A nickel-cobalt-manganese ternary precursor, a preparation method and application thereof

Abstract

The application discloses a nickel-cobalt-manganese ternary precursor as well as a preparation method and application thereof. x Co y Mn z (OH)2, 0.82

Description

Technical Field

[0001] This invention relates to the field of cathode materials for lithium-ion batteries, and more particularly to the preparation of high-nickel ternary precursors, specifically to a nickel-cobalt-manganese ternary precursor, its preparation method, and its application. Background Technology

[0002] In recent years, thanks to strong national support for new energy technologies, the lithium battery industry has developed rapidly. Ternary cathode materials, with their high specific capacity, good rate performance, and high cycle stability, have become a popular research material in the domestic and international lithium battery industry. Among them, the nickel-cobalt-manganese ternary precursor has a significant impact on the cathode material, and nickel-cobalt-manganese ternary cathode materials have a higher energy density than traditional cathode materials such as lithium iron phosphate, thus having greater development potential and a broader market prospect.

[0003] Currently, the preparation of nickel-cobalt-manganese ternary precursors mainly relies on wet precipitation, specifically wet co-precipitation. This involves using a mixed solution of nickel-cobalt-manganese sulfates as the raw material for the molten metal, sodium hydroxide aqueous solution as the precipitant, and ammonia aqueous solution as the complexing agent. Particle size growth is controlled by adjusting the opening of the alkali and ammonia solutions, and the reaction is stopped once the target particle size is reached to obtain the nickel-cobalt-manganese ternary precursor. However, practical experience has shown that conventional methods struggle to obtain precursor particles that are finely sized, have a high specific surface area, and are uniformly spherical. This is especially true for high-nickel ternary precursor materials, where the primary particles are often thicker, which can severely hinder the capacity cycling test during subsequent sintering into a cathode material. + The diffusion of this material makes the cathode material structure prone to collapse, and reduces cycle stability and retention rate.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0005] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide an improved method for preparing nickel-cobalt-manganese ternary precursors. This method is suitable for preparing nickel-cobalt-manganese ternary precursors with high nickel content, and the precursor particles easily possess the characteristics of fine primary particles, high specific surface area, and uniform spherical shape.

[0006] The present invention also provides a nickel-cobalt-manganese ternary precursor prepared by the above method and its application in the preparation of lithium-ion battery cathode materials.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A preparation method of a nickel-cobalt-manganese ternary precursor, wherein the chemical formula of the nickel-cobalt-manganese ternary precursor is Ni x Co y Mn z (OH)₂; wherein 0.82<x<0.90, 0.10<y<0.15, 0.05<z<0.09, and x+y+z=1; The preparation method comprises: (1) Under the protection of a protective atmosphere, mixing a nickel-cobalt-manganese mixed metal salt, an alkali and a complexing agent, and reacting under a first pH condition; when the particle size D50 of the generated seed crystal reaches a first preset median particle size, switching the protective atmosphere to an oxygen-containing gas atmosphere, controlling the volume concentration of oxygen in the oxygen-containing gas to be 2%-5%, and controlling to lower the pH value of the reaction system at a rate of pH decreasing by 0.04-0.06 for every 0.1-0.3 μm growth of the particle size D50 until a second pH value is reached and maintained; stopping the reaction when the particle size D50 of the seed crystal reaches a second preset median particle size, so as to obtain a seed crystal solution; (2) Under the protection of a protective atmosphere, mixing a nickel-cobalt-manganese mixed metal salt, an alkali and a complexing agent to prepare a base solution, continuously introducing the seed crystal solution, the alkali and the complexing agent into the base solution respectively, adjusting to a third pH value and then synchronously introducing the nickel-cobalt-manganese mixed metal salt, and controlling to lower the pH value of the reaction system at a rate of pH decreasing by 0.04-0.06 for every 0.4-0.6 μm growth of the particle size D50 until a fourth pH value is reached and maintained; stopping the reaction when the particle size D50 of the seed crystal reaches a third preset median particle size.

[0008] In some embodiments of the present invention, the volume concentration of oxygen in the oxygen-containing gas is controlled to be 3%-5%.

[0009] According to some specific aspects of the present invention, the volume concentration of oxygen in the oxygen-containing gas is controlled to be 3.0%, 3.5%, 4.0%, 4.5%, 5.0% and the like.

[0010] In some embodiments of the present invention, the first pH value is 11.65-12.65, the second pH value is 11.25-12.25, the third pH value is 11.25-12.25, and the fourth pH value is 11.2-11.6.

[0011] Further, the first pH value is 11.95-12.35, the second pH value is 11.55-11.95, the third pH value is 11.55-11.95, and the fourth pH value is 11.25-11.55.

[0012] In some embodiments of the present invention, the difference between the first pH value and the second pH value is 0.3-0.5, for example, it can be 0.3, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, etc.

[0013] In some embodiments of the present invention, the absolute value of the difference between the second pH value and the third pH value is 0-0.2, further 0-0.1, for example, it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, etc.

[0014] In some embodiments of the present invention, the difference between the third pH value and the fourth pH value is 0.25-0.45, for example, it can be 0.25, 0.26, 0.28, 0.29, 0.3, 0.32, 0.33, 0.35, 0.38, 0.40, 0.42, 0.45, etc.

[0015] In some embodiments of the present invention, the first preset median particle size is 1.3-1.5 μm.

[0016] In some embodiments of the present invention, the second preset median particle size is 2.8-3.2 μm.

[0017] In some embodiments of the present invention, the third preset median particle size is 8-11 μm.

[0018] In some embodiments of the present invention, in step (1), the pH value of the reaction system is controlled to decrease at a rate of 0.045-0.055 when the particle size D50 grows by 0.15-0.25 μm.

[0019] According to some specific aspects of the present invention, in step (1), the pH of the reaction system is controlled to decrease at a rate of 0.045-0.055 for every 0.1 μm, 0.12 μm, 0.15 μm, 0.16 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.22 μm, 0.23 μm, 0.25 μm, 0.26 μm, 0.28 μm, 0.29 μm or 0.3 μm increase in particle size D50.

[0020] According to some specific aspects of the present invention, in step (1), the pH of the reaction system is controlled to decrease at a rate of 0.04, 0.042, 0.045, 0.046, 0.048, 0.05, 0.052, 0.055, 0.056, 0.058 or 0.06 for every 0.1-0.3 μm increase in particle size D50.

[0021] In some embodiments of the present invention, in step (2), the pH of the reaction system is controlled to decrease at a rate of 0.045-0.055 for every 0.4 μm, 0.42 μm, 0.45 μm, 0.48 μm, 0.50 μm, 0.52 μm, 0.55 μm, 0.56 μm, 0.58 μm or 0.6 μm increase in particle size D50.

[0022] According to some specific aspects of the invention, in step (2), the pH of the reaction system is controlled to decrease at a rate of 0.045-0.055 for every 0.45-0.55 μm increase in particle size D50.

[0023] According to some specific aspects of the present invention, in step (2), the pH of the reaction system is controlled to decrease at a rate of 0.04, 0.042, 0.045, 0.046, 0.048, 0.05, 0.052, 0.055, 0.056, 0.058 or 0.06 for every 0.4-0.6 μm increase in particle size D50.

[0024] In this invention, the grain size during the reaction process is monitored in real time, and when the growth increment reaches a set value, the corresponding pH value is reduced.

[0025] In some embodiments of the present invention, the protective atmosphere is a nitrogen atmosphere and / or an inert gas atmosphere. Further, the inert gas atmosphere is achieved by introducing helium, argon, or the like.

[0026] In some embodiments of the present invention, during the reaction process of steps (1) and (2), the concentration of the complexing agent is controlled at 5.0-6.0 g / L, for example, it can be 5.0 g / L, 5.2 g / L, 5.5 g / L, 5.6 g / L, 5.8 g / L, 6.0 g / L, etc.

[0027] In some embodiments of the present invention, the reaction temperature is controlled at 50-60°C during the reaction process of steps (1) and (2), and further, the reaction temperatures of steps (1) and (2) are controlled to be the same.

[0028] In some embodiments of the present invention, in steps (1) and (2), the nickel-cobalt-manganese mixed metal salt, the alkali and the complexing agent are all added in the form of an aqueous solution.

[0029] In some embodiments of the present invention, the nickel-cobalt-manganese mixed metal salt is composed of nickel sulfate, cobalt sulfate and manganese sulfate.

[0030] In some embodiments of the present invention, the alkali is an alkali metal hydroxide, and further, the alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide.

[0031] In some embodiments of the present invention, the complexing agent comprises ammonia.

[0032] According to some specific aspects of the invention, the alkali is added by adding an aqueous solution of sodium hydroxide with a mass concentration of 30%-50%.

[0033] According to some specific aspects of the invention, the complexing agent is added by adding ammonia water with a mass concentration of 5%-20%.

[0034] According to some specific aspects of the present invention, the molar concentration of the metal salt in the nickel-cobalt-manganese mixed metal salt is 1.8-2.3 mol / L.

[0035] In some embodiments of the present invention, after the reaction in step (2) is completed, post-treatment such as centrifugation, washing, drying, and removal of magnetic foreign matter is performed to obtain the nickel-cobalt-manganese ternary precursor product.

[0036] Another technical solution provided by the present invention: a nickel-cobalt-manganese ternary precursor prepared by the above-described method for preparing a nickel-cobalt-manganese ternary precursor.

[0037] According to the present invention, the specific surface area of ​​the nickel-cobalt-manganese ternary precursor can be greater than or equal to 13.65 m². 2 / g, tap density can be greater than or equal to 2.13 g / cm³ 3 The loose bulk density can be greater than or equal to 1.51 g / cm³. 3 .

[0038] Another technical solution provided by the present invention: the application of the above-mentioned nickel-cobalt-manganese ternary precursor in the preparation of lithium-ion battery cathode materials.

[0039] In this invention, the use of terms such as "first," "second," "third," and "fourth" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0040] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: Addressing existing problems in the preparation of high-nickel nickel-cobalt-manganese ternary precursors, such as thick primary particles, insufficient specific surface area, and poor sphericity, this invention innovatively introduces a low-concentration oxygen atmosphere in certain stages of the seed preparation phase. Furthermore, it controls the pH value during both the seed preparation and grain growth stages to be inversely related to particle size. As the particle size increases to a certain extent, the pH value is correspondingly reduced until a preset median particle size is reached. The resulting precursor exhibits fine primary particles, high specific surface area, and uniform sphericity, significantly improving the specific surface area of ​​the ternary precursor and enhancing its morphology and consistency. Attached Figure Description

[0041] Figure 1 This is an SEM image of the seed crystals obtained in step 2 of Embodiment 1 of the present invention; Figure 2 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Example 1 of the present invention; Figure 3 This is a SEM image of the seed crystals obtained in step 2 of Comparative Example 1 of the present invention; Figure 4 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Comparative Example 1 of the present invention; Figure 5 This is a SEM image of the seed crystals obtained in step 2 of Comparative Example 2 of the present invention; Figure 6 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Comparative Example 2 of the present invention; Figure 7 This is a SEM image of the seed crystals obtained in step 2 of Comparative Example 3 of the present invention; Figure 8 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Comparative Example 3 of the present invention; Figure 9 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Comparative Example 4 of the present invention. Figure 10 This is a SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 of Comparative Example 5 of the present invention. Detailed Implementation

[0042] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0043] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0044] Example 1: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor. The preparation method includes: Step 1: Prepare an aqueous solution of nickel cobalt manganese sulfate containing a total nickel cobalt manganese ion concentration of 2.0 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 83:12:5; Step 2: Add half a tank of pure water to the seed crystal reactor, start stirring at 35 Hz, purge with nitrogen for protection, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the seed crystal reactor, adjusting the pH of the bottom solution to 12.15 and the ammonia concentration to 5.5 g / L, and purge with nitrogen for protection. Then, introduce nickel cobalt manganese sulfate aqueous solution, a 42% sodium hydroxide aqueous solution, and an 8% ammonia solution into the reactor to prepare seed crystals. When the seed crystals grow to 1.4 μm, switch to introducing oxygen-containing gas with a volume concentration of 4%. Control the pH to decrease slowly to 11.75 at a rate of 0.05 for every 0.2 μm increase in particle size and maintain this level, while keeping the ammonia concentration, temperature, and stirring speed constant, until seed crystals with a D50 of 3.0 ± 0.05 μm are obtained. Then, stop the seed crystal reactor operation. Step 3: Transfer the seed crystals with a D50 of 3.0 ± 0.05 μm obtained in Step 2 into the corresponding aging tank, retain, stir, and set aside for later use; Step 4: Add half a tank of pure water to the crystal growth vessel, start stirring at 35 Hz, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the crystal growth vessel, adjust the pH of the bottom solution to 11.95, the ammonia concentration to 5.5 g / L, and provide nitrogen protection. Continuously circulate the seed solution, 42% sodium hydroxide aqueous solution, and 8% ammonia solution from the aging tank in Step 3, adjusting the pH to 11.75. Simultaneously add a nickel-cobalt-manganese sulfate aqueous solution in a co-current flow. During crystal growth, control the pH to decrease at a rate of 0.05 for every 0.5 μm of particle size growth, gradually decreasing the pH from 11.75 to 11.40 and maintaining this level. Simultaneously, keep the ammonia concentration, temperature, and stirring speed constant. Continue the reaction until the D50 in the reactor reaches 9.5 ± 0.05 μm, then stop the reaction.

[0045] Step 5: After the reaction is complete, the reactor is stopped, centrifuged, washed, dried, and demagnetized to remove foreign matter, and the nickel-cobalt-manganese ternary precursor product is obtained.

[0046] In this example, the SEM image of the seed crystal obtained in step 2 is as follows: Figure 1 As shown, from Figure 1 It can be seen that the seed crystals are uniform in size and evenly dispersed, with a clear and fine oxide layer covering the surface. There is no agglomeration of the particles, and the core-shell structure is clear.

[0047] The SEM image of the nickel-cobalt-manganese ternary precursor obtained in step 5 is shown below. Figure 2 As shown, from Figure 2 It can be seen that the surface of the nickel-cobalt-manganese ternary precursor is smooth, without any breakage or cracking.

[0048] Example 2: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor. The preparation method includes: Step 1: Prepare an aqueous solution of nickel cobalt manganese sulfate containing a total nickel cobalt manganese ion concentration of 2.0 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 80:12:8; Step 2: Add half a tank of pure water to the seed crystal reactor, start stirring at 35 Hz, purge with nitrogen for protection, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the seed crystal reactor, adjusting the pH of the bottom solution to 12.10 and the ammonia concentration to 5.5 g / L, and purge with nitrogen for protection. Then, introduce nickel cobalt manganese sulfate aqueous solution, a 42% sodium hydroxide aqueous solution, and an 8% ammonia solution into the reactor to prepare seed crystals. When the seed crystals grow to 1.4 μm, switch to introducing oxygen-containing gas with a volume concentration of 4%. Control the pH to decrease slowly to 11.75 at a rate of 0.05 for every 0.2 μm increase in particle size and maintain this level, while keeping the ammonia concentration, temperature, and stirring speed constant, until seed crystals with a D50 of 3.0 ± 0.05 μm are obtained. Then, stop the seed crystal reactor operation. Step 3: Transfer the seed crystals with a D50 of 3.0 ± 0.05 μm obtained in Step 2 into the corresponding aging tank, retain, stir, and set aside for later use; Step 4: Add half a tank of pure water to the crystal growth vessel, start stirring at 35 Hz, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the crystal growth vessel, adjust the pH of the bottom solution to 11.90, the ammonia concentration to 5.5 g / L, and provide nitrogen protection. Continuously circulate the seed solution, 42% sodium hydroxide aqueous solution, and 8% ammonia solution from the aging tank in Step 3, adjusting the pH to 11.75. Simultaneously add a nickel-cobalt-manganese sulfate aqueous solution in a co-current flow. During crystal growth, control the pH to decrease at a rate of 0.05 for every 0.5 μm of particle size growth, gradually decreasing the pH from 11.75 to 11.40 and maintaining this level. Simultaneously, keep the ammonia concentration, temperature, and stirring speed constant. Continue the reaction until the D50 in the reactor reaches 9.5 ± 0.05 μm, then stop the reaction.

[0049] Step 5: After the reaction is complete, the reactor is stopped, centrifuged, washed, dried, and demagnetized to remove foreign matter, and the nickel-cobalt-manganese ternary precursor product is obtained.

[0050] Example 3: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor. The preparation method includes: Step 1: Prepare an aqueous solution of nickel cobalt manganese sulfate containing a total nickel cobalt manganese ion concentration of 2.0 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 83:15:2; Step 2: Add half a tank of pure water to the seed crystal reactor, start stirring at 35 Hz, purge with nitrogen for protection, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the seed crystal reactor, adjusting the pH of the bottom solution to 12.15 and the ammonia concentration to 5.5 g / L, and purge with nitrogen for protection. Then, introduce nickel cobalt manganese sulfate aqueous solution, a 42% sodium hydroxide aqueous solution, and an 8% ammonia solution into the reactor to prepare seed crystals. When the seed crystals grow to 1.4 μm, switch to introducing oxygen-containing gas with a volume concentration of 4%. Control the pH to decrease slowly to 11.75 at a rate of 0.05 for every 0.2 μm increase in particle size and maintain this level, while keeping the ammonia concentration, temperature, and stirring speed constant, until seed crystals with a D50 of 3.0 ± 0.05 μm are obtained. Then, stop the seed crystal reactor operation. Step 3: Transfer the seed crystals with a D50 of 3.0 ± 0.05 μm obtained in Step 2 into the corresponding aging tank, retain, stir, and set aside for later use; Step 4: Add half a tank of pure water to the crystal growth vessel, start stirring at 35 Hz, and heat to 55 ℃. Add a 42% sodium hydroxide aqueous solution and an 8% ammonia aqueous solution to the crystal growth vessel, adjust the pH of the bottom solution to 12.00, the ammonia concentration to 5.5 g / L, and provide nitrogen protection. Continuously circulate the seed solution, 42% sodium hydroxide aqueous solution, and 8% ammonia solution from the aging tank in Step 3, adjusting the pH to 11.75. Simultaneously add a nickel-cobalt-manganese sulfate aqueous solution in a co-current flow. During crystal growth, control the pH to decrease at a rate of 0.05 for every 0.5 μm of particle size growth, gradually decreasing the pH from 11.75 to 11.40 and maintaining this level. Simultaneously, keep the ammonia concentration, temperature, and stirring speed constant. Continue the reaction until the D50 in the reactor reaches 9.5 ± 0.05 μm, then stop the reaction.

[0051] Step 5: After the reaction is complete, the reactor is stopped, centrifuged, washed, dried, and demagnetized to remove foreign matter, and the nickel-cobalt-manganese ternary precursor product is obtained.

[0052] Comparative Example 1: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor, which is basically the same as in Example 1, except that in step 2, the volume concentration of oxygen in the oxygen-containing gas is 1%; the remaining process steps and parameters are consistent with those in Example 1.

[0053] In this example, the SEM image of the oxide seed crystal obtained in step 2 is as follows: Figure 3 As shown, compared to Example 1, reducing the volume concentration of oxygen during the seed growth stage results in seed particles that are thicker, have poor sphericity, and are irregularly spherical.

[0054] The precursor SEM image obtained in step 5 is shown below. Figure 4 As shown, the particle surface is thicker than that of Example 1, with a lamellar structure, poor refining process, and slight cracking of the spheres.

[0055] Comparative Example 2: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor, which is basically the same as in Example 1, except that in step 2, the volume concentration of oxygen in the oxygen-containing gas is 7%; the remaining process steps and parameters are consistent with those in Example 1.

[0056] In this example, the SEM image of the oxide seed crystal obtained in step 2 is as follows: Figure 5 As shown, compared to Example 1, increasing the volume concentration of oxygen during the seed growth stage results in finer and less spherical seed particles due to slight over-oxidation.

[0057] The precursor SEM image obtained in step 5 is shown below. Figure 6 As shown, the particle surface is finer than that of Example 1, the core-shell structure is not dense enough, and there are slight cracks.

[0058] Comparative Example 3: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor, which is basically the same as in Example 1, except that in step 2, the oxygen-containing gas atmosphere is replaced with a nitrogen atmosphere; the remaining process steps and parameters are consistent with those in Example 1.

[0059] In this example, the SEM image of the seed crystal obtained in step 2 is as follows: Figure 7 As shown, from Figure 7 It can be seen that after the oxygen-containing gas was removed during the seed preparation stage, the primary particles on the surface of the seed particles were relatively thick, exhibiting a plate-like shape with a large thickness, length, and width.

[0060] The SEM image of the precursor obtained in step 5 is shown below. Figure 8 As shown, from Figure 8 It can be seen that the obtained nickel-cobalt-manganese ternary precursor has a rough surface, is thick and flat, has large particles, uneven spherical distribution, and a loose core-shell structure.

[0061] Comparative Example 4: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor, which is basically the same as in Example 1, except that: during the reaction process in steps 2 and 4, oxygen-containing gas with a volume concentration of 4% is introduced throughout the process; the remaining process steps and parameters are consistent with those in Example 1.

[0062] In this example, the SEM image of the precursor obtained in step 5 is as follows: Figure 9 As shown, since the entire reaction is carried out with oxygen gas, the resulting precursor exhibits the following microscopic characteristics: the particles are too fine, the surface is too dense, the spherical structure is too loose, and it is easy to crack; the macroscopic characteristics are: the color is dark, the powder is too fine, the agglomeration is serious, it is difficult to sieve, and the washing in the post-processing stage is difficult and the impurities are difficult to remove.

[0063] Comparative Example 5: This example provides a method for preparing a nickel-cobalt-manganese ternary precursor and the prepared nickel-cobalt-manganese ternary precursor, which is basically the same as in Example 1, except that: in step 2, when the seed crystal size grows to 1.4 μm, the pH value is rapidly reduced from 12.15 to 11.75 and maintained at a rate of 0.1 for every 0.8 μm increase in particle size; in step 4, after the nickel-cobalt-manganese sulfate aqueous solution is added in parallel flow, the pH value is rapidly reduced from 11.75 to 11.40 and maintained at a rate of 0.1 for every 1.0 μm increase in particle size; the remaining process steps and parameters are consistent with those in Example 1.

[0064] In this example, the precursor SEM image obtained in step 5 is as follows: Figure 10 As shown, it can be seen that due to the excessively rapid rate of pH reduction in steps 2 and 4, the particle size increased too quickly during crystal growth, the growth rate inside and outside the particles was inconsistent, the internal pressure was unbalanced, and the precursor particles showed severe spherical cracking, structural disorder, and poor spherical morphology integrity.

[0065] Performance testing: The precursors obtained in the examples and comparative examples were tested for tap density, loose density and specific surface area. The higher the tap density value, the higher the density of the precursor and the denser the filling between the particles. The FZS4-4B tap density measuring instrument was used for measurement. A higher loose packing density indicates a larger unit volume mass and smaller voids in the precursor. The loose packing density is measured using a QL-1002 loose packing density meter. The larger the specific surface area value, the greater the porosity of the particles. The BSD-BET400 fully automatic rapid specific surface area meter was used for measurement.

[0066] The test results are shown in Table 1.

[0067] Table 1 The data in the table show that during precursor preparation, moderate oxidation in the seed preparation stage can increase both the specific surface area and the tap density and loose packing density. However, when oxidation is excessive, as in Comparative Examples 2 and 4, although it can significantly increase the specific surface area, it also leads to excessively fine primary particles, spherical breakage, and excessive fine powder, resulting in a significant decrease in tap and loose packing density. Conversely, when oxidation is insufficient, as in Comparative Examples 1 and 3, the lack of oxidation results in rough crystal surfaces, coarse grains, and slight agglomeration, leading to a decrease in both tap and loose packing density, as well as a decrease in specific surface area. Therefore, in the precursor preparation process, moderate oxidation can refine the particle surface, increase the specific surface area, and maintain spherical morphology, as well as high tap and loose packing density. Furthermore, if the pH value is not properly controlled during the reaction, as in Comparative Example 5 where the pH is lowered too quickly, the precursor particles exhibit severe spherical cracking, structural disorder, and poor spherical morphology integrity.

[0068] As used throughout the specification and claims, the term "comprising" is an open-ended term and should be interpreted as "comprising but not limited to." "Substantially" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or system comprising said element.

[0069] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0070] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing a nickel-cobalt-manganese ternary precursor, characterized in that, The chemical formula of the nickel-cobalt-manganese ternary precursor is Ni x Co y Mn z (OH)₂; wherein 0.82<x<0.90, 0.10<y<0.15, 0.05<z<0.09, and x+y+z=1; The preparation method includes: (1) Under a protective atmosphere, a mixture of nickel-cobalt-manganese metal salt, alkali and complexing agent is mixed and reacted under the first pH condition; When the generated seed crystal particle size D50 reaches the first preset median particle size, the protective atmosphere is switched to an oxygen-containing gas atmosphere, the volume concentration of oxygen in the oxygen-containing gas is controlled at 2%-5%, and the pH value of the reaction system is controlled to decrease at a rate of 0.04-0.06 when the particle size D50 grows by 0.1-0.3μm, until the second pH value is reached and maintained. When the seed crystal particle size D50 reaches the second preset median particle size, the reaction is stopped and a seed crystal solution is obtained. (2) Under a protective atmosphere, a nickel-cobalt-manganese mixed metal salt, an alkali and a complexing agent are mixed to prepare a base solution. The seed solution, alkali and complexing agent are continuously introduced into the base solution. After adjusting to the third pH value, the nickel-cobalt-manganese mixed metal salt is introduced simultaneously. The pH value of the reaction system is controlled to decrease at a rate of 0.04-0.06 when the particle size D50 grows by 0.4-0.6 μm, until the fourth pH value is reached and maintained. When the seed particle size D50 reaches the third preset median particle size, the reaction is stopped.

2. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, The volume concentration of oxygen in the oxygen-containing gas is controlled to be 3%-5%.

3. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, The first pH value is 11.65-12.65, the second pH value is 11.25-12.25, the third pH value is 11.25-12.25, and the fourth pH value is 11.2-11.6; further, the first pH value is 11.95-12.35, the second pH value is 11.55-11.95, the third pH value is 11.55-11.95, and the fourth pH value is 11.25-11.

55.

4. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1 or 3, characterized in that, The difference between the first pH value and the second pH value is 0.3-0.5; and / or, the absolute value of the difference between the second pH value and the third pH value is 0-0.2, further 0-0.1; and / or, the difference between the third pH value and the fourth pH value is 0.25-0.

45.

5. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, The first preset median particle size is 1.3-1.5 μm; and / or, the second preset median particle size is 2.8-3.2 μm; and / or, the third preset median particle size is 8-11 μm.

6. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, In step (1), the pH of the reaction system is controlled to decrease at a rate of 0.045-0.055 for every 0.15-0.25 μm increase in particle size D50; and / or, in step (2), the pH of the reaction system is controlled to decrease at a rate of 0.045-0.055 for every 0.45-0.55 μm increase in particle size D50.

7. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, The protective atmosphere is a nitrogen atmosphere and / or an inert gas atmosphere; and / or, during the reaction process of steps (1) and (2), the concentration of the complexing agent is controlled at 5.0-6.0 g / L respectively; and / or, during the reaction process of steps (1) and (2), the reaction temperature is controlled at 50-60℃, and further, the reaction temperatures of steps (1) and (2) are controlled to be the same.

8. The method for preparing the nickel-cobalt-manganese ternary precursor according to claim 1, characterized in that, In steps (1) and (2), the nickel-cobalt-manganese mixed metal salt, the alkali, and the complexing agent are all added in the form of an aqueous solution; and / or, the nickel-cobalt-manganese mixed metal salt is composed of nickel sulfate, cobalt sulfate, and manganese sulfate; and / or, the alkali is an alkali metal hydroxide, further comprising sodium hydroxide and / or potassium hydroxide; and / or, the complexing agent comprises ammonia.

9. A nickel-cobalt-manganese ternary precursor prepared by any one of claims 1-8.

10. The application of the nickel-cobalt-manganese ternary precursor of claim 9 in the preparation of lithium-ion battery cathode materials.

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