Method for reducing sodium ion content in aluminum-doped cobaltosic oxide through auxiliary oxidation

Abstract

The invention discloses a method for reducing the content of sodium ions in aluminum-doped cobaltosic oxide through auxiliary oxidation, and belongs to the technical field of treatment of cobaltosic oxide. According to the method, the oxidizing agent is used for reducing the wrapping degree of a cobaltic acid phase in synthesis, subsequent purification operation is facilitated, the content of sodium ions in aluminum-doped cobaltosic oxide can be effectively reduced, the purity and quality of the product are improved, and the removal degree of the sodium ions can be flexibly controlled by adjusting the concentration of the oxidizing agent and reaction conditions; the method has the advantages that the operation is simple, the cost of used reagents is low, and industrial production is easy to realize.

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 auxiliary oxidation. Background Art

[0002] In the field of battery manufacturing, cobalt oxide has an important value that cannot be ignored. Its core use is to prepare lithium cobalt oxide positive electrode materials. Lithium cobalt oxide positive electrode materials occupy a pivotal position in the field of 3C electronic product batteries and are widely used in many 3C electronic products such as large-capacity mobile phones, portable laptops and digital cameras.

[0003] 3C electronic products, based on their own unique property requirements, are characterized by lightness and compactness, which places strict requirements on the energy density of the batteries used. As the most important positive electrode material in current 3C electronic products, the energy density of lithium cobalt oxide plays a decisive role in the energy density of lithium-ion batteries to a large extent.

[0004] Aluminum-doped cobalt oxide plays an important role in the preparation of lithium cobalt oxide positive electrode materials. By adding aluminum to cobalt oxide, the electrochemical properties of lithium cobalt oxide can be significantly improved, especially the structural stability and cycle performance under high voltage. Aluminum doping can effectively increase the charge cutoff voltage of lithium cobalt oxide, thereby increasing the specific capacity of the material, while also reducing the capacity attenuation under high voltage and improving the cycle stability of the material.

[0005] In the production process of aluminum-doped cobalt tetroxide, there will inevitably be a certain amount of sodium ion impurities. These sodium ion impurities are difficult to remove by simple washing operations. The reason may be that the cobalt tetroxide and cobalt oxyhydroxide are very tightly wrapped during the synthesis process. This tight wrapping condition causes the sodium ions to be wrapped inside the crystal, and these residual sodium ions will have an adverse effect on the performance of cobalt tetroxide and its subsequent applications.

[0006] At present, although there are some commonly used methods to reduce the sodium ion content, these methods all have defects to varying degrees. Some of these methods are extremely inefficient and require a lot of time and resources to reduce the sodium ion content; some methods are too expensive, which will inevitably increase the production costs of enterprises and weaken the competitiveness of products in the market; in addition, although some methods can reduce the sodium ion content, they will cause a certain degree of damage to product quality, which is obviously very unfavorable to the overall benefits of the product. 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 auxiliary oxidation is provided, which has high efficiency, low cost and little damage to product quality, and comprises the following steps: (1) preparing an aluminum-cobalt mixed solution, a precipitant solution, and a complexing agent solution; using one of oxygen, oxygen and sodium chlorate, or oxygen and ozone as an oxidant; (2) adding alkaline solution as bottom water into the reactor, then heating to the reaction temperature, introducing air into the reactor under stirring conditions to complete the reaction preparation; mixing the oxidant and the aluminum-cobalt mixed solution, further mixing with the complexing agent solution, adding the resulting mixed solution into the reactor, then adding the precipitant solution, and controlling the pH of the reaction system to be alkaline; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and separate the reactor when it exceeds a certain concentration; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0008] Preferably, in step (1), the aluminum-cobalt mixed solution is prepared by dissolving water-soluble aluminum salt and cobalt salt in water; wherein the cobalt concentration is 90-160 g / L and the aluminum concentration is 1.0-1.5 g / L.

[0009] Taking into account the availability of raw materials, production costs and other factors, aluminum chloride, aluminum sulfate, aluminum acetate and the like are suitable aluminum salts for the present invention; correspondingly, cobalt sulfate, cobalt chloride, cobalt nitrate and the like can be selected as cobalt salts.

[0010] Further preferably, 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.

[0011] Preferably, in step (1), the precipitant solution is ammonia water or one of sodium hydroxide and potassium hydroxide dissolved in water; the concentration of the precipitant solution is 180-260 g / L.

[0012] Preferably, in step (1), the complexing agent solution is prepared by dissolving one of sodium citrate, EDTA and sodium pyrophosphate in water; the concentration of the complexing agent solution is 0.1-0.5 g / L.

[0013] Preferably, in step (2), the alkali solution is a sodium hydroxide aqueous solution with a concentration of 30-50 g / L; the amount of alkali solution added is sufficient to cover the stirring blade of the reactor.

[0014] Temperature control is particularly important in the preparation of aluminum-doped cobalt oxide. Too high a temperature may cause the reaction to be too violent and difficult to control, and may even cause side reactions, affecting the purity and crystallinity of the product. On the contrary, too low a temperature may cause the reaction rate to be too slow, affecting production efficiency and the microstructure of the product. Proper stirring can ensure that the reactants are fully in contact, promote the transfer of heat and substances, and thus improve the reaction rate and product uniformity.

[0015] Preferably, in step (2), the reaction temperature is 42-72°C; the stirring frequency is 27.5-31.5 Hz; and the air flow rate is 0.9-1.4 m 3 / h.

[0016] Preferably, in step (2), when the oxidant is oxygen, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1; when the oxidant is oxygen and sodium chlorate, the concentration of sodium chlorate added to the aluminum-cobalt mixed solution is 0.01-0.15 g / L, and the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1; when the oxidant is oxygen and ozone, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1, and the volume ratio of ozone addition to oxygen is 1-5:10.

[0017] Preferably, in step (2), the flow rate of the mixed solution is 90-140 L / h; the flow rate of the precipitant solution is 110-240 L / h; and the pH of the reaction system is controlled to be 9.0-10.5.

[0018] As the solid concentration increases, the contact opportunities between reactants decrease, resulting in a decrease in mass transfer efficiency. Separation of reactors can reduce the solid load in a single reactor and increase the contact area between materials, thereby improving mass transfer efficiency. Higher solid concentrations may cause the reaction rate to be too fast and difficult to control accurately. By operating in separate reactors, the reaction conditions in each reactor can be better controlled.

[0019] Preferably, in step (3), the solid concentration of the reaction solution is controlled at 200-400 g / L. When the solid concentration exceeds 400 g / L, the reaction mixture needs to be split into two reactors, with half of the material transferred to another reactor for synchronous growth.

[0020] The product after the reaction can be recovered, purified, dried, and calcined by common methods in the art, such as centrifugation, washing, flash drying, roller kiln calcination or other suitable methods.

[0021] The synthesized intermediate sample is a composite of cobalt acid and cobalt tetroxide. Using oxygen alone can reduce the residual sodium ions to a certain extent, but the cobalt acid in the intermediate sample is relatively compact and the sodium ions are still firmly wrapped inside, which is difficult to reduce through ordinary washing. After adding an auxiliary oxidant and using it in combination with oxygen, the degree of wrapping of the cobalt acid phase can be reduced, which is conducive to subsequent purification to reduce the sodium ion content.

[0022] 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 auxiliary oxidation. The method can effectively reduce the sodium ion content in aluminum-doped cobalt oxide, improve the purity and quality of the product, and can flexibly control the degree of sodium ion removal by adjusting the concentration of the oxidant and the reaction conditions. The method has the advantages of simple operation, low reagent cost, and easy industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of the method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation in Example 1. DETAILED DESCRIPTION

[0024] 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.

[0025] Example 1 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation, comprising the following steps: (1) Prepare an aluminum-cobalt mixed solution (prepared by dissolving aluminum chloride and cobalt chloride in water; wherein the cobalt concentration is 125 g / L and the aluminum concentration is 1.25 g / L), a precipitant solution (sodium hydroxide aqueous solution, 220 g / L), and a complexing agent solution (EDTA aqueous solution, 0.3 g / L); use oxygen as an oxidant, and the volume ratio of oxygen to the aluminum-cobalt mixed solution is 15:1; (2) Alkali solution (sodium hydroxide aqueous solution, 40 g / L) was added to the reactor as bottom water. The amount of alkali solution added was sufficient to cover the stirring blades of the reactor. The temperature was then raised to 57 °C. Air was continuously blown into the reactor under stirring conditions (29.5 Hz) (flow rate: 1.15 m 3 / h), complete the reaction preparation; mix the oxidant and the aluminum-cobalt mixed solution, and further mix it with the complexing agent solution, add the resulting mixed solution (flow rate: 115 L / h) into the reactor, then add the precipitant solution (flow rate: 175 L / h), and control the pH of the reaction system to 10.0; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and when it exceeds 400g / L, split the reactor and transfer half of the material to another reactor for synchronous growth; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, and centrifugal washing, flash drying, and roller kiln calcination are performed to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0026] Example 2 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation, comprising the following steps: (1) Prepare an aluminum-cobalt mixed solution (prepared by dissolving aluminum chloride and cobalt chloride in water; wherein the cobalt concentration is 125 g / L and the aluminum concentration is 1.25 g / L), a precipitant solution (sodium hydroxide aqueous solution, 220 g / L), and a complexing agent solution (EDTA aqueous solution, 0.3 g / L); use oxygen and ozone as oxidants, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 15:1, and the volume ratio of ozone to oxygen is 3:10; (2) Alkali solution (sodium hydroxide aqueous solution, 40 g / L) was added to the reactor as bottom water. The amount of alkali solution added was sufficient to cover the stirring blades of the reactor. The temperature was then raised to 57 °C. Air was continuously blown into the reactor under stirring conditions (29.5 Hz) (flow rate: 1.15 m 3 / h), complete the reaction preparation; mix the oxidant and the aluminum-cobalt mixed solution, and further mix it with the complexing agent solution, add the resulting mixed solution (flow rate: 115 L / h) into the reactor, then add the precipitant solution (flow rate: 175 L / h), and control the pH of the reaction system to 10.0; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and when it exceeds 400g / L, split the reactor and transfer half of the material to another reactor for synchronous growth; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, and centrifugal washing, flash drying, and roller kiln calcination are performed to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0027] Example 3 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation, comprising the following steps: (1) preparing an aluminum-cobalt mixed solution (prepared by dissolving aluminum chloride and cobalt chloride in water; wherein the cobalt concentration is 125 g / L and the aluminum concentration is 1.25 g / L), a precipitant solution (sodium hydroxide aqueous solution, 220 g / L), and a complexing agent solution (EDTA aqueous solution, 0.3 g / L); using oxygen and sodium chlorate as oxidants, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 15:1, and the concentration of sodium chlorate added to the aluminum-cobalt mixed solution is 0.1 g / L; (2) Alkali solution (sodium hydroxide aqueous solution, 40 g / L) was added to the reactor as bottom water. The amount of alkali solution added was sufficient to cover the stirring blades of the reactor. The temperature was then raised to 57 °C. Air was continuously blown into the reactor under stirring conditions (29.5 Hz) (flow rate: 1.15 m 3 / h), complete the reaction preparation; mix the oxidant and the aluminum-cobalt mixed solution, and further mix it with the complexing agent solution, add the resulting mixed solution (flow rate: 115 L / h) into the reactor, then add the precipitant solution (flow rate: 175 L / h), and control the pH of the reaction system to 10.0; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and when it exceeds 400g / L, split the reactor and transfer half of the material to another reactor for synchronous growth; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, and centrifugal washing, flash drying, and roller kiln calcination are performed to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0028] Example 4 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation, comprising the following steps: (1) Prepare an aluminum-cobalt mixed solution (prepared by dissolving aluminum sulfate and cobalt sulfate in water; wherein the cobalt concentration is 90 g / L and the aluminum concentration is 1.0 g / L), a precipitant solution (aqueous solution of potassium hydroxide, 180 g / L), and a complexing agent solution (aqueous solution of sodium citrate, 0.1 g / L); use oxygen as an oxidant, and the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10:1; (2) Alkali solution (sodium hydroxide aqueous solution, 30 g / L) was added to the reactor as bottom water. The amount of alkali solution added was sufficient to cover the stirring blades of the reactor. The temperature was then raised to 72 °C. Air (flow rate: 0.9 m / s) was continuously blown into the reactor under stirring conditions (31.5 Hz). 3 / h), complete the reaction preparation; mix the oxidant and the aluminum-cobalt mixed solution, and further mix it with the complexing agent solution, add the resulting mixed solution (flow rate: 140 L / h) into the reactor, then add the precipitant solution (flow rate: 240 L / h), and control the pH of the reaction system to 9.0; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and when it exceeds 400g / L, split the reactor and transfer half of the material to another reactor for synchronous growth; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, and centrifugal washing, flash drying, and roller kiln calcination are performed to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0029] Example 5 A method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation, comprising the following steps: (1) preparing an aluminum-cobalt mixed solution (prepared by dissolving aluminum acetate and cobalt nitrate in water; wherein the cobalt concentration is 160 g / L and the aluminum concentration is 1.5 g / L), a precipitant solution (potassium hydroxide aqueous solution, 260 g / L), and a complexing agent solution (sodium pyrophosphate aqueous solution, 0.5 g / L); using oxygen as an oxidant, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 20:1; (2) Alkali solution (sodium hydroxide aqueous solution, 50 g / L) was added to the reactor as bottom water. The amount of alkali solution added was sufficient to cover the stirring blades of the reactor. The temperature was then raised to 42°C. Air was continuously blown into the reactor under stirring conditions (27.5 Hz) (flow rate: 1.4 m / s). 3 / h), complete the reaction preparation; mix the oxidant and the aluminum-cobalt mixed solution, and further mix it with the complexing agent solution, add the resulting mixed solution (flow rate: 90 L / h) into the reactor, then add the precipitant solution (flow rate: 110 L / h), and control the pH of the reaction system to 10.5; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and when it exceeds 400g / L, split the reactor and transfer half of the material to another reactor for synchronous growth; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, and centrifugal washing, flash drying, and roller kiln calcination are performed to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

[0030] The aluminum-doped cobalt tetroxide of Example 1-3 was digested with a strong acid, and then the sodium ion content thereof was tested by ICP. The results are shown in Table 1.

[0031] Table 1: Sodium ion content of different aluminum-doped cobalt oxides

[0032] From the results in the table, we can see that using oxygen alone can reduce the residual sodium ions to a certain extent, but the cobalt acid in the intermediate sample is relatively compact, and the sodium ions are still firmly wrapped inside, which is difficult to reduce by ordinary washing. After adding an auxiliary oxidant and using it in combination with oxygen, the degree of wrapping of the cobalt acid phase can be further reduced, which is conducive to the subsequent washing to reduce the sodium ion content. Among them, the combination of ozone and oxygen has a better reduction effect. In summary, the method of reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation of the present invention can effectively reduce the sodium ion content in aluminum-doped cobalt tetroxide, improve the purity and quality of the product, and can flexibly control the degree of sodium ion removal by adjusting the concentration of ozone or sodium chlorate and the reaction conditions; it has the advantages of simple operation, low reagent cost, and easy industrial production.

[0033] 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 tetroxide by auxiliary oxidation, characterized in that: The steps include: (1) preparing an aluminum-cobalt mixed solution, a precipitant solution, and a complexing agent solution; using one of oxygen, oxygen and sodium chlorate, or oxygen and ozone as an oxidant; (2) adding alkaline solution as bottom water into the reactor, then heating to the reaction temperature, introducing air into the reactor under stirring conditions to complete the reaction preparation; mixing the oxidant and the aluminum-cobalt mixed solution, further mixing with the complexing agent solution, adding the resulting mixed solution into the reactor, then adding the precipitant solution, and controlling the pH of the reaction system to be alkaline; (3) When the reaction liquid in the reactor reaches the overflow port, close all feeds, stop stirring, keep the temperature constant, allow sedimentation, siphon off the mother liquor, and then continue to add reaction liquid; during the process, detect the solid concentration of the reaction liquid in the reactor, and separate the reactor when it exceeds a certain concentration; (4) When the particle size D50 of the particles in the reaction solution reaches 3.5-5.5 μm, the reaction is stopped, the product is recovered and purified, dried, and calcined to obtain aluminum-doped cobalt tetroxide with a low sodium ion content.

2. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (1), the aluminum-cobalt mixed solution is prepared by dissolving water-soluble aluminum salt and cobalt salt in water; wherein the cobalt concentration is 90-160 g / L and the aluminum concentration is 1.0-1.5 g / L.

3. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 2, characterized in that: 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 tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (1), the precipitant solution is prepared by dissolving ammonia water or sodium hydroxide or potassium hydroxide in water; the concentration of the precipitant solution is 180-260 g / L.

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

6. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (2), the alkali solution is a sodium hydroxide aqueous solution with a concentration of 30-50 g / L; the amount of alkali solution added is sufficient to cover the stirring blade of the reactor.

7. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (2), the reaction temperature is 42-72°C; the stirring frequency is 27.5-31.5 Hz; the air flow rate is 0.9-1.4 m 3 / h.

8. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (2), when the oxidant is oxygen, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1; when the oxidant is oxygen and sodium chlorate, the concentration of sodium chlorate added to the aluminum-cobalt mixed solution is 0.01-0.15 g / L, and the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1; when the oxidant is oxygen and ozone, the volume ratio of oxygen to the aluminum-cobalt mixed solution is 10-20:1, and the volume ratio of ozone addition to oxygen is 1-5:

10.

9. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (2), the flow rate of the mixed solution is 90-140 L / h; the flow rate of the precipitant solution is 110-240 L / h; and the pH of the reaction system is controlled to be 9.0-10.

5.

10. The method for reducing the sodium ion content in aluminum-doped cobalt tetroxide by auxiliary oxidation according to claim 1, characterized in that: In the step (3), the solid concentration of the reaction solution is controlled at 200-400 g / L. When the solid concentration exceeds 400 g / L, the reaction mixture needs to be split into two reactors, with half of the material transferred to another reactor for synchronous growth.

Images