Methods and applications of using polyanion to promote the growth of large-particle cobalt tetroxide

Abstract

This invention discloses a method and its application for promoting the growth of large-particle cobalt tetroxide using polyanions. The method includes: continuously adding a cobalt solution containing polyanions and hydrogen peroxide, and a precipitant solution in a co-current flow to a reaction substrate for precipitation; obtaining a cobalt hydroxyl oxide slurry when the particle growth rate reaches a target range; and then demagnetizing, filtration, washing, drying, and calcining the cobalt hydroxyl oxide slurry to obtain cobalt tetroxide. This invention introduces polyanions into the synthesis process of the hydroxyl system, utilizing their charge effect to promote the directional stacking and fusion of point-like particles, accelerating particle growth and increasing density. This solves the growth bottleneck of cobalt tetroxide particles synthesized in the hydroxyl system, successfully preparing high-density, large-particle-size cobalt hydroxyl oxide and cobalt tetroxide, significantly improving the tap density of lithium cobalt oxide precursors, and thus contributing to the improvement of the energy density of lithium cobalt oxide batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material precursor technology, and in particular to a method and application of using polyanion to promote the growth of large-particle cobalt tetroxide. Background Technology

[0002] As 3C electronic products iterate towards higher energy density and faster charging, higher requirements are placed on the particle size and density of cobalt tetroxide (Co3O4), the precursor of lithium cobalt oxide (LiCoO2), for cathode materials. In the current mainstream hydroxyl-based synthesis process, the growth of Co3O4 particles faces the following significant bottlenecks: under the hydroxyl reaction environment, particles tend to form plate-like or blocky submicron structures. On the one hand, it is difficult to achieve the target size of ≥10.0μm through conventional precipitation control; on the other hand, the formation of plate-like CoOOH leads to low particle density. Currently, only carbonate systems can be used to prepare large-particle Co3O4, but the synthesis cost of large-particle Co3O4 using carbonate systems is higher. Small-sized, low-density precursors will reduce the compaction density of the electrode, limit the volumetric energy density of the battery, and affect the stability of fast-charging cycles. Therefore, these defects directly restrict the application of Co3O4 in high-end lithium cobalt oxide.

[0003] Therefore, there is an urgent need to provide a green synthesis technology that can accelerate the directional growth of particles and simultaneously improve density within a hydroxyl system, in order to meet the core requirements of 3C lithium batteries for high-performance cathode materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method and application for promoting the growth of large-particle cobalt tetroxide using polyanions, thereby solving the technical problem that the particle size and density of cobalt tetroxide particles synthesized by the hydroxyl system in the prior art need to be improved.

[0005] In a first aspect, the present invention provides a method for promoting the growth of large-particle cobalt tetroxide using polyanions, comprising the following steps: Solution preparation: Prepare the reaction base solution, a cobalt solution containing polyanion and hydrogen peroxide, and a precipitant solution; Wet synthesis: Cobalt solution containing polyanion and hydrogen peroxide and precipitant solution are continuously added to the reaction substrate in a co-current manner to carry out precipitation reaction. When the particle growth rate reaches the target range, cobalt hydroxyl oxide slurry is obtained. Post-processing: Cobalt hydroxyl oxide slurry is demagnetized, filtered, washed, dried and calcined to obtain cobalt tetroxide.

[0006] In this invention, by introducing polyanions during the synthesis of the hydroxyl system, the charge effect of these polyanions is used to promote the directional stacking and fusion of point-like particles, thereby accelerating particle growth and increasing density. This solves the growth bottleneck in the synthesis of cobalt tetroxide particles using the hydroxyl system and successfully prepares high-density, large-particle-size cobalt hydroxyl oxide and cobalt tetroxide.

[0007] Furthermore, the polyanion is at least one of fluorophosphate, fluorosilicate, vanadate, and sulfate.

[0008] Furthermore, the preparation process of the cobalt solution containing polyanion and hydrogen peroxide includes: Cobalt salts were prepared by adding water to form a cobalt solution, and then the cobalt solution was mixed with a polyanionic compound to obtain a cobalt solution containing polyanions. A cobalt solution containing polyanions is mixed with hydrogen peroxide to obtain a cobalt solution containing both polyanions and hydrogen peroxide; wherein, The cobalt salts are cobalt chloride and its hydrates; and / or, In the cobalt solution, the concentration of cobalt ions is 120-140 g / L; and / or, The polyanionic compound is at least one of sodium fluorophosphate, sodium fluorosilicate, sodium vanadate, and sodium sulfate; and / or, In cobalt solutions containing polyanions, the concentration of polyanions is 0.1 wt%–1.0 wt%; and / or, The mass fraction of hydrogen peroxide is 25%-30%; and / or, In a cobalt solution containing polyanion and hydrogen peroxide, the concentration of H2O2 is 0.06wt%-0.08wt%.

[0009] Further, the reaction substrate is a sodium hydroxide solution with a pH of 10.0-11.5; and / or, The precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-35%.

[0010] Furthermore, during the precipitation reaction, a cobalt solution containing polyanion and hydrogen peroxide and a precipitant solution are continuously added to the reaction substrate in a co-current flow. The flow rate of the cobalt solution containing polyanion and hydrogen peroxide is 130-320 L / h, and the flow rate of the precipitant solution is 60-160 L / h; and / or, A cobalt solution containing polyanions and hydrogen peroxide is pressurized and introduced into the reaction substrate along with air; the air flow rate is 130-300 L / h.

[0011] Furthermore, during the precipitation reaction, the pH value was 10.8-11.2, the reaction temperature was 65℃-78℃, and the stirring rate was 180-250 r / min.

[0012] Furthermore, the target range for particle growth rate is: particle growth rate ≤ 0.02 μm / h within 2 hours.

[0013] Furthermore, during the calcination process, the temperature is 600-660℃ and the time is 6-8 hours.

[0014] In a second aspect, the present invention provides a cobalt tetroxide, which is prepared by the method provided in the first aspect of the present invention for promoting the growth of large-particle cobalt tetroxide using polyanions.

[0015] In this invention, both cobalt hydroxyl oxide and cobalt tetroxide prepared by the above method have the characteristics of high density and large particle size.

[0016] Thirdly, the present invention provides an application of cobalt tetroxide, which is used to prepare lithium cobalt oxide cathode materials.

[0017] In this invention, the lithium cobalt oxide cathode material made from the above-mentioned cobalt tetroxide has the characteristics of large particle size and high compaction density, which is beneficial to improving the energy density of lithium cobalt oxide batteries.

[0018] Compared with the prior art, the beneficial effects of the present invention include: This invention introduces polyanions during the synthesis of the hydroxyl system, utilizing their charge effect to promote the directional stacking and fusion of dot-like particles, accelerating particle growth and increasing density. This solves the growth bottleneck of cobalt tetroxide particles synthesized in the hydroxyl system, successfully preparing high-density, large-particle-size hydroxyl cobalt oxide and cobalt tetroxide, significantly improving the tap density of lithium cobalt oxide precursors, and thus contributing to improving the energy density of lithium cobalt oxide batteries. Attached Figure Description

[0019] Figure 1 Here is an XRD image of cobalt hydroxyoxide prepared in Example 1 of this invention; Figure 2 These are SEM images of cobalt hydroxyoxide prepared in Example 1 of this invention; Figure 3 This is a SEM image of cobalt hydroxyoxide prepared in Comparative Example 1 of this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] In a first aspect, the present invention provides a method for promoting the growth of large-particle cobalt tetroxide using polyanions, comprising the following steps: S1. Solution preparation: Prepare the reaction base solution, cobalt solution containing polyanion and hydrogen peroxide, and precipitant solution; S2. Wet synthesis: Cobalt solution containing polyanion and hydrogen peroxide and precipitant solution are continuously added to the reaction substrate in a co-current manner to carry out precipitation reaction. When the particle growth rate reaches the target range, cobalt hydroxyl oxide slurry is obtained. S3. Post-processing: Cobalt hydroxyl oxide slurry is demagnetized, filtered, washed, dried and calcined to obtain cobalt tetroxide.

[0022] In this invention, by introducing polyanions during the synthesis of the hydroxyl system, their charge effect promotes the directional stacking and fusion of point-like particles, accelerating particle growth and increasing density. This solves the growth bottleneck in the synthesis of cobalt tetroxide particles using the hydroxyl system, successfully preparing high-density, large-particle-size cobalt hydroxyl oxide and cobalt tetroxide. The specific mechanism of action of the polyanions during the synthesis of the hydroxyl system includes: Charge neutralization: Polyanions adsorb onto the particle surface, neutralizing the positive charge (Co). 2+ / Co 3+ This reduces electrostatic repulsion and promotes particle collision and fusion.

[0023] Morphology control: Suppress the formation of sheet-like CoOOH (sheet-like particles have low density), guide the accumulation of dot-like particles into spherical shapes, and improve density.

[0024] Accelerated growth: By lowering the nucleation energy barrier and extending the particle growth time window, the particle size and growth rate are significantly improved.

[0025] In this invention, in step S1, the polyanion is at least one selected from fluorophosphate, fluorosilicate, vanadate, and sulfate. By selecting these specific types of polyanions, this invention enhances the surface charge stability of particles, reduces agglomeration, creates steric hindrance, inhibits the formation of plate-like particles, optimizes particle surface energy, promotes the fusion of dot-like particles, and increases the ionic strength of the solution, accelerating the precipitation reaction, thereby better accelerating particle growth and increasing density.

[0026] In this invention, in step S1, the reaction substrate is a sodium hydroxide solution with a pH value of 10.0-11.5.

[0027] In this invention, step S1, the preparation process of the cobalt solution containing polyanion and hydrogen peroxide, includes: Cobalt salts were prepared by adding water to form a cobalt solution, and then the cobalt solution was mixed with a polyanionic compound to obtain a cobalt solution containing polyanions. A cobalt solution containing polyanions is mixed with hydrogen peroxide to obtain a cobalt solution containing both polyanions and hydrogen peroxide.

[0028] Preferably, the cobalt salt includes, but is not limited to, cobalt chloride and its hydrate.

[0029] Preferably, the concentration of cobalt ions in the cobalt solution is 120-140 g / L.

[0030] Preferably, the polyanionic compound is at least one of sodium fluorophosphate, sodium fluorosilicate, sodium vanadate, and sodium sulfate.

[0031] Preferably, the concentration of polyanions in the cobalt solution containing polyanions is 0.1 wt%-1.0 wt%, and more preferably 0.5 wt%. If the concentration of polyanions is too low, it will not sufficiently promote the growth of cobalt tetroxide particles in the hydroxyl system; if the concentration of polyanions is too high, it will not only lead to a decrease in the particle size and density of cobalt hydroxyl oxide particles, but also increase the cost of raw materials and the difficulty of wastewater treatment.

[0032] Preferably, the mass fraction of hydrogen peroxide is 25%-30%.

[0033] Preferably, the concentration of H2O2 in the cobalt solution containing polyanion and hydrogen peroxide is 0.06wt%-0.08wt%.

[0034] In this invention, in step S1, the precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-35%.

[0035] In this invention, during step S2, when the cobalt solution containing polyanions and hydrogen peroxide and the precipitant solution are continuously added to the reaction substrate in a co-current manner to carry out the precipitation reaction, the flow rate of the cobalt solution containing polyanions and hydrogen peroxide is 130-320 L / h, and the flow rate of the precipitant solution is 60-160 L / h.

[0036] In this invention, in step S2, a cobalt solution containing polyanions and hydrogen peroxide is pressurized and introduced into the reaction substrate along with air.

[0037] Preferably, during the process of pressurizing and introducing the cobalt solution containing polyanion and hydrogen peroxide into the reaction substrate along with air, the air flow rate is 130-300 L / h.

[0038] In this invention, during step S2, the pH value is 10.8-11.2, the reaction temperature is 65℃-78℃, and the stirring rate is 180-250 r / min.

[0039] In this invention, in step S2, the target range for particle growth rate is: particle growth rate ≤ 0.02 μm / h within 2 hours.

[0040] In this invention, in step S3, the magnetization is reduced to ≤5ppb.

[0041] In this invention, in step S3, the washing is performed until the chloride ion concentration is ≤20ppm.

[0042] In this invention, in step S3, the product is dried until the moisture content is ≤2.0%.

[0043] In this invention, during step S3, the calcination process is carried out at a temperature of 600-660℃ for 6-8 hours.

[0044] In a second aspect, the present invention provides a cobalt tetroxide, which is prepared by the method provided in the first aspect of the present invention for promoting the growth of large-particle cobalt tetroxide using polyanions.

[0045] In this invention, both cobalt hydroxyl oxide and cobalt tetroxide prepared by the above method have the characteristics of high density and large particle size.

[0046] In this invention, the D50 particle size of the aforementioned cobalt hydroxyoxide is ≥7.0 μm, preferably ≥10.0 μm, and the tap density TD is ≥2.5 g / cm³. 3 Preferably ≥2.6 g / cm³ 3 .

[0047] In this invention, the tap density (TD) of the aforementioned cobalt tetroxide is ≥ 2.4 g / cm³. 3 Preferably ≥2.55 g / cm³ 3 .

[0048] Thirdly, the present invention provides an application of cobalt tetroxide, which is used to prepare lithium cobalt oxide cathode materials.

[0049] In this invention, the lithium cobalt oxide cathode material made from the above-mentioned cobalt tetroxide has the characteristics of large particle size and high compaction density, which is beneficial to improving the energy density of lithium cobalt oxide batteries.

[0050] Example 1 This embodiment provides a method for promoting the growth of large-particle cobalt tetroxide using polyanion, including the following steps: (1) Cobalt chloride hexahydrate was prepared into a cobalt chloride solution with water and the cobalt ion concentration was 130 g / L; sodium fluorophosphate was added to the cobalt chloride solution and the fluorophosphate ion concentration was 0.5 wt% to obtain a cobalt chloride solution containing polyanions; the cobalt chloride solution containing polyanions was mixed with hydrogen peroxide with a mass fraction of 27.5% to obtain a cobalt chloride solution containing polyanions and hydrogen peroxide with a H2O2 concentration of 0.07 wt%; sodium hydroxide was prepared into a solution with a mass fraction of 32% as a precipitant solution.

[0051] (2) Add 4 cubic meters of pure water to the reactor as bottom water, and adjust the pH of the bottom water to 11 using a 32% sodium hydroxide solution as the reaction base liquid; under the conditions of stirring speed of 220 r / min and reaction temperature of 70℃, continuously add cobalt chloride solution containing polyanions and hydrogen peroxide and precipitant solution to the reactor in a co-current manner. Air and cobalt chloride solution containing polyanions and hydrogen peroxide are pressurized and introduced into the reactor through an injector. The flow rate of the cobalt chloride solution with hydrogen peroxide was 260 L / h, the air flow rate was 200 L / h, and the flow rate of the precipitant was 60-160 L / h. During this process, the pH value was controlled to 10.8-11.2 by adjusting the flow rate of the precipitant solution. Samples were taken every 2 hours, and the particle size was measured using a laser particle size analyzer. The particle growth rate within 2 hours was calculated based on the D50 difference. When the particle growth rate gradually slowed down (≤0.02 μm / h), the valve was switched to the finished product tank. It should be noted that the above process does not require a thickener and is a continuous reaction.

[0052] (3) The material in the finished product tank is circulated and demagnetized until it is ≤5ppb. Then it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is less than 20ppm. Then it is purged with air to obtain semi-dry material with a water content of less than 2.0%. The semi-dry material is loaded into each sagger with 10kg of semi-dry material and calcined in a pusher kiln at 630℃ for 6h to obtain cobalt tetroxide finished product.

[0053] Example 2 The only difference from Example 1 is that sodium fluorophosphate is replaced with sodium fluorosilicate.

[0054] Example 3 The only difference from Example 1 is that sodium fluorophosphate is replaced with sodium vanadate.

[0055] Example 4 The only difference from Example 1 is that sodium fluorophosphate is replaced with sodium sulfate.

[0056] Example 5 This embodiment provides a method for promoting the growth of large-particle cobalt tetroxide using polyanion, including the following steps: (1) Cobalt chloride hexahydrate was prepared into a cobalt chloride solution with water and the cobalt ion concentration was 120 g / L; sodium fluorophosphate was added to the cobalt chloride solution and the fluorophosphate ion concentration was 0.1 wt% to obtain a cobalt chloride solution containing polyanions; the cobalt chloride solution containing polyanions was mixed with hydrogen peroxide with a mass fraction of 27.5% to obtain a cobalt chloride solution containing polyanions and hydrogen peroxide with a H2O2 concentration of 0.06 wt%; sodium hydroxide was prepared into a solution with a mass fraction of 30% as a precipitant solution.

[0057] (2) Add 4 cubic meters of pure water to the reactor as bottom water, and adjust the pH of the bottom water to 10 using a 30% sodium hydroxide solution as the reaction base liquid; under the conditions of stirring speed of 180 r / min and reaction temperature of 65℃, continuously add cobalt chloride solution containing polyanions and hydrogen peroxide and precipitant solution to the reactor in a co-current manner. Air and cobalt chloride solution containing polyanions and hydrogen peroxide are pressurized and introduced into the reactor through an injector. The flow rate of the cobalt chloride solution with hydrogen peroxide was 130 L / h, the air flow rate was 130 L / h, and the flow rate of the precipitant was 60-160 L / h. During this process, the pH value was controlled to 10.8-11.2 by adjusting the flow rate of the precipitant solution. Samples were taken every 2 hours, and the particle size was measured using a laser particle size analyzer. The particle growth rate within 2 hours was calculated based on the D50 difference. When the particle growth rate gradually slowed down (≤0.02 μm / h), the valve was switched to the finished product tank. It should be noted that the above process does not require a thickener and is a continuous reaction.

[0058] (3) The material in the finished product tank is circulated and demagnetized until it is ≤5ppb. Then it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is less than 20ppm. Then it is purged with air to obtain semi-dry material with a water content of less than 0.5%. The semi-dry material is loaded into each sagger with 10kg of semi-dry material and calcined in a pusher kiln at 600℃ for 6h to obtain cobalt tetroxide finished product.

[0059] Example 6 This embodiment provides a method for promoting the growth of large-particle cobalt tetroxide using polyanion, including the following steps: (1) Cobalt chloride hexahydrate was prepared into a cobalt chloride solution with water, and the cobalt ion concentration was 140 g / L; sodium fluorophosphate was added to the cobalt chloride solution, and the fluorophosphate ion concentration was 1.0 wt%, to obtain a cobalt chloride solution containing polyanions; the cobalt chloride solution containing polyanions was mixed with hydrogen peroxide with a mass fraction of 27.5% to obtain a cobalt chloride solution containing polyanions and hydrogen peroxide, and the H2O2 concentration was 0.08 wt%; sodium hydroxide was prepared into a solution with a mass fraction of 35% as a precipitant solution.

[0060] (2) Add 4 cubic meters of pure water to the reactor as bottom water, and adjust the pH of the bottom water to 11.5 using a 35% sodium hydroxide solution as the reaction base liquid; under the conditions of stirring speed of 250 r / min and reaction temperature of 78℃, continuously add cobalt chloride solution containing polyanions and hydrogen peroxide and precipitant solution to the reactor in a co-current manner. Air and cobalt chloride solution containing polyanions and hydrogen peroxide are pressurized and introduced into the reactor through an injector. The flow rate of the cobalt chloride solution containing hydrogen peroxide and hydrogen peroxide was 320 L / h, the air flow rate was 300 L / h, and the flow rate of the precipitant was 60-160 L / h. During this process, the pH value was controlled to 10.8-11.2 by adjusting the flow rate of the precipitant solution. Samples were taken every 2 hours, and the particle size was measured using a laser particle size analyzer. The particle growth rate within 2 hours was calculated based on the D50 difference. When the particle growth rate gradually slowed down (≤0.02 μm / h), the valve was switched to the finished product tank. It should be noted that the above process does not require a thickener and is a continuous reaction.

[0061] (3) The material in the finished product tank is circulated and demagnetized until it is ≤5ppb. Then it is transferred to a filter press for filter washing until the chloride ion concentration in the washing liquid is less than 20ppm. Then it is purged with air to obtain semi-dry material with a water content of less than 1%. The semi-dry material is loaded into each sagger with 10kg of semi-dry material and calcined in a pusher kiln at 660℃ for 8h to obtain cobalt tetroxide finished product.

[0062] Comparative Example 1 The only difference from Example 1 is that sodium fluorophosphate was not added.

[0063] Comparative Example 2 Compared with Comparative Example 1, the only difference is that cobalt chloride hexahydrate is replaced with cobalt sulfate heptahydrate.

[0064] Performance testing The physicochemical properties of cobalt hydroxyl oxide (semi-dry material dried in an oven) and cobalt tetroxide (i.e., finished cobalt tetroxide material) prepared in the above examples and comparative examples were tested. The test results are shown in Table 1, and the test methods are as follows: (1) Average particle size D50: tested by laser particle size analyzer method; (2) Tap density: Tested using a tap density meter; (3) The formula for calculating the growth rate increase is as follows: Growth rate increase = (particle growth rate of Comparative Example 2 or Examples 1-6 - particle growth rate of Comparative Example 1) / particle growth rate of Comparative Example 1 × 100%; In the formula, the particle growth rate of the examples or comparative examples = average particle size in Table 1 / precipitation reaction time.

[0065] Table 1

[0066] Please see Figure 1 ,pass Figure 1 It can be seen that the cobalt hydroxyoxide prepared in Example 1 of the present invention contains a small amount of cobalt tetroxide. Among the XRD diffraction peaks, the diffraction intensity corresponding to the 003 crystal plane is the highest, indicating that its main phase is the cobalt hydroxyoxide phase.

[0067] Please see Figure 2 ,pass Figure 2 As can be seen, the cobalt hydroxyoxide prepared in Example 1 of the present invention exhibits a spherical structure formed by the accumulation of dot-like particles, and has the characteristics of high density and large particle size.

[0068] Please see Figure 3 ,pass Figure 3 As can be seen, the cobalt hydroxyoxide prepared in Comparative Example 1 of this invention exhibits a spherical structure formed by the stacking of sheet-like particles, and has low density and small particle size.

[0069] Please refer to Table 1. As can be seen from Table 1, the cobalt hydroxyl oxide prepared in Examples 1-6 of this invention has a large particle size (average particle size ≥ 7.0 μm) and high density (TD ≥ 2.5 g / cm³). 3 This results in cobalt tetroxide, made from the aforementioned cobalt hydroxyl oxide, having a high density (TD≥2.4 g / cm³). 3 The large particle size of the cobalt oxide cathode material makes it have the characteristics of large particle size and high compaction density (more than 10%), which ultimately helps to improve the energy density of the cobalt oxide battery.

[0070] As can be seen from Examples 1-4, when fluorophosphate and fluorosilicate are introduced as polyanions during the synthesis of the hydroxyl system, the prepared cobalt hydroxyl oxide and cobalt tetroxide particles are larger in size and have higher density, indicating that fluorophosphate and fluorosilicate can better accelerate particle growth and improve density when the polyanions are fluorophosphate and fluorosilicate.

[0071] Examples 1, 4, and Comparative Examples 1-2 show that, in Comparative Example 1, the cobalt chloride system did not introduce polyanions, resulting in small particle size and low density of the prepared cobalt hydroxyl oxide. In Comparative Example 2, the cobalt sulfate system introduced sulfate ions, which, although also polyanions, resulted in small particle size and low density of the prepared cobalt hydroxyl oxide. In Example 4, the cobalt chloride system introduced sulfate ions as polyanions; although the particle size and density of the prepared cobalt hydroxyl oxide decreased compared to Example 1, they were still significantly better than those in Comparative Examples 1-2. These results indicate that while introducing polyanions is beneficial for improving particle size and density, their concentration should not be too high, as excessively high concentrations can lead to a significant decrease in particle size and density.

[0072] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for promoting the growth of large-particle cobalt tetroxide using polyanion polymerization, characterized in that, Includes the following steps: Solution preparation: Prepare the reaction base solution, a cobalt solution containing polyanion and hydrogen peroxide, and a precipitant solution; Wet synthesis: The cobalt solution containing polyanion and hydrogen peroxide and the precipitant solution are continuously added to the reaction substrate in a co-current manner to carry out the precipitation reaction. When the particle growth rate reaches the target range, cobalt hydroxyl oxide slurry is obtained. Post-processing: The cobalt hydroxyl oxide slurry is demagnetized, filtered, washed, dried and calcined to obtain cobalt tetroxide.

2. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, The polyanion is at least one of fluorophosphate, fluorosilicate, vanadate, and sulfate.

3. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, The preparation process of the cobalt solution containing polyanion and hydrogen peroxide includes: A cobalt salt is prepared by adding water to form a cobalt solution, and then the cobalt solution is mixed with a polyanionic compound to obtain a cobalt solution containing polyanions; The cobalt solution containing polyanions is mixed with hydrogen peroxide to obtain a cobalt solution containing polyanions and hydrogen peroxide; wherein, The cobalt salt is cobalt chloride and its hydrate; and / or, In the cobalt solution, the concentration of cobalt ions is 120-140 g / L; and / or, The polyanionic compound is at least one selected from sodium fluorophosphate, sodium fluorosilicate, sodium vanadate, and sodium sulfate; and / or, In the cobalt solution containing polyanions, the concentration of polyanions is 0.1 wt%-1.0 wt%; and / or, The hydrogen peroxide has a mass fraction of 25%-30%; and / or, The concentration of H2O2 in the cobalt solution containing polyanion and hydrogen peroxide is 0.06wt%-0.08wt%.

4. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, The reaction substrate is a sodium hydroxide solution with a pH of 10.0-11.5; and / or, The precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-35%.

5. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, In the process of continuously adding a cobalt solution containing polyanion and hydrogen peroxide and a precipitant solution to the reaction substrate in a co-current flow to carry out the precipitation reaction, the flow rate of the cobalt solution containing polyanion and hydrogen peroxide is 130-320 L / h, and the flow rate of the precipitant solution is 60-160 L / h; and / or, The cobalt solution containing polyanion and hydrogen peroxide is pressurized and introduced into the reaction substrate along with air; the air flow rate is 130-300 L / h.

6. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, During the precipitation reaction, the pH value is 10.8-11.2, the reaction temperature is 65℃-78℃, and the stirring rate is 180-250 r / min.

7. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, The target range for particle growth rate is: particle growth rate ≤ 0.02 μm / h within 2 hours.

8. The method for promoting the growth of large-particle cobalt tetroxide using polyanion as described in claim 1, characterized in that, During the calcination process, the temperature is 600-660℃ and the time is 6-8 hours.

9. A cobalt tetroxide, characterized in that, The cobalt tetroxide is prepared by the method described in any one of claims 1-8, which utilizes polyanion-promoted growth of large-particle cobalt tetroxide.

10. An application of cobalt tetroxide as described in claim 9, characterized in that, The cobalt tetroxide is used to prepare lithium cobalt oxide cathode materials.

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