A narrow particle size polycrystalline ternary precursor and its preparation method and application

Abstract

The present invention belongs to the technical field of lithium-ion batteries, and specifically relates to a narrow-particle-size polycrystalline ternary precursor, and a preparation method and application thereof. The preparation method of the narrow-particle-size polycrystalline ternary precursor provided by the present invention comprises the following steps: (1) simultaneously introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into a seed kettle and a growth kettle containing a bottom liquid to react; (2) after the average particle size of the seed in the seed kettle grows to a target value, the seed is pumped into the growth kettle to continue growing, so that the average particle size of the material in the growth kettle grows to the target value; (3) the material obtained in the growth kettle is subjected to solid-liquid separation, aging, washing and drying to obtain a precursor. The primary particles of the precursor prepared by the method are orderly stacked in a needle shape, the secondary particles are porous, have good sphericity and are free of cracks, and have a narrow particle size distribution, so that the precursor has a higher specific surface area and a higher tap density, and can ensure the capacity and cycle performance of the battery after being used to prepare positive electrode materials.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a narrow-grained polycrystalline ternary precursor and a preparation method and application thereof. Background Art

[0002] Ternary cathode materials have the advantages of high specific capacity, good rate performance, and good cycle performance. In recent years, they have gradually become the mainstream new cathode materials for lithium-ion batteries used in electric vehicles at home and abroad. At present, increasing the capacity of ternary batteries to improve endurance has become the mainstream trend, and the particle size, tap density, specific surface area, and morphology of the ternary precursors determine the performance of the ternary cathode materials, which in turn affects the capacity of the ternary batteries.

[0003] At present, the common method for industrial production of ternary precursors is co-precipitation, and then sintering with lithium hydroxide or lithium carbonate to form ternary positive electrode materials. In nickel-cobalt-manganese ternary positive electrode materials, the amount of nickel content determines the capacity of the battery, but too high a nickel content will increase the sintering temperature, which will lead to lithium-nickel mixing, change the crystal structure and reduce the battery's cycle performance. Therefore, it is necessary to study high-nickel ternary materials to improve their performance. Summary of the invention

[0004] The present invention is based on the inventors' discovery and understanding of the following facts and problems: the cycle performance of the positive electrode material is closely related to the particle morphology. Generally speaking, particles with a porous structure can better adapt to the volume changes caused by charging and discharging, thereby improving the cycle performance of the battery; particles without cracks can greatly alleviate electronic short circuits and electrolyte penetration, thereby increasing the cycle performance and safety of the battery.

[0005] Currently, high-nickel polycrystalline products are mostly produced by the continuous production process. The basicity and homogenization speed are controlled at a high level, while the temperature is controlled at a low level, resulting in thick primary particles and disordered growth. The secondary particles have poor sphericity, unclear pore structure and cracks. In addition, the seed amount is not easy to control, the particle size distribution is wide and the control stability is poor, the product consistency is poor, and the secondary particles are prone to spherical cracking, resulting in a large tap density of the precursor and a small specific surface area.

[0006] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, an embodiment of the present invention proposes a method for preparing a narrow particle size polycrystalline ternary precursor, wherein the primary particles of the precursor prepared by the method are orderly stacked in a needle shape, the secondary particles are porous, have good sphericity and are free of cracks, and the particle size distribution is narrow, so that the precursor has a higher specific surface area and a higher tap density, and can be fully mixed at a lower temperature when sintered with a lithium source, reducing lithium-nickel mixing, thereby ensuring the capacity and cycle performance of the battery.

[0007] A method for preparing a narrow-grained polycrystalline ternary precursor according to an embodiment of the present invention comprises the following steps:

[0008] (1) introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into a seed kettle and a growth kettle containing a bottom solution at the same time to react;

[0009] (2) after the average particle size of the seed crystals in the seeding kettle grows to a target value, pumping the seed crystals into the growth kettle for further growth, so that the average particle size of the material in the growth kettle grows to a target value;

[0010] (3) subjecting the material obtained in the growth kettle in step (2) to solid-liquid separation, aging, washing and drying to obtain the precursor.

[0011] The advantages and technical effects brought by the preparation method of narrow particle size polycrystalline ternary precursor of the embodiment of the present invention are as follows: 1. The method of the embodiment of the present invention adopts the seed kettle process to quantitatively control the crystal nucleus, avoids the problem of out-of-control of the crystal nucleus amount, and improves the stability of production; 2. The method of the embodiment of the present invention enables the seed kettle and the growth kettle to carry out growth reaction at the same time, and the growth of the precursor is carried out after the particle size of the seed crystal in the seed kettle is stably controlled, which can effectively improve the stability, improve the particle size consistency, and obtain precursor particles with a narrow particle size distribution; 3. The method of the embodiment of the present invention has a simple process, is efficient and easy to operate, and is convenient for promotion and application in industrial production.

[0012] In some embodiments, in step (1), the reaction temperature in the seed kettle and / or the growth kettle is 80-85° C., and the stirring speed is 500-600 rpm; and / or, there are at least two growth kettles.

[0013] In some embodiments, in step (1), the pH value in the seed kettle is controlled at 11.2-11.8, and the flow rate of the mixed salt solution is 3-6 L / h; and / or, the pH value in the growth kettle is controlled at 10.5-11.1, and the flow rate of the mixed salt solution is 5-8 L / h.

[0014] In some embodiments, in step (1), the base liquid comprises aqueous ammonia with a concentration of 1 to 5 g / L; and / or, the reaction is carried out under the protection of an inert gas with a flow rate of the inert gas of 10 to 30 L / h.

[0015] In some embodiments, in step (1), the nickel-cobalt-manganese mixed salt solution is prepared from NiSO4, CoSO4, and MnSO4 solutions in a ratio of X:Y:Z, wherein X+Y+Z=1, 0.8<X<1, 0<Y<0.2, 0<Z<0.2; and / or, the total concentration of the nickel-cobalt-manganese mixed salt solution is 1.8-2.4 mol / L.

[0016] In some embodiments, in step (1), the precipitant comprises a sodium hydroxide solution with a concentration of 5 to 8 mol / L; and / or the complexing agent comprises an ammonia solution with a concentration of 4 to 10 mol / L.

[0017] In some embodiments, in step (2), the target value of the average particle size of the seed crystals is 4.5 to 5.5 μm; and / or the flow rate of the seed crystals pumped into the growth reactor is 0.4 to 0.6 L / h.

[0018] In some embodiments, in step (2), the target value of the average particle size of the material is 8 to 12 μm.

[0019] The embodiment of the present invention also provides a narrow-grained polycrystalline ternary precursor, which is prepared by the above method.

[0020] The narrow particle size polycrystalline ternary precursor of the embodiment of the present invention brings advantages and technical effects. The primary particles of the precursor are orderly stacked in a needle shape, the secondary particles have a porous structure, good sphericity and no cracks, and the particle size distribution is narrow, so that the precursor has a higher specific surface area and a higher tap density. When sintered with a lithium source, it can be fully mixed at a lower temperature, reducing lithium and nickel mixing, thereby ensuring the capacity and cycle performance of the battery.

[0021] An embodiment of the present invention further provides a positive electrode material, including the narrow-grained polycrystalline ternary precursor prepared by the above method or the above narrow-grained polycrystalline ternary precursor.

[0022] The advantages and technical effects brought about by the positive electrode material in the embodiment of the present invention, the positive electrode material in the embodiment of the present invention has all the technical features of the narrow-grained polycrystalline ternary precursor in the embodiment of the present invention, and therefore has all the advantages and technical effects brought about by the narrow-grained polycrystalline ternary precursor in the embodiment of the present invention, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a SEM image of the precursor prepared in Example 1;

[0024] Figure 2 is a SEM image of the precursor prepared in Example 2;

[0025] Figure 3 This is the SEM image of the precursor prepared in Example 3. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0027] A method for preparing a narrow-grained polycrystalline ternary precursor according to an embodiment of the present invention comprises the following steps:

[0028] (1) introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into a seed kettle and a growth kettle containing a bottom solution at the same time to react;

[0029] (2) after the average particle size of the seed crystals in the seeding kettle grows to a target value, pumping the seed crystals into the growth kettle for further growth, so that the average particle size of the material in the growth kettle grows to a target value;

[0030] (3) subjecting the material obtained from the growth kettle in step (2) to solid-liquid separation, aging, washing, and drying to obtain the precursor.

[0031] The preparation method of the narrow particle size polycrystalline ternary precursor of the embodiment of the present invention adopts a seed-in-series kettle process to quantitatively control the crystal nucleus, avoids the problem of out-of-control of the crystal nucleus amount, and improves the stability of production; the seed kettle and the growth kettle are allowed to carry out growth reaction at the same time, and the growth of the precursor is carried out after the particle size of the seed crystal in the seed kettle is stably controlled, which can effectively improve the stability, improve the particle size consistency, and obtain precursor particles with a narrow particle size distribution; the process is simple, efficient and easy to operate, and is convenient for promotion and application in industrial production.

[0032] In some embodiments, preferably, in the step (1), the reaction temperature in the seed kettle and / or the growth kettle is 80-85° C., and the stirring speed is 500-600 rpm; and / or, there are at least two growth kettles.

[0033] In the embodiment of the present invention, the reaction temperature is 80-85°C. A higher reaction temperature can obtain seed crystals with better crystallinity, which is beneficial to the stable formation of the porous structure of the secondary particles. If the temperature is low, the crystallinity of the particles is poor, the obtained product is prone to ball cracking and fine powder is easily generated during the sintering process; the lower stirring speed greatly reduces the adverse effect of shear force on the appearance of the particles and reduces ball cracking; a single seed kettle can meet the growth needs of multiple growth kettles, effectively improving production efficiency and particle stability.

[0034] In some embodiments, preferably, in the step (1), the pH value in the seed kettle is controlled at 11.2-11.8, and the flow rate of the mixed salt solution is 3-6 L / h; and / or, the pH value in the growth kettle is controlled at 10.5-11.1, and the flow rate of the mixed salt solution is 5-8 L / h.

[0035] In the embodiment of the present invention, controlling the pH of the seed kettle within a higher range is beneficial to the formation of seed crystals, while controlling the pH of the growth kettle within a lower range is beneficial to the stable growth of precursor particles; the growth kettle can control the growth of precursor particles with a fixed pH value, eliminating the influence of the pH value on system changes, and under the premise of stable crystal nuclei and pH values, the material in the growth kettle can achieve high temperature and low speed stable growth, so that the primary particles can grow in an orderly manner, the arrangement of secondary particles can be optimized, and the particles can be promoted to be porous wool-like balls; this method can improve the control stability of the growth kettle, and achieve particle morphology control by adjusting the pH value of the growth kettle without changing the precursor particle size.

[0036] In some embodiments, preferably, in step (1), the base liquid comprises aqueous ammonia with a concentration of 1 to 5 g / L; and / or the reaction is carried out under the protection of an inert gas, and the flow rate of the inert gas is 10 to 30 L / h.

[0037] In the embodiment of the present invention, an aqueous ammonia solution is introduced into the growth kettle and the reaction kettle to control the concentration of the aqueous ammonia solution within the range of 1 to 5 g / L, so that both the seed crystals and the precursor particles grow smoothly under low alkalinity conditions; the reaction is carried out under the protection of an inert gas to prevent the seed crystals and the precursor from being oxidized by oxygen, thereby further improving the performance of the precursor.

[0038] In some embodiments, preferably, in the step (1), the nickel-cobalt-manganese mixed salt solution is prepared from NiSO4, CoSO4, and MnSO4 solutions in a ratio of X:Y:Z, wherein X+Y+Z=1, 0.8<X<1, 0<Y<0.2, 0<Z<0.2; and / or, the total concentration of the nickel-cobalt-manganese mixed salt solution is 1.8-2.4 mol / L. Further preferably, in the step (1), the precipitant comprises a sodium hydroxide solution with a concentration of 5-8 mol / L; and / or, the complexing agent comprises an ammonia solution with a concentration of 4-10 mol / L.

[0039] In some embodiments, preferably, in step (2), the target value of the average particle size of the seed crystal is 4.5-5.5 μm; and / or, the flow rate of the seed crystal pumped into the growth reactor is 0.4-0.6 L / h. Further preferably, in step (2), the target value of the average particle size of the material is 8-12 μm.

[0040] In the embodiment of the present invention, the average particle size of the seed crystal is controlled to be 4.5-5.5 μm, which can control the growth rate of the particles in the growth kettle within a reasonable range; by adjusting the amount of seed crystals introduced into the growth kettle, the particle size of the material in the growth kettle is controlled, which is beneficial to improving the particle size distribution and morphology of the precursor and obtaining precursor particles with a narrow particle size distribution.

[0041] In some embodiments, preferably, in the step (3), the washing includes alkaline washing treatment and water washing treatment.

[0042] The embodiment of the present invention also provides a narrow-grained polycrystalline ternary precursor, which is prepared by the above method.

[0043] The primary particles of the narrow particle size polycrystalline ternary precursor of the embodiment of the present invention are orderly stacked in a needle shape, and the secondary particles have a porous structure, good sphericity and no cracks, and a narrow particle size distribution, so that the precursor has a higher specific surface area and a higher tap density. When sintered with a lithium source, it can be fully mixed at a lower temperature, reducing lithium and nickel mixing, thereby ensuring the capacity and cycle performance of the battery.

[0044] In some embodiments, preferably, the specific surface area of ​​the narrow particle size polycrystalline ternary precursor is 7 to 11 m 2 / g, tap density is 1.8~2.2g / cm 3 , bulk density is 1.4~1.8g / cm 3 , the particle size distribution diameter distance is 0.95±0.1.

[0045] An embodiment of the present invention further provides a positive electrode material, including the narrow-grained polycrystalline ternary precursor prepared by the above method or the above narrow-grained polycrystalline ternary precursor.

[0046] The positive electrode material in the embodiment of the present invention has all the technical features of the narrow-grained polycrystalline ternary precursor in the embodiment of the present invention, and therefore has all the advantages and technical effects brought by the narrow-grained polycrystalline ternary precursor in the embodiment of the present invention, which will not be repeated here.

[0047] The present invention is described in detail below in conjunction with specific embodiments and drawings.

[0048] Example 1

[0049] (1) Pure water was poured into the seed kettle and the growth kettle to the sampling port, stirred and the water temperature in the jacket of the seed kettle and the growth kettle was raised to 80°C, and ammonia water was injected into the seed kettle and the growth kettle to form the bottom liquid before grooving, and the ammonia concentration was controlled at 2.5 g / L. Nitrogen gas was introduced at a flow rate of 20 L / h to ensure that the seed kettle and the growth kettle were in a nitrogen atmosphere;

[0050] (2) using NiSO4, CoSO4, and MnSO4 solutions in a ratio of 89:8:3 to prepare a nickel-cobalt-manganese mixed salt solution with a total concentration of 2.0 mol / L, and preparing 8 mol / L NaOH solution and 4 mol / L ammonia solution;

[0051] (3) introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into the seed kettle and the growth kettle at the same time, wherein the pH value in the seed kettle is controlled at 11.4, the flow rate of the mixed salt solution is 4 L / h, and the stirring speed is 600 rpm; the pH value in the growth kettle is controlled at 10.5, the flow rate of the mixed salt solution is 6 L / h, and the stirring speed is 600 rpm;

[0052] (4) After the seed kettle reacts until the particle size D50 of the seed is stabilized at 4.5 μm, the seed is pumped into the growth kettle at a flow rate of 0.6 L / h through a peristaltic pump. After the particle size of the material in the growth kettle is stabilized at 8 μm, the output product of the growth kettle is subjected to solid-liquid separation, aging, alkali washing, water washing, and drying to obtain a ternary precursor.

[0053] The specific surface area of ​​the ternary precursor prepared in this embodiment is 7.68 m 2 / g, tap density is 2.12g / cm 3 , bulk density is 1.63g / cm 3 The 001 peak of XRD is 0.56, the particle size distribution distance is 0.9, the sodium content is 206ppm, and the sulfur content is 1160ppm.

[0054] The SEM characterization of the ternary precursor prepared in this example is as follows Figure 1 As shown in the figure, it can be seen that the primary particles of the ternary precursor are arranged in an orderly manner, and the secondary particles are in the shape of porous wool balls without cracks.

[0055] Example 2

[0056] (1) Pure water was injected into the seed kettle and the growth kettle to the sampling port, stirred and the water temperature in the jacket of the synthesis kettle was raised to 80°C, and ammonia water was injected into the reaction kettle to form a pre-grooving bottom liquid, the ammonia concentration was controlled at 2.5 g / L, and nitrogen gas was introduced at a flow rate of 20 L / h to ensure that the synthesis kettle was in a nitrogen atmosphere;

[0057] (2) using NiSO4, CoSO4, and MnSO4 solutions in a ratio of 89:8:3 to prepare a nickel-cobalt-manganese mixed salt solution with a total concentration of 2.0 mol / L, and preparing 8 mol / L NaOH solution and 4 mol / L ammonia solution;

[0058] (3) introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into the seed kettle and the growth kettle at the same time, wherein the pH value in the seed kettle is controlled at 11.5, the flow rate of the mixed salt solution is 4 L / h, and the stirring speed is 600 rpm; the pH value in the growth kettle is 10.6, the flow rate of the mixed salt solution is 6 L / h, and the stirring speed is 600 rpm;

[0059] (4) After the seed kettle reacts until the particle size D50 of the seed is stabilized at 5 μm, the seed is pumped into the growth kettle at a flow rate of 0.5 L / h through a peristaltic pump. After the particle size of the material in the growth kettle is stabilized at 10 μm, the output product of the growth kettle is subjected to solid-liquid separation, aging, alkali washing, water washing, and drying to obtain a ternary precursor.

[0060] The specific surface area of ​​the ternary precursor prepared in this embodiment is 8.91 m 2 / g, tap density is 2.08g / cm 3 , bulk density is 1.63g / cm 3 The 001 peak of XRD is 0.51, the particle size distribution distance is 0.93, the sodium content is 193ppm, and the sulfur content is 1032ppm.

[0061] The SEM characterization of the ternary precursor prepared in this example is as follows Figure 2 As shown in the figure, it can be seen that the primary particles of the ternary precursor are arranged in an orderly manner, and the secondary particles are in the shape of porous wool balls without cracks.

[0062] Example 3

[0063] (1) Pure water was injected into the seed kettle and the growth kettle to the sampling port, stirred and the water temperature in the jacket of the synthesis kettle was raised to 80°C, and ammonia water was injected into the reaction kettle to form a pre-grooving bottom liquid, the ammonia concentration was controlled at 2.5 g / L, and nitrogen gas was introduced at a flow rate of 20 L / h to ensure that the synthesis kettle was in a nitrogen atmosphere;

[0064] (2) using NiSO4, CoSO4, and MnSO4 solutions in a ratio of 89:8:3 to prepare a nickel-cobalt-manganese mixed salt solution with a total concentration of 2.0 mol / L, and preparing 8 mol / L NaOH solution and 4 mol / L ammonia solution;

[0065] (3) introducing a nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent into the seed kettle and the growth kettle at the same time, wherein the pH value in the seed kettle is controlled at 11.6, the flow rate of the mixed salt solution is 4 L / h, and the stirring speed is 600 rpm; the pH value in the growth kettle is 10.7, the flow rate of the mixed salt solution is 6 L / h, and the stirring speed is 600 rpm;

[0066] (4) After the seed kettle reacts until the particle size D50 of the seed is stabilized at 5.5 μm, the seed is pumped into the growth kettle at a flow rate of 0.4 L / h through a peristaltic pump. After the particle size of the material in the growth kettle is stabilized at 12 μm, the output product of the growth kettle is subjected to solid-liquid separation, aging, alkali washing, water washing, and drying to obtain a ternary precursor with orderly arranged primary particles and porous wool ball-like secondary particles without cracks.

[0067] The specific surface area of ​​the ternary precursor prepared in this embodiment is 9.62 m2 / g, tap density is 2.03g / cm 3 , bulk density is 1.60g / cm 3 The 001 peak of XRD is 0.49, the particle size distribution distance is 0.99, the sodium content is 189ppm, and the sulfur content is 1066ppm.

[0068] The SEM characterization of the ternary precursor prepared in this example is as follows Figure 3 As shown in the figure, it can be seen that the primary particles of the ternary precursor are arranged in an orderly manner, and the secondary particles are in the shape of porous wool balls without cracks.

[0069] Example 4

[0070] The preparation method of this embodiment is the same as that of embodiment 1, except that in step (1), the water temperature in the jackets of the seed kettle and the growth kettle is raised to 85° C. to carry out the reaction.

[0071] The specific surface area of ​​the ternary precursor prepared in this embodiment is 7.98 m 2 / g, tap density is 2.09g / cm 3 , bulk density is 1.61g / cm 3 The 001 peak of XRD is 0.58, the particle size distribution distance is 0.92, the sodium content is 223ppm, and the sulfur content is 1236ppm.

[0072] Example 5

[0073] The preparation method of this embodiment is the same as that of embodiment 1, except that in step (1), the water temperature in the jackets of the seed kettle and the growth kettle is raised to 70° C. to carry out the reaction.

[0074] The specific surface area of ​​the ternary precursor prepared in this embodiment is 6.32 m 2 / g, tap density is 2.03g / cm 3 , bulk density is 1.60g / cm 3 The 001 peak of XRD is 0.43, the particle size distribution distance is 1.09, the sodium content is 256ppm, and the sulfur content is 1280ppm.

[0075] Example 6

[0076] The preparation method of this embodiment is the same as that of embodiment 1, except that in step (3), the stirring speed is 800 rpm.

[0077] The specific surface area of ​​the ternary precursor prepared in this embodiment is 5.93 m 2 / g, tap density is 2.21g / cm 3 , bulk density is 1.78g / cm 3The 001 peak of XRD is 0.72, the particle size distribution distance is 1.12, the sodium content is 332ppm, and the sulfur content is 1255ppm.

[0078] Example 7

[0079] The preparation method of this embodiment is the same as that of embodiment 1, except that in step (3), the pH value in the seed kettle is controlled at 10.5, and the pH value in the growth kettle is controlled at 11.5.

[0080] The specific surface area of ​​the ternary precursor prepared in this embodiment is 12.65 m 2 / g, tap density is 1.79g / cm 3 , bulk density is 1.33g / cm 3 The 001 peak of XRD is 0.31, the particle size distribution distance is 1.93, the sodium content is 396ppm, and the sulfur content is 1908ppm.

[0081] The ternary precursor prepared in Examples 1 to 7 was mixed with lithium hydroxide at a ratio of 1:1.05, ball milled for 4 hours to make the mixture uniform, heat treated in a tube furnace, heated at a heating rate of 1°C / min, first heated to 600°C for 6 hours, then heated to 1000°C for 8 hours, and crushed, screened, and surface treated after natural cooling to obtain a ternary positive electrode material; the positive electrode material was then assembled with raw materials such as the treated metal lithium sheet negative electrode and lithium hexafluorophosphate electrolyte into a lithium ion battery. The performance of the lithium ion battery was measured and shown in Table 1 below.

[0082] Table 1

[0083] Capacity (mAh / g) Cycle performance (weeks) Example 1 212 2050 Example 2 239 2100 Example 3 209 1935 Example 4 196 1800 Example 5 186 1560 Example 6 171 1370 Example 7 136 1030

[0084] Note: (1) The capacity is the capacity when charged to 4.2V at a constant current of 0.33C;

[0085] (2) Cyclic performance refers to the cycle period when the final capacity retention rate is 80% when charged and discharged at a constant current of 1C.

[0086] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0087] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing a narrow particle size polycrystalline ternary precursor, characterized in that: The following steps are involved: (1) A nickel-cobalt-manganese mixed salt solution, a precipitant and a complexing agent are simultaneously introduced into a seed kettle and a growth kettle containing a bottom liquid to carry out a reaction; the reaction temperature in the seed kettle and / or the growth kettle is 80-85° C., and the stirring speed is 500-600 rpm; when the pH value in the seed kettle is controlled at 11.4, the pH value in the growth kettle is controlled at 10.5, when the pH value in the seed kettle is controlled at 11.5, the pH value in the growth kettle is controlled at 10.6, and when the pH value in the seed kettle is controlled at 11.6, the pH value in the growth kettle is controlled at 10.7; the flow rate of the mixed salt solution in the seed kettle is 3-4 L / h; the flow rate of the mixed salt solution in the growth kettle is 6-8 L / h; the bottom liquid comprises ammonia water with a concentration of 1-5 g / L; (2) after the average particle size of the seed crystals in the seeding kettle grows to a target value, pumping the seed crystals into the growth kettle for further growth, so that the average particle size of the material in the growth kettle grows to a target value; (3) subjecting the material obtained from the growth kettle in step (2) to solid-liquid separation, aging, washing, and drying to obtain the precursor.

2. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 1, characterized in that: In the step (1), there are at least two growth reactors.

3. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 1, characterized in that: In the step (1), the reaction is carried out under the protection of an inert gas, and the flow rate of the inert gas is 10 to 30 L / h.

4. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 1 or 3, characterized in that: In the step (1), the nickel-cobalt-manganese mixed salt solution is prepared from NiSO4, CoSO4, and MnSO4 solutions in a ratio of X:Y:Z, wherein X+Y+Z=1, 0.8<X<1, 0<Y<0.2, 0<Z<0.2; and / or the total concentration of the nickel-cobalt-manganese mixed salt solution is 1.8-2.4 mol / L.

5. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 4, characterized in that: In the step (1), the precipitant comprises a sodium hydroxide solution with a concentration of 5 to 8 mol / L; and / or the complexing agent comprises an ammonia solution with a concentration of 4 to 10 mol / L.

6. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 1, characterized in that: In the step (2), the target value of the average particle size of the seed crystals is 4.5 to 5.5 μm; and / or the flow rate of the seed crystals pumped into the growth reactor is 0.4 to 0.6 L / h.

7. The method for preparing a narrow-grained polycrystalline ternary precursor according to claim 1 or 6, characterized in that: In the step (2), the target value of the average particle size of the material is 8 to 12 μm.

8. A narrow particle size polycrystalline ternary precursor, characterized in that: The method according to any one of claims 1 to 7 is used to prepare the product.

9. A positive electrode material, characterized in that: It comprises a narrow-grained polycrystalline ternary precursor prepared by the method described in any one of claims 1 to 7 or a narrow-grained polycrystalline ternary precursor described in claim 8.

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