A nickel-cobalt positive electrode precursor material, a preparation method thereof, a positive electrode material and a battery

Abstract

This invention provides a nickel-cobalt cathode precursor material, its preparation method, the cathode material, and a battery. The preparation method includes the following steps: adding a nickel-cobalt mixed salt solution, a precipitant solution, and a complexing agent solution concurrently to a base liquid for a first coprecipitation reaction; after reacting to a first target reaction time, performing a separate reactor treatment; after the separate reactor treatment, continuing the second coprecipitation reaction to obtain the nickel-cobalt cathode precursor material; wherein, during the first coprecipitation reaction, the stirring speed increases in stages; during the second coprecipitation reaction, the stirring speed decreases in stages. This invention effectively solves the problems of spheroidization and twinning in the nickel-cobalt cathode precursor material by controlling the stirring speed during the coprecipitation reactions before and after the separate reactor treatment, thus laying a solid foundation for the subsequent preparation of the cathode material and effectively improving the electrochemical performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a nickel-cobalt cathode precursor material and its preparation method, cathode material and battery. Background Technology

[0002] The new energy vehicle industry has developed rapidly over the past decade, with power battery materials mainly consisting of three types: lithium manganese oxide, ternary lithium, and lithium iron phosphate. Due to its poor conductivity, lithium iron phosphate requires doping with other materials, has low tap density, relatively small specific capacity, and stringent and specialized manufacturing processes, making it difficult to manufacture. Furthermore, the development of its supporting electrolytes has lagged behind, resulting in a slower industrialization process for lithium iron phosphate power batteries. Ternary cathode materials, on the other hand, have a more pronounced advantage.

[0003] Currently, ternary cathode materials include nickel-cobalt-manganese (NiCoMn) or nickel-cobalt-aluminum (NiCoA) cathode materials. The performance of ternary cathode materials mainly depends on the ternary precursor. Requirements such as high capacity, high voltage, and excellent cycle performance make NiCoA ternary precursors more advantageous than NiCoMn ternary precursors. However, the synthesis process of NiCoA ternary precursors is difficult. Aluminum salts require a separate feeding system and cannot be mixed with nickel and cobalt. Furthermore, ammonia water has poor complexation effect with aluminum ions, making it extremely difficult to control the precipitation reaction. The current method mainly involves synthesizing nickel-cobalt binary precursors from nickel-cobalt raw materials.

[0004] In addition, compared with traditional cathode materials such as lithium manganese oxide, ternary materials, and lithium iron phosphate, nickel-cobalt binary materials have advantages such as high voltage platform, good safety performance, superior cycle performance and rate performance, and easy high-voltage battery pack assembly, and have broad application prospects in the field of power batteries.

[0005] In summary, nickel-cobalt binary precursor materials can serve as precursors for both nickel-cobalt-aluminum (NiCoA) and nickel-cobalt binary cathode materials, making their preparation process crucial. Currently, conventional co-precipitation methods for preparing precursors typically involve preparing a mixed solution of soluble salts of nickel and cobalt metals, then adding a precipitant to obtain amorphous hydroxide or carbonate precursors. However, traditional co-precipitation processes result in nickel-cobalt binary precursors with a wide particle size distribution, thick and large primary particles, significant spheroidization in secondary particles, unstable control, poor batch-to-batch consistency, and excessively high tap density. Furthermore, the reaction time is limited, and particle size fragmentation occurs once it reaches a certain range. Additionally, during the co-precipitation reaction, primary particles are prone to agglomeration, forming twins. These problems severely impact the subsequent preparation of cathode materials and limit the performance of the resulting cathode materials.

[0006] Therefore, how to solve the problem of split spheres and twin spheres in the preparation process of nickel-cobalt binary precursor materials is an urgent issue that needs to be explored. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a nickel-cobalt cathode precursor material, its preparation method, the cathode material, and a battery. By controlling the stirring speed during the co-precipitation reaction before and after the separation process, the present invention effectively solves the problems of spheroidization and twinning in the nickel-cobalt cathode precursor material, thus laying a solid foundation for the subsequent preparation of the cathode material and effectively improving the electrochemical performance of the battery.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a nickel-cobalt cathode precursor material, the method comprising the following steps:

[0010] The nickel-cobalt mixed salt solution, precipitant solution, and complexing agent solution were added to the bottom liquid in a co-flow manner to carry out the first co-precipitation reaction. After the reaction reached the first target reaction time, the mixture was processed in separate reactors.

[0011] After separate processing in separate reactors, a second co-precipitation reaction is carried out to obtain the nickel-cobalt cathode precursor material.

[0012] In the first coprecipitation reaction, the stirring speed increases in stages; in the second coprecipitation reaction, the stirring speed decreases in stages.

[0013] It should be noted that the stirring speed in this invention gradually increases from 130 r / min to 160 r / min at the initial stage of the reaction (e.g., 130 r / min, 140 r / min, 150 r / min, or 160 r / min, etc.); in addition, the separation operation described in this invention specifically refers to transferring half of the material to another vessel after the separation requirements are met; and the second coprecipitation reaction is carried out in the newly separated reaction vessel, and the addition of raw materials is consistent with the first coprecipitation reaction stage.

[0014] In the preparation method of the present invention, in the first coprecipitation reaction stage, the stirring speed is gradually increased, which increases the probability of collision between particles during particle growth, reduces the agglomeration of primary particles, and avoids the problem of twinned particles. As the stirring speed and reaction time increase, the particle growth rate will slow down and the solid content in the reaction system will increase. At this time, in conjunction with the second coprecipitation reaction stage, by reducing the stirring speed of the reaction, the excessive increase of particle tap density is suppressed, and the problem of particle splitting is avoided.

[0015] In this invention, the gradient increase of stirring speed in the first coprecipitation reaction process and the gradient decrease of stirring speed in the second coprecipitation reaction process must be coordinated to jointly solve the problem of split and twinned spheres.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0017] Preferably, the total concentration of metal ions in the nickel-cobalt mixed salt solution is 1.0 mol / L to 2.5 mol / L, such as 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L, or 2.5 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] This invention does not impose any specific limitation on the molar ratio of nickel and cobalt in the nickel-cobalt mixed salt solution. Those skilled in the art can make adaptive modifications and adjustments according to actual needs. With the total molar amount of nickel and cobalt as 100%, the molar amount of nickel is greater than 50% and less than 100%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99%.

[0019] Furthermore, the salt type in the nickel-cobalt mixed salt solution of this invention is also a conventional technical solution, and can be any conventional salt used in the preparation of cathode precursors. This invention is applicable to all such salts, such as at least one of chloride, sulfate, nitrate or acetate.

[0020] Preferably, the concentration of the precipitant solution is 5 mol / L to 10 mol / L, such as 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] Preferably, the concentration of the complexing agent solution is 6 mol / L to 12 mol / L, such as 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] It is understood that the precipitant and complexing agent in this invention are all types of substances used in the conventional positive electrode precursor preparation stage, and all types of substances that can be reasonably known by those skilled in the art are applicable to this invention.

[0023] For example, the precipitant includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate; the complexing agent includes, but is not limited to, at least one of ammonia, citric acid, or ethylenediaminetetraacetic acid.

[0024] Preferably, the base liquid includes a solvent, a complexing agent, and a precipitant.

[0025] The base liquid mentioned in this invention is the solution system initially located in the reaction vessel, i.e., the start-up base liquid.

[0026] Preferably, the concentration of the complexing agent in the base liquid is 9 g / L to 10 g / L, such as 9 g / L, 9.1 g / L, 9.2 g / L, 9.3 g / L, 9.4 g / L, 9.5 g / L, 9.6 g / L, 9.7 g / L, 9.8 g / L, 9.9 g / L, or 10 g / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] Preferably, the pH value of the base solution is 11.0 to 11.2, such as 11.0, 11.1 or 11.2, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Because the increased stirring speed during the initial coprecipitation reaction may lead to cracks, this invention appropriately increases the amount of complexing agent in the base solution and lowers the pH value of the base solution. In particular, it is preferred that the concentration of the complexing agent in the base solution is 9-10 g / L and / or the pH value of the base solution is 11.0-11.2. This appropriately reduces the control reaction time and solves the problem of particle cracking in the early stage.

[0029] Preferably, during the first coprecipitation reaction, the stirring speed is increased by 7 r / h to 15 r / h, such as 7 r / h, 8 r / h, 9 r / h, 10 r / h, 11 r / h, 12 r / h, 13 r / h, 14 r / h or 15 r / h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] In this invention, the increase in stirring speed is 7-15 r / h, which is more conducive to reducing agglomeration while reducing the generation of small particles caused by sudden increase in speed.

[0031] Preferably, during the second coprecipitation reaction, the reduction in stirring speed is 5 r / h to 10 r / h, such as 5 r / h, 6 r / h, 7 r / h, 8 r / h, 9 r / h, 10 r / h, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] In this invention, the stirring speed is reduced by 5 to 10 r / h, further reducing the risk of ball breakage caused by continuous high speed.

[0033] Preferably, with the sum of the reaction times of the first coprecipitation reaction and the second coprecipitation reaction being 100%, the proportion of the first target reaction time is ≤40%, such as 5%, 10%, 15%, 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 38%, or 40%, etc., preferably 30% to 35%, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] For the technical solution of the present invention, the time for increasing the stirring speed gradient should not be too long, and a suitable first target reaction time is beneficial to the uniform growth of particles; further preferably, it is 30% to 35%.

[0035] Preferably, the median particle size D50 of the particles obtained by the first coprecipitation reaction is 6μm to 7μm, such as 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm or 7μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] In addition to controlling the first target reaction time, this invention further uses the median particle size during particle growth as the separation condition, which can ensure uniform particle growth throughout the entire reaction process.

[0037] Preferably, the reaction temperatures of the first coprecipitation reaction and the second coprecipitation reaction are each independently between 30°C and 80°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the pH values ​​of the first coprecipitation reaction and the second coprecipitation reaction are each independently 9.5 to 12, such as 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.81 or 2, but are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0039] Preferably, the median particle size D50 of the nickel-cobalt cathode precursor material is 14 μm to 17 μm, such as 14 μm, 14.3 μm, 14.5 μm, 14.8 μm, 15 μm, 15.3 μm, 15.5 μm, 15.8 μm, 16 μm, 16.3 μm, 16.5 μm, 16.8 μm or 17 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] It should also be noted that, apart from the above-mentioned feature limitations, the remaining preparation processes in the preparation method provided by this invention are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0041] Optionally, the solvent in the base liquid is selected from water, and the volume ratio of the base liquid in the reaction vessel is 2 / 3 to 4 / 5.

[0042] Optionally, after the second coprecipitation reaction is completed, no aging treatment is required; the slurry after the reaction is directly washed and dried sequentially.

[0043] In a second aspect, the present invention provides a nickel-cobalt cathode precursor material, which is prepared by the preparation method described in the first aspect.

[0044] The nickel-cobalt cathode precursor material prepared by this invention has high sphericity, stable structure, uniform particle size, and no cracked or twinned particles.

[0045] Thirdly, the present invention provides a cathode material, wherein the nickel-cobalt cathode material is obtained by mixing and sintering the nickel-cobalt cathode precursor material as described in the second aspect with raw materials including a lithium source.

[0046] The nickel-cobalt cathode precursor material provided by this invention can be directly mixed with a lithium source and sintered to obtain a nickel-cobalt binary cathode material; alternatively, an aluminum source can be added at the same time as the lithium source and then sintered to obtain a nickel-cobalt-aluminum ternary cathode material. Moreover, the preparation details such as the lithium source, aluminum source, mixing method, sintering conditions, and specific dosage ratios used are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0047] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material as described in the third aspect.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] In the preparation method of the present invention, in the first coprecipitation reaction stage, the stirring speed is gradually increased, which increases the probability of collision between particles during particle growth, reduces the agglomeration of primary particles, and avoids the problem of twinned particles. As the stirring speed and reaction time increase, the particle growth rate will slow down and the solid content in the reaction system will increase. At this time, in conjunction with the second coprecipitation reaction stage, by reducing the stirring speed of the reaction, the excessive increase of particle tap density is suppressed, and the problem of particle splitting is avoided. Attached Figure Description

[0050] Figure 1SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1.

[0051] Figure 2 SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1.

[0052] Figure 3 SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1.

[0053] Figure 4 SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1.

[0054] Figure 5 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 2.

[0055] Figure 6 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 2.

[0056] Figure 7 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 2.

[0057] Figure 8 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 2.

[0058] Figure 9 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 4.

[0059] Figure 10 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 4.

[0060] Figure 11 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 4.

[0061] Figure 12 SEM image of the nickel-cobalt hydroxide cathode precursor material provided for Comparative Example 4. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having” and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0064] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0065] Example 1

[0066] This embodiment provides a method for preparing a nickel-cobalt hydroxide cathode precursor material, the preparation method being as follows:

[0067] S1: Prepare a nickel-cobalt mixed sulfate solution with a concentration of 2 mol / L and a molar ratio of nickel and cobalt of 1:1; prepare a sodium hydroxide precipitant solution with a concentration of 8 mol / L; and prepare an ammonia complexing agent solution with a concentration of 10 mol / L.

[0068] S2: Add water with a volume ratio of 2 / 3 to the reaction vessel, then add ammonia and sodium hydroxide to prepare a reaction base solution with an ammonia concentration of 10g / L and a pH value of 11.0.

[0069] A nickel-cobalt mixed sulfate solution, a sodium hydroxide precipitant solution, and an ammonia complexing agent solution were added concurrently to the base solution. The first coprecipitation reaction was initiated at an initial speed of 130 r / min. During the reaction, the stirring speed was continuously increased by 10 r / h, the reaction temperature was 40℃, and the pH value was 10.8. The first coprecipitation reaction was completed when the first target reaction time reached 33% of the total reaction time, and the first coprecipitation reaction was completed, yielding a first coprecipitation reaction slurry with a median particle size D50 of 7 μm.

[0070] S3: The first coprecipitation reaction slurry is processed in separate reactors. Then, nickel-cobalt mixed sulfate solution, sodium hydroxide precipitant solution and ammonia complexing agent solution are added in parallel to the newly added reactor under the same conditions as in S1 to carry out the second coprecipitation reaction. During the reaction, the stirring speed is continuously reduced by 7 r / h, the reaction temperature is 40℃, the pH value is 10.8, and the reaction time is 68% of the total reaction time. The second coprecipitation reaction is completed, and the second coprecipitation reaction slurry is obtained.

[0071] S4: The second coprecipitation reaction slurry is fed to a filter press, washed, and then dried to obtain a nickel-cobalt hydroxide cathode precursor material Ni with a median particle size D50 of 16 μm. 0.5 Co 0.5 (OH)2.

[0072] Example 2

[0073] This embodiment provides a method for preparing a nickel-cobalt hydroxide cathode precursor material, the preparation method being as follows:

[0074] S1: Prepare a nickel-cobalt mixed sulfate solution with a concentration of 2.5 mol / L and a molar ratio of nickel to cobalt of 1:1; prepare a sodium hydroxide precipitant solution with a concentration of 10 mol / L; and prepare an ammonia complexing agent solution with a concentration of 12 mol / L.

[0075] S2: Add water with a volume ratio of 2 / 3 to the reaction vessel, then add ammonia and sodium hydroxide to prepare a reaction base solution with an ammonia concentration of 9.5 g / L and a pH value of 11.1;

[0076] A nickel-cobalt mixed sulfate solution, a sodium hydroxide precipitant solution, and an ammonia complexing agent solution were added concurrently to the base solution. The first coprecipitation reaction was initiated at an initial speed of 140 r / min. During the reaction, the stirring speed was continuously increased by 15 r / h, the reaction temperature was 45℃, and the pH value was 11.0. The first coprecipitation reaction was completed when the first target reaction time reached 30% of the total reaction time, resulting in a first coprecipitation reaction slurry with a median particle size D50 of 6 μm.

[0077] S3: The first coprecipitation reaction slurry is processed in separate reactors. Then, nickel-cobalt mixed sulfate solution, sodium hydroxide precipitant solution and ammonia complexing agent solution are added in parallel to the newly added reactors under the same conditions as in S1 to carry out the second coprecipitation reaction. During the reaction, the stirring speed is continuously reduced by 10 r / h, the reaction temperature is 45℃, the pH value is 11, and the reaction time is 70% of the total reaction time. The second coprecipitation reaction is completed, and the second coprecipitation reaction slurry is obtained.

[0078] S4: The second coprecipitation reaction slurry is fed to a filter press, washed, and then dried to obtain a nickel-cobalt hydroxide cathode precursor material Ni with a median particle size D50 of 14 μm. 0.5 Co 0.5 (OH)2.

[0079] Example 3

[0080] This embodiment provides a method for preparing a nickel-cobalt hydroxide cathode precursor material, the preparation method being as follows:

[0081] S1: Prepare a nickel-cobalt mixed sulfate solution with a concentration of 1.5 mol / L and a molar ratio of nickel to cobalt of 1:1; prepare a sodium hydroxide precipitant solution with a concentration of 5 mol / L; and prepare an ammonia complexing agent solution with a concentration of 6 mol / L.

[0082] S2: Add water with a volume ratio of 7 / 10 to the reaction vessel, then add ammonia and sodium hydroxide to prepare a reaction base solution with an ammonia concentration of 9 g / L and a pH value of 11.2.

[0083] A nickel-cobalt mixed sulfate solution, a sodium hydroxide precipitant solution, and an ammonia complexing agent solution were added concurrently to the base solution. The first coprecipitation reaction was initiated at an initial stirring speed of 160 r / min. During the reaction, the stirring speed was continuously increased by 7 r / h, the reaction temperature was 40℃, and the pH value was 10.8. The first coprecipitation reaction was completed when the first target reaction time reached 35% of the total reaction time, resulting in a first coprecipitation reaction slurry with a median particle size D50 of 6.5 μm.

[0084] S3: The first coprecipitation reaction slurry is processed in separate reactors. Then, nickel-cobalt mixed sulfate solution, sodium hydroxide precipitant solution and ammonia complexing agent solution are added in parallel to the newly added reactors under the same conditions as in S1 to carry out the second coprecipitation reaction. During the reaction, the stirring speed is continuously reduced by 5 r / h, the reaction temperature is 40℃, the pH value is 10.8, and the reaction time is 65% of the total reaction time. The second coprecipitation reaction is then completed, and the second coprecipitation reaction slurry is obtained.

[0085] S4: The second coprecipitation reaction slurry is fed to a filter press, washed, and then dried to obtain a nickel-cobalt hydroxide cathode precursor material Ni with a median particle size D50 of 15 μm. 0.5 Co 0.5 (OH)2.

[0086] Example 4

[0087] The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, a nickel-cobalt mixed sulfate solution with a nickel-cobalt molar ratio of 85:15 is prepared; ultimately, the nickel-cobalt hydroxide cathode precursor material Ni is obtained. 0.85 Co 0.15 (OH)2.

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Example 5

[0090] The difference between this embodiment and embodiment 1 is that the concentration of ammonia in the bottom solution of step S2 in this embodiment is 8 g / L.

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] Example 6

[0093] The difference between this embodiment and embodiment 1 is that the pH value of the bottom solution in step S2 of this embodiment is 11.4.

[0094] The remaining preparation methods and parameters are consistent with those in Example 1.

[0095] Example 7

[0096] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the stirring speed is increased by 5 r / h.

[0097] The remaining preparation methods and parameters are consistent with those in Example 1.

[0098] Example 8

[0099] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the stirring speed is increased by 18 r / h.

[0100] The remaining preparation methods and parameters are consistent with those in Example 1.

[0101] Example 9

[0102] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the first target reaction time is 40% of the total reaction time, and the feed flow rate of the raw materials is adaptively adjusted to ensure that the D50 value remains unchanged.

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Example 10

[0105] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the feed flow rate of the raw materials is adjusted so that the obtained first coprecipitation reaction slurry has a median particle size D50 of 9 μm.

[0106] The remaining preparation methods and parameters are consistent with those in Example 1.

[0107] Example 11

[0108] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the feed flow rate of the raw materials is adjusted so that the obtained first coprecipitation reaction slurry has a median particle size D50 of 5 μm.

[0109] The remaining preparation methods and parameters are consistent with those in Example 1.

[0110] Example 12

[0111] The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the stirring speed is reduced by 3 r / h.

[0112] The remaining preparation methods and parameters are consistent with those in Example 1.

[0113] Example 13

[0114] The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the stirring speed is reduced by 15 r / h.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 1 is that this comparative example does not perform the separate reactor treatment in step S3. After the first coprecipitation reaction is completed, the second coprecipitation reaction is carried out directly in the original reactor.

[0118] The remaining preparation methods and parameters are consistent with those in Example 1.

[0119] Comparative Example 2

[0120] The difference between this comparative example and Example 1 is that in the first coprecipitation reaction of step S2 in this comparative example, the stirring speed remains unchanged, and the reaction is carried out directly at the highest stirring speed.

[0121] The remaining preparation methods are consistent with those in Example 1.

[0122] Comparative Example 3

[0123] The difference between this comparative example and Example 1 is that in the second coprecipitation reaction of step S3 in this comparative example, the stirring speed remains unchanged, and the reaction is carried out directly at the lowest stirring speed.

[0124] The remaining preparation methods and parameters are consistent with those in Example 1.

[0125] Comparative Example 4

[0126] The difference between this comparative example and Example 1 is that the variation patterns of the stirring speed in the first coprecipitation reaction in step S2 and the variation patterns of the stirring speed in the second coprecipitation reaction in step S3 are directly interchanged, and the initial speed in step S2 is adjusted to the highest speed during the reaction process.

[0127] The remaining preparation methods and parameters are consistent with those in Example 1.

[0128] The nickel-cobalt cathode precursor materials prepared in Examples 1-13 and Comparative Examples 1-4 were tested for particle size, tap density and specific surface area, and the micromorphology of the particles was characterized to determine whether there were any problems with split spheres and twin spheres.

[0129] Particle size: Particle size was measured using a laser particle size analyzer.

[0130] Specific surface area: nitrogen adsorption method.

[0131] Tap density: Tested using a tap density meter.

[0132] Microscopic morphology of particles: Scanning electron microscopy (SEM).

[0133] Figure 1 The SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1 is shown.

[0134] Figure 2 The SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1 is shown.

[0135] Figure 3 The SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1 is shown.

[0136] Figure 4 The SEM image of the nickel-cobalt hydroxide cathode precursor material provided in Example 1 is shown.

[0137] Figure 5 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 2 are shown.

[0138] Figure 6 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 2 are shown.

[0139] Figure 7 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 2 are shown.

[0140] Figure 8 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 2 are shown.

[0141] Figure 9 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 4 are shown.

[0142] Figure 10 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 4 are shown.

[0143] Figure 11 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 4 are shown.

[0144] Figure 12 SEM images of the nickel-cobalt hydroxide cathode precursor material provided in Comparative Example 4 are shown.

[0145] from Figures 1 to 4 It can be seen that the nickel-cobalt hydroxide binary precursor material obtained by the preparation method provided by the present invention has good particle size uniformity and no twinned or split spheres appear.

[0146] from Figures 5 to 8 It can be seen that the nickel-cobalt hydroxide binary precursor material obtained by the preparation method of Comparative Example 2 exhibits obvious twinning phenomenon, and some individual particles also show spherical splitting phenomenon.

[0147] from Figures 9 to 12 It can be seen that the nickel-cobalt hydroxide binary precursor material obtained using Comparative Example 4 not only exhibits obvious spheroid splitting and very obvious particle cracks, but also obvious twinning.

[0148] The test results are shown in Table 1.

[0149] Table 1

[0150]

[0151]

[0152] Note: The standard for "slight" is that less than one-fifth of the particles in the SEM image have twinned or split spheres at the same magnification; while some standards in the table are that more than one-fifth of the particles have twinned or split spheres.

[0153] In summary, in the preparation method of the present invention, during the first coprecipitation reaction stage, the stirring speed is gradually increased, which increases the probability of collision between particles during particle growth, reduces the agglomeration of primary particles, and avoids the problem of twinned particles. As the stirring speed and reaction time increase, the particle growth rate will slow down, and the solid content in the reaction system will increase. At this time, in conjunction with the second coprecipitation reaction stage, by reducing the stirring speed of the reaction, the excessive increase in particle tap density is suppressed, and the problem of particle splitting is avoided.

[0154] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a nickel-cobalt cathode precursor material, characterized in that, The preparation method includes the following steps: The nickel-cobalt mixed salt solution, precipitant solution, and complexing agent solution were added to the bottom liquid in a co-flow manner to carry out the first co-precipitation reaction. After the reaction reached the first target reaction time, the mixture was processed in separate reactors. After separate processing in separate reactors, a second co-precipitation reaction is carried out to obtain the nickel-cobalt cathode precursor material. In the first coprecipitation reaction, the stirring speed increases in stages; in the second coprecipitation reaction, the stirring speed decreases in stages. The stirring speed gradually increases from 130 r / min to 160 r / min at the initial stage of the reaction; During the first coprecipitation reaction, the stirring speed was increased by 7 r / h to 15 r / h. During the second coprecipitation reaction, the stirring speed was reduced by 5 r / h to 10 r / h.

2. The preparation method according to claim 1, characterized in that, The total concentration of metal ions in the nickel-cobalt mixed salt solution is 1.0 mol / L to 2.5 mol / L.

3. The preparation method according to claim 1, characterized in that, The concentration of the precipitant solution is 5 mol / L to 10 mol / L.

4. The preparation method according to claim 1, characterized in that, The concentration of the complexing agent solution is 6 mol / L to 12 mol / L.

5. The preparation method according to claim 1, characterized in that, The base liquid includes a solvent, a complexing agent, and a precipitant.

6. The preparation method according to claim 5, characterized in that, The concentration of the complexing agent in the substrate is 9 g / L to 10 g / L, and the pH value of the substrate is 11.0 to 11.

2.

7. The preparation method according to claim 1, characterized in that, With the sum of the reaction times of the first coprecipitation reaction and the second coprecipitation reaction being 100%, the proportion of the first target reaction time is ≤40%.

8. The preparation method according to claim 7, characterized in that, Assuming the sum of the reaction times of the first coprecipitation reaction and the second coprecipitation reaction is 100%, the proportion of the first target reaction time is 30% to 35%.

9. The preparation method according to claim 1, characterized in that, The median particle size D50 of the particles obtained by the first coprecipitation reaction is 6 μm to 7 μm.

10. The preparation method according to claim 1, characterized in that, The reaction temperatures of the first coprecipitation reaction and the second coprecipitation reaction are each independently 30℃~80℃.

11. The preparation method according to claim 1, characterized in that, The pH values ​​of the first coprecipitation reaction and the second coprecipitation reaction are each independently 9.5~12.

12. The preparation method according to claim 1, characterized in that, The median particle size D50 of the nickel-cobalt cathode precursor material is 14 μm to 17 μm.

13. A nickel-cobalt cathode precursor material, characterized in that, The nickel-cobalt cathode precursor material is prepared by the preparation method according to any one of claims 1-12.

14. A positive electrode material, characterized in that, The nickel-cobalt cathode material is obtained by mixing and sintering the nickel-cobalt cathode precursor material as described in claim 13 with raw materials including a lithium source.

15. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 14.

Images