A method for preparing large-particle cobalt tetroxide for batteries

Abstract

The present invention relates to a method for preparing large-particle cobalt tetroxide for batteries, belonging to the technical field of battery preparation. The method first dissolves a cobalt salt in deionized water to obtain a high-concentration cobalt ion solution, then mixes sodium oxalate and ammonium niobium oxalate to form a specific precursor structure. The cobalt ions, oxalate, and ammonium niobium oxalate undergo a coprecipitation reaction in the aqueous solution to generate a complex precipitate of oxalate and niobate containing cobalt. Hydrogen peroxide is then used to promote the oxidation of the cobalt ions, further promoting the formation and crystallization of the cobalt oxalate precipitate. During the preparation process, freeze-drying is used to effectively remove moisture while maintaining the morphology and structure of the precipitate. Organic matter and volatile impurities are removed through calcination and re-calcination, promoting the formation and stabilization of the cobalt tetroxide crystal structure. This stable crystal structure helps to improve the cycle life and safety of the battery.

Description

Technical Field

[0001] The invention belongs to the technical field of battery preparation and relates to a method for preparing large-particle cobalt tetroxide for batteries. Background Art

[0002] As one of the most widely used secondary batteries, lithium-ion batteries (LIBs) have long been a hot topic of research. Cathode materials are key factors in LIB performance, and optimizing the performance of cobalt trioxide (Co3O4), an important cathode material precursor, is crucial for improving the energy density, cycle stability, and safety of LIBs.

[0003] In lithium-ion batteries, the particle size of the cathode material directly affects the performance of the battery. Generally speaking, smaller particle sizes can provide higher specific surface area and shorter ion diffusion paths, which are conducive to the rapid deintercalation and extraction of lithium ions and the high rate performance of the battery. However, in some cases, such as improving the cycle stability and processing performance of the battery, large-particle cathode materials may be more advantageous. Large-particle cobalt tetroxide can improve the processing performance and cycle stability of the material while ensuring battery performance by optimizing the particle size distribution and morphology. With the development of electric vehicles, energy storage systems and other fields, the performance requirements of lithium-ion batteries are getting higher and higher. As an important precursor of cathode materials, large-particle cobalt tetroxide has significant advantages in improving battery performance.

[0004] As an important component of lithium battery positive electrode materials, large-particle cobalt tetroxide can improve the cycle stability of the battery. Therefore, how to prepare high-performance large-particle cobalt tetroxide has become a hot topic. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing large-particle cobalt tetroxide for batteries, wherein the cobalt tetroxide prepared by the method has the characteristic of high cycle stability.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing large-particle cobalt tetroxide for batteries, the specific process of the large-particle cobalt tetroxide preparation method is as follows:

[0008] S1: dissolving a cobalt salt in deionized water to obtain a cobalt ion solution A having a mass fraction of 30 to 50%;

[0009] S2: Sodium oxalate and ammonium niobium oxalate are mixed in a mass ratio of 1:(0.5-3), and dispersed in deionized water to obtain a mixed solution B with a mass fraction of 10%;

[0010] S3: Add cobalt ion solution A dropwise to mixed solution B in a volume ratio of 2:1, stirring at a speed of 150 r / min while adding, and heating to 50°C for 2 to 3 hours. Then, add 1 wt% of a 10% hydrogen peroxide solution, slowly heat to 65°C at a rate of 2°C / min, and continue stirring for 0.5 to 1 hour to obtain a mixed solution C;

[0011] S4: freezing the mixed solution C in liquid nitrogen for 15 min, and then drying it at -50°C under a nitrogen atmosphere for 6 h to obtain a mixture D;

[0012] S5: Transfer mixture D to a muffle furnace, heat from room temperature to 500-600°C, and calcine for 3 hours. After calcination, purge with nitrogen and cool to room temperature to obtain mixture E.

[0013] S6: Mix the mixture E and glycine in a mass ratio of 4:1, grind at a speed of 300 r / min for 0.5 h, then place the mixture in a muffle furnace preheated to 200° C. and burn for 10 to 20 min, then slowly heat it to 600° C. and continue roasting for 2 h. After roasting, purge with nitrogen and quickly cool to room temperature, and crush to obtain the large-particle cobalt tetroxide.

[0014] Furthermore, the cobalt salt in S1 is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0015] Furthermore, the cobalt ion solution A in S3 is added dropwise to the mixed solution B at a rate of 3 s / drop.

[0016] Furthermore, the heating rate in S5 is 10°C / min.

[0017] Furthermore, the purge flow rate of nitrogen in S5 is 10 m / s.

[0018] Furthermore, the rate of slowly heating in S6 is 3°C / min.

[0019] Furthermore, the flow rate of the nitrogen purge in S6 is 20 m / s.

[0020] Furthermore, the large-particle cobalt tetroxide prepared in S6 has a particle size of 20 to 25 μm.

[0021] The present invention first dissolves a cobalt salt in deionized water to obtain a high-concentration cobalt ion solution A, which provides a sufficient cobalt source for subsequent reactions. The use of deionized water can avoid the introduction of impurity ions and improve the purity of the product. The mixed use of sodium oxalate and ammonium niobium oxalate helps to form a specific precursor structure, thereby affecting the morphology and particle size of the final product. Cobalt ions undergo a coprecipitation reaction with oxalate and ammonium niobium oxalate in an aqueous solution to generate a complex precipitate of oxalate and niobate containing cobalt. After sodium oxalate and ammonium niobium oxalate are dissolved in water, the oxalate ions can undergo a coordination reaction or precipitation reaction with the cobalt ions to form a cobalt-containing precipitate.

[0022] Sodium oxalate acts as a precipitant, reacting with cobalt ions to form cobalt oxalate precipitate. This step is key to forming the cobalt tetroxide precursor, ensuring that cobalt ions can be precipitated from the solution in a controlled manner, providing a good starting material for the subsequent high-temperature calcination process.

[0023] Ammonium niobium oxalate not only provides oxalate ions for the precipitation reaction but, more importantly, introduces the element niobium. This addition significantly impacts the properties and crystal structure of cobalt trioxide. The addition of ammonium niobium oxalate alters the kinetics and thermodynamics of the precipitation reaction, thereby affecting the formation and growth of the cobalt oxalate precipitate.

[0024] Niobium is a metallic element with unique properties. Its introduction can significantly alter the crystal structure and properties of cobalt oxide. Niobium incorporation into the cobalt oxide lattice causes lattice distortion. This distortion reduces the grain boundary energy, lowering the energy barrier required for grain growth and thus promoting grain growth. Niobium exists as a solid solution in cobalt oxide, resulting in solid solution strengthening that enhances grain strength and stability while also facilitating grain growth. During the precipitation reaction, niobium acts as a nucleation center or promoter, promoting the formation and growth of cobalt oxalate nuclei. These nuclei further grow into cobalt oxide grains during the subsequent high-temperature calcination process. Therefore, niobium doping promotes cobalt oxide grain growth, contributing to the formation of larger particle sizes. Niobium doping can also improve the conductivity and stability of cobalt oxide. Niobium can enhance its conductivity by altering its band structure and carrier concentration. Specifically, the introduction of niobium may form new energy levels or impurity energy levels, making it easier for electrons or holes to migrate in the crystal lattice; niobium also reduces the probability of electron scattering at grain boundaries by promoting grain growth and reducing grain boundaries, thereby improving conductivity. Due to the strong interaction between niobium and cobalt, they may form stable chemical bonds or structural units, allowing cobalt tetroxide to maintain good structural stability during the electrochemical cycle; the introduction of niobium also improves cobalt tetroxide's tolerance to ions in the electrolyte, reduces the destructive effect on the crystal lattice during ion insertion / extraction, and thus improves the battery's cycle stability, which is very important for battery applications.

[0025] Hydrogen peroxide is a strong oxidant that participates in chemical reactions, oxidizing substances to higher valence states. During this preparation process, hydrogen peroxide promotes the oxidation of cobalt ions, helping to form a more stable cobalt compound precursor. The addition of hydrogen peroxide alters the redox potential of the reaction system, which further promotes the formation and crystallization of cobalt oxalate precipitates. Good crystallinity is crucial for the preparation of large-particle, high-purity cobalt tetroxide.

[0026] Freeze drying can effectively remove moisture while maintaining the morphology and structure of the precipitate; drying under a nitrogen atmosphere can prevent oxidation and protect the chemical properties of the product.

[0027] The calcination process helps remove organic matter and volatile impurities while promoting the conversion of the precursor to cobalt oxide. Glycine, a fuel, burns at high temperatures to produce a large amount of gas, which helps form a porous structure and promotes the formation of large particles. The re-calcination process further consolidates the cobalt oxide's crystal structure, improving the purity and stability of the product. The calcination and re-calcination process not only removes organic matter and volatile impurities but also promotes the formation and stabilization of the cobalt oxide's crystal structure. This stable crystal structure helps improve the battery's cycle life and safety.

[0028] Beneficial effects of the present invention:

[0029] In the preparation process of the present invention, sodium oxalate and ammonium niobium oxalate are mixed and used, which not only realizes the effective precipitation of cobalt ions, but also optimizes the performance of cobalt tetroxide by introducing niobium element;

[0030] The present invention removes organic matter and volatile impurities through the roasting and re-roasting processes, and also promotes the formation and stabilization of the cobalt oxide crystal structure. The stable crystal structure helps to improve the cycle life and safety of the battery. DETAILED DESCRIPTION

[0031] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0032] Example 1

[0033] S1: dissolving cobalt sulfate in deionized water to obtain a cobalt ion solution A with a mass fraction of 40%;

[0034] S2: Sodium oxalate and ammonium niobium oxalate were mixed in a mass ratio of 1:2 and dispersed in deionized water to obtain a mixed solution B with a mass fraction of 10%;

[0035] S3: Add cobalt ion solution A dropwise to mixed solution B at a rate of 3 s / drop, with a volume ratio of 2:1. Stir at a speed of 150 r / min while adding, and heat to 50° C. for 2.5 h. Then, add 1 wt % of 10% hydrogen peroxide solution, slowly heat to 65° C. at a rate of 2° C. / min, and continue stirring for 0.5 h to obtain mixed solution C.

[0036] S4: freezing the mixed solution C in liquid nitrogen for 15 min, and then drying it at -50°C under a nitrogen atmosphere for 6 h to obtain a mixture D;

[0037] S5: Transferring the mixture D to a muffle furnace, heating it from room temperature to 500°C at a heating rate of 10°C / min, and calcining it for 3 hours. After calcination, purging with nitrogen at a nitrogen purge rate of 10 m / s was performed, and cooling it to room temperature to obtain a mixture E.

[0038] S6: Mix mixture E and glycine in a mass ratio of 4:1, grind at a speed of 300 r / min for 0.5 h, then place the mixture in a muffle furnace preheated to 200°C and burn for 15 min, then slowly heat it to 600°C and continue roasting for 2 h, with a slow heating rate of 3°C / min. After roasting, use nitrogen purge to quickly cool to room temperature, the nitrogen purge flow rate is 20 m / s, and crush to obtain the large-particle cobalt tetroxide with a particle size of 20 to 25 μm.

[0039] Example 2

[0040] S1: dissolving cobalt chloride in deionized water to obtain a cobalt ion solution A with a mass fraction of 30%;

[0041] S2: Sodium oxalate and ammonium niobium oxalate were mixed in a mass ratio of 1:0.5 and dispersed in deionized water to obtain a mixed solution B with a mass fraction of 10%;

[0042] S3: Add cobalt ion solution A dropwise to mixed solution B at a rate of 3 s / drop, with a volume ratio of 2:1. Stir at a speed of 150 r / min while adding the cobalt ion solution A. Raise the temperature to 50°C and stir for 2 h. Then, add 1 wt% (mass fraction) 10% hydrogen peroxide solution. Slowly raise the temperature to 65°C at a rate of 2°C / min and continue stirring for 0.5 h to obtain mixed solution C.

[0043] S4: freezing the mixed solution C in liquid nitrogen for 15 min, and then drying it at -50°C under a nitrogen atmosphere for 6 h to obtain a mixture D;

[0044] S5: Transferring the mixture D to a muffle furnace, heating it from room temperature to 500°C at a heating rate of 10°C / min, and calcining it for 3 hours. After calcination, purging with nitrogen at a nitrogen purge rate of 10 m / s was performed, and cooling it to room temperature to obtain a mixture E.

[0045] S6: Mix mixture E and glycine in a mass ratio of 4:1, grind at a speed of 300 r / min for 0.5 h, then place the mixture in a muffle furnace preheated to 200°C and burn for 20 min, then slowly heat it to 600°C and continue roasting for 2 h, with a slow heating rate of 3°C / min. After roasting, use nitrogen purge to quickly cool to room temperature, the nitrogen purge flow rate is 20 m / s, and crush to obtain the large-particle cobalt tetroxide with a particle size of 20 to 25 μm.

[0046] Example 3

[0047] S1: dissolving cobalt nitrate in deionized water to obtain a cobalt ion solution A with a mass fraction of 50%;

[0048] S2: Sodium oxalate and ammonium niobium oxalate were mixed in a mass ratio of 1:3 and dispersed in deionized water to obtain a mixed solution B with a mass fraction of 10%;

[0049] S3: Add cobalt ion solution A dropwise to mixed solution B at a rate of 3 s / drop, with a volume ratio of 2:1. Stir at a speed of 150 r / min while adding the cobalt ion solution A. Raise the temperature to 50°C and stir for 3 h. Then, add 1 wt% of a 10% hydrogen peroxide solution, slowly raise the temperature to 65°C at a rate of 2°C / min, and continue stirring for 1 h to obtain a mixed solution C.

[0050] S4: freezing the mixed solution C in liquid nitrogen for 15 min, and then drying it at -50°C under a nitrogen atmosphere for 6 h to obtain a mixture D;

[0051] S5: Transfer mixture D to a muffle furnace, heat it from room temperature to 600°C at a heating rate of 10°C / min, and calcine it for 3 hours. After calcination, purge it with nitrogen at a nitrogen purge rate of 10 m / s, and cool it to room temperature to obtain mixture E.

[0052] S6: Mix mixture E and glycine in a mass ratio of 4:1, grind at a speed of 300 r / min for 0.5 h, then place the mixture in a muffle furnace preheated to 200°C and burn for 10 min, then slowly heat it to 600°C and continue roasting for 2 h, with a slow heating rate of 3°C / min. After roasting, use nitrogen purge to quickly cool to room temperature, the nitrogen purge flow rate is 20 m / s, and crush to obtain the large-particle cobalt tetroxide with a particle size of 20 to 25 μm.

[0053] Comparative Example 1

[0054] In this comparative example, no ammonium niobium oxalate was added during the preparation process, and the remaining steps were consistent with those in Example 1.

[0055] Comparative Example 2

[0056] In this comparative example, hydrogen peroxide was not added during the preparation process, and the remaining steps were consistent with those in Example 1.

[0057] Comparative Example 3

[0058] In this comparative example, S6 was not re-calcined during the preparation process, and the remaining steps were consistent with those in Example 1.

[0059] Comparative Example 4

[0060] In this comparative example, the calcination operation of S5 is not performed during the preparation process, and the remaining steps are consistent with those of Example 1.

[0061] The embodiments and comparative examples were tested for performance.

[0062] The cycle retention rate test was carried out according to the standard GB / T 23366-2009. The experimental results are summarized in the following table:

[0063] 200-cycle cycle retention rate (%) Example 1 85 Example 2 83 Example 3 83 Comparative Example 1 70 Comparative Example 2 76 Comparative Example 3 74 Comparative Example 4 75

[0064] The data of the examples and comparative examples show that the addition of ammonium niobium oxalate and hydrogen peroxide, as well as the secondary calcination treatment, all result in the obtained large-particle cobalt trioxide having a better cycle life.

[0065] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing large-particle cobalt tetroxide for batteries, characterized in that: The specific process of the large-particle cobalt tetroxide preparation method is as follows: S1: dissolving cobalt salt in deionized water to obtain a cobalt ion solution A with a mass fraction of 30-50%; S2: Sodium oxalate and ammonium niobium oxalate were mixed in a mass ratio of 1:(0.5-3), and dispersed in deionized water to obtain a mixed solution B with a mass fraction of 10%; S3: Add cobalt ion solution A dropwise to mixed solution B in a volume ratio of 2:1, stirring at a speed of 150 r / min while adding, and heating to 50°C for 2-3 hours. Then, add 1 wt% of 10% hydrogen peroxide solution, slowly heat to 65°C at a rate of 2°C / min, and continue stirring for 0.5-1 hour to obtain mixed solution C; S4: freezing the mixed solution C in liquid nitrogen for 15 min, and then drying it at -50°C under a nitrogen atmosphere for 6 h to obtain a mixture D; S5: Transferring the mixture D to a muffle furnace, heating it from room temperature to 500-600°C, and calcining it for 3 hours. After calcination, purging with nitrogen was performed, and cooling it to room temperature to obtain a mixture E. S6: Mixing mixture E and glycine in a mass ratio of 4:1, grinding at a speed of 300 r / min for 0.5 h, then placing the mixture in a muffle furnace preheated to 200° C. and burning for 10-20 min, then slowly heating to 600° C. and continuing to roast for 2 h. After the roasting is completed, purging with nitrogen is used and rapidly cooled to room temperature, and crushing is performed to obtain the cobalt oxide with large particle size; The large-particle cobalt tetroxide prepared in S6 has a particle size of 20-25 μm.

2. The method for preparing large-particle cobalt tetroxide for batteries according to claim 1, characterized in that: The cobalt salt in S1 is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate.

3. The method for preparing large-particle cobalt tetroxide for battery according to claim 1, characterized in that: The cobalt ion solution A in S3 is added dropwise to the mixed solution B at a rate of 3s / drop.

4. The method for preparing large-particle cobalt tetroxide for battery according to claim 1, characterized in that: The heating rate in S5 is 10°C / min.

5. The method for preparing large-particle cobalt tetroxide for battery according to claim 1, characterized in that: The purge flow rate of nitrogen in S5 is 10 m / s.

6. The method for preparing large-particle cobalt tetroxide for battery according to claim 1, characterized in that: The rate of slow heating in S6 is 3°C / min.

7. The method for preparing large-particle cobalt tetroxide for battery according to claim 1, characterized in that: The flow rate of nitrogen purge in S6 is 20 m / s.