WO2023207281A1 - Method for preparing magnesium-titanium co-doped cobalt carbonate and use thereof - Google Patents

Abstract

Disclosed in the present invention is a method for preparing magnesium-titanium co-doped cobalt carbonate and use thereof. The method comprises: adding a mixed cobalt-magnesium metal solution, a precipitant solution, and a titanium salt solution into a base solution in parallel for reaction, so as to give a magnesium-titanium co-doped cobalt carbonate slurry, wherein the precipitant solution is a mixed solution of a carbonate and a surfactant, and the titanium salt solution is a mixed solution of an acidic complexing agent and a titanium salt; and conducting solid-liquid separation on the magnesium-titanium co-doped cobalt carbonate slurry, and washing and drying the resultant solid to give the magnesium-titanium co-doped cobalt carbonate. According to the present invention, the independent feeding of the titanium salt and the addition of the acidic complexing agent in the titanium salt solution can achieve the effects of complexing titanium ions and inhibiting titanium hydrolysis at the same time. The mixing of the surfactant and the carbonate solution improves the adsorption capacity of the surface of the precursor secondary particle sphere in the synthesis stage and promotes the growth of the magnesium-titanium co-doped cobalt carbonate. Doping a bulk phase with magnesium and titanium elements significantly improves the rate capability of a lithium cobaltate positive material.

Description

Preparation method and application of magnesium and titanium co-doped cobalt carbonate Technical field

The invention belongs to the technical field of preparation of lithium ion battery cathode material precursors, and specifically relates to a preparation method and application of magnesium and titanium co-doped cobalt carbonate.

Background technique

Lithium cobalt oxide cathode material is mainly used in the 3C field due to its high energy density. With the popularity of 5G mobile phones, the requirements for lithium-ion battery life, size, and fast charging performance continue to increase. Doping cobalt carbonate with titanium element can increase the hexagonal structure layer spacing of lithium cobalt oxide cathode material, which is conducive to the deintercalation of lithium ions, making the lithium cobalt oxide crystal grains finer and increasing grain boundaries, shortening the lithium ion diffusion distance and reducing material diffusion. Internal resistance; Doping magnesium into cobalt carbonate can change the valence state of cobalt ions in lithium cobalt oxide, causing it to generate holes and electrons, improving the electronic conductivity of the material and improving the thermal stability of the material.

Patent CN112010354A discloses a titanium-doped cobalt tetroxide and its preparation method and application. The preparation process uses nanometer titanium dioxide as the titanium source to synthesize titanium-doped cobalt tetroxide. However, according to the electron microscope results, the particle size distribution is wide, which will affect lithium cobalt oxide. Processing performance. Patent CN112537801A discloses a continuous concentration gradient aluminum-titanium doped cobalt tetroxide and its preparation method. In the preparation process, nano-titanium dioxide is used as the titanium source. The doping amount of aluminum element and titanium element continuously increases in concentration gradient from the inside to the outside, making the material both doped and doped. The combination of hybrid and coating enhances the surface and cross-sectional stability of the material. However, since nano-titanium dioxide is difficult to dissolve in water, it requires powerful stirring equipment and effective dispersants.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention proposes a preparation method and application of magnesium and titanium co-doped cobalt carbonate.

According to one aspect of the present invention, a preparation method for magnesium and titanium co-doped cobalt carbonate is proposed, which includes the following steps:

S1: Add cobalt-magnesium mixed metal liquid, precipitant solution and titanium salt solution to the bottom liquid in parallel flow to react to obtain a magnesium-titanium co-doped cobalt carbonate slurry, wherein the bottom liquid is a carbonate solution, and the cobalt The magnesium mixed metal liquid is a mixed solution of cobalt salt and magnesium salt, the precipitant solution is a mixed solution of carbonate and surfactant, and the titanium salt solution is acidic. A mixed solution of a complexing agent and a titanium salt, the carbonate being ammonium bicarbonate or ammonium carbonate;

S2: The magnesium titanium co-doped cobalt carbonate slurry is subjected to solid-liquid separation, and the obtained solid is washed and dried to obtain the magnesium titanium co-doped cobalt carbonate.

In some embodiments of the present invention, in step S1, the surfactant is one or more of ammonium lauryl sulfate, sodium laurate or polyacrylamide.

In some embodiments of the present invention, in step S1, the titanium salt is one or more of titanium sulfate, titanium oxysulfate or titanium chloride.

In some embodiments of the present invention, in step S1, the cobalt salt is one or more of cobalt sulfate, cobalt nitrate or cobalt chloride.

In some embodiments of the present invention, in step S1, the magnesium salt is one or more of magnesium chloride, magnesium sulfate or magnesium nitrate.

In some embodiments of the present invention, in step S1, the acidic complexing agent is one or more of citric acid, tartaric acid or gluconic acid.

In some embodiments of the present invention, in step S1, the concentration of cobalt ions in the cobalt-magnesium mixed metal liquid is 1.5-2.0 mol/L, and the mass ratio of magnesium element to cobalt element is 0.005-0.01:1.

In some embodiments of the present invention, in step S1, the concentration of carbonate in the precipitant solution is 2.0-3.0 mol/L, and the mass ratio of surfactant to carbonate is 0.02-0.06:1.

In some embodiments of the present invention, in step S1, the concentration of titanium ions in the titanium salt solution is 0.05-0.20 mol/L, the molar ratio of the acidic complexing agent to titanium is 0.2-1.0:1, and the titanium The pH of the salt solution is 0.5-1.0.

In some embodiments of the present invention, in step S1, the inlet flow ratio of the cobalt-magnesium mixed metal liquid, precipitant solution and titanium salt solution is (20-30): (35-50): (2-5 ). Further, the flow rate of the titanium salt solution is 1/10 of the flow rate of the cobalt-magnesium mixed metal liquid. Since titanium salt is very unstable and can only exist in the form of cations under extremely low pH conditions, the pH of the titanium salt solution is very low and its acidity is very strong. Therefore, controlling a small amount of liquid inlet can reduce the amount of liquid in the system. The fluctuation of pH is beneficial to the control of the precipitation reaction process.

In some embodiments of the present invention, in step S1, the concentration of carbonate in the bottom liquid is 0.8-1.6 mol/L, pH is 8.0-8.5.

In some embodiments of the present invention, in step S1, as the reaction proceeds, when the pH of the reaction material drops to 7.1-7.5, the flow rate of the precipitant solution is adjusted to maintain the pH of the reaction stage at 7.1-7.5. .

In some embodiments of the present invention, in step S1, the reaction is carried out in a reaction kettle. The bottom liquid is first added to the reaction kettle, and the bottom liquid accounts for 40-50% of the volume of the reaction kettle. The reaction proceeds. When the liquid level in the reaction kettle reaches 80-85% of the total volume, the concentration is started. During the concentration, the cobalt-magnesium mixed metal liquid, precipitant solution and titanium salt solution are continuously introduced, and the liquid level in the reaction kettle is kept stable at The total volume is 80-85%, and the magnesium-titanium co-doped cobalt carbonate slurry is obtained after 60-80 hours of synthesis.

In some embodiments of the present invention, in step S1, the reaction is performed at 35-45°C.

In some embodiments of the present invention, in step S1, the cobalt-magnesium mixed metal liquid and precipitant solution are added below the liquid surface, and the titanium salt solution is added above the liquid surface. Since the feed flow rate of the titanium salt solution is small, a small amount of carbon dioxide gas will be released during the reaction of cobalt carbonate. The pressure in the lower part of the reactor will be greater. The above-liquid feed method can avoid the feed flow rate caused by excessive pressure in the reactor. of instability.

In some embodiments of the present invention, in step S1, the reaction is performed under stirring. Further, the stirring adopts propeller blades. The propeller blades can increase the axial flow of the slurry in the reactor, so that the titanium salt solution added above the liquid can be fully mixed and precipitated uniformly in the system.

In some embodiments of the present invention, in step S2, ethanol at 20-25°C is used for washing, and the washing time is 20-30 minutes. Using ethanol to wash away impurities such as residual ammonium chloride and ammonium sulfide in the slurry can effectively prevent the hydrolysis of amorphous titanium carbonate on the particle surface into crystalline titanium hydroxide.

In some embodiments of the present invention, in step S2, the drying temperature is 80-85°C, and the drying time is 10-15 hours.

The invention also provides the application of the preparation method in preparing lithium cobalt oxide or lithium ion battery.

According to a preferred embodiment of the present invention, the present invention at least has the following beneficial effects:

1. Since titanium salt is very unstable and can only exist in the form of cations under extremely low pH conditions, the present invention chooses to enter the titanium salt into the liquid separately, which is beneficial to the process control of the precipitation reaction, and a certain amount is added to the titanium salt solution. acidic complexation agent, which can simultaneously achieve the functions of complexing titanium ions and inhibiting titanium hydrolysis. Using an acidic complexing agent to complex the titanium element first can control the precipitation rate of titanium. If it is a cobalt-magnesium-titanium mixed metal liquid, the acidic complexing agent will complex at the same time. It is difficult to complex cobalt and magnesium, and it is difficult to complex titanium. Compared with using nano-titanium dioxide as the titanium source, this method has a more concentrated particle size distribution of the product.

2. Due to the variety of doping elements and the difference in the valence state of titanium and cobalt ions, titanium element doping will accelerate the nucleation process, refine the primary grain size, and reduce the surface activity of secondary particles, which is not conducive to the growth of cobalt carbonate particles. To affect the particle size distribution of the final product, the present invention mixes surfactant with carbonate solution to increase the adsorption capacity of the secondary particle sphere surface of the precursor in the synthesis stage and promote the growth of magnesium and titanium co-doped cobalt carbonate.

3. The present invention significantly improves the rate performance of the lithium cobalt oxide cathode material by bulk-doping magnesium and titanium elements in the cobalt carbonate precursor, and can be applied to a new generation of fast-charging lithium-ion batteries.

Description of the drawings

The present invention will be further described below in conjunction with the accompanying drawings and examples, wherein:

Figure 1 is an SEM image of magnesium-titanium co-doped cobalt carbonate prepared in Example 1 of the present invention at a magnification of 20,000 times;

Figure 2 is a 5000 times SEM image of magnesium titanium co-doped cobalt carbonate prepared in Example 1 of the present invention;

Figure 3 is a 20,000 times SEM image of the magnesium titanium co-doped cobalt carbonate prepared in Example 2 of the present invention;

Figure 4 is a 1000 times SEM image of magnesium titanium co-doped cobalt carbonate prepared in Example 2 of the present invention;

Figure 5 is a 50,000-fold SEM image of magnesium-titanium co-doped cobalt carbonate prepared in Example 3 of the present invention;

Figure 6 is a 5000 times SEM image of magnesium titanium co-doped cobalt carbonate prepared in Example 3 of the present invention;

Figure 7 is a 5000 times SEM image of the magnesium-doped cobalt carbonate prepared in Comparative Example 1 of the present invention;

Figure 8 is a 20,000 times SEM image of the magnesium-doped cobalt carbonate prepared in Comparative Example 1 of the present invention;

Figure 9 is a comparison chart of the rate performance of Comparative Examples and Examples after they were prepared into lithium cobalt oxide cathode materials under the same conditions.

Detailed ways

The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without exerting creative efforts are all protection scope of the present invention.

Example 1

In this embodiment, a magnesium-titanium co-doped cobalt carbonate is prepared. The specific process is:

Step 1. Prepare the solution: prepare a cobalt-magnesium mixed metal liquid A of cobalt chloride and magnesium chloride, in which the cobalt concentration is 2.0 mol/L, and the mass ratio of magnesium to cobalt is 0.005:1. Prepare a mixed solution C of citric acid and titanium chloride. , where the concentration of titanium ions is 0.05mol/L, the molar ratio of citric acid to titanium is 0.2:1, the pH of mixed solution C tested at room temperature is 0.8, and a mixed precipitant of ammonium bicarbonate solution and ammonium dodecyl sulfate is prepared. Solution B, in which the concentration of ammonium bicarbonate is 3mol/L, and the mass ratio of ammonium lauryl sulfate to ammonium bicarbonate is 0.05:1;

Step 2. Synthesis of magnesium and titanium co-doped cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.2 mol/L. The bottom liquid accounts for 50% of the volume of the reaction kettle. The liquid pH value is 8.3, the temperature is 45°C, and the reactor blades are propeller blades. Under high-speed stirring conditions, cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are added in parallel flow, where the mixed solution Add liquid C above the liquid, add cobalt-magnesium mixed metal liquid A and mixed precipitant solution B under the liquid, the flow rate of cobalt-magnesium mixed metal liquid A is 30L/h, the flow rate of mixed precipitant solution B is 50L/h, the flow rate of mixed solution C The flow rate is 3L/h. When the pH value drops to 7.1, the flow rate of mixed precipitant solution B is adjusted through the PLC control system to maintain the pH value at the synthesis stage of 7.1. When the liquid level in the kettle reaches 80-85% of the total volume, concentration is started. During the concentration, the cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are continuously introduced and the liquid level in the kettle is kept stable at 80-85% of the total volume. After 70 hours of synthesis, a magnesium-titanium co-doped cobalt carbonate slurry is obtained. ;

Step 3: Wash, dry and sieve the magnesium and titanium co-doped cobalt carbonate slurry: Put the magnesium and titanium co-doped cobalt carbonate slurry into a centrifuge for filtration, wash it with ethanol at 20-25°C for 30 minutes, and take the filter cake at 85°C. Dry for 12 hours, pass the dried material through a 400-mesh vibrating screen, and package to obtain the finished product of magnesium and titanium co-doped cobalt carbonate.

The measured D50 of magnesium titanium co-doped cobalt carbonate is 17.5 μm, and the span value is 0.35. The titanium element content is 1468 ppm and the magnesium element content is 2335 ppm. Figures 1 and 2 show the magnesium titanium co-doped carbonate prepared in this example. The SEM image of cobalt shows that its primary particles are in the form of lumps.

Example 2

In this embodiment, a magnesium-titanium co-doped cobalt carbonate is prepared. The specific process is:

Step 1. Prepare the solution: Prepare a cobalt-magnesium mixed metal liquid A of cobalt sulfate and magnesium sulfate, in which the cobalt concentration is 1.8 mol/L, and the magnesium-cobalt element mass ratio is 0.008:1. Prepare a mixed solution C of tartaric acid and titanium sulfate, where Titanium ions The concentration is 0.18mol/L, the molar ratio of tartaric acid to titanium is 0.6:1, the pH of the prepared mixed solution is 0.5 when tested at room temperature, and the mixed precipitant solution B of ammonium bicarbonate solution and sodium laurate is prepared, in which ammonium bicarbonate The solution concentration is 2.5 mol/L, and the mass ratio of sodium laurate and ammonium bicarbonate is 0.10:1;

Step 2. Synthesis of magnesium and titanium co-doped cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.6 mol/L. The bottom liquid accounts for 45% of the volume of the reaction kettle. The liquid pH value is 8.5, the temperature is 38°C, and the reactor blades are propeller blades. Under high-speed stirring conditions, cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are added in parallel flow, in which cobalt and magnesium are added in parallel. The flow rate of mixed metal liquid A is 25L/h, the flow rate of mixed precipitant solution B is 40L/h, and the flow rate of mixed solution C is 2.5L/h. When the pH value drops to 7.3, the mixed precipitant is adjusted through the PLC control system The flow rate of solution B maintained the pH value of 7.3 during the synthesis stage. When the liquid level in the kettle reaches 80-85% of the total volume, the concentration is started. During the concentration, the cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are continuously introduced to keep the liquid level in the kettle stable at 80-85% of the total volume. %. After 80 hours of synthesis, a magnesium-titanium co-doped cobalt carbonate slurry was obtained;

Step 3: Wash, dry and sieve the magnesium and titanium co-doped cobalt carbonate slurry: Put the magnesium and titanium co-doped cobalt carbonate slurry into a centrifuge for filtration, wash it with ethanol at 20-25°C for 30 minutes, and take the filter cake at 80°C. Dry for 12 hours, pass the dried material through a 400-mesh vibrating screen, and package to obtain the finished product of magnesium and titanium co-doped cobalt carbonate.

The measured D50 of magnesium titanium co-doped cobalt carbonate is 18.0 μm, and the span value is 0.31. The titanium element content is 5980 ppm and the magnesium element content is 3820 ppm. Figures 3 and 4 show the magnesium titanium co-doped carbonic acid prepared in this example. The SEM image of cobalt shows that its primary particles are in the form of powder.

Example 3

In this embodiment, a magnesium-titanium co-doped cobalt carbonate is prepared. The specific process is:

Step 1. Prepare the solution: prepare a cobalt-magnesium mixed metal liquid A of cobalt nitrate and magnesium nitrate, in which the cobalt concentration is 1.5 mol/L, and the mass ratio of magnesium and cobalt elements is 0.01:1; prepare a mixed solution C of gluconic acid and titanyl sulfate , where the concentration of titanium ions is 0.1mol/L, the molar ratio of gluconic acid to titanium is 0.5:1, the pH of the prepared mixed metal liquid is 1.0 when tested at room temperature, and the mixed precipitant solution of ammonium bicarbonate solution and polyacrylamide is prepared B, where the concentration of ammonium bicarbonate solution is 2.0mol/L, and the mass ratio of polyacrylamide to ammonium bicarbonate is 0.15:1;

Step 2. Synthesis of magnesium and titanium co-doped cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.6 mol/L. The bottom liquid accounts for 40% of the volume of the reaction kettle. The liquid pH value is 8.0 and the temperature is 40°C. The reactor blades are pusher blades. Cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are added in parallel under high-speed stirring conditions. The flow rate of cobalt-magnesium mixed metal liquid A is 20L/h. The flow rate of mixed precipitant solution B is 38L/h, and the flow rate of mixed solution C is 2L/h. When the pH value drops to 7.5, the flow rate of mixed precipitant solution B is adjusted through the PLC control system to maintain the pH value at 7.5 during the synthesis stage. When the liquid level in the kettle reaches 80-85% of the total volume, the concentration is started. During the concentration, the cobalt-magnesium mixed metal liquid A, mixed precipitant solution B and mixed solution C are continuously introduced and the liquid level in the kettle is kept stable at 80-85% of the total volume. %, after 65 hours of synthesis, a magnesium-titanium co-doped cobalt carbonate slurry was obtained;

Step 3: Wash, dry and sieve the magnesium and titanium co-doped cobalt carbonate slurry: Put the magnesium and titanium co-doped cobalt carbonate slurry into a centrifuge for filtration, wash it with ethanol at 20-25°C for 30 minutes, and take the filter cake at 80°C. Dry for 12 hours, pass the dried material through a 400-mesh vibrating screen, and package to obtain the finished product of magnesium and titanium co-doped cobalt carbonate.

The measured D50 of magnesium titanium co-doped cobalt carbonate is 17.0 μm, and the span value is 0.35. The titanium element content is 4396 ppm, and the magnesium element content is 4712 ppm. Figures 5 and 6 show the magnesium titanium co-doped carbonate prepared in this embodiment. The SEM image of cobalt shows that its primary particles are in the form of powder.

Comparative example 1

In this comparative example, a magnesium-doped cobalt carbonate was prepared. The specific process is:

Step 1. Prepare the solution: Prepare a cobalt-magnesium mixed metal liquid, in which the cobalt concentration is 1.8 mol/L, the mass ratio of magnesium and cobalt elements is 0.008:1, and the ammonium bicarbonate solution concentration is 3 mol/L;

Step 2. Synthesis of magnesium-doped cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.2 mol/L. The bottom liquid accounts for 50% of the volume of the reaction kettle. The pH value of the bottom liquid is 8.3, the temperature is 45°C, and the cobalt-magnesium mixed metal liquid and ammonium bicarbonate solution are added in parallel flow under high-speed stirring conditions. The flow rate of the cobalt-magnesium mixed metal liquid is 30L/h, and the flow rate of the ammonium bicarbonate solution is 50L/h. When When the pH value drops to 7.1, the ammonium bicarbonate flow rate is adjusted through the PLC control system to maintain the pH value at the synthesis stage of 7.1. When the liquid level in the kettle reaches 80-85% of the total volume, the concentration is started. During the concentration period, cobalt and magnesium mix the metal liquid and bicarbonate. The ammonium solution is continuously introduced and the liquid level in the kettle is kept stable at 80-85% of the total volume. After 78 hours of synthesis, a magnesium-doped cobalt carbonate slurry was obtained;

Step 3: Wash, dry and sieve the magnesium-doped cobalt carbonate slurry: Put the magnesium-doped cobalt carbonate slurry into a centrifuge for filtration, wash with pure water at 20-25°C for 30 minutes, take the filter cake and dry it at 85°C for 12 hours. The dried material passes through a 400-mesh vibrating screen and is packaged to obtain the finished product of magnesium-doped cobalt carbonate.

The D50 of the magnesium-doped cobalt carbonate was measured to be 18.2 μm, the span value was 0.42, and the magnesium element content was 3851 ppm. Figures 7 and 8 are SEM images of the magnesium-doped cobalt carbonate prepared in this comparative example. From the figure, it can be seen that the primary particles are Mountain peak shape.

Comparative example 2

This comparative example prepared a titanium-doped cobalt carbonate. The difference between Comparative Example 2 and Example 2 is that no magnesium element was added to the mixed metal liquid in Comparative Example 2. The specific process is:

Step 1. Prepare solution: Prepare cobalt sulfate solution, where the cobalt concentration is 1.8mol/L, prepare mixed solution C of tartaric acid and titanium sulfate, where the titanium ion concentration is 0.18mol/L, and the molar ratio of tartaric acid to titanium is 0.6:1 , the pH of the prepared mixed solution is tested to be 0.5 at room temperature, and the mixed precipitant solution B of ammonium bicarbonate solution and sodium laurate is prepared, in which the concentration of ammonium bicarbonate solution is 2.5mol/L, and the mass of sodium laurate and ammonium bicarbonate The ratio is 0.10:1;

Step 2. Synthesis of titanium-doped cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.6 mol/L. The bottom liquid accounts for 45% of the volume of the reaction kettle. The pH value of the bottom liquid is 8.5, the temperature is 38°C, the reactor blades are propeller blades, cobalt sulfate solution, mixed precipitant solution B and mixed solution C are added in parallel flow under high-speed stirring conditions, where the flow rate of the cobalt sulfate solution is 25L/ h, the flow rate of mixed precipitant solution B is 40L/h, and the flow rate of mixed precipitant solution C is 2.5L/h. When the pH value drops to 7.3, the flow rate of mixed precipitant solution B is adjusted through the PLC control system to maintain the pH value in the synthesis stage. When the liquid level in the kettle reaches 80-85% of the total volume, the concentration is started. During the concentration, the cobalt sulfate solution, mixed precipitant solution B and mixed solution C are continuously introduced and the liquid level in the kettle is kept stable at 80-85% of the total volume. %, after 80 hours of synthesis, titanium-doped cobalt carbonate slurry was obtained;

Step 3: Wash, dry and sieve the titanium-cobalt carbonate-doped slurry: Put the titanium-cobalt carbonate-doped slurry into a centrifuge for filtration, wash with ethanol at 20-25°C for 30 minutes, take the filter cake and dry it at 80°C for 12 hours. The dry material passes through a 400-mesh vibrating screen and is packaged to obtain the finished product of titanium-doped cobalt carbonate.

Comparative example 3

This comparative example prepared a kind of undoped cobalt carbonate. The difference between Comparative Example 3 and Example 2 is that Comparative Example 3 did not add magnesium, titanium elements and acidic complexing agents. The specific process is:

Step 1. Prepare solution: Prepare cobalt sulfate solution, where the cobalt concentration is 1.8mol/L, prepare a mixed precipitant solution of ammonium bicarbonate solution and sodium laurate, where the ammonium bicarbonate solution concentration is 2.5mol/L, sodium laurate The mass ratio to ammonium bicarbonate is 0.10:1;

Step 2. Synthesis of cobalt carbonate: Add pure water and ammonium bicarbonate solution to the reaction kettle as the bottom liquid. The concentration of ammonium bicarbonate in the bottom liquid is 1.6 mol/L. The bottom liquid accounts for 45% of the volume of the reaction kettle. The pH value of the bottom liquid is 8.5. , the temperature is 38°C, the reactor blades are propeller blades, cobalt sulfate solution and mixed precipitant solution are added in parallel under high-speed stirring conditions, where the flow rate of cobalt sulfate solution is 25L/h, and the flow rate of mixed precipitant solution is The flow rate is 40L/h. When the pH value drops to 7.3, the flow rate of the mixed precipitant solution is adjusted through the PLC control system to maintain the pH value at the synthesis stage of 7.3. When the liquid level in the kettle reaches 80-85% of the total volume, concentration is started. During this period, the cobalt sulfate solution and the mixed precipitant solution were continuously introduced and the liquid level in the kettle was kept stable at 80-85% of the total volume. After 80 hours of synthesis, the cobalt carbonate slurry was obtained;

Step 3. Cobalt carbonate washing, drying and sieving: Pulse the cobalt carbonate slurry into a centrifuge for filtration, wash with ethanol at 20-25°C for 30 minutes, take the filter cake and dry it at 80°C for 12 hours, and pass the drying material through 400 mesh vibrating screen, and the undoped cobalt carbonate finished product is obtained after packaging.

Test example

Examples 1-3 and Comparative Examples 1-3 were prepared into lithium cobalt oxide cathode materials according to the following steps: the prepared cobalt carbonate was calcined in a box furnace at 700°C for 3-4 hours to obtain magnesium titanium doped with cobalt tetroxide, which was mixed with lithium carbonate according to After mixing in a certain proportion, the lithium cobalt oxide cathode material is made, and the metal lithium sheet is used as the negative electrode to conduct a button battery charge and discharge test. The charge and discharge voltage range is 3.0-4.55V, and the test rate is 0.1C, 0.2C, 0.5C, 1C, 2C, 4C, 5C, the test temperature is 25℃.

Figure 9 is a comparison chart of the rate performance tested after Comparative Example 1-3 and Example 1-3 were prepared into lithium cobalt oxide cathode materials under the same conditions. It can be seen from Example 2 and Comparative Example 1-3 that when magnesium is added alone , co-doping magnesium and titanium on the basis of doping titanium alone or without doping can further improve the rate performance of lithium cobalt oxide materials; at the same time, comparing Examples 1, 2, and 3, it can be found that the titanium doping of 5980 ppm in Example 2 has the best effect. At the same time, as the doping amount of titanium element increases, it can be seen from the electron microscope morphology that the primary particles of cobalt carbonate become smaller.

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various modifications can be made without departing from the purpose of the present invention. Variety. In addition, the embodiments of the present invention and the features in the embodiments may be combined with each other without conflict.

Claims (10)

A method for preparing magnesium and titanium co-doped cobalt carbonate, which is characterized by comprising the following steps: S1: Add cobalt-magnesium mixed metal liquid, precipitant solution and titanium salt solution to the bottom liquid in parallel flow to react to obtain a magnesium-titanium co-doped cobalt carbonate slurry, wherein the bottom liquid is a carbonate solution, and the cobalt The magnesium mixed metal liquid is a mixed solution of cobalt salt and magnesium salt, the precipitant solution is a mixed solution of carbonate and surfactant, the titanium salt solution is a mixed solution of acidic complexing agent and titanium salt, the Carbonate is ammonium bicarbonate or ammonium carbonate; S2: The magnesium titanium co-doped cobalt carbonate slurry is subjected to solid-liquid separation, and the obtained solid is washed and dried to obtain the magnesium titanium co-doped cobalt carbonate. The preparation method according to claim 1, characterized in that in step S1, the surfactant is one or more of ammonium lauryl sulfate, sodium laurate or polyacrylamide. The preparation method according to claim 1, characterized in that in step S1, the acidic complexing agent is one or more of citric acid, tartaric acid or gluconic acid. The preparation method according to claim 1, characterized in that, in step S1, the concentration of cobalt ions in the cobalt-magnesium mixed metal liquid is 1.5-2.0 mol/L, and the mass ratio of magnesium element and cobalt element is 0.005-0.01 :1. The preparation method according to claim 1, characterized in that, in step S1, the concentration of carbonate in the precipitant solution is 2.0-3.0 mol/L, and the mass ratio of surfactant to carbonate is 0.05- 0.15:1. The preparation method according to claim 1, characterized in that, in step S1, the concentration of titanium ions in the titanium salt solution is 0.05-0.20 mol/L, and the molar ratio of the acidic complexing agent to titanium is 0.2-1.0: 1. The pH of the titanium salt solution is 0.5-1.0. The preparation method according to claim 1, characterized in that in step S1, the inlet flow rate ratio of the cobalt-magnesium mixed metal liquid, precipitant solution and titanium salt solution is (20-30): (35-50) :(2-5). The preparation method according to claim 1, characterized in that, in step S1, the concentration of carbonate in the bottom liquid is 0.8-1.6 mol/L, and the pH is 8.0-8.5. The preparation method according to claim 8, characterized in that in step S1, as the reaction proceeds, when the pH of the reaction material drops to 7.1-7.5, the flow rate of the precipitant solution is adjusted to maintain the pH value of the reaction stage. pH is between 7.1-7.5. Application of the preparation method according to any one of claims 1 to 9 in the preparation of lithium cobalt oxide or lithium ion batteries.