A method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-treatment

Abstract

The application discloses a method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-treatment, and belongs to the technical field of tricobalt tetraoxide treatment. The method comprises the following steps: (1) powder slurry: mixing tricobalt tetraoxide powder and water to form slurry material; (2) adding reagent: adding an aqueous solution of ammonium chloride or ammonia water to the slurry material to obtain mixed material; (3) ion exchange: the mixed material is subjected to ion exchange reaction under stirring, and after completion, a crude product is obtained; (4) purification: filtering the crude product to collect solid tricobalt tetraoxide, mixing the obtained filter cake with water again, repeating the filtration to remove the ions remaining on the surface of the solid, and drying to obtain tricobalt tetraoxide. The application has the advantages of high efficiency, low cost and small damage to product quality. The method is simple to operate, the cost of the reagent used is low, and industrial production can be easily realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tricobalt tetraoxide processing, and particularly relates to a method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-processing. BACKGROUND

[0002] The batteries of 3C electronic products such as large-capacity mobile phones, notebook computers and digital cameras are used in their terminal application fields. 3C electronic products have the requirements of being light and small, so the corresponding batteries must have high energy density. Lithium cobalt oxide (LiCoO2) is the most important positive electrode material for 3C electronic products at present, and the energy density of lithium ion batteries depends on the energy density of lithium cobalt oxide to a certain extent.

[0003] Tricobalt tetraoxide (Co3O4) is an important precursor for preparing lithium cobalt oxide positive electrode material. In lithium ion batteries, lithium cobalt oxide is widely used as a positive electrode material due to its high theoretical specific capacity and good electrochemical performance. The main role of tricobalt tetraoxide in the preparation process is to provide a cobalt source and to be converted into lithium cobalt oxide in the subsequent high-temperature calcination process. The particle size and morphology of tricobalt tetraoxide have an important influence on the performance of the final lithium cobalt oxide material. For example, by controlling the particle size distribution of tricobalt tetraoxide, the compaction density of lithium cobalt oxide can be improved, thereby increasing the volumetric energy density of the battery. In addition, the microstructure and purity of tricobalt tetraoxide also affect the electrochemical performance of lithium cobalt oxide, including cycle stability and rate performance.

[0004] In the production process of tricobalt tetraoxide, there are often a certain amount of sodium ion impurities. Sodium ions may be due to the fact that tricobalt tetraoxide and hydroxyl cobalt oxide are too dense during the synthesis process, causing sodium ions to be wrapped inside the crystal. In addition, sodium-containing raw materials or reagents may be used in the production process of tricobalt tetraoxide, which also leads to the enrichment of sodium ions in the material. Even in the subsequent purification steps, if not handled properly, sodium ions may remain in the material. The reason why sodium ion impurities are difficult to remove may be related to their distribution in the crystal structure of tricobalt tetraoxide. In some cases, sodium ions may penetrate deep into the crystal and form a tight combination with cobalt ions, making it difficult to remove them effectively through simple washing or chemical treatment.

[0005] The residual sodium ions will have adverse effects on the performance and application of tricobalt tetraoxide. The presence of sodium ions may affect the electrochemical performance of tricobalt tetraoxide, especially when used as a positive electrode material for lithium ion batteries, sodium ions may also replace lithium ions in the electrode material, thereby reducing the energy density and cycle stability of the battery. In addition, the presence of sodium ions may also affect the structural integrity and thermal stability of the material, thereby affecting the processing performance and final application of the material.

[0006] In order to reduce the content of sodium ions, more sophisticated and specially designed purification methods are required. However, the current methods for reducing sodium ions have low efficiency, high cost or certain damage to product quality. SUMMARY

[0007] In view of the above-mentioned defects of the prior art, in the first aspect of the present application, a method for reducing sodium ions in tricobalt tetroxide by ion exchange post-treatment is provided, which has high efficiency, low cost and little damage to product quality, comprising the following steps:

[0008] (1) Powder slurrying: mixing tricobalt tetroxide powder and water to form a slurry;

[0009] (2) Adding reagent: adding ammonium chloride aqueous solution or ammonia water to the slurry to obtain a mixture;

[0010] (3) Ion exchange: the mixture is subjected to ion exchange reaction under stirring to obtain a crude product;

[0011] (4) Purification: filtering the crude product to collect solid tricobalt tetroxide, mixing the obtained filter cake with water again, repeating the filtration to remove the ions remaining on the surface of the solid, and drying to obtain tricobalt tetroxide.

[0012] In the process of mixing tricobalt tetroxide powder and water to form a slurry, the control of solid-liquid ratio is very important, because it directly affects the rheological properties and stability of the slurry. If the water is too much, the slurry may be too fluid, resulting in a decrease in the effect of the shearing force of the stirring paddle, which is not conducive to the kneading and stirring to crush the agglomerates. On the contrary, if the content of tricobalt tetroxide powder is too high, the slurry may be too dense and difficult to stir uniformly, affecting the homogeneity of the slurry. A suitable solid-liquid ratio helps to maintain the stability of the slurry and prevent the particles from re-agglomerating.

[0013] Preferably, in step (1), the solid-liquid ratio of tricobalt tetroxide powder and water is 1:20-30 g / g.

[0014] Preferably, in step (1), the mixing mode is stirring, and the stirring speed is 300-500 rpm.

[0015] In the present application, the removal degree of sodium ions can be flexibly controlled by adjusting the concentration of ammonia water or ammonium chloride aqueous solution and the reaction conditions. In order to ensure the high efficiency of the ion exchange reaction, the reaction temperature and the concentration of the reactants need to be controlled within a suitable range. Appropriate temperature and concentration can ensure the stable progress of the ion exchange process, reduce the energy consumption of the reaction and improve the efficiency. In industrial production, maintaining constant operating conditions can also ensure the consistency of product quality and reduce energy consumption

[0016] The rate of ion exchange reaction is affected by the concentration of ions. Generally, the higher the ion concentration, the faster the rate of ion exchange reaction, as more ions in solution increase the chance of collision, thus speeding up the reaction process. However, the increase of ion concentration can also cause the shift of ion exchange equilibrium, affecting the final exchange efficiency and selectivity. Temperature has a significant impact on both the rate and equilibrium position of ion exchange reactions.

[0017] Preferably, in step (2), the concentration of the aqueous ammonium chloride solution is 10-20 g / L; and the concentration of the ammonia solution is 5 wt.%-25.0 wt.%.

[0018] Preferably, in step (2), the volume ratio of the aqueous ammonium chloride solution or the ammonia solution to the slurry is 1:3-5.

[0019] Preferably, in step (3), the stirring speed is 300-500 rpm.

[0020] Temperature increase generally accelerates the rate of ion exchange reaction, as high temperature can provide more energy to the reaction system, increasing the speed of molecular motion. Temperature can also change the selectivity of ion exchange, i.e. the affinity for different ions, thus improving the separation efficiency and purity in some applications. However, excessive temperature increase can cause changes in the physicochemical properties of ion exchange, thus damaging its performance.

[0021] Preferably, in step (3), the temperature of the ion exchange reaction is 60-80 ℃, and the reaction time is 4-8 h.

[0022] A suitable solid-liquid ratio can ensure that the filter cake is not too tight, so as to maintain a reasonable filtration channel, allowing the filtrate to pass smoothly, and enabling smooth multiple filtration. If the solid-liquid ratio is too high, i.e. the solid content in the filter cake is too much, it will cause the filter cake layer to become too dense, increasing the filtration resistance, thus reducing the filtration speed. In addition, controlling a suitable solid-liquid ratio helps to form a loose filter cake, which is very beneficial for the subsequent washing and drying steps. If the filter cake is too tight, it may cause uneven washing and drying, affecting the purity and yield of the final cobaltosic oxide.

[0023] Preferably, in step (4), the solid-liquid ratio of the filter cake mixed with water is 1:40-100 g / g.

[0024] Preferably, in step (4), the filtration method is suction filtration; and the suction filtration is repeated 1-5 times to remove the residual ions on the surface of the solid.

[0025] Ion exchange reaction is a process based on selective adsorption and release between ions. In this process, when a solution containing different ions passes through an ion exchange medium, the ions in the solution will be adsorbed or released according to their affinity difference with the selected ions. The present application utilizes the different ion exchange ability of ammonium ion and sodium ion, and effectively realizes the reduction of sodium ion content based on the selectivity of ion exchange through the above-mentioned operating conditions and ion exchange medium.

[0026] The sodium ions in the tricobalt tetraoxide are difficult to remove by normal washing. The part of the ions are adsorbed to the surface of the material crystal grains when the cobalt ions and the complexing agent are complexed and then react with the precipitating agent. The adsorption force of this part is strong. The ammonium ion, which belongs to the same cation as the sodium ion, has a much stronger adsorption capacity to the negative groups on the surface of the material than the sodium ion. When the ammonium ion is added, the sodium ions in the tricobalt tetraoxide will be gradually replaced by the ammonium ion, which can be removed by washing, so as to achieve the purpose of reducing the sodium ions.

[0027] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0028] The present application provides a method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-treatment, which has the advantages of high efficiency, low cost, and small damage to product quality. The method is simple to operate, the reagent cost is low, and it is easy to realize industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a flowchart of the method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-treatment in Example 1. DETAILED DESCRIPTION

[0030] The present application will be further described by way of examples, but the present application is not limited to the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0031] Example 1

[0032] A method for reducing sodium ions in tricobalt tetraoxide by ion exchange post-treatment, as shown in Figure 1 , the steps are as follows:

[0033] (1) Powder slurrying: tricobalt tetraoxide powder (black powder) and deionized water are placed in a clean beaker according to the solid-liquid ratio of 1:20 g / g, stirred uniformly, the stirring speed is 450 rpm, and the mixed slurry is formed;

[0034] (2) Add reagent: add 10 g / L of ammonium chloride aqueous solution to the slurry, the volume ratio of ammonium chloride aqueous solution to slurry is 1:3, and the mixed material is obtained;

[0035] (3) Ion exchange: the mixture was subjected to ion exchange reaction under stirring at 400 rpm, keeping the slurry temperature at 72 °C, and the ion exchange time was 5 h, and the crude product was obtained after completion;

[0036] (4) Purification: the crude product was suction filtered to collect the solid tricobalt tetroxide, and the obtained filter cake was placed in a beaker, deionized water was added again, the solid-liquid ratio was 1:40-1:100 g / g, after uniform dispersion assisted by ultrasonic, suction filtration was continued, and the above process was repeated for 3 times to remove the residual ions on the surface of the solid, and tricobalt tetroxide (black powder) was obtained after drying.

[0037] Example 2

[0038] This example is basically the same as Example 1, the only difference is that the concentration of the sodium chloride aqueous solution used in this example is 20 g / L.

[0039] Example 3

[0040] This example is basically the same as Example 1, the only difference is that the concentration of the sodium chloride aqueous solution used in this example is 30 g / L.

[0041] Example 4

[0042] This example is basically the same as Example 1, the only difference is that the concentration of the sodium chloride aqueous solution used in this example is 40 g / L.

[0043] Example 5

[0044] This example is basically the same as Example 1, the only difference is that the concentration of the sodium chloride aqueous solution used in this example is 50 g / L.

[0045] Example 6

[0046] This example is basically the same as Example 1, the only difference is that the reagent used in this example is 5 wt.% ammonia water.

[0047] Example 7

[0048] This example is basically the same as Example 6, the only difference is that the concentration of the ammonia water used in this example is 10 wt.%.

[0049] Example 8

[0050] This example is basically the same as Example 6, the only difference is that the concentration of the ammonia water used in this example is 15 wt.%.

[0051] Example 9

[0052] This example is basically identical to Example 6, except that the concentration of the ammonia water used in this example is 20 wt.%.

[0053] Example 10

[0054] This example is basically identical to Example 6, except that the concentration of the ammonia water used in this example is 25 wt.%.

[0055] Comparative Example 1

[0056] This comparative example uses a treatment method without adding ammonia water or aqueous ammonium chloride solution, and the steps are as follows:

[0057] (1) Powder slurrying: The tricobalt tetraoxide powder and deionized water are placed in a clean beaker at a solid-liquid ratio of 1:20 g / g, stirred uniformly at a stirring speed of 450 rpm, and mixed to form a slurry;

[0058] (2) Purification: The slurry is suction filtered to collect the solid tricobalt tetraoxide, the obtained filter cake is placed in a beaker, deionized water is added again at a solid-liquid ratio of 1:40-1:100 g / g, and after ultrasonic-assisted dispersion, suction filtration is continued, and this is repeated for 3 times to remove the residual ions on the surface of the solid, and the tricobalt tetraoxide is obtained after drying.

[0059] First, the tricobalt tetraoxide is digested with a strong acid, and then ICP is used to test the sodium ion content therein. The sodium ion content in the product under different concentrations of aqueous ammonium chloride solution and ammonia water, and without ion exchange, is tested, and the results are shown in Tables 1 and 2 in turn.

[0060] Table 1: Relationship between sodium ion content in tricobalt tetraoxide and concentration of aqueous ammonium chloride solution

[0061]

[0062] Table 2: Relationship between sodium ion content in tricobalt tetraoxide and concentration of ammonia water

[0063]

[0064] The increase in the concentration of the aqueous ammonium chloride solution or ammonia water does not show a positive correlation with the degree of reduction of the sodium ion content, and after the concentration increases to a certain degree, the effect of reducing the sodium ion content rebounds. Therefore, the degree of removal of sodium ions can be flexibly controlled by adjusting the concentration of the ammonia water or aqueous ammonium chloride solution and the reaction conditions.

[0065] The ion exchange post-treatment method of the present application for reducing sodium ions in tricobalt tetraoxide has the advantages of high efficiency, low cost, and small damage to product quality. The method is simple to operate, the cost of the reagents used is relatively low, and it is easy to realize industrial production.

[0066] The preferred embodiments of the application have been described above in detail. It should be understood that modifications and variations to the preferred embodiments could be made by those skilled in the art in light of the teachings above. It is therefore contemplated that the application can encompass other variations and modifications that fall within the scope of the claims.

Claims

1. A method for reducing sodium ions in cobalt tetroxide through ion exchange post-treatment, characterized in that, Includes the following steps: (1) Powder slurry: Cobalt tetroxide powder and water are mixed to form a slurry; the solid-liquid ratio of cobalt tetroxide powder and water is 1:20-30 g / g; (2) Adding reagents: Add ammonium chloride aqueous solution or ammonia water to the slurry to obtain a mixture; the concentration of ammonium chloride aqueous solution is 10-20 g / L; the concentration of ammonia water is 5 wt.%-25.0 wt.%; the volume ratio of ammonium chloride aqueous solution or ammonia water to slurry is 1:3-5; (3) Ion exchange: The mixture undergoes ion exchange reaction under stirring conditions, and crude product is obtained after the reaction is completed; the temperature of the ion exchange reaction is 60-80 ℃, and the reaction time is 4-8 h; (4) Purification: Filter the crude product to collect solid cobalt tetroxide, mix the obtained filter cake with water again, filter repeatedly to remove residual ions on the solid surface, and dry to obtain cobalt tetroxide; the solid-liquid ratio of the filter cake to water is 1:40-100 g / g.

2. The method for reducing sodium ions in cobalt tetroxide using the ion exchange post-treatment method according to claim 1, characterized in that: In step (1), the mixing method is stirring, and the stirring speed is 300-500 rpm.

3. The method for reducing sodium ions in cobalt tetroxide using the ion exchange post-treatment method according to claim 1, characterized in that: In step (3), the stirring speed is 300-500 rpm.

4. The method for reducing sodium ions in cobalt tetroxide using the ion exchange post-treatment method according to claim 1, characterized in that: In step (4), the filtration method is vacuum filtration; the vacuum filtration is repeated 1-5 times to remove residual ions on the solid surface.

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