CN114044544B - Method for preparing ternary precursor material with wide particle size distribution by oxidation method - Google Patents

Abstract

The invention relates to a method for preparing a wide particle size distribution ternary precursor material by an oxidation method, and belongs to the technical field of technical lithium battery materials. The method of preparing a wide particle size distribution ternary precursor material by the oxidation method of the present invention includes: mixing the reaction bottom liquid with a mixed metal salt solution, a sodium hydroxide solution, and an ammonia solution in a stirred state, and the pH of the reaction is 10.5 to 10.5. 11.4. The temperature of the reaction is controlled at 55~65℃, and the concentration of ammonia solution is maintained at 11.5~15.5g/L during the reaction; when 7μm≤D50≤12μm, K90≤0.8, add peak-forming gas at one time, and then react within 10 minutes. The pH value is reduced by 1.0 to 1.5, and the pH value is stabilized, and the reaction continues until the particle size distribution returns to the normal curve. The invention broadens the particle size distribution and at the same time the particle size distribution is in a normal distribution state; the peak-forming material is cheap; and it saves equipment, time and cost.

Description

Method for preparing ternary precursor materials with wide particle size distribution by oxidation method

Technical field

The invention relates to a method for preparing a wide particle size distribution ternary precursor material by an oxidation method, and belongs to the technical field of technical lithium battery materials.

Background technique

New energy vehicles can reduce carbon emissions. New energy sources such as hybrid vehicles, plug-in hybrid vehicles and pure electric vehicles all need to be loaded with lithium-ion batteries as electric drive devices. Ternary materials have become the main cathode materials for current power batteries due to their high energy density and good rate performance. However, traditional ternary materials cannot meet battery manufacturers' requirements for high energy density and high cycle characteristics of power batteries.

There is a certain gap between the primary particles and the secondary spherical particles of the wide particle size distribution ternary precursor material. The gaps between the particles are smaller, which can provide a higher tap density, and the energy density of the cathode material is relatively higher. The narrow-grained ternary precursor material has good uniformity, high output power and high cycle characteristics, but its structural characteristics determine that its tap density improvement is limited.

How to control the particle size distribution in a wide range? This is of great significance for the preparation of ternary precursor materials with smaller gaps, high tap density, and relatively higher energy density. At this stage, it is difficult and technically difficult to change the particle size distribution of the product by adjusting the parameters in the production process. For example, changing the particle size distribution by adjusting temperature. Although the particle size distribution is broadened, the pH adjustment will be affected. It becomes insensitive, the control is not precise, and the surface of the obtained material particles is rough and not smooth. At present, in order to obtain ternary precursor materials with wide particle size distribution, the existing technology adopts the method of first obtaining precursor products with different particle size distributions, and then selecting several precursor products according to customer requirements and mixing them in a certain proportion to achieve the particle size distribution. requirements.

CN111908517A. During the synthesis process of high nickel precursor, this invention patent mechanically mixes small-sized and medium-sized precursor particles for batch preparation. The purpose is to use this method to maintain the diameter span during the particle growth process. In a wider range, the collision of particles in the reaction system plays a buffering role due to the presence of large and small particles, avoiding cracking of particles during the synthesis process. The solution is to intermittently dope small and medium-sized particles during the synthesis process to maintain a wide particle size distribution. However, it first uses the solid lifter intermittent method to prepare small particle size precursors and medium particle size precursors respectively, and solid-liquid separation obtains small particle size precursor particles and medium particle size precursor particles, and also controls the small particle size precursors. The diameter span of the particles is 0.8-1.2, and the diameter span of the medium-sized precursor particles is 0.6-1.0. After mixing the two types of particles, the maximum diameter span can reach 1.5. The process operation is very complex and the cost is high.

CN109244450A discloses a method for preparing a high-compact, high-capacity lithium manganate composite cathode material mixed with ternary materials, including the following steps: Step 1. Prepare small particles and narrow particle size distribution lithium manganate cathode materials; Step 2. Prepare large particles and wide particle size distribution lithium manganate cathode materials; Step 3. Mix lithium manganate cathode materials with two particle size distributions. This invention solves the problem by precisely controlling manganese sources and lithium sources with two different particle size distributions, fully considering the growth effect of crystal grains under high-temperature reactions, preparing cathode materials with wide and narrow distributions, and finally mixing them in a certain proportion. The shortcomings of insufficient compaction of a single material are avoided, while the morphological defects caused by conventional secondary classification are avoided, thereby obtaining a cathode material with a 1C gram capacity of 122 to 125 mAh/g and a compacted density of more than 3.15g/ ^cm3 . It is necessary to prepare the raw materials of large particles and small particles separately, sieve and mix them, which is a complicated process and high cost.

Contents of the invention

The object of the present invention is to provide a method for preparing ternary precursor materials with wide particle size distribution by oxidation.

In order to achieve the purpose of the present invention, the method for preparing a wide particle size distribution ternary precursor material by the oxidation method includes:

a. Mix the reaction bottom solution with mixed metal salt solution, sodium hydroxide solution, and ammonia solution under stirring. The pH of the reaction is 10.5-11.4. The temperature of the reaction is controlled at 55-65°C and maintained during the reaction. The concentration of ammonia water is 11.5~15.5g/L;

b. When 7μm≤D50≤12μm and K90≤0.8, add the peak-forming gas at one time, then reduce the pH value of the reaction by 1.0 to 1.5 within 10 minutes, stabilize the pH value, and continue the reaction until the particle size distribution returns to normal. curve;

Wherein the peak-forming gas is at least one of air, oxygen or ozone, and the added amount of the peak-forming gas is 1‰ to 5‰ of the volume of the reacted slurry;

Preferably, the feeding rate of the mixed metal salt solution, sodium hydroxide solution, and ammonia solution is maintained at a residence time of 9 to 10 hours.

The air is conventional air with an oxygen concentration of approximately 21%.

In a specific implementation, the added amount of air is 4-5‰ of the volume of the reacted slurry; the added amount of oxygen is 1-2‰ of the reacted slurry volume; and the added amount of ozone It is 0.5~1‰ of the reaction slurry volume.

In a specific embodiment, the pH of the reaction in step a is 10.5-11.

In a specific embodiment, the mixed metal salt solution in step a is a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate.

In a specific embodiment, the total metal concentration of the mixed metal salt solution in step a is 2 to 4 mol/L.

In a specific embodiment, the molar ratio of nickel, cobalt and manganese in the mixed metal salt solution is 5:2:3 or 6:2:2 or 8:1:1.

In a specific implementation, the stirring speed in step a is 450 to 600 rpm.

In a specific implementation, the concentration of the ammonia solution is 150-200g/L, preferably 150-180g/L.

In a specific embodiment, the concentration of the sodium hydroxide solution is 4-6 mol/L.

In a specific embodiment, the reaction bottom liquid is ammonia water with a concentration of 12.5 to 14.5 g/L; the volume of the reaction bottom liquid is preferably 20% to 40% of the total volume of the solution after the final reaction is completed.

The total volume of the solution after the final reaction is completed is the total volume of the slurry in the reactor. In a specific implementation, the amount of bottom liquid is generally selected based on the volume of the reaction kettle, and the volume of bottom liquid is usually 20 to 40% of the volume of the reaction kettle. For example: add 3L bottom liquid to a 10L reaction kettle, and the volume of the bottom liquid is 30% of the volume of the reaction kettle.

Beneficial effects:

1. The peak-forming material of the present invention can be obtained normally through conventional channels and is cheap;

2. The peak-making method of the present invention has a convenient process and only needs to be added to the reaction system once at a certain time, which will not affect the normal production activities;

3. The effect of adjusting particle size distribution is significant, and the product K90 can be adjusted from 0.64 to 1.34;

4. The Malvern particle size distribution curve of the product conforms to the normal curve and has no abrupt peaks;

5. Compared with conventional methods, this method saves more equipment and time. There is no need to use batch mixing equipment, and the reaction equipment only needs one set of crystallization reactors, which greatly saves the purchase cost and layout space.

Description of the drawings

Figure 1 is an SEM image before peak formation in Example 3.

Figure 2 is an SEM image after peak formation in Example 3.

Detailed ways

In order to achieve the purpose of the present invention, the method for preparing a wide particle size distribution ternary precursor material by the oxidation method includes:

a. Mix the reaction bottom solution with mixed metal salt solution, sodium hydroxide solution, and ammonia solution under stirring. The pH of the reaction is 10.5-11.4. The temperature of the reaction is controlled at 55-65°C and maintained during the reaction. The concentration of ammonia water is 11.5~15.5g/L;

b. When 7μm≤D50≤12μm and K90≤0.8, add the peak-forming gas at one time, then reduce the pH value of the reaction by 1.0 to 1.5 within 10 minutes, stabilize the pH value, and continue the reaction until the particle size distribution returns to normal. curve;

Wherein the peak-forming gas is at least one of air, oxygen or ozone, and the added amount of the peak-forming gas is 1‰ to 5‰ of the volume of the reacted slurry;

Preferably, the feeding rate of the mixed metal salt solution, sodium hydroxide solution, and ammonia solution is maintained at a residence time of 9 to 10 hours.

The air is conventional air with an oxygen concentration of approximately 21%.

In a specific implementation, the added amount of air is 4-5‰ of the volume of the reacted slurry; the added amount of oxygen is 1-2‰ of the reacted slurry volume; and the added amount of ozone It is 0.5~1‰ of the reaction slurry volume.

In a specific embodiment, the pH of the reaction in step a is 10.5-11.

In a specific embodiment, the mixed metal salt solution in step a is a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate.

In a specific embodiment, the total metal concentration of the mixed metal salt solution in step a is 2 to 4 mol/L.

In a specific embodiment, the molar ratio of nickel, cobalt and manganese in the mixed metal salt solution is 5:2:3 or 6:2:2 or 8:1:1.

In a specific implementation, the stirring speed in step a is 450 to 600 rpm.

In a specific implementation, the concentration of the ammonia solution is 150-200g/L, preferably 150-180g/L.

In a specific embodiment, the concentration of the sodium hydroxide solution is 4-6 mol/L.

In a specific embodiment, the reaction bottom liquid is ammonia water with a concentration of 12.5 to 14.5 g/L; the volume of the reaction bottom liquid is preferably 20% to 40% of the total volume of the solution after the final reaction is completed.

The total volume of the solution after the final reaction is completed is the total volume of the slurry in the reactor. In a specific implementation, the amount of bottom liquid is generally selected based on the volume of the reaction kettle, and the volume of bottom liquid is usually 20 to 40% of the volume of the reaction kettle. For example: add 3L bottom liquid to a 10L reaction kettle, and the volume of the bottom liquid is 30% of the volume of the reaction kettle.

Specific implementations of the present invention will be further described below in conjunction with examples, but the present invention is not limited to the scope of the described embodiments.

Example 1

Prepare nickel sulfate, cobalt sulfate, and manganese sulfate solutions. The total metal concentration of the solution is 2mol/L, and the molar ratio of nickel, cobalt, and manganese is 5:2:3. Mix to obtain a mixed metal salt solution; prepare a sodium hydroxide solution as a precipitant. Solution, concentration 5.2mol/L; prepare an ammonia solution as a complexing agent solution for later use, the ammonia concentration of the solution is 150g/L; this experiment uses a 10L reaction kettle, and the bottom liquid volume is 3L. The reaction bottom liquid is 3L of ammonia concentration of 13.5g/L. Add 2L of reaction bottom liquid to the reaction kettle, then start stirring at a rotation speed of 450 rpm. Then use a peristaltic pump to add the above-mentioned mixed salt solution, sodium hydroxide solution and ammonia solution to react. The feeding rate of the mixed metal salt solution, sodium hydroxide and ammonia solution is maintained at a residence time of 9 hours. During the reaction, the pH value was maintained at 10.5, the reaction temperature was 55°C, and the ammonia concentration was controlled at 13.5±2g/L.

After a period of reaction. As shown in the table below, D50=11.97μm, particle size distribution K90=0.64. At this time, use a syringe to quickly inject air into the system, with a volume equal to 5‰ of the slurry volume in the reactor. In this experiment, the slurry volume in the reaction kettle was 6.5L, so the injected air volume was 32.5mL. After that, the flow rate of the alkali solution was adjusted immediately, and it took 7 minutes to adjust the pH value to 9.3 and stabilize the pH value. The particles resumed growth until the particle size distribution returned to the normal curve. The test results show that before and after peaking, K90 increases from 0.64 to 1.33;

Table 1 Example 1 Particle size distribution

D10 D50 D90 K90 Before the peak 8.17 11.97 15.83 0.64 After peak building 5.68 7.77 16.02 1.33

Note: K90＝(D90-D10)/D50

Example 2

Prepare a solution of nickel sulfate, cobalt sulfate, and manganese sulfate. The total metal concentration of the solution is 4mol/L, and the molar ratio of nickel, cobalt, and manganese is 8:1:1. Mix to obtain a mixed metal salt solution; prepare a sodium hydroxide solution as a precipitant. Solution, concentration 4mol/L; prepare aqueous ammonia solution as complexing agent solution for later use, solution ammonia concentration 180g/L; This experiment uses a 10L reaction kettle, with a bottom liquid volume of 4L. The reaction bottom solution is 4L of ammonia concentration of 13.5g/L. Add 2L of reaction bottom liquid into the reaction kettle, then start stirring at a rotation speed of 580 rpm. Then use a peristaltic pump to add the above-mentioned mixed salt solution, sodium hydroxide solution and ammonia solution to react. The feeding rate of the mixed metal salt solution, sodium hydroxide and ammonia solution is maintained at a residence time of 9.5h. During the reaction, the pH value was maintained at 11.2, the reaction temperature was 60°C, and the ammonia concentration was controlled at 13.5±2g/L.

After a period of reaction. As shown in the table below, D50=7.18μm, particle size distribution K90=0.72. At this time, use a syringe to quickly inject oxygen into the system, with a volume equal to 2‰ of the slurry volume in the reactor. In this experiment, the injected oxygen volume was calculated to be 10.2 mL. After that, the flow rate of the alkali solution was adjusted immediately, and it took 8 minutes to adjust the pH value to 10.2 and stabilize the pH value. The particles resumed growth until the particle size distribution returned to the normal curve. The test results show that before and after peaking, K90 increases from 0.72 to 1.34.

Table 2 Example 2 Particle size distribution

D10 D50 D90 K90 Before the peak 4.59 7.18 9.78 0.72 After peak building 3.21 4.95 9.85 1.34

Example 3

Prepare nickel sulfate, cobalt sulfate, and manganese sulfate solutions. The total metal concentration of the solution is 2.9 mol/L, and the molar ratio of nickel, cobalt, and manganese is 6:2:2. Mix to obtain a mixed metal salt solution; prepare a sodium hydroxide solution as a precipitate. agent solution with a concentration of 6 mol/L; prepare an ammonia solution as a complexing agent solution for later use. The ammonia concentration of the solution is 200g/L. This experiment uses a 10L reaction kettle with a bottom liquid volume of 2L. The reaction bottom solution is 2L of ammonia concentration of 13.5g/L. Add 2L of reaction bottom liquid into the reaction kettle, then start stirring at a rotation speed of 600 rpm. Then use a peristaltic pump to add the above-mentioned mixed salt solution, sodium hydroxide solution and ammonia solution to react. The feeding rate of the mixed metal salt solution, sodium hydroxide and ammonia solution is maintained at a residence time of 10 hours. During the reaction, the pH value was maintained at 11.4, the reaction temperature was 65°C, and the ammonia concentration was controlled at 13.5±2g/L.

After a period of reaction. As shown in the table below, D50=10.47μm, particle size distribution K90=0.71. At this time, use a syringe to quickly inject ozone into the system, with a volume equal to 1‰ of the slurry volume in the reactor. In this experiment, the injected ozone volume was calculated to be 5.5mL. After that, the flow rate of the alkali solution was adjusted immediately, and it took 8 minutes to adjust the pH value to 10.0 and stabilize the pH value. The particles resumed growth until the particle size distribution returned to the normal curve. The test results show that before and after peaking, K90 increases from 0.71 to 1.26.

Table 3 Example 3 Particle size distribution

D10 D50 D90 K90 Before the peak 6.78 10.47 14.19 0.71 After peak building 4.58 7.81 14.45 1.26

Comparative example 1

Prepare nickel sulfate, cobalt sulfate, and manganese sulfate solutions. The total metal concentration of the solution is 2.5 mol/L, and the molar ratio of nickel, cobalt, and manganese is 8:1:1. Mix to obtain a mixed metal salt solution; prepare a sodium hydroxide solution as a precipitate. agent solution with a concentration of 5 mol/L; prepare an ammonia solution as a complexing agent solution for later use. The ammonia concentration of the solution is 169g/L. This experiment uses a 10L reaction kettle with a bottom liquid volume of 2L. The reaction bottom solution is 2L of ammonia concentration of 13.5g/L. Add 2L of reaction bottom liquid into the reaction kettle, then start stirring at a rotation speed of 600 rpm. Then use a peristaltic pump to add the above-mentioned mixed salt solution, sodium hydroxide solution and ammonia solution to react. The feeding rate of the mixed metal salt solution, sodium hydroxide and ammonia solution is maintained at a residence time of 9 hours. During the reaction, the pH value was maintained at 11.3, the reaction temperature was 65°C, and the ammonia concentration was controlled at 13.5±2g/L.

After a period of reaction. As shown in the table below, D50=10.47μm, particle size distribution K90=0.71. At this time, use a syringe to quickly inject oxygen into the system, with a volume equal to 5‰ of the slurry volume in the reactor. In this experiment, the injected oxygen volume was calculated to be 26 mL. Afterwards, it was observed that the color of the slurry changed from matcha to black, the slurry was seriously oxidized, and the experiment failed.

Table 4 Comparative Example 1 Particle Size Distribution

D10 D50 D90 K90 Before the peak 6.10 9.42 12.88 0.72 After peak building — — — —

Claims (11)

1. A method for preparing a ternary precursor material with wide particle size distribution by an oxidation method, which is characterized by comprising the following steps:

a. mixing reaction base solution with mixed metal salt solution, sodium hydroxide solution and ammonia water solution for reaction under the stirring state, wherein the pH value of the reaction is 10.5-11.4, the temperature of the reaction is controlled to be 55-65 ℃, the concentration of the ammonia water is maintained to be 11.5-15.5 g/L during the reaction, the molar ratio of nickel, cobalt and manganese in the mixed metal salt solution is 5:2:3 or 6:2:2 or 8:1:1, and the reaction base solution is the ammonia water with the concentration of 12.5-14.5 g/L;

b. when D50 is more than or equal to 7 mu m and less than or equal to 12 mu m, K90 is less than or equal to 0.8, adding peak forming gas at a time, then reducing the pH value of the reaction by 1.0-1.5 within 10min, stabilizing the pH value, and continuing the reaction until the particle size distribution is recovered to a normal curve;

wherein the peaking gas is at least one of air, oxygen or ozone, and the addition amount of the peaking gas is 1-5 per mill of the volume of the reacted slurry.

2. The method for preparing ternary precursor materials with wide particle size distribution by using the oxidation method according to claim 1, wherein the feeding rates of the mixed metal salt solution, the sodium hydroxide solution and the ammonia water solution are kept for 9-10 h at the residence time.

3. The method for preparing a ternary precursor material with wide particle size distribution by an oxidation method according to claim 1, wherein the addition amount of air is 4-5 per mill of the volume of the reacted slurry; the addition amount of the oxygen is 1-2 per mill of the volume of the reacted slurry; the addition amount of the ozone is 0.5 to 1 per mill of the volume of the reacted slurry.

4. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the pH of the reaction in the step a is 10.5-11.

5. The method for preparing ternary precursor materials with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the mixed metal salt solution in the step a is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate.

6. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the total metal concentration of the mixed metal salt solution in the step a is 2-4 mol/L.

7. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the stirring rotation speed in the step a is 450-600 rpm.

8. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the concentration of the ammonia water solution is 150-200 g/L.

9. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 8, wherein the concentration of the ammonia water solution is 150-180 g/L.

10. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the concentration of the sodium hydroxide solution is 4-6 mol/L.

11. The method for preparing a ternary precursor material with wide particle size distribution by using an oxidation method according to claim 1 or 2, wherein the volume of the reaction base solution is 20% -40% of the total volume of the solution after the final reaction is completed.