CN116812991A - Preparation method, device and precursor of a ternary precursor - Google Patents

Abstract

The present application relates to the technical field of precursor preparation, and in particular to a preparation method, device and precursor of a ternary precursor. The preparation method includes the following steps: step A), react the reaction solution at pH1 for t1 time to generate a preset number of precursor crystal nuclei; step B), reduce the pH1 of the reaction solution to pH2 within t2 time; step C), react the reaction solution at pH2 for t3 time to obtain a precursor with a preset median particle size; where the difference between pH1 and pH2 is 0.4-1; at least the reaction solution in step A) is obtained by solid-liquid separation The clarified liquid is refluxed into the reaction solution of step C), so that the precursor particle size distribution is highly concentrated, the shape is good, and there are very few small particles of precursor, thereby improving the performance of the cathode material and the safety performance of the battery, and this method The prepared precursor has uniform particle distribution, good sphericity, relatively high tap density, and stable product quality.

Description

Preparation method, device and precursor of ternary precursor

Technical field

The present application relates to the technical field of precursor preparation, and in particular to a preparation method, device and precursor of a ternary precursor.

Background technique

The performance of the cathode material has a crucial impact on the performance of the battery. Among them, the ternary cathode material has a significant ternary synergistic effect, high energy density, relatively low cost, and good safety functions. It has become the current cathode material for lithium batteries. the main development direction. Ternary precursor is the key raw material for preparing ternary cathode materials, which largely determines the performance of cathode materials. The ternary precursor is usually synthesized by the reaction of ternary liquid, alkali liquid and ammonia water under certain conditions, and is then made into finished products through aging, solid-liquid separation and other steps. Among them, the solid-liquid separation process produces a large amount of mother liquor, and each ton of ternary precursor produced produces 15m ³ of mother liquor. At present, the traditional process for treating ternary precursor wastewater is to use a gas stripping process to recover ammonia water for recycling, heavy metals to produce hydroxides, stripping drainage to adjust the pH, and then using a freezing crystallization process to recover the salt solution. The above-mentioned wastewater treatment methods have many steps, complex processes, and high operating costs.

Contents of the invention

This application discloses a preparation method, device and precursor of a ternary precursor to solve the problems of complex wastewater treatment processes and high operating costs caused by the existing ternary precursor preparation process.

In order to achieve the above purpose, this application provides the following technical solutions:

In a first aspect, this application provides a method for preparing a ternary precursor, which method includes the following steps:

Step A): react the reaction solution at pH 1 for t1 time to generate a preset number of precursor crystal nuclei;

Step B), within t2 time, reduce the pH1 of the reaction solution to pH2;

Step C): react the reaction solution at pH 2 for t3 to obtain a precursor with a preset median particle size;

Wherein, the difference between pH1 and pH2 is 0.4-1; at least the clear liquid obtained by solid-liquid separation of the reaction solution in step A) is refluxed into the reaction solution in step C).

Further, 10.7≤pH1≤11.5, 1h≤t1≤8h; 10≤pH2≤10.5, 10h≤t2≤20h, 70h≤t3≤80h, t=t1+t2+t3, t≤100h.

Further, the ammonia concentration of the reaction solution in step A) is C1, and the ammonia concentration of the reaction solution in step C) is C2, where 1g/L≤C1≤8g/L and 1g/L≤C2≤8g/L.

Further, the pH value of the clarified liquid is adjusted to pH3, and the ammonia concentration of the clarified liquid is adjusted to C3, where 13≤pH3≤14 and 10g/L≤C3≤15g/L.

Further, it also includes regulating the feed flow rate Q of the reaction solution according to the reaction time t:

0h≤t≤8h, 100L/h≤Q≤200L/h;

8h＜t≤16h, 400L/h≤Q≤600L/h;

16h<t, 800L/h≤Q≤1000L/h.

Further, it also includes regulating the stirring speed M of the reaction solution according to the solid content G of the reaction solution:

G≤100g/L, 450r/min≤M≤500r/min;

100g/L＜G≤200g/L, 350r/min≤Q≤400r/min;

200g/L＜G≤300g/L, 250r/min≤Q≤300r/min;

300g/L＜G, 150r/min≤Q≤200r/min.

In a second aspect, this application provides a device for applying the preparation method of the first aspect. The device includes a reaction kettle and a recovery component connected to the reaction kettle; the reaction kettle is used to prepare a ternary precursor, and the recovery component is used to recover and process the reaction. reaction solution in the kettle.

Further, the recovery component includes a first liquid storage tank connected to the reaction kettle and a second liquid storage tank connected to the first liquid storage tank. The drain pipe of the second liquid storage tank is connected to the reaction kettle; the first liquid storage tank It is used to filter the reaction solution to obtain the clarified liquid, and the second liquid storage tank is used to store the clarified liquid and regulate the pH value and ammonia concentration of the clarified liquid.

Further, a longitudinally extending partition plate is provided in the first liquid storage tank. The partition plate divides the chamber of the first liquid storage tank into a left chamber and a right chamber. The left chamber is connected to the reaction kettle, and the right chamber is connected to the reactor. The chamber is connected with the second liquid storage tank; the partition plate includes a lower plate body and an upper plate body connected to the lower plate body, and the upper plate body is provided with a plurality of filter holes.

Further, the bottom of the left chamber gradually rises from the end far away from the partition plate to the partition plate, and the bottom of the right chamber gradually decreases from the end far away from the partition plate to the end far away from the partition plate.

In a third aspect, the present application provides a precursor prepared by applying the preparation method of the first aspect. The specific surface area of the precursor is 7 to 15 m ² /g, and the span of the particle size distribution of the precursor is 0.5 to 0.7.

Further, the tap density of the precursor is 1.9~2.3g/cm ³ ; in the powder compaction test of the precursor, when the pressure is 0.5T, the median particle size before the precursor is compressed and the median diameter after the precursor is compressed The ratio of the difference in particle size to the median particle size before compression of the precursor is less than or equal to 3%.

Further, along the direction from the core of the precursor to the outer surface of the precursor, the precursor includes a loose core, a tight layer and a loose layer.

The beneficial effects produced by adopting the technical solution of this application are as follows:

In the preparation method of the ternary precursor provided by this application, the pH value (pH1) of the reaction solution in step A) is higher, which helps the reaction solution to form a preset number and size of crystal nuclei, and then makes the reaction solution The pH value drops from pH1 to pH2 within t2, switching the reaction solution from a nucleation environment to a growth environment. During this process, the particles will complete the transition from nucleation to growth; after the nucleation is completed, the pH of the reaction solution is changed. The value is stable at pH2 until it grows to the preset median particle size. In this application, the precursor made by controlling the difference between pH1 and pH2 and the reaction time has uniform particle distribution, good sphericity, and a relatively high tap density. The product quality is stable; the concentration of the recovered clarified liquid is lower than the alkali concentration of the raw material, and the dispersion of the clarified liquid into the reaction solution in step C) is better, which can effectively avoid the reaction solution due to excessive local pH. The phenomenon of fine powder makes the precursor particle size distribution highly concentrated and good in shape. There are very few small particles of precursor, thereby improving the performance of the cathode material and the safety performance of the battery.

Description of the drawings

Figure 1 is a schematic structural diagram of a device provided by an embodiment of the present application;

Figure 2 is a schematic structural diagram of a first liquid storage tank provided by an embodiment of the present application;

Figure 3 is a top view of a reactor provided by an embodiment of the present application;

Figure 4 is a top view of a reactor provided by another embodiment of the present application;

Figure 5 is a top view of a reactor provided by another embodiment of the present application;

Figure 6 is a top view of a second liquid storage tank provided by an embodiment of the present application;

Figure 7 is a 2K times SEM image of the ternary precursor prepared in Example 1 of the present application;

Figure 8 is a 10K times SEM image of the ternary precursor prepared in Example 1 of the present application;

Figure 9 is a 6K times SEM cross-sectional view of the ternary precursor prepared in Example 1 of the present application;

Figure 10 is a 1K times SEM image of the ternary precursor prepared in Comparative Example 1 of the present application;

Figure 11 is a 1K times SEM image of the ternary precursor prepared in Comparative Example 3 of the present application.

Reference signs:

100-reactor; 110-first feed pipe; 120-first alkali feed pipe; 130-first ammonia feed pipe; 140-first nitrogen feed pipe; 150-first reflux pipe; 160-second reflux pipe ; 170-guide tube; 200-recovery component; 210-first liquid storage tank; 211-separator plate; 211a-upper plate body; 211b-lower plate body; 220-second liquid storage tank; 221-second Alkali inlet pipe; 222-second ammonia inlet pipe; 223-second water inlet pipe; 300-transfer kettle; 400-thickener;

01-left chamber; 02-right chamber; 03-filter hole; 04-overflow port; 05-discharge port; 06-discharge port; 07-liquid inlet;.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in further detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, not all of them. . Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

The application scenarios described in the embodiments of the present application are for the purpose of more clearly explaining the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Persons of ordinary skill in the art will know that with the emergence of new application scenarios It appears that the technical solutions provided by the embodiments of this application are also applicable to similar technical problems. Among them, in the description of this application, unless otherwise stated, the meaning of "plurality" is two or more.

Ternary cathode materials have excellent comprehensive properties and have become one of the key materials for making lithium batteries. However, the ternary precursor will generate a large amount of wastewater during the co-precipitation preparation process. The existing wastewater treatment methods have many steps, complex processes, and high operating costs.

In view of this, embodiments of the present application provide a method for preparing a ternary precursor. The preparation method includes the following steps:

Step A): react the reaction solution at pH 1 for t1 time to generate a preset number of precursor crystal nuclei;

Step B), within t2 time, reduce the pH1 of the reaction solution to pH2;

Step C): react the reaction solution at pH 2 for t3 to obtain a precursor with a preset median particle size;

Among them, the difference between pH1 and pH2 is 0.4-1; the difference between pH1 and pH2 can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, but is not limited to the listed values. Other values within the range are not listed. The same numerical values apply; at least the clear liquid obtained by solid-liquid separation of the reaction solution in step A) is refluxed into the reaction solution in step C).

In an embodiment of the present application, 10.7≤pH1≤11.5, 1h≤t1≤8h; 10≤pH2≤10.5, 10h≤t2≤20h, 70h≤t3≤80h, t=t1+t2+t3, t≤ 100h. The pH value (pH1) of the reaction solution in step A) is higher to generate a preset number and size of crystal nuclei, and the pH value (pH2) of the reaction solution in step C) is lower to allow the crystal nuclei to grow rapidly to Default particle size.

In an embodiment of the present application, the ammonia concentration of the reaction solution in step A) is C1, and the ammonia concentration of the reaction solution in step C) is C2, where 1g/L≤C1≤8g/L, 1g/L≤ C2≤8g/L. By controlling the ammonia concentration in steps A) and C), it helps to control the complexation intensity of the reaction process and regulate the morphology of the primary particles.

In one embodiment of the present application, the pH value of the clarified liquid is adjusted to pH3, and the ammonia concentration of the clarified liquid is adjusted to C3, where 13≤pH3≤14 and 10g/L≤C3≤15g/L. It can be understood that the pH value and ammonia concentration of the clarified liquid are adjusted so that it can be used as the raw material in step C) to avoid introducing alkali liquor and ammonia water into the reaction kettle. The method in the embodiment of the present application can make the reaction The alkali and ammonia in the generated waste liquid are recycled to reduce the amount of wastewater treatment, the amount of raw materials used, and the cost.

In an embodiment of the present application, it also includes regulating the feed flow rate Q of the reaction solution according to the reaction time t:

0h≤t≤8h, 100L/h≤Q≤200L/h;

8h＜t≤16h, 400L/h≤Q≤600L/h;

16h<t, 800L/h≤Q≤1000L/h.

It can be understood that in order to ensure the same increase in crystal nucleation particle size during the reaction, more feed liquid is required for growth in the later stages of the reaction. Therefore, the feed liquid flow rate Q needs to be increased in stages according to the reaction time t.

In an embodiment of the present application, it also includes regulating the stirring speed M of the reaction solution according to the solid content G of the reaction solution:

G≤100g/L, 450r/min≤M≤500r/min;

100g/L＜G≤200g/L, 350r/min≤Q≤400r/min;

200g/L＜G≤300g/L, 250r/min≤Q≤300r/min;

300g/L＜G, 150r/min≤Q≤200r/min.

In order to ensure that the final product has high sphericity, the stirring speed is set to 450r/min in the early stage of the reaction, that is, the frequency display of the reactor motor is set to 45Hz. As the reaction proceeds, the solid content of the slurry increases, and the stirring speed is reduced in stages to make The particle size increases evenly, and the particles do not break into balls or produce small particles during the middle and late stages of the reaction.

Based on the same inventive concept, the present application provides a device for applying the preparation methods in various possible embodiments of the present application. Figure 1 is a schematic structural diagram of the device provided by an embodiment of the present application. Referring to Figure 1, the device includes a reaction The kettle 100 and the recovery component 200 are connected with the reaction kettle 100; the reaction kettle 100 is used to prepare the ternary precursor, and the recovery component 200 is used to recover and process the reaction solution in the reaction kettle 100.

Referring to Figure 1, the reaction kettle 100 includes a flow guide tube 170 and a baffle located in the inner cavity of the reaction kettle 100. The flow guide tube 170 helps to feed materials uniformly and does not cause disturbance to the materials being stirred; the baffle prevents reaction. The material rotates with the stirring, forming a vortex, causing the equipment to vibrate.

Continuing to refer to FIG. 1 , the recovery assembly 200 includes a first liquid storage tank 210 connected to the reaction kettle 100 and a second liquid storage tank 220 connected to the first liquid storage tank 210 . The drain pipe of the second liquid storage tank 220 is connected to the reaction kettle 100 . The kettle 100 is connected; the first liquid storage tank 210 is used to filter the reaction solution to obtain a clear liquid, and the second liquid storage tank 220 is used to store the clear liquid and regulate the pH value and ammonia concentration of the clear liquid.

Figure 2 is a schematic structural diagram of a first liquid storage tank provided by an embodiment of the present application. Referring to Figure 2, the first liquid storage tank 210 is provided with a longitudinally extending partition plate 211. The partition plate 211 separates the first liquid storage tank. The chamber of the tank 210 is divided into a left chamber 01 and a right chamber 02. The left chamber 01 is connected to the reaction kettle 100, and the right chamber 02 is connected to the second liquid storage tank 220; the partition plate 211 includes a lower plate body 211b and a The upper plate body 211a is connected to the lower plate body 211b. The upper plate body 211a is provided with a plurality of filter holes 03. The partition plate 211 is used to filter the reaction solution. Among them, the size of the filter hole 03 is set as needed.

Continuing to refer to FIG. 2 , the bottom of the left chamber 01 gradually rises from the end far away from the partition plate 211 to the partition plate 211 , so that the flow rate of the reaction solution gradually decreases from the end far away from the partition plate 211 to the partition plate 211 . , is conducive to solid-liquid separation, and is conducive to the accumulation of precipitation at the end away from the partition plate 211; the bottom of the right chamber 02 gradually decreases from the partition plate 211 to the end away from the partition plate 211, which is conducive to the liquid in the liquid storage tank Empty, and subsequent cleanup work.

Continuing to refer to Figures 1 and 2, the first liquid storage tank 210 is provided with a liquid inlet 07, a discharge port 05 and a liquid discharge port 06. The reaction solution enters the first liquid storage tank 210 from the liquid inlet 07 and passes through the solid-liquid The separated clarified liquid is discharged through the discharge port 06 and enters the second liquid storage tank 220 , and the precipitate is discharged from the first liquid storage tank 210 through the discharge port 05 . Among them, the discharge port 05 is provided at the lower part of the side wall of the left chamber 01 opposite to the partition plate 211, so that the sediment caused by solid-liquid separation can be discharged from the discharge port 05. The precipitate can be directly dissolved into a metal liquid for reuse. If the particle size is suitable, it can also be used as a seed crystal. The drain port 06 is provided at the upper part of the side wall of the right chamber 02 opposite to the partition plate 211, so that the clarified liquid produced by solid-liquid separation can flow out of the drain port 06. The liquid inlet 07 is provided at the upper part of the side wall of the left chamber 01 opposite to the partition plate 211, so that the reaction solution flows from the end far away from the partition plate 211 to the partition plate 211, and the speed gradually decreases.

Wherein, in order to isolate the solids in the reaction solution from the left chamber, the height of the lower plate body is 50%-80% of the height of the partition plate. For example, the height of the lower plate body is 50%, 60%, 70% or 80%.

Among them, the volume ratio of the volume of the first liquid storage tank to the volume of the reactor is 2-3, which is specifically set according to the storage capacity of the first liquid storage tank and the reaction requirements of the reactor.

Preferably, the volume of the first reaction kettle is 40m ³ -50m ³ and the height is 3m -5m.

FIG. 3 is a top view of a reaction kettle provided by an embodiment of the present application. Referring to FIG. 3 , the reaction kettle 100 is provided with a first feed pipe 110 , a first alkali feed pipe 120 , a first ammonia feed pipe 130 and a first feed pipe 130 . The nitrogen tube 140 promotes the full progress of the synthesis reaction of the ternary precursor by reasonably setting the position and thickness of the tube body.

Continuing to refer to FIG. 3 , the reaction kettle 100 is provided with a first reflux pipe 150 , and the clarified liquid obtained after solid-liquid separation is refluxed into the reaction kettle 100 through the first reflux pipe 150 . In order to improve the dispersion of the clarified liquid in the reaction kettle 100, the diameter of the first reflux pipe is larger than the diameters of other feed pipes of the reaction kettle 100. Preferably, the outlet of the first reflux pipe 150 is close to the stirring blade of the reaction kettle 100, and the number of the first reflux pipes 150 is 1-4, which is specifically set according to the flow rate of the feed liquid. The flow rate of the clarified liquid in the first return pipe 150 ranges from 500L/h to 3000L/h.

Among them, the number and layout of the feed pipes of the reactor tube are set according to the requirements of the reaction process for the feed flow rate Q and the dispersion of the feed liquid in the reactor. Specifically divided into the following three situations:

First, Q≤300L/h. Referring to Figure 3, the numbers of the first feed pipe 110, the first reflux pipe 150, the first alkali feed pipe 120, the first ammonia feed pipe 130 and the first nitrogen feed pipe 140 are all 1;

Second, 300L/h≤Q≤600L/h. Figure 4 is a top view of a reactor provided by another embodiment of the present application. Referring to Figure 4, the first reflux pipe 150, the first alkaline feed pipe 120, the first alkaline feed pipe The number of the ammonia pipe 130 and the first nitrogen feed pipe 140 is both one, and the number of the first feed pipe 110 is two;

Third, 800L/h≤Q≤1200L/h. Figure 5 is a top view of a reactor provided by another embodiment of the present application. Referring to Figure 5, the number of the first reflux pipe 150 and the first nitrogen inlet pipe 140 is 1, the number of the first alkali feeding pipes 120 and the first ammonia feeding pipes 130 is both 2, and the number of the first feeding pipes 110 is 4.

In order to further improve the solid-liquid separation effect of the reaction solution, continue to refer to Figure 1. The device in the embodiment of the present application also includes a thickener 400. The reaction kettle 100 and the first liquid storage tank 210 are connected through the thickener 400. The thickener 400 is used for solid-liquid separation of the reaction solution in the reaction kettle 100. The separated supernatant flows to the first liquid storage tank 210, and the separated slurry can be returned to the reaction kettle 100 to continue the reaction. Specifically, referring to FIGS. 1 and 3 , the reaction kettle 100 is provided with a second reflux pipe 160 , and the slurry concentrated by the thickener 400 can be refluxed into the reaction kettle 100 through the second reflux pipe 160 .

Among them, in order to facilitate pumping of the reaction solution in the reaction kettle 100, the thickener 400 and the reaction kettle 100 are connected through a transfer kettle 300. When using the batch method to prepare precursors, the transfer kettle can play a transfer role and make the flow of slurry to the thickener stable. In addition, the volume of the transfer kettle is much smaller than that of the reaction kettle. Overflowing from the transfer kettle to the aging kettle can prevent the slurry from emerging from the transfer kettle.

In one embodiment of the present application, the transfer kettle is connected to the aging kettle. When using a continuous method to prepare the precursor, the device does not need to include a thickener. Before the particle size of the precursor in the reaction solution is qualified or the performance does not meet the requirements, it will overflow through the transfer kettle to the unqualified aging kettle until the particle size is qualified and the performance meets the requirements. Finally, switch the pipeline to allow the slurry to overflow to the qualified aging kettle.

Among them, the reaction solution is processed by the thickener and the first liquid storage tank to obtain a pure clarified liquid. The clarified liquid does not contain the crystal nuclei of the ternary precursor. The clarified liquid flows to the second liquid storage tank, and the second liquid storage tank is used. To store the clarified liquid. Preferably, the second liquid storage tank can be heated so that the temperature of the clarified liquid is the same as the temperature of the reaction solution in the reactor, thereby improving reaction efficiency.

Figure 6 is a top view of a second liquid storage tank provided by an embodiment of the present application. Referring to Figure 6 , the second liquid storage tank 220 is provided with a second alkali inlet pipe 221, a second ammonia inlet pipe 222 and a second water inlet pipe 223. . By regulating the pH value and ammonia concentration of the clarified liquid in the second liquid storage tank 220 so that it can be used as the raw material in step C), it is avoided that the alkali liquid is introduced into the reaction kettle 100 through the first alkali inlet pipe 120 , or ammonia water is introduced through the first ammonia inlet pipe 130, thereby saving the amount of raw materials.

Based on the same inventive concept, embodiments of the present application provide a ternary precursor. The ternary precursor is prepared using the preparation method in the embodiments of the present application.

The primary particles on the surface of the ternary precursor provided by the embodiments of the present application are compactly packed and present in short clusters; the specific surface area of the precursor is 7 to 15 m ² /g, and the span of the particle size distribution of the precursor is 0.5 to 0.7.

In one embodiment of the present application, the tap density of the precursor is 1.9-2.3g/cm ³ ; in the powder compaction test of the precursor, when the pressure is 0.5T, the median particle size and The difference between the median particle diameter after the precursor is compressed and the ratio of the median particle diameter before the precursor is compressed is less than or equal to 3%.

In one embodiment of the present application, along the direction from the core of the precursor to the outer surface of the precursor, the precursor includes a loose core, a tight layer and a loose layer. There are more and irregular pores distributed in the loose core, the tight layer contains fewer pores, and the loose layer contains a large number of pores derived from the core of the precursor to the outer surface of the precursor. The above structure is formed because the growth of the precursor is controlled by controlling pH and material flow in the preparation method of the present application. The environment of pH 1 in step A) has a higher supersaturation environment, which is more conducive to the generation of crystal nucleation. Step C) The material flow in is larger, which is more conducive to the rapid growth of crystal nuclei. Therefore, the particle size increase in step C) is greater than the particle size increase in step A) and the particle size increase in step B), thereby obtaining the particle size increase along the core of the precursor to the precursor. In the direction of the outer surface, the precursor includes a structure of loose core, tight layer and loose layer. Among them, the loose core is the seed crystal formed quickly during the nucleation process. The outermost loose layer can increase the contact area between the precursor and the electrolyte, increase the number of lithium ion transmission channels, shorten the diffusion path of lithium ions, and effectively improve the electrochemical performance of lithium ion batteries.

The ternary precursor and its preparation method and device in this application will be further described in detail below with reference to specific examples and comparative examples.

Example 1

This embodiment is a device for preparing a ternary precursor. Referring to Figure 1, the device includes a reaction kettle 100, a transfer kettle 300 connected to the overflow port 04 of the reaction kettle 100, and a thickener connected to the transfer kettle 300. 400. The first liquid storage tank 210 communicates with the thickener 400, and the second liquid storage tank 220 communicates with the first liquid storage tank 210. The second liquid storage tank 220 communicates with the reaction kettle 100 through the first return pipe 150.

Among them, the volumes of the reaction kettle 100, the transfer kettle 300, the thickener 400, the first liquid storage tank 210, and the second liquid storage tank 220 are 15m ³ , 3m ³ , 5m ³ , 40m ³ , and 40m ³ respectively;

The reactor 100 is provided with a first feed pipe 110, a first alkali feed pipe 120, a first ammonia feed pipe 130 and a first nitrogen feed pipe 140. The outlet of the first feed pipe 110 is at the same height as the lower stirring blade of the reactor 100. The outlet of the first alkali inlet pipe 120 is at the same height as the upper stirring blade of the reactor 100, and the outlet of the first ammonia inlet pipe 130 is below the liquid level of the reaction solution, preferably at the same height as the lower stirring blade of the reactor 100. The distance between the outlet of the first nitrogen inlet pipe 140 and the top cover of the reactor 100 is 10cm. The height of the outlet of the first reflux pipe 150 is flush with the height of the lower stirring blade of the reactor 100; The distance between the bottom walls is 0.8m, and the distance between the upper stirring blade and the lower stirring blade of the reactor 100 is 1.5m; the bottom opening of the guide tube 170 is aligned with the height of the lower stirring blade, and the distance between the guide tube 170 and the lower stirring blade is aligned. The top cover of the kettle 100 is provided with a diversion opening 0.5m away. Referring to Figure 5, the number of the first reflux pipe 150 and the first nitrogen feed pipe 140 is both one, the number of the first alkali feed pipe 120 and the first ammonia feed pipe 130 is both two, and the number of the first feed pipe 110 is Quantity is 4 pieces.

The distance between the stirring blade of the transfer kettle and the bottom wall of the transfer kettle is 0.3m. The distance between the lower stirring blade of the thickener and the bottom wall of the thickener is 0.5m. The distance between the upper stirring blade and the lower stirring blade of the thickener is 0.3m. The distance between them is 1m, and the distance between the stirring blades and the bottom wall of the first liquid storage tank and the second liquid storage tank is 0.5m.

The method for preparing a ternary precursor using the above device includes the following steps:

1) Add clean water to the reaction kettle, transfer kettle and thickener. The amount of clean water added reaches the overflow port of the reaction kettle, submerges the transfer kettle stirring paddle, and submerges the upper stirring paddle of the thickener;

2) Pour 1000L of 5mol/L ammonia solution and 10L of 10mol/L alkali solution into the reaction kettle to form a reaction bottom liquid with a pH1 of 10.8~10.9 and a C1 of 3~3.5g/L. The reaction time t1 is 4h. This stage is the nucleation stage, and the starting particle size corresponding to pH1 (the particle size of the precursor when reacting for 1 hour after the salt solution is introduced) is 2.8um ~ 3.2um;

3) Within 12 hours, reduce the pH1 of the reaction solution to pH2, pH2 is 10.2~10.3; C2 is 3~3.5g/L;

4) React for 70 to 75 hours at pH 2 to obtain a precursor with a preset median particle size;

Wherein, in steps 3) and 4), the first alkali inlet pipe and the first ammonia inlet pipe are closed, and the pH value and ammonia water concentration of the reaction solution are adjusted through the second alkali inlet pipe and the second ammonia inlet pipe; the second storage liquid The pH3 of the clear liquid in the tank is 13-14, and the ammonia concentration C3 is 4g/L;

The stirring speed of the reaction solution is controlled according to the solid content G of the reaction solution:

In the early stage of the reactor, under the premise that the current is not overloaded, the frequency display of the reactor motor is set to 45Hz (stirring speed is 450r/min). When the solid content G ≤ 100g/L, the frequency display of the reactor motor is set to 45Hz (stirring speed is 450r/min). /min), when 100g/L＜G≤200g/L, the frequency display of the reactor motor is set to 35Hz (stirring speed is 350r/min), when 200g/L＜G≤300g/L, the frequency display of the reactor motor is set to 25Hz (stirring speed is 250r/min), when G>300g/L, the reactor motor frequency display is set to 15Hz (stirring speed is 150r/min);

The feed flow rate Q of the reaction solution is controlled according to the reaction time t:

0h≤t≤8h, Q=100L/h;

8h＜t≤16h, Q=400L/h;

16h<t, Q=800L/h.

The temperature of the above reaction process is fixed at 60°C, the ammonia concentration is 3~3.5g/L, the nitrogen flow is fixed at ^7m3 /h, the main content Ni:Co:Mn=83:11:6, and the feed liquid concentration is 1.8mol/L. The final precursor particle size is 13.6um.

The median particle diameter of the ternary precursor prepared by the above method is 13.6um, the span of the particle size distribution is 0.6, the specific surface area is ^8m2 /g, and the tap density is 2g/ ^cm3 ; the precursor was tested in the powder compaction test When the pressure is 0.5T, the difference between the median particle diameter before precursor compression and the median particle diameter after precursor compression is 2%.

Figure 7 is a 2K times SEM image of the ternary precursor prepared in Example 1 of the present application. Figure 8 is a 10K times SEM image of the ternary precursor prepared in Example 1 of the present application. Referring to Figures 7 and 8, the precursor The primary particles are compactly packed. Figure 9 is a 6K times SEM cross-sectional view of the ternary precursor prepared in Example 1 of the present application. Referring to Figure 9, along the direction from the core of the precursor to the outer surface of the precursor, the precursor includes loose Core, tight layer and loose layer.

Examples 2-8 and Comparative Examples 1-3

Examples 2-8 and Comparative Examples 1-3 are respectively a kind of ternary precursor. The preparation process can refer to the preparation of Example 1. The difference lies in the difference in reaction conditions, steps 3) and 4 in Comparative Example 3. ), the first alkali inlet pipe and the first ammonia inlet pipe are used to control the pH and ammonia concentration in the reaction system. The specific differences are listed in Table 1.

Table 1

Among them, the concentration of concentrated alkali is 10.8mol/L, and the concentration of concentrated ammonia is 10mol/L.

Performance tests were performed on the ternary precursors of the above embodiments and comparative examples, and the batteries prepared therefrom. The specific test results are listed in Table 2.

Table 2

Referring to Table 2, the differences between pH1 and pH2 in Examples 1-8 are all between 0.4-1. The differences between pH1 and pH2 in Comparative Examples 1-2 are all greater than 1. The ratio of precursors in Examples 1-8 The surface areas are all greater than or equal to 8.5m ² /g. The specific surface areas of the precursors in Comparative Examples 1-3 are all less than 7. The specific surface areas of the precursors in Examples 1-8 are significantly higher than those of the precursors in Comparative Examples 1-3. The specific surface area helps to transport lithium ions, thereby improving the rate performance of the battery prepared by it. The particle size distribution of the precursors in Examples 1-8 are all between 0.6-0.7, and the particle size distributions of the precursors in Comparative Examples 1-3 are all greater than 0.9. The particle size distribution of the precursors in Examples 1-8 is more concentrated, and the cycle performance and rate performance are improved.

Continuing to refer to Table 2, comparing Examples 1-8 with Comparative Examples 1-2, the discharge capacity, first effect, and cycle performance are significantly improved.

Figure 10 is a 1K times SEM image of the ternary precursor prepared in Comparative Example 1 of the present application. Referring to Figure 10 and Table 2, there are obvious cracks on the particle surface of the precursor. This is because the pH1 in Comparative Example 1 is high and the corresponding crystal The seed particle size is small, the number of crystal seeds is large, and the growth rate is slow in the later stage of the reaction. The reaction time is 125 hours, resulting in a final solid content of 530g/L. The collision intensity between particles is high, causing cracks on the surface, which interacts with the electrolyte. The increase in side reactions leads to a decrease in battery performance; in addition, the reaction solution in Comparative Example 1 has a high solid content and a high viscosity of the reaction system, making it difficult to disperse solute ions and locally generating small particles, resulting in some precursors having larger particle sizes. If it is small, it will be over-sintered during the sintering process, and the prepared cathode material will have the problem of excessive delithiation, so the electrical performance of the battery prepared by it will be reduced.

Comparative Example 2 and Comparative Example 1 have the same problems, which will not be described again here.

Figure 11 is a 1K times SEM image of the ternary precursor prepared in Comparative Example 3 of the present application. Referring to Figure 11 and Table 2, the particle size distribution concentration of the precursor prepared in Comparative Example 3 is low because the reaction step of Comparative Example 3 is In 3) and 4), the first alkali inlet pipe and the first ammonia inlet pipe are used to control the pH and ammonia concentration in the reaction system. The first alkali inlet pipe contains concentrated alkali, and the concentrated alkali cannot be dispersed in time when entering the reaction kettle. The local pH is high, which easily produces precursors with smaller particle sizes, resulting in reduced performance of the batteries prepared.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present application, and all of them should be covered. within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims (13)

1. A method for preparing a ternary precursor, characterized in that it includes the following steps: Step A): react the reaction solution at pH 1 for t1 time to generate a preset number of precursor crystal nuclei; Step B), within t2 time, reduce the pH1 of the reaction solution to pH2; Step C): react the reaction solution at pH 2 for t3 to obtain a precursor with a preset median particle size; Wherein, the difference between pH1 and pH2 is 0.4-1; at least the clear liquid obtained by solid-liquid separation of the reaction solution in step A) is refluxed into the reaction solution in step C). 2. The preparation method according to claim 1, characterized in that, 10.7≤pH1≤11.5, 1h≤t1≤8h; 10≤pH2≤10.5, 10h≤t2≤20h, 70h≤t3≤80h, t=t1+ t2+t3, t≤100h. 3. The preparation method according to claim 1, characterized in that the ammonia concentration of the reaction solution in step A) is C1, and the ammonia concentration of the reaction solution in step C) is C2, wherein 1g/L≤ C1≤8g/L, 1g/L≤C2≤8g/L. 4. The preparation method according to any one of claims 1-3, characterized in that the pH value of the clarified liquid is adjusted to pH3, and the ammonia concentration of the clarified liquid is adjusted to C3, wherein 13≤pH3≤14 ,10g/L≤C3≤15g/L. 5. The preparation method according to claim 4, further comprising regulating the feed flow rate Q of the reaction solution according to the reaction time t: 0h≤t≤8h, 100L/h≤Q≤200L/h; 8h＜t≤16h, 400L/h≤Q≤600L/h; 16h<t, 800L/h≤Q≤1000L/h. 6. The preparation method according to claim 4, further comprising regulating the stirring speed M of the reaction solution according to the solid content G of the reaction solution: G≤100g/L, 450r/min≤M≤500r/min; 100g/L＜G≤200g/L, 350r/min≤Q≤400r/min; 200g/L＜G≤300g/L, 250r/min≤Q≤300r/min; 300g/L＜G, 150r/min≤Q≤200r/min. 7. A device for applying the preparation method according to any one of claims 1 to 6, characterized in that it includes a reaction kettle and a recovery component connected to the reaction kettle; The reaction kettle is used to prepare the ternary precursor, and the recovery component is used to recover and process the reaction solution in the reaction kettle. 8. The device according to claim 7, wherein the recovery component includes a first liquid storage tank connected to the reaction kettle and a second liquid storage tank connected to the first liquid storage tank, so The drain pipe of the second liquid storage tank is connected with the reaction kettle; The first liquid storage tank is used to filter the reaction solution to obtain the clarified liquid, and the second liquid storage tank is used to store the clarified liquid and regulate the pH value and ammonia concentration of the clarified liquid. 9. The device according to claim 8, wherein a longitudinally extending partition plate is provided in the first liquid storage tank, and the partition plate divides the chamber of the first liquid storage tank into A left chamber and a right chamber, the left chamber is connected to the reaction kettle, and the right chamber is connected to the second liquid storage tank; The partition plate includes a lower plate body and an upper plate body connected to the lower plate body, and the upper plate body is provided with a plurality of filter holes. 10. The device according to claim 9, wherein the bottom of the left chamber gradually rises from an end away from the partition plate to the partition plate, and the bottom of the right chamber rises from the end away from the partition plate. The partition plate gradually lowers to an end away from the partition plate. 11. A precursor prepared by the preparation method according to any one of claims 1 to 6, characterized in that the specific surface area of the precursor is 7 to 15 m ² /g, and the particle size distribution of the precursor The span is 0.5~0.7. 12. The precursor according to claim 11, wherein the tap density of the precursor is 1.9-2.3g/ ^cm3 ; in the powder compaction test of the precursor, when the pressure is 0.5T, The ratio of the difference between the median particle diameter before the precursor is compressed and the median particle diameter after the precursor is compressed and the median particle diameter before the precursor is compressed is less than or equal to 3%. 13. The precursor according to claim 11 or 12, characterized in that, along the direction from the core of the precursor to the outer surface of the precursor, the precursor includes a loose core, a tight layer and a loose layer.