-doped large-particle spherical cobalt hydroxide and its preparation method and application, aiming to solve the technical problems of low tap density, poor structural stability and low material purity of cobalt hydroxide.

[0005] In a first aspect, the present invention provides a method for preparing aluminum-doped large-particle spherical cobalt hydroxide, comprising the following steps: dispersing aluminum salt and cobalt salt in water to obtain an aluminum-cobalt salt solution; Add EDTA-2Na and ascorbic acid to the first sodium hydroxide solution, stir evenly, and then heat to 68-70°C to obtain a base solution; Adding the aluminum-cobalt salt solution, the second sodium hydroxide solution and the ammonia solution into the bottom liquid in parallel at a set feed flow rate, stirring for reaction; When the particle size D50 of the cobalt hydroxide in the bottom liquid reaches 19-20 μm, the addition of material is stopped, the temperature is lowered to 30-35° C. for aging, and then filtered, washed, dried and calcined to obtain aluminum-doped large-particle spherical cobalt hydroxide.

[0006] In the technical solution of the embodiment of the present application, Al is doped into cobalt hydroxide by a coprecipitation method. 3+ , which can enhance lattice stability and inhibit the structural collapse of lithium batteries during the charge and discharge cycle.

[0007] Through the EDTA-2Na complex-coprecipitation method, EDTA-2Na was used to 2+ and Al 3+ The selective complexation of aluminum doped cobalt hydroxide can delay the release rate of metal ions, control the nucleation and growth process, and realize the controllable preparation of aluminum doped large-particle spherical cobalt hydroxide. At the same time, ascorbic acid is added to the bottom solution to avoid the 2+ It is oxidized to form CoOOH or Co3O4 impurity phase, which improves the purity of the material.

[0008] Adding ammonia water during the reaction is beneficial to the reaction of ammonia ions and Co 2+ Complexation, then OH - To precipitate free Co 2+ , destroying the complex balance and causing the cobalt ammonia complex ion to gradually release Co 2+ , with OH - Precipitation controls the precipitation speed, so that the growth rate of the cobalt hydroxide precipitate crystals is greater than the nucleation speed, thereby obtaining a cobalt hydroxide precipitate with a relatively compact structure and relatively large particles.

[0009] The start-up temperature should be controlled between 68 and 70°C. After one hour of reaction, the reaction temperature should be maintained at 45 to 50°C. A higher start-up temperature can accelerate the nucleation rate and increase the number of nuclei. However, the high temperature stage should not be prolonged, as it may cause the nuclei to agglomerate due to excessive energy, resulting in a wider particle size distribution. After one to two hours of reaction, the temperature should be lowered to slow the crystal growth rate, allowing the particles to gradually become spherical through surface energy minimization.

[0010] In some embodiments, the aluminum ion concentration in the aluminum-doped cobalt salt solution is 4.2-4.4 g / L, and the aluminum salt is at least one of aluminum oxide and aluminum sulfate; The cobalt ion concentration in the aluminum-doped cobalt salt solution is 110-130 g / L, and the cobalt salt includes at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate.

[0011] In some embodiments, the pH of the first sodium hydroxide solution is 10.2-10.3.

[0012] In some embodiments, the concentration of the second sodium hydroxide solution is 3-3.5 g / L, and the concentration of the ammonia solution is 1.5-2 g / L.

[0013] In some embodiments, the feed rates of the aluminum-doped cobalt salt solution, the second sodium hydroxide solution, and the ammonia solution are 4-9 kg / h, 2-5 kg / h, and 2-3 kg / h, respectively.

[0014] In the technical solution of the embodiment of the present application, a feeding rate that is too fast will lead to a phenomenon of high local supersaturation in the reactor, and there is a risk of generating small particles. A feeding rate that is too slow will delay the reaction process and increase costs. Therefore, the second sodium hydroxide feeding rate is selected to be 2-3 kg / h, the feeding rate of the sodium hydroxide solution is selected to be 2-5 kg / h, and the feeding rate of the cobalt salt is selected to be 4-9 kg / h.

[0015] In some embodiments, the stirring reaction conditions are: stirring speed 520~550r / min, controlling the pH of the bottom liquid during the reaction to be 10.3~10.5, cooling to 45~50°C after 1~2h of reaction, and controlling the particle size growth rate to be 0.05~0.06μm / h.

[0016] In the technical scheme of the embodiment of the present application, when the pH is low during the reaction, the amount of sodium hydroxide added in the system is small, and the cobalt content in the supernatant is high, resulting in incomplete reaction, affecting the purity of the product, and increasing the processing cost of the mother water. A high pH will cause the generation rate of the crystal nucleus to be greater than the growth rate of the crystal nucleus, resulting in a large number of small crystal nuclei in the system. Therefore, the pH during the reaction is controlled to be in the range of 10.3 to 10.5.

[0017] After 1 hour of reaction, the temperature is controlled at 45~50℃. It should be noted that the temperature should not be too low, otherwise it may lead to incomplete growth, rough particle surface or the formation of flaky structure.

[0018] In some embodiments, the aging time is 5 to 7 hours, and the stirring speed during the aging process is 270 to 300 r / min.

[0019] In the technical solution of the embodiment of the present application, after stopping the reaction, the rotation speed is reduced to 270~300r / min, the temperature is slowly reduced to 30~35℃, and the mixture is kept warm for 5~7h. Reducing the stirring speed can weaken the shear force of the fluid and prevent the formed spherical particles from being broken or secondary nucleated due to violent collisions. Cooling and aging can dissolve small particles and allow large particles to continue to grow, making the particle size distribution more uniform. At the same time, the surface of the particles is rearranged through the dissolution-redeposition process, which can further improve the sphericity of the particles.

[0020] In some embodiments, the drying conditions are: drying at a temperature of 70-100° C. for 4-6 hours; The calcination conditions are: calcination at a temperature of 300~550℃ for 5~9h.

[0021] In a second aspect, an embodiment of the present application provides a large-particle spherical aluminum-doped cobalt hydroxide, which is prepared using the above method.

[0022] In a third aspect, the embodiments of the present application provide an application of aluminum-doped large-particle spherical cobalt hydroxide in the fields of lithium batteries, supercapacitors and catalysts.

[0023] Different from the existing technical solutions, the beneficial effects of this application include: The present invention prepares aluminum-doped large-particle spherical cobalt hydroxide by EDTA-2Na complex-coprecipitation method, and aluminum doping can be achieved by Al 3+ Replace Co 2+ , enhance lattice stability and inhibit structural collapse during the cycle; add ammonia water to the bottom liquid, use ammonium ions to 2+ The complexation effect gradually releases Co during the reaction. 2+ , so that the growth rate of the cobalt hydroxide precipitate crystals is greater than the nucleation rate, thereby obtaining a cobalt hydroxide precipitate with a relatively compact structure and relatively large particles; by controlling the reaction temperature and stirring speed, large-particle spherical cobalt hydroxide doped with aluminum with good sphericity is obtained, thereby improving the tap density; adding ascorbic acid to the bottom liquid can avoid oxidation to form CoOOH or Co3O4 impurities, thereby improving the purity of the material.

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0026] Figure 1 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Example 1 of the present application.

[0027] Figure 2 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Example 1 of the present application.

[0028] Figure 3 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Example 2 of this application.

[0029] Figure 4 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Example 3 of this application.

[0030] Figure 5 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Example 4 of the present application.

[0031] Figure 6 This is an SEM image of the aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Example 5 of the present application. DETAILED DESCRIPTION

[0032] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0034] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0035] 1. Preparation method Example 1 A method for preparing aluminum-doped large-particle spherical cobalt hydroxide comprises the following steps: 1. Prepare solution Preparation of Al 3+ The concentration is 4.2g / L, Co 2+ The concentration of the aluminum-doped cobalt salt solution is 110 g / L, as well as 3.0 g / L sodium hydroxide solution and 1.5 g / L ammonia solution. The above cobalt salt solution is cobalt chloride.

[0036] 2. Reaction After adding 100L of pure water to the reactor, sodium hydroxide solution was added to adjust the pH to 10.2. 7g of disodium ethylenediaminetetraacetate (EDTA-2Na) and 10g of ascorbic acid were then added. The stirring speed was set to 520r / min, and the kettle temperature was controlled at 68°C. Subsequently, aluminum-doped cobalt salt solution, sodium hydroxide solution, and ammonia solution were added to the reactor in parallel. The feed rates of cobalt salt solution, sodium hydroxide solution, and ammonia solution were 4kg / h, 2kg / h, and 2kg / h, respectively. The pH of the reaction was controlled at 10.3. After 1h of reaction, the reaction temperature was controlled at 45°C, and the particle size growth rate was controlled at 0.05-0.06μm / h. The reaction was stopped when the particle size D50 reached 19-20μm. The rotation speed was reduced to 270r / min, the temperature was slowly lowered to 35°C, and the mixture was kept warm for 5h.

[0037] 3. Washing, drying and calcining Use a centrifuge to wash with pure water, then use a flash dryer to dry for 6 hours at a temperature of 70°C, and then use a rotary kiln to calcine the synthetic product. Using a multi-stage calcination process, calcine at a temperature of 550°C for 5 to 9 hours to obtain aluminum-doped large-particle spherical cobalt hydroxide.

[0038] Example 2 A method for preparing aluminum-doped large-particle spherical cobalt hydroxide comprises the following steps: 1. Prepare solution Preparation of Al 3+ The concentration is 4.3g / L, Co 2+ The concentration of the aluminum-doped cobalt salt solution is 120 g / L, as well as 3.2 g / L sodium hydroxide solution and 1.7 g / L ammonia solution. The above cobalt salt solution is cobalt sulfate.

[0039] 2. Reaction After adding 100L of pure water to the reactor, sodium hydroxide solution was added to adjust the pH to 10.2. Then, 9g of disodium ethylenediaminetetraacetate (EDTA-2Na) and 12g of ascorbic acid were added. The stirring speed was set to 530r / min, and the kettle temperature was controlled at 69°C. After that, aluminum-doped cobalt salt solution, sodium hydroxide solution, and ammonia solution were added to the reactor in parallel. The feed rates of cobalt salt solution, sodium hydroxide solution, and ammonia solution were 6kg / h, 3kg / h, and 2.5kg / h, respectively. The pH of the reaction process was controlled at 10.4. After reacting for 1h, the reaction temperature was controlled at 47°C, and the particle size growth rate was controlled at 0.05-0.06μm / h. The reaction was stopped when the particle size D50 reached 19-20μm. The rotation speed was reduced to 300r / min, the temperature was slowly reduced to 30°C, and the mixture was kept warm for 7h.

[0040] 3. Washing, drying and calcining Use a centrifuge, wash with pure water, then use a flash dryer to dry for 4 hours at a temperature of 100°C, and then use a rotary kiln to calcine the synthetic product. Using a multi-stage calcination process, calcine at a temperature of 300°C for 5 to 9 hours to obtain large-particle spherical cobalt hydroxide doped with aluminum.

[0041] Example 3 A method for preparing aluminum-doped large-particle spherical cobalt hydroxide comprises the following steps: 1. Prepare solution Preparation of Al 3+ The concentration is 4.4g / L, Co 2+ The concentration of the aluminum-doped cobalt salt solution is 130 g / L, as well as 3.5 g / L sodium hydroxide solution and 2 g / L ammonia solution. The above cobalt salt solution is cobalt nitrate.

[0042] 2. Reaction After adding 100L of pure water to the reactor, sodium hydroxide solution was added to adjust the pH to 10.3. Then, 10g of disodium ethylenediaminetetraacetate (EDTA-2Na) and 13g of ascorbic acid were added. The stirring speed was set to 550r / min and the kettle temperature was controlled at 70°C. After that, aluminum-doped cobalt salt solution, sodium hydroxide solution and ammonia solution were added to the reactor in parallel. The feed rates of cobalt salt solution, sodium hydroxide solution and ammonia solution were 9kg / h, 5kg / h and 3kg / h, respectively. The pH of the reaction process was controlled at 10.5. After reacting for 1h, the reaction temperature was controlled at 50°C and the particle size growth rate was controlled at 0.05-0.06μm / h. The reaction was stopped when the particle size D50 reached 19-20μm. The rotation speed was reduced to 270r / min, the temperature was slowly reduced to 35°C, and the mixture was kept warm for 5h.

[0043] 3. Washing, drying and calcining Use a centrifuge to wash with pure water, then use a flash dryer to dry for 6 hours at a temperature of 70°C, and then use a rotary kiln to calcine the synthetic product. Using a multi-stage calcination process, calcine at a temperature of 550°C for 5 to 9 hours to obtain aluminum-doped large-particle spherical cobalt hydroxide.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that EDTA-2Na is not added.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no ascorbic acid is added.

[0046] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that no ammonia water is added.

[0047] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the reaction temperature and the reaction temperature are both 70°C. Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that after stopping the reaction, the mixture is kept warm at 45° C. for 5 hours.

[0048] 2. Test Method 1. Particle size D50 detection method: Malvern 3000 particle size analyzer is used to detect particle size D50.

[0049] 2. Tap density detection method: Use a tap density meter for detection.

[0050] 3. Analysis of test results of various embodiments and comparative examples (1) SEM scanning was performed on the aluminum-doped large-particle spherical cobalt hydroxide prepared in Example 1 and Comparative Examples 1 to 5 to obtain Figures 1 to 6 .from Figure 1 As can be seen from the figure, the aluminum-doped large-particle spherical cobalt hydroxide prepared by the method of Example 1 has good sphericity. The aluminum-doped large-particle spherical cobalt hydroxide prepared in Comparative Examples 1 and 2 has poor sphericity, indicating that EDTA-2Na and ascorbic acid are beneficial for controlling the nucleation and growth of cobalt hydroxide.

[0051] No ammonia was added in Comparative Example 3. Figure 4 As shown, the obtained cobalt hydroxide crystals are excessively nucleated and cannot form a relatively regular spherical shape.

[0052] In Comparative Example 4, the temperature remained unchanged during the reaction. Figure 5 As shown, the cobalt hydroxide nuclei agglomerated due to excessively high energy, resulting in a wide particle size distribution of the obtained cobalt hydroxide crystals.

[0053] In Comparative Example 5, the temperature during the aging process was too high. Figure 6 As shown, the particle size distribution of the prepared cobalt hydroxide crystals is relatively wide.

[0054] (2) The particle size D50 and tap density of the large-particle spherical cobalt hydroxide prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested. The test results are shown in Table 1 below.

[0055] Table 1 Particle size and tap density test data of cobalt hydroxide in various examples and comparative examples

[0056] As can be seen from the data in Table 1, the aluminum-doped large-particle spherical cobalt hydroxide prepared in Examples 1 to 3 has a large particle size and a high tap density. The aluminum-doped large-particle spherical cobalt hydroxide in Comparative Examples 1 to 5 has a reduced particle size and tap density, indicating that under the action of EDTA-2Na and ammonia water, temperature control during the synergistic reaction process can produce aluminum-doped large-particle spherical cobalt hydroxide with a large particle size and a narrow particle size distribution.

[0057] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing aluminum-doped large-particle spherical cobalt hydroxide, characterized in that: The steps include: dispersing aluminum salt and cobalt salt in water to obtain an aluminum-cobalt salt solution; Add EDTA-2Na and ascorbic acid to the first sodium hydroxide solution, stir evenly, and then heat to 68-70°C to obtain a base solution; The aluminum-doped cobalt salt solution, the second sodium hydroxide solution and the ammonia solution are added to the bottom liquid in parallel at a set feed flow rate, and stirred for reaction; When the particle size D50 of the cobalt hydroxide in the bottom solution reaches 19-20 μm, the addition of the material is stopped, the temperature is lowered to 30-35° C. for aging, and then filtered, washed, dried and calcined to obtain aluminum-doped large-particle spherical cobalt hydroxide.

2. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The aluminum ion concentration in the aluminum-doped cobalt salt solution is 4.2-4.4 g / L, and the aluminum salt is at least one of aluminum oxide and aluminum sulfate; The cobalt ion concentration in the aluminum-doped cobalt salt solution is 110-130 g / L, and the cobalt salt includes at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate.

3. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The pH of the first sodium hydroxide solution is 10.2-10.

3.

4. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The concentration of the second sodium hydroxide solution is 3-3.5 g / L, and the concentration of the ammonia solution is 1.5-2 g / L.

5. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The feed flow rates of the aluminum-doped cobalt salt solution, the second sodium hydroxide solution and the ammonia solution are 4-9 kg / h, 2-5 kg / h and 2-3 kg / h respectively.

6. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The stirring reaction conditions are as follows: stirring speed of 520-550 r / min, controlling the pH of the bottom liquid to 10.3-10.5 during the reaction, cooling to 45-50° C. after 1-2 hours of reaction, and controlling the particle size growth rate to 0.05-0.06 μm / h.

7. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The aging time is 5-7 hours, and the stirring speed during the aging process is 270-300 r / min.

8. The method for preparing aluminum-doped large-particle spherical cobalt hydroxide according to claim 1, characterized in that: The drying conditions are: drying at a temperature of 70-100°C for 4-6 hours; The calcination conditions are: calcining at a temperature of 300-550° C. for 5-9 hours.

9. A large-particle spherical aluminum-doped cobalt hydroxide, characterized in that: The method is as described in any one of claims 1 to 8.

10. Use of the aluminum-doped large-particle spherical cobalt hydroxide as claimed in claim 9 in the fields of lithium batteries, supercapacitors and catalysts.

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