A method for reducing sodium ion content in aluminum-doped cobalt oxide in situ ion occupation

Abstract

The application discloses a method for reducing the content of sodium ions in doped aluminum-containing tricobalt tetraoxide in situ by ion occupation, and belongs to the technical field of tricobalt tetraoxide processing. The method is simple in operation, low in reagent cost, and easy to realize industrial production. The removal degree of sodium ions can be flexibly controlled by adjusting an additive solution and reaction conditions, the content of sodium ions in the doped tricobalt tetraoxide 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 crucial 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] Aluminum doping can improve the stability of lithium cobalt oxide's crystal structure. During high-voltage charging, lithium cobalt oxide materials may undergo irreversible structural phase transitions, leading to crystal collapse. Aluminum doping can mitigate this risk, thereby improving the cycling performance of lithium cobalt oxide at high voltages. The high voltage and high density of aluminum-doped cobalt oxide make it an ideal material for high-energy density batteries. This is particularly important for 3C electronic products, which require batteries that are lightweight and compact while still providing sufficient energy to meet device endurance requirements. Aluminum-doping cobalt oxide can improve the electrochemical performance of lithium cobalt oxide cathode materials, including increasing specific capacity and cycling stability. Controlling the aluminum doping level within a certain range can optimize the material's electrochemical properties, enabling better performance at high voltages. During high-voltage charging, lithium cobalt oxide materials may react with the electrolyte, posing a safety hazard. Aluminum doping can mitigate this risk by forming a stable structure that reduces adverse reactions with the electrolyte, thereby improving battery safety. 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] During the production of aluminum-doped cobalt oxide (Al-COO), the presence of sodium ion impurities is a significant issue. These impurities are often difficult to remove through conventional washing processes and can become embedded in the Co-COO crystal lattice, negatively impacting the material's electrochemical performance. To improve the quality of Al-doped Co-COO and ensure its efficient application in lithium-ion batteries, developing effective impurity removal technologies is crucial.

[0005] In industrial production, repeated centrifugal washing or high-temperature calcination is often used to reduce the sodium ion content. For centrifugal washing, the efficiency of sodium ion removal 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 becomes less and less obvious. This is because the sodium ions are deeply embedded in the structure of cobalt trioxide, and simple physical washing is difficult to completely remove them. For high-temperature calcination, although it can change the structure of cobalt trioxide 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. In addition, the high-temperature calcination process itself requires a large amount of energy supply. Coupled with the 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 battery safety and cycle stability, meet the stringent requirements of 3C electronic products for 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 oxide by in-situ ion occupancy is provided, which is efficient, low-cost, and has little damage to product quality. The method comprises the following steps:

[0008] (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;

[0009] (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;

[0010] (3) Starting from the overflow, the mother liquor density of the reaction system is measured regularly and the mother liquor density is controlled by adding water;

[0011] (4) When the particle size D50 of the aluminum-doped cobalt tetroxide produced by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain the impurity-free aluminum-doped cobalt tetroxide.

[0012] 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.

[0013] 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.

[0014] Preferably, in step (1), the concentration of the precipitant solution is 180-260 g / L; the precipitant includes sodium hydroxide or potassium hydroxide.

[0015] 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.

[0016] Preferably, in step (1), the concentration of the additive solution is 0.01-0.15 g / L.

[0017] Based on the reactor volume commonly used in the art, the amount of aluminum-cobalt mixed solution used in industrial production is generally 140-180 L. Accordingly, the amounts of other raw materials are also controlled within appropriate ranges. Based on the dosage relationship of the present invention, those skilled in the art can scale up or down the raw materials according to the actual scale of synthesis.

[0018] 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.

[0019] 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.

[0020] Under the reaction conditions of the present invention, the mother liquor specific gravity is suitably controlled at 1-1.1. This ratio 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 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 mother liquor specific gravity is too high, the particles may grow too fast, forming larger particles, while if the mother liquor specific gravity is too low, the particles may grow too slowly, forming smaller particles.

[0021] Preferably, in step (3), the specific gravity of the mother liquor of 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.

[0022] During wet synthesis, to better control reaction conditions and improve product quality and production efficiency, those skilled in the art can split the reactors as necessary, depending on their actual conditions. Splitting allows each reactor to independently control parameters such as temperature, pH, and stirring speed, ensuring optimal reaction conditions. This allows for better control of reaction conditions, reduces the introduction of impurities, improves product purity and consistency, and allows for simultaneous processing of multiple batches, shortening production cycles and increasing production efficiency.

[0023] It should be noted that the applicant's application in the same period includes a scheme of adding an aqueous ammonium chloride solution or ammonia water to the cobalt oxide 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 oxide product will gradually be 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 utilizes in-situ ion occupancy to complex with the complexing agent, thereby reducing the complexation of the complexing agent with sodium ions, effectively reducing the sodium ion content in the subsequent aluminum-doped cobalt oxide product, and improving product quality. The present invention and the scheme of 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.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] The present invention provides a method for reducing the sodium ion content in aluminum-doped cobalt oxide by in-situ ion occupancy. The method is simple to operate, uses low-cost reagents, and is easy to implement in industrial production. The degree of sodium ion removal can be flexibly controlled by adjusting the additive solution and reaction conditions, thereby effectively reducing the sodium ion content in the doped cobalt oxide and improving the purity and quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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

[0027] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0028] Example 1

[0029] 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:

[0030] (1) Dissolve aluminum chloride and cobalt chloride in water to obtain an aluminum-cobalt mixed solution (cobalt concentration is 110 g / L and 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); and use an aqueous ammonium chloride solution (concentration is 0.01 g / L) as an additive solution;

[0031] (2) Add the aluminum-cobalt mixed solution (160 L), the precipitant solution (195 L), the complexing agent solution (containing 0.12 mol of EDTA), and the additive solution (containing 0.09 mol of ammonium ions) into a reaction kettle to perform wet synthesis, and control the pH value of the reaction system to be 10 and the reaction temperature to be 60 ℃;

[0032] (3) After overflow, measure the specific gravity of the mother liquor of the reaction system every 2 h, and control the specific gravity of the mother liquor to be between 1 and 1.1 by supplementing pure water;

[0033] (4) When the particle size D50 of the aluminum-doped tricobalt tetraoxide generated in the reaction reaches 3-5 μm, stop the reaction, recover the product, and perform pressure filtration, washing, drying, and calcination to obtain the aluminum-doped tricobalt tetraoxide with impurities removed.

[0034] Example 2

[0035] This example is basically the same as Example 1, and the only difference is that the concentration of the aqueous ammonium chloride solution used in this example is 0.05 g / L.

[0036] Example 3

[0037] This example is basically the same as Example 1, and the only difference is that the concentration of the aqueous ammonium chloride solution used in this example is 0.09 g / L.

[0038] Example 4

[0039] This example is basically the same as Example 1, and the only difference is that the concentration of the aqueous ammonium chloride solution used in this example is 0.13 g / L.

[0040] Example 5

[0041] This example is basically the same as Example 1, and the only difference is that the concentration of the aqueous ammonium chloride solution used in this example is 0.15 g / L.

[0042] Example 6

[0043] A method for reducing the content of sodium ions in aluminum-doped tricobalt tetraoxide in situ by ion occupation, comprising the following steps:

[0044] (1) Dissolve aluminum chloride and cobalt chloride in water to obtain an aluminum-cobalt mixed solution (cobalt concentration is 110 g / L and 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); and use ammonia water (concentration is 0.01 g / L) as an additive solution;

[0045] (2) Add the aluminum-cobalt mixed solution (160 L), the precipitant solution (195 L), the complexing agent solution (containing 0.12 mol of EDTA) and the additive solution (containing 0.09 mol of ammonium ions) into a reaction kettle to perform wet synthesis, and control the pH value of the reaction system to be 10 and the reaction temperature to be 60 ℃;

[0046] (3) After overflow, measure the specific gravity of the mother liquor of the reaction system every 2 h, and control the specific gravity of the mother liquor to be between 1 and 1.1 by supplementing pure water;

[0047] (4) When the particle size D50 of the aluminum-doped tricobalt tetraoxide generated in the reaction reaches 3-5 μm, stop the reaction, recover the product and perform pressure filtration, washing, drying and calcination to obtain the aluminum-doped tricobalt tetraoxide after impurity removal.

[0048] Example 7

[0049] This example is basically the same as Example 1, and the only difference is that the concentration of ammonia water used in this example is 0.05 g / L.

[0050] Example 8

[0051] This example is basically the same as Example 1, and the only difference is that the concentration of ammonia water used in this example is 0.09 g / L.

[0052] Example 9

[0053] This example is basically the same as Example 1, and the only difference is that the concentration of ammonia water used in this example is 0.13 g / L.

[0054] Example 10

[0055] This example is basically the same as Example 1, and the only difference is that the concentration of ammonia water used in this example is 0.15 g / L.

[0056] Comparative Example 1

[0057] This comparative example uses a processing method without adding an additive solution as a comparison, and the steps are as follows:

[0058] (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);

[0059] (2) Aluminum-cobalt mixed solution (160 L), precipitant solution (195 L), and complexing agent solution (containing 0.12 mol EDTA) were added to the reactor for wet synthesis. The pH value of the reaction system was controlled to be 10 and the reaction temperature was 60 °C.

[0060] (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;

[0061] (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 impurity-free aluminum-doped cobalt tetroxide.

[0062] The aluminum-doped cobalt oxides of the examples and comparative examples were first digested with strong acid, and then the sodium ion content was measured using ICP. The sodium ion content of the products was measured in the presence of different concentrations of aqueous ammonium chloride and ammonia, as well as in the absence of treatment. The results are shown in Tables 1 and 2, respectively.

[0063] Table 1: Relationship between the sodium ion content in aluminum-doped cobalt oxide and the concentration of ammonium chloride aqueous solution

[0064]

[0065] Table 2: Relationship between the sodium ion content in aluminum-doped cobalt oxide and the concentration of ammonia water

[0066]

[0067] The increase in the concentration of the ammonium chloride solution or ammonia water does not show a positive correlation with the degree of reduction in sodium ion content. When the concentration increases to a certain level, the effect of reducing sodium ion content will rebound. By adjusting the concentration of the ammonia water or ammonium chloride solution and the reaction conditions, the present invention can flexibly control the degree of sodium ion removal.

[0068] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined 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; 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; (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; When the amount of aluminum-cobalt mixed solution is 140-180 L, the amount of precipitant solution is 180-220 L, the amount of complexing agent introduced by the complexing agent solution is 0.09-0.15 mol, and the amount of ammonium ions introduced by the additive solution is 0.05-0.10 mol; (3) Starting from the overflow, the mother liquor density of the reaction system is measured regularly and the mother liquor density is controlled by adding water; (4) When the particle size D50 of the aluminum-doped cobalt tetroxide produced by the reaction reaches 3-5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain the impurity-free aluminum-doped cobalt tetroxide.

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 of 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 additive solution is 0.01-0.15 g / L.

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 (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.

7. 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 of 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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