A kind of high-doped aluminum cobalt tetroxide and preparation method thereof

Abstract

The present invention discloses a method for preparing highly doped aluminum cobalt oxide, comprising the following steps: preparing a mixed solution A containing a cobalt salt, an aluminum salt, and a complexing agent; the complexing agent being a mixture of a soluble sulfide and a soluble phosphate; adding the mixed solution A and an alkaline solution to a bottom solution, adjusting the pH, controlling the reaction temperature, and reacting to obtain a reactant B; filtering and washing the reactant B, performing a first calcination and subsequent washing; then performing a second calcination and screening to obtain the product. The product prepared by the method of the present invention utilizes a mixture of sulfide and phosphate as a dual complexing agent instead of an ammonia complexing agent, significantly improving the environmental pollution of the production process and effectively reducing environmental treatment costs. The prepared product has a more uniform morphology, good particle consistency, a high specific surface area, and can achieve an aluminum content of up to approximately 10,000 ppm of cobalt oxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion positive electrode materials, and in particular relates to a method for preparing highly doped aluminum cobalt tetroxide. Background Art

[0002] Lithium batteries are currently one of the most important components in mobile phones and new energy vehicles and are widely used. Lithium cobalt oxide is an important cathode material for lithium batteries. Lithium cobalt oxide is primarily formed by sintering cobalt tetroxide with lithium carbonate or lithium hydroxide. Therefore, cobalt tetroxide is the most important factor in determining the quality of lithium cobalt oxide. Its specific surface area and electron microscopic morphology have a crucial impact on the final cathode material. As the price of cobalt materials has been rising due to supply constraints, finding a way to replace or reduce the amount of cobalt metal is undoubtedly the best option, and doping is one of the most effective methods. Doping elements can not only improve the stability of the lattice but also significantly enhance the cycling performance of battery materials. Aluminum doping is one of the most common doping elements. Studies have shown that doping can improve the sensing performance of nanometal oxide gas sensors, and doping can increase the sensitivity and stability of the material.

[0003] Chinese patent CN110078133A discloses an aluminum-doped quasi-spherical cobalt oxide, its preparation method, and application. The preparation method is as follows: a soluble aluminum salt is mixed with a first precipitant to produce an amorphous aluminum hydroxide emulsion. The aluminum hydroxide emulsion is then reacted with a soluble cobalt salt solution, a second precipitant solution, and other additives in parallel to produce an aluminum-doped cobalt oxide precursor. The precursor is then calcined to produce the quasi-spherical cobalt oxide.

[0004] Disadvantages of this patent include:

[0005] 1. The steps are complicated. The addition of doping element aluminum requires the pre-preparation of emulsion, which is equivalent to an extra step in industrial application and greatly increases the reaction cost;

[0006] 2. The reaction uses two precipitants, and the process is more complicated;

[0007] 3. Ammonia water is used as the second precipitant, and an ammonia absorption device is required during the synthesis process, which increases capital investment. Moreover, due to the use of ammonia, if the volatilized ammonia gas cannot be completely treated, it will cause great damage to the environment.

[0008] Based on this, there is an urgent need for an aluminum-doped cobalt tetroxide and a preparation method thereof that can achieve good doping effect, is easy to operate, and is environmentally friendly. Summary of the Invention

[0009] In order to solve the above technical problems, the present invention provides a highly doped aluminum cobalt oxide and a preparation method thereof.

[0010] The technical solutions provided by the present invention are as follows:

[0011] In a first aspect, a method for preparing highly doped aluminum cobalt oxide is provided, comprising the following steps:

[0012] Prepare a mixed solution A containing cobalt salt, aluminum salt and a complexing agent; the complexing agent is a mixture of soluble sulfide and soluble phosphate;

[0013] Adding the mixed solution A and the alkali solution to the bottom solution, adjusting the pH, controlling the reaction temperature, and reacting to obtain the reactant B;

[0014] The reactant B is filtered and washed, calcined for the first time and then washed; then calcined for the second time and sieved to obtain the product.

[0015] In a possible implementation manner, the cobalt salt includes one or a mixture of cobalt chloride and cobalt sulfate; and the aluminum salt includes one or a mixture of aluminum chloride and aluminum sulfate.

[0016] Furthermore, in the mixed solution A, the concentration of the cobalt salt is 100-140 g / L, the concentration of the aluminum salt is 1-10 g / L, and the concentration of the complexing agent is 1-3 g / L.

[0017] In a possible implementation manner, the soluble sulfide is sodium sulfide or potassium sulfide; and the soluble phosphate is disodium hydrogen phosphate or dipotassium hydrogen phosphate.

[0018] Furthermore, in the complexing agent, the mass ratio of soluble phosphate to soluble sulfide is 1:(1-3).

[0019] In one possible implementation method, the reaction temperature is controlled at 65° C.-71° C., and the pH is adjusted to 7-12.

[0020] In a possible implementation manner, the first calcination temperature is 300-500°C.

[0021] In a possible implementation manner, the second calcination temperature is 600-750°C.

[0022] In a possible implementation manner, the base liquid is water.

[0023] The present invention provides an improved method that, through improvements to the control process, selects a dual complexing agent and adds it to the reaction process in a suitable manner, ensuring that the aluminum doping level in the synthesized cobalt oxide product reaches 10,000 ppm or more, and is evenly distributed throughout the cobalt oxide particles. Furthermore, while ensuring the aluminum doping level, the resulting aluminum-doped cobalt oxide product exhibits a uniform spherical morphology with minimal morphological variation and uniform particle size distribution. Two washing and calcining steps are used during the process, maintaining a stable BET value of the product between 3 and 4. Furthermore, the dual complexing agent replaces the commonly used complexing agent, such as ammonia, in the process, effectively alleviating the problem of atmospheric ammonia pollution during the production process.

[0024] In a second aspect, a highly doped aluminum cobalt tetroxide is provided, which is prepared by the method described in the first aspect.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The method provided by the present invention uses a mixture of sulfide and phosphate as a dual complexing agent instead of an ammonia complexing agent, significantly reducing environmental pollution during the production process and effectively reducing environmental treatment costs. This dual complexing agent has a precipitation coefficient of the same order of magnitude when precipitating aluminum-doped cobalt oxide, thus achieving a good coprecipitation effect and ensuring high aluminum content in the cobalt oxide.

[0027] 2. The method provided by the present invention effectively synthesizes highly aluminum-doped cobalt tetroxide particles by controlling the reaction conditions, making the reaction process more stable and the high-concentration aluminum doping more uniform. The stable reaction conditions also lead to a more uniform morphology of the reaction product and better particle consistency.

[0028] 3. The method of the present invention uses a staged calcination process to effectively control the BET and morphology stability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 EPMA (electron probe) image of the product prepared in Example 1;

[0030] Figure 2 EPMA (electron probe) image of the product prepared in Example 2;

[0031] Figure 3 EPMA (electron probe) image of the product prepared in Example 3;

[0032] Figure 4 EPMA (electron probe) image of the product prepared in Comparative Example 1;

[0033] Figure 5 This is the SEM image of the product prepared in Comparative Example 2. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited thereto.

[0035] A method for preparing highly doped aluminum cobalt oxide comprises the following steps:

[0036] Prepare a mixed solution A containing cobalt salt, aluminum salt and a complexing agent; the complexing agent is a mixture of soluble sulfide and soluble phosphate;

[0037] Adding the mixed solution A and the alkali solution to the bottom solution, adjusting the pH, controlling the reaction temperature, and reacting to obtain the reactant B;

[0038] The reactant B is filtered and washed, calcined for the first time and then washed; then calcined for the second time and sieved to obtain the product.

[0039] In a possible implementation manner, the cobalt salt includes one or a mixture of cobalt chloride and cobalt sulfate; and the aluminum salt includes one or a mixture of aluminum chloride and aluminum sulfate.

[0040] Furthermore, in the mixed solution A, the concentration of the cobalt salt is 100-140 g / L, the concentration of the aluminum salt is 1-10 g / L, and the concentration of the complexing agent is 1-3 g / L.

[0041] In a possible implementation manner, the soluble sulfide is sodium sulfide or potassium sulfide; and the soluble phosphate is disodium hydrogen phosphate or dipotassium hydrogen phosphate.

[0042] Furthermore, in the complexing agent, the mass ratio of soluble phosphate to soluble sulfide is 1:(1-3). The complexing agent is a double complexing agent, which has the same order of magnitude of precipitation coefficient (Ksp is 10 -7 About, (HPO4) 2- In the precipitation of Co 2+ When Ksp is , S 2- In the precipitation of Al 3+ When Ksp is ), have the same precipitation coefficient, so a better co-precipitation effect can be achieved, and high content Al doping in cobalt tetroxide is guaranteed.

[0043] In one possible implementation method, the reaction temperature is controlled at 65° C.-71° C., and the pH is adjusted to 7-12.

[0044] In a possible implementation manner, the first calcination temperature is 300-500°C.

[0045] In a possible implementation manner, the second calcination temperature is 600-750°C.

[0046] In a possible implementation manner, the base liquid is water.

[0047] The relevant principles of the method of the present invention are as follows:

[0048] The two complexing agents have different coordination capabilities. Phosphate ions can form stable complexes with cobalt and aluminum ions, reducing the mobility of the metal ions and thus controlling their precipitation rate. Sulfide can form coordination complexes with aluminum ions, further stabilizing the presence of aluminum ions and preventing their premature precipitation. Both complexing agents can regulate the distribution and morphology of cobalt and aluminum ions during the precursor formation process, ensuring a uniform distribution of aluminum ions in the precursor. This also ensures that aluminum ions are uniformly incorporated into the Co3O4 lattice after heat treatment, improving the uniformity of aluminum doping.

[0049] Staged calcination can effectively control the size and surface properties of the particles, thereby affecting the specific surface area of ​​the material. At lower temperatures, aluminum ions can diffuse more evenly into the cobalt oxide lattice, and low-temperature calcination can reduce the adsorbed moisture on the surface and inside the precursor, reducing the adhesion between particles, so that the sodium salts on the surface or in the gaps no longer adhere tightly to the precursor. These sodium salts are therefore more easily dissolved and carried away by water during the washing process. At high temperatures, the doping of aluminum ions can be more stable, thereby ensuring the uniform chemical composition of the final product. Staged calcination can gradually reduce the stress and defects inside the material, which is very important for improving the stability of the material in high temperature and chemical environments.

[0050] Example 1

[0051] A method for preparing highly doped aluminum cobalt oxide, comprising the following steps:

[0052] (1) Preparation of mixed solution A:

[0053] Cobalt chloride, aluminum chloride, sodium sulfide, and disodium hydrogen phosphate were dissolved in water to obtain a mixed solution A. The concentration of cobalt chloride was 130 g / L, the concentration of aluminum chloride was 1.2 g / L, the concentration of sodium sulfide was 1 g / L, and the concentration of disodium hydrogen phosphate was 1 g / L.

[0054] (2) Add the mixed solution A and alkali solution (sodium hydroxide solution) to the bottom liquid (water), adjust the pH to 7-12, control the reaction temperature to 65°C-71°C, and react to obtain reactant B;

[0055] (3) The reactant B is filtered and washed until the conductivity reaches the standard of pure water; then the reactant B is calcined for the first time at a temperature of 420°C; then the reactant B is washed for the second time at a temperature of 700°C, and then sieved through 200 mesh.

[0056] After testing, the particle size consistency of the product of this embodiment is 0.208, and the BET is 3.6m 2 / g, aluminum content is 6600ppm. EPMA (electron probe) graph is as follows Figure 1 As shown in the figure, it can be seen that the aluminum is doped evenly, and the blue is aluminum.

[0057] Example 2

[0058] A method for preparing highly doped aluminum cobalt oxide, comprising the following steps:

[0059] (1) Preparation of mixed solution A:

[0060] Cobalt chloride, aluminum chloride, sodium sulfide, and disodium hydrogen phosphate were dissolved in water to obtain a mixed solution A. The concentration of cobalt chloride was 140 g / L, the concentration of aluminum chloride was 2 g / L, the concentration of sodium sulfide was 3 g / L, and the concentration of disodium hydrogen phosphate was 2 g / L.

[0061] (2) Add the mixed solution A and alkali solution (sodium hydroxide solution) to the bottom liquid (water), adjust the pH to 7-12, control the reaction temperature to 65°C-71°C, and react to obtain reactant B;

[0062] (3) The reactant B is filtered and washed until the conductivity reaches the standard of pure water; then the reactant B is calcined for the first time at a temperature of 350°C; then the reactant B is washed for the second time at a temperature of 740°C, and then sieved through 200 mesh.

[0063] After testing, the particle size consistency of the product of this embodiment is 0.226, and the BET is 3.25m 2 / g, aluminum content is 10300ppm. EPMA chart as shown Figure 2 As shown, it can be seen from the figure that the aluminum doping is uniform.

[0064] Example 3

[0065] A method for preparing highly doped aluminum cobalt oxide, comprising the following steps:

[0066] (1) Preparation of mixed solution A:

[0067] Cobalt chloride, aluminum chloride, sodium sulfide, and disodium hydrogen phosphate were dissolved in water to obtain a mixed solution A. The concentration of cobalt chloride was 110 g / L, the concentration of aluminum chloride was 1.27 g / L, the concentration of sodium sulfide was 2 g / L, and the concentration of disodium hydrogen phosphate was 1 g / L.

[0068] (2) Add the mixed solution A and alkali solution (sodium hydroxide solution) to the bottom liquid (water), adjust the pH to 7-12, control the reaction temperature to 65°C-71°C, and react to obtain reactant B;

[0069] (3) The reactant B is filtered and washed until the conductivity reaches the standard of pure water; then the reactant B is calcined for the first time at a temperature of 420°C; then the reactant B is washed for the second time at a temperature of 680°C, and then sieved through 200 mesh.

[0070] After testing, the particle size consistency of the product of this embodiment is 0.195, and the BET is 3.81m 2 / g, aluminum content is 8300ppm. EPMA chart as shown Figure 3 As shown, it can be seen from the figure that the aluminum doping is uniform.

[0071] Comparative Example 1

[0072] A method for preparing highly doped aluminum cobalt oxide, comprising the following steps:

[0073] (1) Preparation of mixed solution A:

[0074] Cobalt chloride, aluminum chloride, and sodium sulfide were dissolved in water to obtain a mixed solution A, wherein the concentration of cobalt chloride was 130 g / L, the concentration of aluminum chloride was 1.2 g / L, and the concentration of sodium sulfide was 1 g / L.

[0075] (2) Add the mixed solution A and alkali solution (sodium hydroxide solution) to the bottom liquid (water), adjust the pH to 7-12, control the reaction temperature to 65°C-71°C, and react to obtain reactant B;

[0076] (3) The reactant B is filtered and washed until the conductivity reaches the standard of pure water; then the reactant B is calcined for the first time at a temperature of 420°C; then the reactant B is washed for the second time at a temperature of 700°C, and then sieved through 200 mesh.

[0077] After testing, the particle size consistency of the product of this embodiment is 0.431, and the BET is 3.89m 2 / g, aluminum content is 6600ppm. EPMA chart as shown Figure 4 As shown in the figure, it can be seen that there is a place with high aluminum content and uneven doping.

[0078] Comparative Example 2

[0079] A method for preparing highly doped aluminum cobalt oxide, comprising the following steps:

[0080] (1) Preparation of mixed solution A:

[0081] Cobalt chloride, aluminum chloride, and disodium hydrogen phosphate were dissolved in water to obtain a mixed solution A, wherein the concentration of cobalt chloride was 110 g / L, the concentration of aluminum chloride was 1.27 g / L, and the concentration of disodium hydrogen phosphate was 1 g / L.

[0082] (2) Add the mixed solution A and alkali solution (sodium hydroxide solution) to the bottom liquid (water), adjust the pH to 7-12, control the reaction temperature to 65°C-71°C, and react to obtain reactant B;

[0083] (3) The reactant B is filtered and washed until the conductivity reaches the standard of pure water; then it is calcined at a temperature of 680°C and sieved through 200 mesh.

[0084] After testing, the particle size consistency of the product of this embodiment is 0.480, and the BET is 4.18m 2 / g, aluminum content is 8300ppm. SEM picture Figure 5 As shown in the figure, it can be seen that the particle size is uneven and there are many small particles.

[0085] Related test results and analysis:

[0086] The relevant test results are shown in Table 1.

[0087] Table 1 Performance test results

[0088]

[0089] Note: Aluminum content is based on cobalt tetroxide.

[0090] Table 1 shows that the use of a dual complexing agent and secondary calcination process results in more uniform aluminum doping, improved particle size consistency, and a more stable specific surface area. Good particle size control increases the material's bulk density, thereby improving the battery's energy density and extending its life. A stable specific surface area ensures more consistent electrochemical performance across batches of material, enhancing product controllability and reliability.

[0091] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent replacements and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention should be included in the scope of protection of the invention.

Claims

1. A method for preparing highly doped aluminum cobalt oxide, characterized in that: The following steps are involved: A mixed solution A containing a cobalt salt, an aluminum salt and a complexing agent is prepared; the complexing agent is a mixture of a soluble sulfide and a soluble phosphate, and the mass ratio of the soluble phosphate to the soluble sulfide is 1:(1-3); the soluble sulfide is sodium sulfide or potassium sulfide; and the soluble phosphate is disodium hydrogen phosphate or dipotassium hydrogen phosphate; Adding mixed solution A and alkali solution to the bottom solution, adjusting the pH to 7-12, controlling the reaction temperature to 65°C-71°C, and reacting to obtain reactant B; in the mixed solution A, the concentration of cobalt salt is 100-140 g / L, the concentration of aluminum salt is 1-10 g / L, and the concentration of complexing agent is 1-3 g / L; The reactant B is filtered and washed, calcined for the first time and then washed; then calcined for the second time and sieved to obtain the product.

2. The method for preparing highly doped aluminum cobalt oxide according to claim 1, characterized in that: The cobalt salt includes one of cobalt chloride and cobalt sulfate or a mixture of the two; the aluminum salt includes one of aluminum chloride and aluminum sulfate or a mixture of the two.

3. The method for preparing highly doped aluminum cobalt oxide according to claim 1, characterized in that: The first calcination temperature is 300~500℃.

4. The method for preparing highly doped aluminum cobalt oxide according to claim 1, wherein: The second calcination temperature is 600~750℃.

5. The method for preparing highly doped aluminum cobalt oxide according to claim 1, characterized in that: The base liquid is water.

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