Narrow particle size distribution nickel-rich precursor, preparation method thereof and positive electrode material

Abstract

The invention relates to a narrow particle size distribution nickel-rich precursor, a preparation method thereof and a positive electrode material, the preparation method is a co-precipitation method, accurate regulation and control of precursor crystal nucleation and growth are realized by adjusting process conditions of different reaction stages and metal solution feeding flow and complexing agent types in different reaction stages, and the nickel-rich precursor with the narrow particle size distribution is obtained. The nickel-rich precursor with uniform morphology and good sphericity degree and narrow particle size distribution is finally obtained, so that the electrochemical performance of the positive electrode material is remarkably improved; moreover, the preparation method provided by the invention does not need to adopt specific reaction kettle equipment, does not need a complicated kettle separation process, is simple and controllable in preparation process, and is easy for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-ion batteries and relates to a positive electrode precursor, in particular to a nickel-rich precursor with a narrow particle size distribution, a preparation method thereof and a positive electrode material. Background Art

[0002] Lithium-ion batteries have high operating voltage, high energy density and long cycle life, and have shown broad application prospects in the fields of new energy electric vehicles, digital products and mobile phones. However, with the rapid development of industries such as electric vehicles, the requirements for the safety, charge and discharge specific capacity and cycle life of lithium-ion batteries are getting higher and higher. Among them, the energy density of electrode materials has become a key consideration. Nickel-rich ternary positive electrode materials with narrow particle size distribution can provide more consistent electrochemical performance. The stress on each particle during the charge and discharge process is relatively uniform, and it is not easy to produce microcracks and structural degradation, thus having better cycle stability and thermal stability.

[0003] Ternary precursors are key raw materials for preparing ternary cathode materials. Due to the inheritance of cathode materials to their precursors, the particle size distribution, micromorphology and crystal structure of the precursors directly determine the particle size distribution, micromorphology and crystal structure of the battery cathode materials. Therefore, if you want to obtain a nickel-rich cathode material with a narrow particle size distribution, you should also start with the controlled synthesis of the precursor with a narrow particle size distribution.

[0004] The overflow method is a commonly used method for preparing ternary precursors with a narrow particle size distribution. It can control the morphology of the precursor more accurately, which is crucial to improving battery performance. However, during the overflow method, as the excess material continues to overflow, the total number of particles in the reactor decreases over time, and the total surface area of ​​the particles decreases as the particles continue to grow, resulting in a reduction in the active sites available for the growth of newly generated hydroxides; in addition, due to the presence of a large number of precursor grains in the reactor, secondary nucleation is likely to occur on the surface of the grains to generate small particles. If the high metal solution feed rate in the early stage of the reaction is maintained, the amount of solute provided will eventually exceed the amount of solute required for the actual stable growth of the particles in the reactor, thereby destroying its stable growth process and causing large-scale secondary nucleation in the reactor.

[0005] Therefore, it is necessary to provide a new preparation method that can synthesize nickel-rich precursors with narrow particle size distribution, controllable morphology, and high sphericity, so as to improve the comprehensive performance of lithium-ion batteries. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a nickel-rich precursor with a narrow particle size distribution, a preparation method thereof and a positive electrode material, wherein the preparation method achieves precise control of the nucleation and growth of the precursor crystal by adjusting the metal solution feed flow rate and the type of complexing agent in different reaction stages, and finally obtains a nickel-rich precursor with a narrow particle size distribution with uniform morphology and good sphericity, thereby significantly improving the electrochemical performance of the positive electrode material; moreover, the preparation method provided by the present invention does not require the use of specific reactor equipment, nor does it require a complicated reactor separation process, the preparation process is simple and controllable, and is easy to industrialize.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, the preparation method comprising the following steps:

[0009] (1) under a protective atmosphere, adding a mixed metal salt solution, a precipitant solution and a first complexing agent solution to a base liquid in parallel to carry out a nucleation stage reaction to obtain a precursor crystal nucleus slurry having a first median particle size;

[0010] (2) adjusting the feed flow rates of the precipitant solution and the first complexing agent solution to perform a first growth stage reaction to obtain a precursor slurry having a second median particle size;

[0011] (3) replacing the first complexing agent solution with a second complexing agent solution, adjusting the flow rate of the mixed metal salt solution, the precipitant solution, and the second complexing agent solution and the stirring speed step by step according to the particle size, performing a second growth stage reaction, stopping the feeding after the particle size reaches the shutdown particle size, and post-treating the obtained slurry to obtain the narrow particle size distribution nickel-rich precursor;

[0012] The first complexing agent in the first complexing agent solution includes aqueous ammonia;

[0013] The second complexing agent in the second complexing agent solution includes ammonia water and an additive; the additive includes any one of citric acid, oxalic acid, polyvinyl pyrrolidone, triethanolamine or ethylenediaminetetraacetic acid, or a combination of at least two thereof.

[0014] The additive in the second complexing agent solution of the present invention is a substance that can complex with the metal ions in the mixed salt solution, including any one of citric acid, oxalic acid, polyvinylpyrrolidone (PVP), triethanolamine or ethylenediaminetetraacetic acid (EDTA) or a combination of at least two thereof. Typical but non-limiting combinations include a combination of citric acid and oxalic acid, a combination of oxalic acid and PVP, a combination of PVP and triethanolamine, a combination of triethanolamine and EDTA, or a combination of citric acid, oxalic acid, PVP, triethanolamine and EDTA.

[0015] The preparation method provided by the present invention is a co-precipitation method. By adjusting the metal solution feed amount and the type of complexing agent in different reaction stages, precise regulation of the nucleation and growth of the precursor crystal is achieved, and finally a nickel-rich precursor with uniform morphology, good sphericity and narrow particle size distribution is obtained, thereby significantly improving the electrochemical performance of the positive electrode material; moreover, the preparation method provided by the present invention does not require the use of specific reactor equipment, nor does it require a complicated reactor separation process. The preparation process is simple and controllable, and is easy to industrialize.

[0016] Preferably, the concentration of aqueous ammonia in the first complexing agent solution is 10wt%-20wt%, for example, it can be 10wt%, 12wt%, 15wt%, 16wt%, 18wt% or 20wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the concentration of aqueous ammonia in the second complexing agent solution is 10wt%-20wt%, and the concentration of the additive is 0.1wt%-3wt%.

[0018] In the preparation method provided by the present invention, the concentration of aqueous ammonia in the second complexing agent solution used is 10wt%-20wt%, for example, it can be 10wt%, 12wt%, 15wt%, 16wt%, 18wt% or 20wt%, but is not limited to the listed values, and the remaining values ​​not listed within the numerical range are also applicable.

[0019] In the preparation method provided by the present invention, the additive concentration in the second complexing agent solution used is 0.1wt%-3wt%, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values, and the remaining values ​​not listed within the numerical range are also applicable.

[0020] Preferably, during the reaction of the second growth stage in step (3), the parameter adjustments made for each increase of 0.4 μm-1 μm in particle size are as follows: the flow rate of the mixed metal salt solution is adjusted to be reduced by 5%-15%, the flow rate of the precipitant solution is adjusted to reduce the pH value by 0.05-0.2, the stirring speed is adjusted to be reduced by 20 rpm-100 rpm, and the flow rate of the second complexing agent solution is adjusted to maintain a stable ammonia concentration in the system.

[0021] When the reaction of the second growth stage is carried out, the flow rate of the mixed metal salt solution is reduced by 5%-15% for each increase of 0.4μm-1.0μm in particle size, for example, it can be 5%, 8%, 10%, 12% or 15%, but it is not limited to the listed values, and the other values ​​not listed in the numerical range are also applicable. The flow rate of the mixed metal salt solution is reduced by 5%-15%, and the flow rate of the mixed metal salt solution at each reduction is used as a reference.

[0022] During the second growth stage reaction, the flow rate of the precipitant solution is adjusted to reduce the pH value by 0.05-0.2 for every 0.4 μm-1.0 μm increase in particle size. For example, it can be 0.05, 0.08, 0.1, 0.12, 0.15, 0.18 or 0.2, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0023] During the second growth stage reaction, the stirring speed is gradually reduced to prevent the broken small particles generated by the vigorous stirring from becoming the nucleation sites for heterogeneous nucleation. Specifically, the rotation speed is reduced by 20rpm-100rpm for every 0.4μm-1μm increase in particle size, for example, it can be 20rpm, 40rpm, 50rpm, 60rpm, 80rpm or 100rpm, but it is not limited to the listed values, and the other values ​​not listed in the numerical range are also applicable.

[0024] Preferably, the shutdown particle size in step (3) refers to a median particle size of 6 μm-18 μm, for example, it can be 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm or 18 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the metal salts in the mixed metal salt solution in step (1) include nickel salts, manganese salts and cobalt salts.

[0026] Preferably, the nickel salt comprises any one of nickel sulfate, nickel nitrate or nickel halide or a combination of at least two thereof, typical but non-limiting combinations include a combination of nickel sulfate and nickel nitrate, a combination of nickel sulfate and nickel halide, a combination of nickel sulfate and nickel halide, or a combination of nickel sulfate, nickel nitrate and nickel halide, preferably nickel sulfate.

[0027] Preferably, the nickel halide includes any one of nickel chloride, nickel bromide or nickel iodide, or a combination of at least two of them.

[0028] Preferably, the manganese salt comprises any one or a combination of at least two of manganese sulfate, manganese nitrate or manganese halide, typical but non-limiting combinations include a combination of manganese sulfate and manganese nitrate, a combination of manganese sulfate and manganese halide, a combination of manganese sulfate and manganese halide, or a combination of manganese sulfate, manganese nitrate and manganese halide, preferably manganese sulfate.

[0029] Preferably, the manganese halide includes any one of manganese chloride, manganese bromide or manganese iodide, or a combination of at least two thereof.

[0030] Preferably, the cobalt salt comprises any one of cobalt sulfate, cobalt nitrate or cobalt halide or a combination of at least two thereof, typical but non-limiting combinations include a combination of cobalt sulfate and cobalt nitrate, a combination of cobalt sulfate and cobalt halide, a combination of cobalt sulfate and cobalt halide, or a combination of cobalt sulfate, cobalt nitrate and cobalt halide, preferably cobalt sulfate.

[0031] Preferably, the cobalt halide includes any one of cobalt chloride, cobalt bromide or cobalt iodide, or a combination of at least two of them.

[0032] Preferably, the total concentration of metal ions in the mixed metal salt solution in step (1) is 1 mol / L-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values, and the remaining values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the precipitant in the precipitant solution of step (1) comprises any one of sodium hydroxide, potassium hydroxide, lithium hydroxide or sodium carbonate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of nickel hydroxide and potassium hydroxide, a sum of potassium hydroxide and lithium hydroxide, a combination of lithium hydroxide and sodium carbonate, or a combination of sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium carbonate.

[0034] Preferably, the concentration of the precipitant in the precipitant solution in step (1) is 10wt%-40wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%, but is not limited to the listed values, and the remaining values ​​within the numerical range not listed are also applicable.

[0035] Preferably, the base liquid in step (1) is a mixed solution of a precipitant solution, ammonia water and water; the pH value of the base liquid is 12-12.8, and the ammonia concentration is 0.5 g / L-4 g / L.

[0036] The pH value of the base solution of the present invention is 12-12.8, for example, it can be 12, 12.2, 12.5, 12.6 or 12.8, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] The ammonia concentration of the base solution of the present invention is 0.5g / L-4g / L, for example, it can be 0.5g / L, 1g / L, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L or 4g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the protective atmosphere in step (1) comprises nitrogen and / or an inert gas.

[0039] Optionally, the inert gas includes any one of helium, neon or argon, or a combination of at least two of them. Typical but non-limiting combinations include a combination of helium and neon, a combination of neon and argon, a combination of helium and argon, or a combination of helium, neon and argon.

[0040] In the preparation method provided by the present invention, the supersaturation of the solution system is increased by controlling a higher pH and a lower ammonia concentration in the nucleation stage, so that the nucleation rate of the crystal is much greater than the growth rate, thereby forming a large number of fine crystal nuclei with a narrow particle size distribution.

[0041] Preferably, the pH value of the nucleation stage reaction in step (1) is 12-13, and the ammonia concentration is 0.5 g / L-4 g / L.

[0042] The pH value of the nucleation stage reaction in step (1) is 12-13, for example, it can be 12, 12.2, 12.5, 12.8 or 13, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0043] The ammonia concentration in the nucleation stage reaction of step (1) is 0.5 g / L-4 g / L, for example, it can be 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L or 4 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, in step (1), the first median particle size is 0.6 μm-1.5 μm, for example, 0.6 μm, 0.9 μm, 1 μm, 1.2 μm or 1.5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The pH value of the first growth stage of the present invention is lower than that of the nucleation stage, and the ammonia concentration is higher than that of the nucleation stage. In the first growth stage, by lowering the pH value and increasing the ammonia concentration, the supersaturation of the solution system is reduced, so that the growth rate of the crystal is much greater than the nucleation rate, and the crystal is promoted to grow gradually at a certain rate.

[0046] Preferably, the pH value of the first growth stage reaction in step (2) is 10.3-11.3, and the ammonia concentration is 2 g / L-10 g / L.

[0047] The pH value of the first growth stage reaction of the present invention is 10.3-11.3, for example, it can be 10.3, 10.5, 10.8, 11 or 11.3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] The ammonia concentration of the first growth stage reaction of the present invention is 2g / L-10g / L, for example, it can be 2g / L, 4g / L, 5g / L, 6g / L, 8g / L or 10g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the second median particle size is 1 / 3-2 / 3 of the shutdown particle size.

[0050] Preferably, the temperatures of the nucleation stage reaction, the first growth stage reaction and the second growth stage reaction are independently 40°C-80°C, for example, 40°C, 50°C, 60°C, 70°C or 80°C, but are not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0051] Preferably, the nucleation stage reaction, the first growth stage reaction and the second growth stage reaction are independently carried out under stirring conditions; the stirring speed of the stirring conditions is 100rpm-700rpm, for example, it can be 100rpm, 300rpm, 500rpm, 600rpm or 700rpm, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0052] Preferably, the post-treatment in step (3) comprises washing and drying performed sequentially.

[0053] Preferably, the drying temperature is 80°C-150°C, for example, 80°C, 90°C, 100°C, 120°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the drying end point is when the moisture content reaches below 0.8 wt %.

[0055] In a second aspect, the present invention provides a narrow particle size distribution nickel-rich precursor, wherein the particle size distribution of the narrow particle size distribution nickel-rich precursor satisfies (D 90 -D 10 ) / D 50 <0.5.

[0056] D10 refers to the particle size corresponding to when the cumulative particle size distribution percentage reaches 10% in the particle system, that is, the volume of particles below this particle size accounts for 10% of the total volume.

[0057] D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage reaches 50% in the particle system, that is, the volume of particles below this particle size accounts for 50% of the total volume.

[0058] D90 refers to the particle size corresponding to when the cumulative particle size distribution percentage reaches 90% in the particle system, that is, the volume of particles below this particle size accounts for 90% of the total volume.

[0059] The chemical formula of the narrow particle size distribution nickel-rich precursor is Ni x Co y Mn 1-x-y (OH) 2 , where 0.5≤x<1, 0≤y<0.5.

[0060] In a third aspect, the present invention provides a positive electrode material, which is prepared from the nickel-rich precursor with narrow particle size distribution described in the second aspect.

[0061] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The preparation method provided by the present invention is a co-precipitation method. By adjusting the flow rate of the metal solution and the type of the complexing agent in different reaction stages, the nucleation and growth of the precursor crystal are precisely regulated, and finally a nickel-rich precursor with uniform morphology, good sphericity and narrow particle size distribution is obtained, thereby significantly improving the electrochemical performance of the positive electrode material; moreover, the preparation method provided by the present invention does not require the use of specific reactor equipment, nor does it require a complicated reactor separation process, the preparation process is simple and controllable, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is the SEM image of the nickel-rich precursor with narrow particle size distribution obtained in Example 1.

[0065] Figure 2 This is the SEM image of the nickel-rich precursor obtained in Comparative Example 1. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] Example 1

[0068] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, the preparation method comprising the following steps:

[0069] (1) According to the molecular formula Ni 0.90 Co 0.05Mn 0.05 (OH) 2 Prepare a mixed metal sulfate solution with a total metal ion concentration of 2 mol / L; prepare ammonia water with a concentration of 16 wt% as a first complexing agent solution; prepare a mixed solution with ammonia water concentration of 16 wt% and EDTA concentration of 1 wt% as a second complexing agent solution; prepare a sodium hydroxide solution with a concentration of 25 wt% as a precipitant solution; use the sodium hydroxide solution, ammonia water and water to prepare a base solution with a pH value of 12.7 and an ammonia concentration of 1.5 g / L;

[0070] (2) under the protection of nitrogen atmosphere, adding the mixed metal sulfate solution, the first complexing agent solution and the sodium hydroxide solution into the reactor containing the bottom liquid in parallel, and carrying out the nucleation stage reaction at a temperature of 55° C. to obtain a precursor crystal nucleus slurry having a median particle size D50 of 1.1 μm; the pH value of the nucleation stage reaction was controlled to be 12.7, the ammonia concentration was 1.5 g / L, and the stirring speed was 600 rpm;

[0071] (3) After the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution and the first complexing agent is adjusted, and the first growth stage reaction is carried out at a temperature of 55° C. to obtain a precursor slurry with a median particle size D50 of 5 μm; the pH value of the first growth stage reaction is 10.8, the ammonia concentration is 3 g / L, and the stirring speed is 600 rpm;

[0072] (4) After the first growth stage reaction is completed, the first complexing agent solution is replaced with the second complexing agent solution, and the process parameters are adjusted step by step according to the particle size. The second growth stage reaction is carried out at a temperature of 55° C. After the particle size reaches the shutdown median particle size, the feeding is stopped. The obtained slurry is washed with sodium hydroxide solution three times and hot water three times, and dried at 100° C. for 12 hours to obtain the narrow particle size distribution nickel-rich precursor Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 ;

[0073] During the second growth stage, for every 0.5 μm increase in particle size D50, the flow rate of the mixed metal sulfate solution decreased by 10%, the pH dropped by 0.1, the stirring speed decreased by 40 rpm, the ammonia concentration was maintained at 3 g / L, and the shutdown median particle size D50 was 10 μm.

[0074] Figure 1 This is the SEM image of the nickel-rich precursor with narrow particle size distribution obtained in this example. Figure 1 It can be seen that the present invention achieves precise control of the crystal nucleation and growth of the precursor by adjusting the pH value and rotation speed of the second growth stage reaction and introducing additives, and finally obtains a nickel-rich precursor with narrow particle size distribution, uniform morphology and good sphericity.

[0075] Example 2

[0076] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, the preparation method comprising the following steps:

[0077] (1) According to the molecular formula Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 Prepare a mixed metal sulfate solution with a total metal ion concentration of 1 mol / L; prepare 10wt% ammonia water as a first complexing agent solution; prepare a mixed solution with 10wt% ammonia water and 0.1wt% EDTA as a second complexing agent solution; prepare 10wt% sodium hydroxide solution as a precipitant solution; use sodium hydroxide solution, ammonia water and water to prepare a base solution with a pH value of 12 and an ammonia concentration of 0.5g / L;

[0078] (2) under the protection of nitrogen atmosphere, adding the mixed metal sulfate solution, the first complexing agent solution and the sodium hydroxide solution into the reactor containing the bottom liquid in parallel, and carrying out the nucleation stage reaction at a temperature of 40° C. to obtain a precursor crystal nucleus slurry having a median particle size D50 of 0.6 μm; the pH value of the nucleation stage reaction was controlled to be 12, the ammonia concentration was 0.5 g / L, and the stirring speed was 300 rpm;

[0079] (3) After the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution and the first complexing agent is adjusted, and the first growth stage reaction is carried out at a temperature of 55° C. to obtain a precursor slurry with a median particle size D50 of 2 μm; the pH value of the first growth stage reaction is 10.3, the ammonia concentration is 2 g / L, and the stirring speed is 300 rpm;

[0080] (4) After the first growth stage reaction is completed, the first complexing agent solution is replaced with the second complexing agent solution, and the process parameters are adjusted step by step according to the particle size. The second growth stage reaction is carried out at a temperature of 55° C., and the feeding is stopped after the particle size reaches the shutdown median particle size. The obtained slurry is washed with sodium hydroxide solution three times and hot water three times, and dried at 80° C. for 12 hours to obtain the narrow particle size distribution nickel-rich precursor Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 ;

[0081] During the second growth stage, for every 0.5 μm increase in particle size D50, the flow rate of the mixed metal sulfate solution decreased by 5%, the pH dropped by 0.05, the stirring speed decreased by 20 rpm, the ammonia concentration was maintained at 2 g / L, and the shutdown median particle size D50 was 6 μm.

[0082] Example 3

[0083] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, the preparation method comprising the following steps:

[0084] (1) According to the molecular formula Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 Prepare a mixed metal sulfate solution with a total metal ion concentration of 3 mol / L; prepare 20 wt% ammonia water as a first complexing agent solution; prepare a mixed solution with 20 wt% ammonia water and 3 wt% EDTA as a second complexing agent solution; prepare 40 wt% sodium hydroxide solution as a precipitant solution; use the sodium hydroxide solution, ammonia water and water to prepare a base solution with a pH value of 12.8 and an ammonia concentration of 4 g / L;

[0085] (2) under the protection of nitrogen atmosphere, adding the mixed metal sulfate solution, the first complexing agent solution and the sodium hydroxide solution into the reactor containing the bottom liquid in parallel, and carrying out the nucleation stage reaction at a temperature of 80° C. to obtain a precursor crystal nucleus slurry having a median particle size D50 of 1.5 μm; the pH value of the nucleation stage reaction was controlled to be 13, the ammonia concentration was 4 g / L, and the stirring speed was 700 rpm;

[0086] (3) After the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution and the first complexing agent is adjusted, and the first growth stage reaction is carried out at a temperature of 80° C. to obtain a precursor slurry with a median particle size D50 of 12 μm; the pH value of the first growth stage reaction is 11.3, the ammonia concentration is 10 g / L, and the stirring speed is 700 rpm;

[0087] (4) After the first growth stage reaction is completed, the first complexing agent solution is replaced with the second complexing agent solution, and the process parameters are adjusted step by step according to the particle size. The second growth stage reaction is carried out at a temperature of 80° C. After the particle size reaches the shutdown median particle size, the feeding is stopped. The obtained slurry is washed with sodium hydroxide solution three times and hot water three times, and dried at 120° C. for 12 hours to obtain the narrow particle size distribution nickel-rich precursor Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 ;

[0088] During the second growth stage, for every 1 μm increase in particle size D50, the flow rate of the mixed metal sulfate solution decreased by 15%, the pH dropped by 0.2, the stirring speed decreased by 100 rpm, the ammonia concentration was maintained at 10 g / L, and the shutdown median particle size D50 was 18 μm.

[0089] Example 4

[0090] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as that of Embodiment 1 except that the mass of EDTA in the second complexing agent solution is replaced by triethanolamine.

[0091] Example 5

[0092] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as that of Embodiment 1 except that the mass of EDTA in the second complexing agent solution is replaced by citric acid.

[0093] Example 6

[0094] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as that of Embodiment 1 except that the mass of EDTA in the second complexing agent solution is replaced by oxalic acid.

[0095] Example 7

[0096] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as that of Embodiment 1 except that the mass of EDTA in the second complexing agent solution is replaced by polyvinylpyrrolidone (PVP).

[0097] Example 8

[0098] This embodiment provides a method for preparing a nickel-rich precursor with a narrow particle size distribution. Except that the ammonia concentration in the first and second growth stage reactions is the same as that in the nucleation stage reaction, both are 1.5 g / L, the rest is the same as Example 1.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing a nickel-rich precursor, comprising the following steps:

[0101] (1) According to the molecular formula Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 Prepare a mixed metal sulfate solution with a total metal ion concentration of 2 mol / L; prepare ammonia water with a concentration of 16 wt% as a first complexing agent solution; prepare a sodium hydroxide solution with a concentration of 25 wt% as a precipitant solution; use the sodium hydroxide solution, ammonia water and water to prepare a base solution with a pH value of 12.7 and an ammonia concentration of 1.5 g / L;

[0102] (2) under the protection of nitrogen atmosphere, adding the mixed metal sulfate solution, the first complexing agent solution and the sodium hydroxide solution into the reactor containing the bottom liquid in parallel, and carrying out the nucleation stage reaction at a temperature of 55° C. to obtain a precursor crystal nucleus slurry having a median particle size D50 of 1.1 μm; the pH value of the nucleation stage reaction was controlled to be 12.7, the ammonia concentration was 1.5 g / L, and the stirring speed was 600 rpm;

[0103] (3) After the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution and the first complexing agent is adjusted, and the first growth stage reaction is carried out at a temperature of 55° C. to obtain a precursor slurry with a median particle size D50 of 5 μm; the pH value of the first growth stage reaction is 10.8, the ammonia concentration is 1.5 g / L, and the stirring speed is 600 rpm;

[0104] (4) After the first growth stage reaction is completed, the second growth stage reaction is carried out at a temperature of 55° C., and the feeding is stopped after the particle size reaches the shutdown median particle size. The obtained slurry is washed with sodium hydroxide solution three times and hot water three times, and dried at 100° C. for 12 hours to obtain the nickel-rich precursor Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 ;

[0105] The reaction conditions of the second growth stage are the same as those of the first growth stage, that is, the flow rate, pH value and rotation speed of the mixed metal sulfate solution are not adjusted as the particle size increases during the second growth stage.

[0106] Figure 2 is the SEM image of the nickel-rich precursor with narrow particle size distribution obtained in this comparative example. Figure 2 It can be seen that when the pH value and rotation speed of the second growth stage reaction are not adjusted, precise control of the crystal nucleation and growth of the precursor cannot be achieved, and the final nickel-rich precursor has more small particles, a wide particle size distribution, and poor sphericity.

[0107] Comparative Example 2

[0108] This comparative example provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as Example 1 except that the flow rate of the mixed metal sulfate solution does not decrease with the increase of the particle size D50 during the second growth stage reaction.

[0109] Comparative Example 3

[0110] This comparative example provides a method for preparing a nickel-rich precursor, comprising the following steps:

[0111] (1) According to the molecular formula Ni 0.90 Co 0.05 Mn0.05 (OH) 2 Prepare a mixed metal sulfate solution with a total metal ion concentration of 2 mol / L; prepare ammonia water with a concentration of 16 wt% as a first complexing agent solution; prepare a sodium hydroxide solution with a concentration of 25 wt% as a precipitant solution; use the sodium hydroxide solution, ammonia water and water to prepare a base solution with a pH value of 12.7 and an ammonia concentration of 1.5 g / L;

[0112] (2) under the protection of nitrogen atmosphere, adding the mixed metal sulfate solution, the first complexing agent solution and the sodium hydroxide solution into the reactor containing the bottom liquid in parallel, and carrying out the nucleation stage reaction at a temperature of 55° C. to obtain a precursor crystal nucleus slurry having a median particle size D50 of 1.1 μm; the pH value of the nucleation stage reaction was controlled to be 12.7, the ammonia concentration was 1.5 g / L, and the stirring speed was 600 rpm;

[0113] (3) After the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution and the first complexing agent is adjusted, and the first growth stage reaction is carried out at a temperature of 55° C. to obtain a precursor slurry with a median particle size D50 of 5 μm; the pH value of the first growth stage reaction is 10.8, the ammonia concentration is 3 g / L, and the stirring speed is 600 rpm;

[0114] (4) After the first growth stage reaction is completed, the process parameters are adjusted step by step according to the particle size, and the second growth stage reaction is carried out at a temperature of 55° C. After the particle size reaches the shutdown median particle size, the feeding is stopped. The obtained slurry is washed with sodium hydroxide solution three times and hot water three times, and dried at 100° C. for 12 hours to obtain the nickel-rich precursor Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 ;

[0115] During the second growth stage, for every 0.5 μm increase in particle size D50, the flow rate of the mixed metal sulfate solution decreased by 10%, the pH dropped by 0.1, the stirring speed decreased by 40 rpm, the ammonia concentration was maintained at 3 g / L, and the shutdown median particle size D50 was 10 μm.

[0116] Comparative Example 4

[0117] This comparative example provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as Example 1 except that the pH value does not decrease with the increase of the particle size D50 during the second growth stage reaction.

[0118] Comparative Example 5

[0119] This comparative example provides a method for preparing a nickel-rich precursor with a narrow particle size distribution, which is the same as Example 1 except that the stirring speed does not decrease with the increase of the particle size D50 during the second growth stage reaction.

[0120] Performance Characterization

[0121] The particle size and distribution (D10, D50, D90), sphericity and small particle ratio of the nickel-rich precursor with narrow particle size distribution obtained in the above embodiment and the nickel-rich precursor obtained in the comparative example were tested and analyzed.

[0122] Among them, the test method for particle size and distribution is: use Malvern Mastersizer 3000 particle size analyzer to perform particle size test, take a certain amount of precursor powder, add 500mL dispersion medium (deionized water) and 5mL0.1% sodium hexametaphosphate (dispersant) for sufficient ultrasonic dispersion (40kHz, 200W, pump speed 2400rpm), after background measurement, sample and detect in the range of shading rate of 10-12%, repeat the measurement 3 times and take the average value, use Mie scattering theory to calculate the particle size distribution, output the cumulative distribution curve to read the D10 / D50 / D90 value, and calculate the particle size distribution according to (D90-D10) / D50 (the smaller the value, the more concentrated the particle size distribution).

[0123] The test method for sphericity is as follows: using an Apreo 2S Hivac field emission scanning electron microscope, 5 areas are randomly collected at an accelerating voltage of 5 kV and a working distance of 10 mm, high-resolution images of more than 20 main particles in each area, and a total of 100 particles are randomly selected to measure the major axis (a) and minor axis (b) of these particles (unit: μm or pixel, at least 3 different directions must be selected for measurement, and the average value is taken to reduce projection errors), and then the sphericity is calculated according to the sphericity formula ψ=b / a×100% (the physical meaning is to directly reflect the "flatness" of the particles. When ψ=100%, it is a perfect sphere, and the smaller ψ is, the more oblate the particle is an ellipsoidal particle), and finally the average value of the sphericity of each particle is taken.

[0124] The test method for the proportion of small particles is as follows: based on the typical size D50 of the main particles, define particles with a size <0.3×D50 as small particles, randomly select 10 areas, randomly select 20 main particles in each area, and count the percentage of small particles in the total number of particles, and then take the average value of the proportion of small particles in each area. The test results are shown in Table 1.

[0125] Table 1

[0126]

[0127]

[0128] As can be seen from Table 1, the preparation method provided by the present invention can obtain a nickel-rich precursor with a narrow particle size distribution, uniform morphology, good sphericity and a small proportion of small particles. As a preferred technical scheme of the present invention, the particle size distribution can be controlled below 0.45, the sphericity is above 95% and the proportion of small particles is below 4.4%.

[0129] The preparation method provided by the present invention makes the ammonia concentration in the first growth stage higher than the nucleation stage reaction, reduces the supersaturation of the solution system, makes the growth rate of the crystal much greater than the nucleation rate, and promotes the crystal to grow up gradually at a certain rate. As can be seen from the comparison of Example 8 with Example 1, when the ammonia concentration in the first growth stage is the same as the nucleation stage, the sphericity of the obtained nickel-rich precursor is significantly reduced, and the proportion of small particles increases, and the particle size distribution becomes wider, which is not conducive to obtaining a nickel-rich precursor with a narrow particle size distribution, uniform morphology, good sphericity and a small proportion of small particles. Therefore, as a preferred technical solution of the present invention, it is necessary to make the ammonia concentration in the first growth stage higher than the nucleation stage reaction.

[0130] The gradient adjustment in the second growth stage is conducive to the preparation of a nickel-rich precursor with a narrow particle size distribution, uniform morphology, good sphericity and a small proportion of small particles. From the comparison of Comparative Examples 2, 4, and 5 with Example 1, it can be seen that when the flow rate, pH value and stirring speed of the mixed metal sulfate solution are not adjusted with the increase of particle size in the second growth stage, the sphericity of the obtained nickel-rich precursor is significantly reduced, the proportion of small particles increases, and the particle size distribution becomes wider, which is not conducive to obtaining a nickel-rich precursor with a narrow particle size distribution, uniform morphology, good sphericity and a small proportion of small particles.

[0131] From the comparison between Comparative Example 3 and Example 1, it can be seen that when the second complexing agent solution containing the additive is not used, the sphericity of the nickel-rich precursor is significantly reduced, the proportion of small particles increases, and the particle size distribution becomes wider.

[0132] From the comparison between Comparative Example 1 and Example 1, it can be seen that when the ammonia concentration in the first growth stage is the same as that in the nucleation stage, the second complexing agent solution containing additives is not used, and the flow rate, pH value and stirring speed of the mixed metal sulfate solution are not adjusted with the increase of particle size in the second growth stage, the test results of the sphericity, particle size distribution and small particle proportion of the obtained nickel-rich precursor are the worst. Therefore, in order to achieve precise control of the nucleation and growth of the precursor crystal, it is necessary to specifically control the process parameters in the preparation method of the present invention to obtain a nickel-rich precursor with uniform morphology and good sphericity and narrow particle size distribution.

[0133] In summary, the preparation method provided by the present invention is a co-precipitation method. By adjusting the metal solution feed flow rate and the type of complexing agent in different reaction stages, precise control of the nucleation and growth of the precursor crystal is achieved, and finally a nickel-rich precursor with uniform morphology, good sphericity and narrow particle size distribution is obtained, thereby significantly improving the electrochemical performance of the positive electrode material; moreover, the preparation method provided by the present invention does not require the use of specific reactor equipment, nor does it require a complicated reactor separation process. The preparation process is simple and controllable, and is easy to industrialize.

[0134] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a nickel-rich precursor with a narrow particle size distribution, characterized in that: The preparation method comprises the following steps: (1) under a protective atmosphere, adding a mixed metal salt solution, a precipitant solution and a first complexing agent solution to a base liquid in parallel to carry out a nucleation stage reaction to obtain a precursor crystal nucleus slurry having a first median particle size; (2) adjusting the feed flow rates of the precipitant solution and the first complexing agent solution to perform a first growth stage reaction to obtain a precursor slurry having a second median particle size; (3) replacing the first complexing agent solution with a second complexing agent solution, adjusting the flow rate of the mixed metal salt solution, the precipitant solution, and the second complexing agent solution and the stirring speed step by step according to the particle size, performing a second growth stage reaction, stopping the feeding after the particle size reaches the shutdown particle size, and post-treating the obtained slurry to obtain the narrow particle size distribution nickel-rich precursor; The first complexing agent in the first complexing agent solution includes aqueous ammonia; The second complexing agent in the second complexing agent solution includes ammonia water and an additive; the additive includes any one of citric acid, oxalic acid, polyvinyl pyrrolidone, triethanolamine or ethylenediaminetetraacetic acid, or a combination of at least two thereof.

2. The preparation method according to claim 1, characterized in that: The concentration of ammonia in the first complexing agent solution is 10wt%-20wt%; Preferably, the concentration of aqueous ammonia in the second complexing agent solution is 10wt%-20wt%, and the concentration of the additive is 0.1wt%-3wt%.

3. The preparation method according to claim 1 or 2, characterized in that: In step (3), when the reaction of the second growth stage is carried out, the parameters are adjusted as follows for each increase of 0.4 μm-1.0 μm in particle size: the flow rate of the mixed metal salt solution is adjusted to decrease by 5%-15%, the flow rate of the precipitant solution is adjusted to decrease the pH value by 0.05-0.2, the stirring speed is adjusted to decrease by 20 rpm-100 rpm, and the flow rate of the second complexing agent solution is adjusted to maintain a stable ammonia concentration in the system; Preferably, the shutdown particle size in step (3) refers to a median particle size of 6 μm-18 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The metal salts in the mixed metal salt solution of step (1) include nickel salt, manganese salt and cobalt salt; Preferably, the nickel salt comprises any one of nickel sulfate, nickel nitrate or nickel halide, or a combination of at least two thereof; Preferably, the manganese salt comprises any one or a combination of at least two of manganese sulfate, manganese nitrate or manganese halide; Preferably, the cobalt salt comprises any one or a combination of at least two of cobalt sulfate, cobalt nitrate or cobalt halide; Preferably, the total concentration of metal ions in the mixed metal salt solution in step (1) is 1 mol / L-3 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The precipitant in the precipitant solution of step (1) comprises any one of sodium hydroxide, potassium hydroxide, lithium hydroxide or sodium carbonate, or a combination of at least two thereof; Preferably, the concentration of the precipitant in the precipitant solution in step (1) is 10wt%-40wt%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The base liquid in step (1) is a mixed solution of a precipitant solution, ammonia water and water; The pH value of the base solution in step (1) is 12-12.8, and the ammonia concentration is 0.5 g / L-4 g / L; Preferably, the protective atmosphere in step (1) comprises nitrogen and / or an inert gas.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The pH value of the nucleation stage reaction in step (1) is 12-13, and the ammonia concentration is 0.5 g / L-4 g / L; Preferably, in step (1), the first median particle size is 0.6 μm-1.5 μm; Preferably, the pH value of the first growth stage reaction in step (2) is 10.3-11.3, and the ammonia concentration is 2 g / L-10 g / L; Preferably, the second median particle size is 1 / 3-2 / 3 of the shutdown particle size; Preferably, the temperature of the nucleation stage reaction, the first growth stage reaction and the second growth stage reaction are independently 40° C.-80° C.; Preferably, the nucleation stage reaction, the first growth stage reaction and the second growth stage reaction are independently carried out under stirring conditions; the stirring speed of the stirring conditions is 100 rpm-700 rpm.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The post-treatment in step (3) includes washing and drying in sequence; Preferably, the drying temperature is 80°C-150°C; Preferably, the drying end point is when the moisture content reaches below 0.8 wt %.

9. A nickel-rich precursor with a narrow particle size distribution, characterized in that: The particle size distribution of the narrow particle size distribution nickel-rich precursor satisfies (D 90 -D 10 ) / D 50 <0.5; The chemical formula of the narrow particle size distribution nickel-rich precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.5≤x<1, 0≤y<0.

5.

10. A positive electrode material, characterized in that: The positive electrode material is prepared from the nickel-rich precursor with narrow particle size distribution as described in claim 9.

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