Method for reducing sodium ion content in aluminum-doped cobaltosic oxide through in-situ ion occupation

Abstract

The invention discloses a method for reducing the content of sodium ions in aluminum-doped cobaltosic oxide through in-situ ion occupation, and belongs to the technical field of treatment of cobaltosic oxide. The method is simple to operate, the used reagent is low in cost, and industrial production is easy to realize; the removal degree of sodium ions can be flexibly controlled by adjusting the additive solution and reaction conditions, the content of sodium ions in the doped cobaltosic oxide can be effectively reduced, and the purity and quality of the product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of cobalt oxide processing, and in particular to a method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation. Background Art

[0002] Aluminum-doped cobalt oxide plays a vital role in the preparation of lithium cobalt oxide cathode materials. Aluminum-doped cobalt oxide has a series of advantages, making it an ideal precursor for high-voltage lithium cobalt oxide cathode materials.

[0003] Doping with aluminum can improve the stability of the crystal structure of lithium cobalt oxide. During high-voltage charging, lithium cobalt oxide materials may undergo irreversible structural phase changes, resulting in the collapse of the crystal structure. Doping with aluminum can reduce this risk, thereby improving the cycle performance of lithium cobalt oxide at high voltage. The high voltage and high density characteristics of aluminum-doped cobalt tetroxide make it an ideal material for high-energy density batteries. This is particularly important for 3C electronic products, as these products require batteries to be both light and compact while also providing enough energy to meet the endurance requirements of the device. Doping with aluminum-doped cobalt tetroxide can improve the electrochemical properties of lithium cobalt oxide positive electrode materials, including improving specific capacity and cycle stability. When the amount of aluminum doping is controlled within a certain range, the electrochemical properties of the material can be optimized, allowing it to perform better at high voltage. During high-voltage charging, lithium cobalt oxide materials may react with the electrolyte, creating safety hazards. Doping with aluminum can reduce this risk and reduce adverse reactions with the electrolyte by forming a stable structure, thereby improving the safety of the battery. Aluminum-doped cobalt tetroxide has a multi-porous structure, which is conducive to the rapid diffusion of lithium ions and improves the charge and discharge rate of the battery.

[0004] In the production process of aluminum-doped cobalt tetroxide, the presence of sodium ion impurities is a problem that cannot be ignored. These impurities are usually difficult to remove through conventional washing processes. They may be embedded in the lattice of cobalt tetroxide, thereby negatively affecting the electrochemical properties of the material. In order to improve the quality of aluminum-doped cobalt tetroxide and ensure its efficient application in lithium-ion batteries, it is particularly important to develop effective impurity removal technology.

[0005] Repeated centrifugal washing or high-temperature calcination is often used in industrial production to reduce the sodium ion content. For centrifugal washing, the removal efficiency of sodium ions gradually decreases with the increase in the number of centrifugal washings. The initial few washings can significantly reduce the sodium content, but the effect of subsequent washings is becoming less and less obvious. This is because the sodium ions are deeply embedded in the structure of cobalt tetroxide, and simple physical washing is difficult to completely remove them. For high-temperature calcination, although it can change the structure of cobalt tetroxide to make it easier to discharge the sodium inside, it also brings the risk of material structure damage. High-temperature operation may cause changes in the crystal form, which in turn affects the electrochemical properties of the material. And the high-temperature calcination process itself requires a large amount of energy supply, coupled with cooling and subsequent washing steps, the overall energy consumption is very high, further raising the production cost.

[0006] In summary, designing a suitable method to effectively remove impurities such as sodium ions and reduce energy consumption and costs can significantly improve the safety and cycle stability of batteries, meet the stringent requirements of 3C electronic products on battery performance, and make the application of aluminum-doped cobalt tetroxide in high-energy density batteries more extensive, providing a more solid material foundation for the lightweight and compact design of 3C electronic products. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by in-situ ion occupancy with high efficiency, low cost and low damage to product quality is provided, comprising the following steps: (1) dissolving aluminum salt and cobalt salt in water to obtain an aluminum-cobalt mixed solution; dissolving a precipitant in water to obtain a precipitant solution; dissolving a complexing agent in water to obtain a complexing agent solution; using an ammonium salt aqueous solution or ammonia water as an additive solution; (2) mixing the aluminum-cobalt mixed solution, the precipitant solution, the complexing agent solution, and the additive solution for wet synthesis, and controlling the pH of the reaction system to be alkaline; (3) Starting from the overflow, the specific gravity of the mother liquor in the reaction system is measured regularly and controlled by adding water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide generated by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain the aluminum-doped cobalt tetroxide without impurities.

[0008] Preferably, in step (1), the aluminum concentration of the aluminum-cobalt mixed solution is 1.0-1.5 g / L, and the cobalt concentration is 90-160 g / L.

[0009] Preferably, in step (1), the aluminum salt includes one of aluminum chloride, aluminum sulfate, and aluminum acetate; and the cobalt salt includes one of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0010] Preferably, in step (1), the concentration of the precipitant solution is 180-260 g / L; the precipitant comprises sodium hydroxide or potassium hydroxide.

[0011] Preferably, in step (1), the concentration of the complexing agent solution is 0.1-0.5 g / L; the complexing agent includes one of sodium citrate, EDTA, and sodium pyrophosphate.

[0012] Preferably, in step (1), the concentration of the additive solution is 0.01-0.15 g / L.

[0013] According to the volume of the reactor commonly used in the art, the amount of aluminum-cobalt mixed solution used in industrial production is usually 140-180L, and correspondingly, the amount of other raw materials is also controlled within an appropriate range. Under the dosage relationship of the present invention, those skilled in the art can enlarge or reduce the ratio of each raw material according to the actual scale of synthesis.

[0014] Preferably, in step (2), when the amount of the aluminum-cobalt mixed solution is 140-180 L, the amount of the precipitant solution is 180-220 L, the amount of the complexing agent introduced into the complexing agent solution is 0.09-0.15 mol, and the amount of ammonium ions introduced into the additive solution is 0.05-0.10 mol.

[0015] Preferably, in step (2), the reaction temperature of the wet synthesis is 45-75°C; and the pH of the reaction system is controlled to be 9.2-10.8.

[0016] Under the reaction conditions of the present invention, the specific gravity of the mother liquor is appropriately controlled at 1-1.1, which can maintain the viscosity of the solution in the reaction system and the balance of the coprecipitation reaction, promote the stability of the aluminum-doped cobalt oxide wet precipitation system, and thus obtain a high-quality aluminum-doped cobalt oxide product. This specific gravity range helps to optimize the growth and morphology of the particles, making the size and shape of the particles more uniform, thereby improving the quality and performance of the product. If the specific gravity of the mother liquor is too high, it may cause the particles to grow too fast and form larger particles, while if the specific gravity of the mother liquor is too low, it may cause the particles to grow too slowly and form smaller particles.

[0017] Preferably, in step (3), the specific gravity of the mother liquor in the reaction system is measured every 1-2 h, and the specific gravity of the mother liquor is controlled to be 1-1.1 by adding water.

[0018] In the process of wet synthesis, in order to better control the reaction conditions and improve product quality and production efficiency, technicians in this field can perform split-reactor operation when necessary according to the actual situation of the reactor. Split-reactor allows each reactor to independently control parameters such as temperature, pH value, stirring speed, etc. to ensure that the reaction is carried out under optimal conditions. By splitting the reactor, the reaction conditions can be better controlled, the introduction of impurities can be reduced, the purity and consistency of the product can be improved, and multiple batches of reactions can be carried out simultaneously, shortening the production cycle and improving production efficiency.

[0019] It should be noted that the applicant's application in the same period includes a scheme of adding an aqueous solution of ammonium chloride or ammonia water to the cobalt tetroxide slurry. This scheme uses the fact that the adsorption capacity of ammonium ions and negatively charged groups on the surface of the material is much stronger than that of sodium ions. After adding ammonium ions, the sodium ions in the cobalt tetroxide product will be gradually replaced by ammonium ions and removed by washing, thereby achieving the purpose of reducing sodium ions at the source of the raw materials. The present invention adds ammonium ions in the wet synthesis stage, and uses in-situ ion occupancy to complex with a complexing agent, thereby reducing the complexing of the complexing agent with sodium ions, effectively reducing the sodium ion content in the subsequent aluminum-doped cobalt tetroxide product, and improving product quality. The present invention and the scheme in the same period each have their advantages, and the concentration of the additive solution of the present invention can be controlled within a lower range.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: The invention provides a method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation. The method is simple to operate, uses reagents at low cost, and is easy to realize industrial production. The degree of sodium ion removal can be flexibly controlled by adjusting an additive solution and reaction conditions, thereby effectively reducing the sodium ion content in doped cobalt oxide and improving the purity and quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the process of reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupancy in the embodiment. DETAILED DESCRIPTION

[0022] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0023] Example 1 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by in-situ ion occupation, such as Figure 1 As shown, the steps are as follows: (1) Aluminum chloride and cobalt chloride are dissolved in water to obtain an aluminum-cobalt mixed solution (cobalt concentration is 110 g / L, aluminum concentration is 1.2 g / L); sodium hydroxide is dissolved in water to obtain a precipitant solution (concentration is 220 g / L); EDTA is dissolved in water to obtain a complexing agent solution (concentration is 0.3 g / L); an ammonium chloride aqueous solution (concentration is 0.01 g / L) is used as an additive solution; (2) Adding aluminum-cobalt mixed solution (160 L), precipitant solution (195 L), complexing agent solution (containing 0.12 mol EDTA), and additive solution (containing 0.09 mol ammonium ion) into a reactor for wet synthesis, the pH value of the reaction system was controlled to be 10, and the reaction temperature was controlled to be 60 °C; (3) Starting from the overflow, measure the specific gravity of the mother liquor in the reaction system every 2 hours, and control the specific gravity of the mother liquor between 1 and 1.1 by adding pure water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide generated by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and filtered, washed, dried, and calcined to obtain the aluminum-doped cobalt tetroxide without impurities.

[0024] Example 2 This embodiment is basically the same as Embodiment 1, except that the concentration of the aqueous ammonium chloride solution used in this embodiment is 0.05 g / L.

[0025] Example 3 This embodiment is basically the same as Embodiment 1, except that the concentration of the aqueous ammonium chloride solution used in this embodiment is 0.09 g / L.

[0026] Example 4 This embodiment is basically the same as Embodiment 1, except that the concentration of the aqueous ammonium chloride solution used in this embodiment is 0.13 g / L.

[0027] Example 5 This embodiment is basically the same as Embodiment 1, except that the concentration of the aqueous ammonium chloride solution used in this embodiment is 0.15 g / L.

[0028] Example 6 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by in-situ ion occupation, comprising the following steps: (1) Aluminum chloride and cobalt chloride are dissolved in water to obtain an aluminum-cobalt mixed solution (cobalt concentration is 110 g / L, aluminum concentration is 1.2 g / L); sodium hydroxide is dissolved in water to obtain a precipitant solution (concentration is 220 g / L); EDTA is dissolved in water to obtain a complexing agent solution (concentration is 0.3 g / L); ammonia water (concentration is 0.01 g / L) is used as an additive solution; (2) Adding aluminum-cobalt mixed solution (160 L), precipitant solution (195 L), complexing agent solution (containing 0.12 mol EDTA), and additive solution (containing 0.09 mol ammonium ion) into a reactor for wet synthesis, the pH value of the reaction system was controlled to be 10, and the reaction temperature was controlled to be 60 °C; (3) Starting from the overflow, measure the specific gravity of the mother liquor in the reaction system every 2 hours, and control the specific gravity of the mother liquor between 1 and 1.1 by adding pure water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide generated by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and filtered, washed, dried, and calcined to obtain the aluminum-doped cobalt tetroxide without impurities.

[0029] Example 7 This embodiment is basically the same as Embodiment 1, except that the concentration of ammonia water used in this embodiment is 0.05 g / L.

[0030] Example 8 This embodiment is basically the same as Embodiment 1, except that the concentration of ammonia water used in this embodiment is 0.09 g / L.

[0031] Example 9 This embodiment is basically the same as Embodiment 1, except that the concentration of ammonia water used in this embodiment is 0.13 g / L.

[0032] Example 10 This embodiment is basically the same as Embodiment 1, except that the concentration of ammonia water used in this embodiment is 0.15 g / L.

[0033] Comparative Example 1 This comparative example uses the treatment method without adding the additive solution as a comparison, and the steps are as follows: (1) Dissolve aluminum chloride and cobalt chloride in water to obtain an aluminum-cobalt mixed solution (cobalt concentration is 110 g / L, aluminum concentration is 1.2 g / L); dissolve sodium hydroxide in water to obtain a precipitant solution (concentration is 220 g / L); dissolve EDTA in water to obtain a complexing agent solution (concentration is 0.3 g / L); (2) Adding aluminum-cobalt mixed solution (160 L), precipitant solution (195 L), and complexing agent solution (containing 0.12 mol EDTA) into a reactor for wet synthesis, the pH value of the reaction system was controlled to be 10, and the reaction temperature was controlled to be 60 °C; (3) Starting from the overflow, measure the specific gravity of the mother liquor in the reaction system every 2 hours, and control the specific gravity of the mother liquor between 1 and 1.1 by adding pure water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide generated by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and filtered, washed, dried, and calcined to obtain the aluminum-doped cobalt tetroxide without impurities.

[0034] First, the aluminum-doped cobalt tetraoxide of the embodiment and the comparative example was digested with a strong acid, and then the sodium ion content thereof was tested by ICP. The sodium ion content of the product was tested under different concentrations of ammonium chloride aqueous solution and ammonia water, and when it was not treated, and the results are shown in Table 1 and Table 2 respectively.

[0035] Table 1: Relationship between the sodium ion content in aluminum-doped cobalt oxide and the concentration of ammonium chloride aqueous solution

[0036] Table 2: Relationship between the sodium ion content in aluminum-doped cobalt oxide and the concentration of ammonia water

[0037] 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 in the sodium ion content. When the concentration increases to a certain level, the effect of reducing the sodium ion content will rebound. By adjusting the concentration of the aqueous ammonia water or the aqueous ammonium chloride solution and the reaction conditions, the present invention can flexibly control the degree of sodium ion removal.

[0038] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation, characterized in that: The steps include: (1) dissolving aluminum salt and cobalt salt in water to obtain an aluminum-cobalt mixed solution; dissolving a precipitant in water to obtain a precipitant solution; dissolving a complexing agent in water to obtain a complexing agent solution; using an ammonium salt aqueous solution or ammonia water as an additive solution; (2) mixing the aluminum-cobalt mixed solution, the precipitant solution, the complexing agent solution, and the additive solution for wet synthesis, and controlling the pH of the reaction system to be alkaline; (3) Starting from the overflow, the specific gravity of the mother liquor in the reaction system is measured regularly and controlled by adding water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide generated by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain the aluminum-doped cobalt tetroxide without impurities.

2. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (1), the aluminum concentration of the aluminum-cobalt mixed solution is 1.0-1.5 g / L, and the cobalt concentration is 90-160 g / L.

3. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (1), the aluminum salt includes one of aluminum chloride, aluminum sulfate, and aluminum acetate; the cobalt salt includes one of cobalt sulfate, cobalt chloride, and cobalt nitrate.

4. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (1), the concentration of the precipitant solution is 180-260 g / L; the precipitant includes sodium hydroxide or potassium hydroxide.

5. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (1), the concentration of the complexing agent solution is 0.1-0.5 g / L; the complexing agent includes one of sodium citrate, EDTA, and sodium pyrophosphate.

6. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (1), the concentration of the additive solution is 0.01-0.15 g / L.

7. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by in-situ ion occupation according to claim 1, characterized in that: In the step (2), when the amount of the aluminum-cobalt mixed solution is 140-180 L, the amount of the precipitant solution is 180-220 L, the amount of the complexing agent introduced into the complexing agent solution is 0.09-0.15 mol, and the amount of ammonium ions introduced into the additive solution is 0.05-0.10 mol.

8. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (2), the reaction temperature of the wet synthesis is 45-75°C; and the pH of the reaction system is controlled to be 9.2-10.

8.

9. The method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupation according to claim 1, characterized in that: In the step (3), the specific gravity of the mother liquor in the reaction system is measured every 1-2 hours, and the specific gravity of the mother liquor is controlled to be 1-1.1 by adding water.

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