Large-particle ternary precursor with compact surface as well as preparation method and application of large-particle ternary precursor

Abstract

The invention provides a large-particle ternary precursor with a compact surface as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing a seed crystal; introducing the mixed metal salt solution, the precipitant solution and the complexing agent solution into a second base solution containing a seed crystal, and carrying out a second co-precipitation reaction to obtain the large-particle ternary precursor with a compact surface; and changing the flows of the mixed metal salt solution, the precipitator solution and the complexing agent solution, so that the growth amplitude of the particle size D50 per hour in the initial stage of the second coprecipitation reaction is less than or equal to 4 / 100 of the target particle size D50, the growth amplitude of the particle size D50 per hour in the middle stage of the reaction is less than or equal to 3 / 100 of the target particle size D50, and the growth amplitude of the particle size D50 per hour in the last stage of the reaction is less than or equal to 2 / 100 of the target particle size D50. According to the preparation method, the growth speed of the precursor is delayed by regulating and controlling the reaction feeding flow in time, so that the large-particle ternary precursor with a compact surface is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a large-particle ternary precursor with a dense surface, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in portable electronic devices and electric vehicles due to their high energy density. Among them, ternary materials (such as NCM) are one of the most promising cathode materials for lithium-ion batteries due to their advantages of high discharge capacity, low cost, and safety. However, poor cycle stability and rate performance are the main disadvantages of NCM cathode materials. Improving the overall density of ternary precursor materials is an effective way to improve the cycle stability of NCM cathode materials, which can not only enhance the thermal stability and structural stability of ternary cathode materials, but also reduce the dissolution of transition metals and improve the cycle life of the battery.

[0003] At present, the main method for regulating the morphology and structure of ternary precursors is to adjust the pH, ammonia concentration, alkali concentration, and stirring speed during the reaction, so as to prepare precursors with different morphologies, particle sizes, and densities. For example, CN119284991A discloses a nickel cobalt manganese hydroxide precursor with fine whiskers and a preparation method thereof. Without introducing compressed air, the morphology of the product can be regulated by controlling the temperature and the pH value of the particle size in the growth reaction stage, and a precursor product with fine whisker morphology and large specific surface area can be prepared, which has the advantages of good repeatability and controllability. However, the regulation process in the reaction is complicated and has high requirements for timeliness.

[0004] Based on the above research, a preparation method of ternary precursors is needed, and the preparation method can obtain a large-particle ternary precursor material with a dense surface and a radial structure. Summary of the Invention

[0005] The purpose of the present invention is to provide a large-particle ternary precursor with a dense surface, a preparation method thereof, and an application thereof. The preparation method can delay the growth rate of the precursor by timely regulating the reaction feed flow rate, so as to obtain a large-particle ternary precursor with a dense surface and a radial structure.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a preparation method of a large-particle ternary precursor with a dense surface, and the preparation method includes the following steps:

[0008] (1) Introduce a mixed metal salt solution, a precipitant solution, and a complexing agent solution into a first bottom liquid to carry out a first co-precipitation reaction to obtain crystal seeds;

[0009] (2) Introduce the mixed metal salt solution, precipitant solution, and complexing agent solution into the second bottom liquid, where the second bottom liquid includes the seed crystal described in step (1), and conduct a second co-precipitation reaction to obtain the large-particle ternary precursor with a dense surface;

[0010] During the second co-precipitation reaction, by changing the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution introduced into the second bottom liquid, make the growth rate of the particle size D50 per hour in the initial stage of the second co-precipitation reaction ≤ 4 / 100 of the target particle size D50, make the growth rate of the particle size D50 per hour in the middle stage of the second co-precipitation reaction ≤ 3 / 100 of the target particle size D50, and make the growth rate of the particle size D50 per hour in the final stage of the second co-precipitation reaction ≤ 2 / 100 of the target particle size D50.

[0011] In the present invention, by timely regulating the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution, controlling the growth rates of the particle sizes in the initial, middle, and final stages of the reaction, thereby controlling the growth rate of the particles and delaying the growth of the precursor, a large-particle precursor with a dense surface and a radial structure is obtained. Compared with the precursor prepared without changing the flow rate, the surface density of the precursor obtained in the present invention is significantly improved.

[0012] It should be noted that the "large particles" in the large-particle ternary precursor with a dense surface described in the present invention refer to the case where the particle size D50 of the ternary precursor is not less than 6 μm; a dense surface means that the tap density of the ternary precursor is 1.7 g / cm 3 or more, preferably 2.0 g / cm 3 or more.

[0013] Making the growth rate of the particle size D50 per hour in the initial stage of the second co-precipitation reaction ≤ 4 / 100 of the target particle size D50 can be, for example, 4 / 100, 3.5 / 100, 3 / 100, or 2.5 / 100, preferably ≤ 4 / 100 of the target particle size D50 and ≥ 3 / 100 of the target particle size D50; the growth rate of the particle size D50 per hour in the middle stage of the second co-precipitation reaction ≤ 3 / 100 of the target particle size D50 can be, for example, 3 / 100, 2.5 / 100, 2 / 100, or 1.5 / 100, preferably ≤ 3 / 100 of the target particle size D50 and ≥ 2 / 100 of the target particle size D50; the growth rate of the particle size D50 per hour in the final stage of the second co-precipitation reaction ≤ 2 / 100 of the target particle size D50 can be, for example, 2 / 100, 1.5 / 100, 1 / 100, or 0.5 / 100, preferably ≤ 2 / 100 of the target particle size D50 and ≥ 1 / 100 of the target particle size D50.

[0014] The hourly growth rate of the particle size D50 in the present invention refers to the magnitude of the change in the particle size D50 per hour; the target particle size D50 refers to the particle size D50 of the product obtained by the final second coprecipitation reaction.

[0015] In the present invention, the growth rate of the particles is preferably within a specific range, avoiding the problem that too large a growth rate affects the density of the particle surface and too small a growth rate generates small particles.

[0016] Preferably, if the hourly growth rate of the particle size D50 in the middle stage of the second coprecipitation reaction in step (2) exceeds the constraint value, the flow rates of the mixed metal salt solution, the precipitant solution and the complexing agent solution are adjusted to 0.8 to 0.95 times the flow rate at the initial stage of the reaction. For example, it can be 0.8 times, 0.85 times, 0.9 times or 0.95 times, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Preferably, if the hourly growth rate of the particle size D50 in the final stage of the second coprecipitation reaction in step (2) exceeds the constraint value, the flow rates of the mixed metal salt solution, the precipitant solution and the complexing agent solution are adjusted to 0.8 to 0.95 times the flow rate in the middle stage of the reaction. For example, it can be 0.8 times, 0.85 times, 0.9 times or 0.95 times, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] The present invention provides guidance on how to regulate the flow rate. When the hourly particle size growth rate exceeds the constraint value, the flow rates of the mixed metal salt solution, the precipitant solution and the complexing agent solution are all adjusted to 0.8 - 0.95 times the flow rate in the previous stage (the flow rate in the previous stage at the initial stage of the reaction is the initial flow rate) to better control the growth of the precursor and provide guidance on how to regulate the flow rate. The present invention preferably adjusts to 0.8 - 0.95 times the flow rate in the previous stage. If it is not within this range, when it is less than 0.8 times, it will cause the growth of the precursor to be too slow and the reaction time to be too long, which is not conducive to large-scale production and may also generate small particles. When it is greater than 0.95 times, it will cause the growth rate of the precursor to increase, making the product have a loose porous structure.

[0019] Preferably, the initial flow rate of the mixed metal salt solution introduced into the second bottom liquid in step (2) is 2% / h - 4% / h of the volume of the reaction kettle. For example, it can be 2% / h, 2.5% / h, 3% / h, 3.5% / h or 4% / h, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the initial flow rate of the precipitant solution introduced into the second bottom liquid in step (2) is 0.5% / h - 2% / h of the volume of the reaction kettle. For example, it can be 0.5% / h, 1% / h, 1.5% / h, or 2% / h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the initial flow rate of the complexing agent solution introduced into the second bottom liquid in step (2) is 0.1% / h - 0.5% / h of the volume of the reaction kettle. For example, it can be 0.1% / h, 0.2% / h, 0.3% / h, 0.4% / h, or 0.5% / h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0022] It should be noted that the volume unit of the reaction kettle described in the present invention is L.

[0023] Preferably, the initial stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 4.5 μm - 7 μm (for example, it can be 4.5 μm, 5 μm, 6 μm, or 7 μm) to 6.5 μm - 10 μm (for example, it can be 6.5 μm, 7.0 μm, 8.0 μm, 9.0 μm, or 10 μm).

[0024] Preferably, the middle stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 6.5 μm - 10 μm (for example, it can be 6.5 μm, 7.0 μm, 8.0 μm, 9.0 μm, or 10 μm) to 9.5 μm - 13 μm (for example, it can be 9.5 μm, 10.0 μm, 11.0 μm, 12.0 μm, or 13 μm).

[0025] Preferably, the final stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 9.5 μm - 13 μm (for example, it can be 9.5 μm, 10.0 μm, 11.0 μm, 12.0 μm, or 13 μm) to 12 μm - 17 μm (for example, it can be 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, or 17 μm).

[0026] Preferably, the target particle size D50 in step (2) is 12 μm - 17 μm. For example, it can be 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, or 17 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the pH of the second coprecipitation reaction in step (2) is 10 - 11, for example, it can be 10, 10.5 or 11, the complexing agent concentration is 3 g / L - 6 g / L, for example, it can be 3 g / L, 4 g / L, 5 g / L or 6 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the temperature of the second coprecipitation reaction in step (2) is 40°C - 60°C, for example, it can be 40°C, 45°C, 50°C, 55°C or 60°C, the stirring speed is 600 rpm - 1000 rpm, for example, it can be 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] Preferably, in the second bottom solution of step (2), the seed crystal content is 40 g / L - 70 g / L, for example, it can be 40 g / L, 50 g / L, 60 g / L or 70 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the pH of the second bottom solution in step (2) is 10 - 11, for example, it can be 10, 10.5 or 11, the complexing agent concentration is 3 g / L - 6 g / L, for example, it can be 3 g / L, 4 g / L, 5 g / L or 6 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the D50 of the seed crystal in step (1) is 3 μm - 5 μm, for example, it can be 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the pH of the first bottom solution in step (1) is 10 - 12, for example, it can be 10, 10.5, 11, 11.5 or 12, the complexing agent concentration is 8 g / L - 10 g / L, for example, it can be 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L or 10 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the pH of the first coprecipitation reaction in step (1) is 11 - 12, for example, it can be 11, 11.5 or 12, the complexing agent concentration is 8 g / L - 10 g / L, for example, it can be 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L or 10 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the temperature of the first coprecipitation reaction in step (1) is 40°C - 60°C, for example, it can be 40°C, 45°C, 50°C, 55°C or 60°C, and the stirring speed is 600 rpm - 1000 rpm, for example, it can be 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] In a second aspect, the present invention provides a large particle ternary precursor with a dense surface, and the large particle ternary precursor with a dense surface is prepared by the preparation method as described in the first aspect.

[0036] In a third aspect, the present invention provides a ternary cathode material, and the raw materials for preparing the ternary cathode material include the large particle ternary precursor with a dense surface as described in the second aspect.

[0037] The ternary cathode material of the present invention is obtained by mixing and sintering a lithium source and the large particle ternary precursor with a dense surface as described in the second aspect.

[0038] In a fourth aspect, the present invention provides a lithium ion battery, and the lithium ion battery includes the ternary cathode material as described in the third aspect.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] By timely regulating the flow rates of the mixed metal salt solution, the precipitant solution and the complexing agent solution, the present invention controls the particle size growth amplitude in the initial stage, the middle stage and the final stage of the reaction, thereby controlling the growth rate of the particles and delaying the growth of the precursor, and obtaining a large particle precursor with a dense surface and a radial structure. Specific Embodiments

[0041] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0042] Example 1

[0043] This example provides a preparation method of a large particle ternary precursor with a dense surface, and the preparation method includes the following steps:

[0044] (1) In a reaction kettle, pure water, liquid alkali and ammonia water are used to prepare a first bottom liquid, nitrogen is introduced, the temperature of the first bottom liquid is controlled at 50°C, the pH is 11, and the ammonia concentration is 9 g / L;

[0045] (2) Inject the nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia into the first bottom liquid in parallel flow. Under the conditions of a stirring speed of 800 rpm, a pH value in the range of 11 - 12, and an ammonia concentration in the range of 8 - 10 g / L, perform the first co-precipitation reaction to grow seed crystals with a D50 of 4 μm.

[0046] (3) Re-inject the seed crystals into another reaction kettle to form a second bottom liquid. The content of the seed crystals in the second bottom liquid is 70 g / L, the pH is 11, and the complexing agent concentration is 6 g / L. Inject the nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia into the second bottom liquid in parallel flow. At 50 °C, perform the second co-precipitation reaction. During the process, the stirring speed is 800 rpm, the pH is controlled in the range of 10 - 11, and the ammonia concentration is controlled in the range of 5 - 6 g / L, and grow to large particle ternary precursors with a dense surface and a target particle size D50 of 14 μm.

[0047] Among them, the initial flow rate of the mixed metal salt solution into the second bottom liquid is 3% / h of the reaction kettle volume, the initial flow rate of the liquid caustic soda into the second bottom liquid is 1% / h of the reaction kettle volume, and the initial flow rate of the ammonia into the second bottom liquid is 0.3% / h of the reaction kettle volume.

[0048] During the second co-precipitation reaction, by changing the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia into the second bottom liquid, make the hourly growth rate of the particle size D50 in the initial stage of the second co-precipitation reaction be 3.5 / 100 of the target particle size D50, make the hourly growth rate of the particle size D50 in the middle stage of the second co-precipitation reaction be 2.5 / 100 of the target particle size D50, and make the hourly growth rate of the particle size D50 in the final stage of the second co-precipitation reaction be 1.5 / 100 of the target particle size D50. If the hourly particle size growth rate exceeds the constraint value, the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia are all adjusted to 0.9 times the flow rate of the previous stage.

[0049] The initial stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 4.5 μm to 7.5 μm. The middle stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 7.5 μm to 10.5 μm. The final stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 10.5 μm to 14 μm.

[0050] Example 2

[0051] This example provides a method for preparing large particle ternary precursors with a dense surface. The preparation method includes the following steps:

[0052] (1) In the reaction kettle, configure the first bottom liquid with pure water, liquid caustic soda, and ammonia, introduce nitrogen, control the temperature of the first bottom liquid at 60 °C, the pH at 10, and the ammonia concentration at 10 g / L.

[0053] (2) Inject the nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia into the first bottom liquid in parallel flow. Under the conditions of a stirring speed of 1000 rpm, a pH value in the range of 11 - 12, and an ammonia concentration in the range of 8 - 10 g / L, carry out the first coprecipitation reaction to grow seed crystals with a D50 of 3 μm.

[0054] (3) Backfeed the seed crystals into another reaction kettle to form a second bottom liquid. The content of the seed crystals in the second bottom liquid is 70 g / L, the pH is 11, and the complexing agent concentration is 5 g / L. Add the nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia into the second bottom liquid in parallel flow. At 50 °C, carry out the second coprecipitation reaction. During the process, the stirring speed is 1000 rpm, the pH is controlled in the range of 10 - 11, and the ammonia concentration is controlled in the range of 3 - 5 g / L, and grow to large particle ternary precursors with a dense surface and a target particle size D50 of 12 μm.

[0055] Among them, the initial flow rate of the mixed metal salt solution into the second bottom liquid is 2% / h of the reaction kettle volume, the initial flow rate of the liquid caustic soda into the second bottom liquid is 0.5% / h of the reaction kettle volume, and the initial flow rate of the ammonia into the second bottom liquid is 0.1% / h of the reaction kettle volume.

[0056] During the second coprecipitation reaction, by changing the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia into the second bottom liquid, make the growth rate of the particle size D50 per hour in the initial stage of the second coprecipitation reaction be 3 / 100 of the target particle size D50, make the growth rate of the particle size D50 per hour in the middle stage of the second coprecipitation reaction be 2 / 100 of the target particle size D50, and make the growth rate of the particle size D50 per hour in the final stage of the second coprecipitation reaction be 1 / 100 of the target particle size D50. If the particle size growth rate per hour exceeds the constraint value, the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia are all adjusted to 0.95 times the flow rates in the previous stage.

[0057] The initial stage of the second coprecipitation reaction refers to the stage where the particle size D50 grows from 4.5 μm to 6.5 μm. The middle stage of the second coprecipitation reaction refers to the stage where the particle size D50 grows from 6.5 μm to 9.5 μm. The final stage of the second coprecipitation reaction refers to the stage where the particle size D50 grows from 9.5 μm to 12 μm.

[0058] Example 3

[0059] This example provides a preparation method for large particle ternary precursors with a dense surface. The preparation method includes the following steps:

[0060] (1) In the reaction kettle, configure a first bottom liquid with pure water, liquid caustic soda, and ammonia. Introduce nitrogen. Control the temperature of the first bottom liquid at 40 °C, the pH at 12, and the ammonia concentration at 8 g / L.

[0061] (2) The nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia water are injected into the first bottom solution in parallel. Under the conditions of a stirring speed of 600 rpm, a pH value in the range of 11 - 12, and an ammonia content in the range of 8 - 10 g / L, a first co-precipitation reaction is carried out to grow seed crystals with a D50 of 5 μm.

[0062] (3) The seed crystals are reversely added into another reaction kettle to form a second bottom solution. The content of the seed crystals in the second bottom solution is 40 g / L, the pH is 11, and the complexing agent concentration is 5 g / L. The nickel-cobalt-manganese mixed salt solution, liquid caustic soda, and ammonia water are added into the second bottom solution in parallel. At 50 °C, a second co-precipitation reaction is carried out. During the process, the stirring speed is 600 rpm, the pH is controlled in the range of 10 - 11, and the ammonia concentration is controlled in the range of 5 - 6 g / L, growing to large particle ternary precursors with a dense surface and a target particle size D50 of 17 μm.

[0063] Among them, the initial flow rate of the mixed metal salt solution into the second bottom solution is 4% / h of the reaction kettle volume, the initial flow rate of the liquid caustic soda into the second bottom solution is 2% / h of the reaction kettle volume, and the initial flow rate of the ammonia water into the second bottom solution is 0.5% / h of the reaction kettle volume.

[0064] During the second co-precipitation reaction, by changing the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia water into the second bottom solution, the growth rate of the particle size D50 per hour in the initial stage of the second co-precipitation reaction is 3.5 / 100 of the target particle size D50, the growth rate of the particle size D50 per hour in the middle stage of the second co-precipitation reaction is 2.5 / 100 of the target particle size D50, and the growth rate of the particle size D50 per hour in the final stage of the second co-precipitation reaction is 1.5 / 100 of the target particle size D50. If the particle size growth rate per hour exceeds the constraint value, the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia water are all adjusted to 0.8 times the flow rate of the previous stage.

[0065] The initial stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 7 μm to 10 μm, the middle stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 10 μm to 13 μm, and the final stage of the second co-precipitation reaction refers to the stage where the particle size D50 grows from 13 μm to 17 μm.

[0066] Example 4

[0067] This embodiment provides a method for preparing a large-sized ternary precursor with a dense surface. Except that in the initial stage of the second co-precipitation reaction in step (3), the hourly growth rate of the particle size D50 is 4 / 100 of the target particle size D50, in the middle stage of the second co-precipitation reaction, the hourly growth rate of the particle size D50 is 3 / 100 of the target particle size D50, and in the final stage of the second co-precipitation reaction, the hourly growth rate of the particle size D50 is 2 / 100 of the target particle size D50, the rest is the same as that in Example 1.

[0068] Example 5

[0069] This embodiment provides a method for preparing a large-sized ternary precursor with a dense surface. Except that in the initial stage of the second co-precipitation reaction in step (3), the hourly growth rate of the particle size D50 is 1 / 100 of the target particle size D50, in the middle stage of the second co-precipitation reaction, the hourly growth rate of the particle size D50 is 1 / 100 of the target particle size D50, and in the final stage of the second co-precipitation reaction, the hourly growth rate of the particle size D50 is 1 / 100 of the target particle size D50, the rest is the same as that in Example 1.

[0070] Example 6

[0071] This embodiment provides a method for preparing a large-sized ternary precursor with a dense surface. Except that when the hourly growth rate of the particle size exceeds the constraint value, the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia water are all adjusted to 0.75 times the flow rate of the previous stage to adaptively change the growth rate of the particle size D50, the rest is the same as that in Example 1.

[0072] Example 7

[0073] This embodiment provides a method for preparing a large-sized ternary precursor with a dense surface. Except that when the hourly growth rate of the particle size exceeds the constraint value, the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia water are all adjusted to 1 times the flow rate of the previous stage to adaptively change the growth rate of the particle size D50, the rest is the same as that in Example 1.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a large-sized ternary precursor. Except that during the second co-precipitation reaction in step (2), the flow rate of the mixed metal salt solution into the second bottom liquid has always been 3% / h of the reaction kettle volume, the flow rate of the liquid caustic soda into the second bottom liquid has always been 1% / h of the reaction kettle volume, the flow rate of the ammonia water into the second bottom liquid is 0.3% / h of the reaction kettle volume, and the flow rates of the mixed metal salt solution, liquid caustic soda, and ammonia water do not change to adaptively change the growth rate of the particle size D50, the rest is the same as that in Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing large-particle ternary precursors. Except that the hourly growth rate of the particle size D50 in the initial stage of the second co-precipitation reaction described in step (3) is 8 / 100 of the target particle size D50, the hourly growth rate of the particle size D50 in the middle stage of the second co-precipitation reaction is 6 / 100 of the target particle size D50, and the hourly growth rate of the particle size D50 in the final stage of the second co-precipitation reaction is 3 / 100 of the target particle size D50, the rest are the same as in Example 1.

[0078] The tap densities of the ternary precursors obtained in the above examples and comparative examples are shown in Table 1; the ternary precursors obtained in the above examples and comparative examples are sintered with LiOH at 450 °C for 5 h and then at 850 °C for 14 h to obtain the positive electrode active material. The obtained positive electrode active material is made into a positive electrode plate, and then assembled into a CR2032 type button half cell with a polypropylene film separator, a lithium metal negative electrode, a mixed solution of LiPF6 (1M) and EC:DMC:EMC (volume ratio 1:1:1) as the electrolyte. After the battery assembly is completed, its capacity and cycle performance are tested. The test conditions are as follows: charge and discharge at 0.1C / 0.1C in a voltage window of 2.0V - 4.0V to obtain the first discharge specific capacity and the capacity retention rate after 100 cycles; the test results are shown in Table 1:

[0079] Table 1

[0080]

[0081]

[0082] As can be seen from Table 1:

[0083] From Example 1 and Comparative Example 1, it can be seen that by regulating the flow rates of the mixed metal salt solution, the precipitant solution, and the complexing agent solution, and controlling the particle size growth rate at different reaction stages, the present invention can improve the tap density, the capacity, and the cycle performance of the battery; from Example 1 and Comparative Example 2, it can be seen that although the present invention regulates the raw material feed flow rate, it makes the particle growth rate too fast, which is not conducive to the formation of dense particles, thus affecting the tap density of the material and the performance of the battery; from Example 1 and Examples 4 - 5, it can be seen that the particle size D50 at different reaction stages of the present invention is preferably within a specific numerical range; from Example 1 and Examples 6 - 7, it can be seen that the amplitude of flow rate adjustment of the present invention will affect the growth stability and also the particle growth amplitude, thus affecting the tap density of the material and the performance of the battery.

[0084] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a large-particle ternary precursor with a dense surface, characterized in that, The preparation method includes the following steps: (1) Introduce the mixed metal salt solution, precipitant solution, and complexing agent solution into the first bottom liquid to conduct the first coprecipitation reaction to obtain seeds; (2) Introduce the mixed metal salt solution, precipitant solution, and complexing agent solution into the second bottom liquid, where the second bottom liquid includes the seeds obtained in step (1), and conduct the second coprecipitation reaction to obtain the large-sized ternary precursor with a dense surface; During the second coprecipitation reaction, by changing the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution introduced into the second bottom liquid, the growth rate of the particle size D50 per hour in the initial stage of the second coprecipitation reaction is ≤ 4 / 100 of the target particle size D50, the growth rate of the particle size D50 per hour in the middle stage of the second coprecipitation reaction is ≤ 3 / 100 of the target particle size D50, and the growth rate of the particle size D50 per hour in the final stage of the second coprecipitation reaction is ≤ 2 / 100 of the target particle size D50.

2. The preparation method according to claim 1, characterized in that, The growth rate of the particle size D50 per hour in the initial stage of the second coprecipitation reaction is ≤ 4 / 100 of the target particle size D50 and ≥ 3 / 100 of the target particle size D50, the growth rate of the particle size D50 per hour in the middle stage of the second coprecipitation reaction is ≤ 3 / 100 of the target particle size D50 and ≥ 2 / 100 of the target particle size D50, and the growth rate of the particle size D50 per hour in the final stage of the second coprecipitation reaction is ≤ 2 / 100 of the target particle size D50 and ≥ 1 / 100 of the target particle size D50; Preferably, if the growth rate of the particle size D50 per hour in the middle stage of the second coprecipitation reaction described in step (2) exceeds the constraint value, adjust the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution to 0.8 to 0.95 times the flow rates in the initial stage of the reaction; Preferably, if the growth rate of the particle size D50 per hour in the final stage of the second coprecipitation reaction described in step (2) exceeds the constraint value, adjust the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution to 0.8 to 0.95 times the flow rates in the middle stage of the reaction.

3. The preparation method according to claim 1 or 2, characterized in that, The initial flow rate of the mixed metal salt solution introduced into the second bottom liquid in step (2) is 2% / h - 4% / h of the volume of the reaction kettle; Preferably, the initial flow rate of the precipitant solution introduced into the second bottom liquid in step (2) is 0.5% / h - 2% / h of the volume of the reaction kettle; Preferably, the initial flow rate of the complexing agent solution introduced into the second bottom liquid in step (2) is 0.1% / h - 0.5% / h of the volume of the reaction kettle.

4. The preparation method according to any one of claims 1-3, characterized in that, The initial stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 4.5 μm - 7 μm to 6.5 μm - 10 μm; Preferably, the middle stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 6.5 μm - 10 μm to 9.5 μm - 13 μm.

5. The preparation method according to any one of claims 1-4, characterized in that, The final stage of the second coprecipitation reaction in step (2) refers to the stage where the particle size D50 grows from 9.5 μm - 13 μm to 12 μm - 17 μm; Preferably, the target particle size D50 in step (2) is 12 μm - 17 μm.

6. The preparation method according to any one of claims 1-5, characterized in that, The pH of the second coprecipitation reaction described in step (2) is 10 - 11, and the complexing agent concentration is 3 g / L - 6 g / L; Preferably, the temperature of the second coprecipitation reaction described in step (2) is 40°C - 60°C, and the stirring speed is 600 rpm - 1000 rpm; Preferably, in the second bottom solution described in step (2), the content of the seed crystal is 40 g / L - 70 g / L; Preferably, the pH of the second bottom solution described in step (2) is 10 - 11, and the complexing agent concentration is 3 g / L - 6 g / L.

7. The preparation method according to any one of claims 1-6, characterized in that, The particle size D50 of the seed crystal described in step (1) is 3 μm - 5 μm; Preferably, the pH of the first bottom solution described in step (1) is 10 - 12, and the complexing agent concentration is 8 g / L - 10 g / L; Preferably, the pH of the first coprecipitation reaction described in step (1) is 11 - 12, and the complexing agent concentration is 8 g / L - 10 g / L; Preferably, the temperature of the first coprecipitation reaction described in step (1) is 40°C - 60°C, and the stirring speed is 600 rpm - 1000 rpm.

8. A large-particle ternary precursor with a dense surface, characterized in that, The surface-dense large-particle ternary precursor is prepared by the preparation method according to any one of claims 1 - 7.

9. A ternary cathode material, characterized in that, The raw materials for preparing the ternary cathode material include the surface-dense large-particle ternary precursor according to claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the ternary cathode material according to claim 9.

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