Ultra-small particle high-nickel precursor, preparation method, small-size single crystal and application

Abstract

The invention provides an ultra-small particle high-nickel precursor, a preparation method, a small-size single crystal and application, and the preparation method comprises the following steps: (1) nucleation period: adding a metal salt solution, a precipitator solution and a complexing agent solution into a reaction base solution in a parallel flow manner, and carrying out a co-precipitation reaction; the adding flow of the metal salt solution is the first flow; (2) transition period: adding a metal salt solution, a precipitant solution and a complexing agent solution into the obtained solution containing the crystal nucleus in a parallel flow manner, carrying out coprecipitation reaction, and controlling the pH to be reduced in the coprecipitation reaction process; the adding flow of the metal salt solution is second flow; (3) growing period: adding a metal salt solution, a precipitant solution and a complexing agent solution in a parallel flow manner, and carrying out a co-precipitation reaction; the adding flow of the metal salt solution is third flow; a second traffic lt; a third traffic lt; and a first flow. According to the preparation method, the ultra-small-particle high-nickel precursor with thicker primary crystal grains is obtained, and meanwhile, the particle size concentration ratio of the precursor is better, so that subsequent sintering of a single-crystal positive electrode material is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a preparation method of ultra-small particle high-nickel precursors, in particular to an ultra-small particle high-nickel precursor and a preparation method thereof, small-size single crystals and applications. Background Art

[0002] Solid-state batteries with high safety and high energy density are one of the important directions for the development of next-generation lithium-ion batteries. In solid-state batteries, since the solid electrolyte cannot penetrate into the interior of polycrystalline particles, the lithium-ion diffusion path in the polycrystalline cathode is the longest in solid-state batteries, and its rate performance is the worst. For small-size single crystals, due to their small size, the capacity remains the highest at high rates. Large single crystals are in between the two.

[0003] Small-size single crystals can effectively relieve the volume strain of particles, thereby achieving close solid-solid interface contact and having the highest discharge capacity; in addition, small-size single crystals can also relieve the H2-H3 volume contraction effect (during the charging process of high-nickel materials, when the voltage is greater than 4.2V, the phase transformation from H2 to H3 occurs), so they have strong structural stability. To prepare small-size single crystals, ultra-small particle precursors are required.

[0004] The traditional method for large-scale production of ternary precursors is the co-precipitation method. To obtain precursors with good dispersion and a concentrated particle size distribution, the reaction process is usually divided into a nucleation stage and a growth stage. Ultra-small particles are only slightly larger in particle size than traditional crystal nuclei. During the process of switching from the nucleation stage to the growth stage, particle agglomeration often occurs, which will lead to poor dispersion of the precursors and an uneven particle size distribution, resulting in premature sintering and uneven sintering of some particles in the next-step sintered single crystal, and the mixing of single crystals and polycrystals, which greatly affects the electrochemical performance of the material.

[0005] Therefore, in order to prevent particle agglomeration, the common method for preparing ultra-small particles in the prior art is to control the growth conditions to always remain in the nucleation stage while increasing the solid content in the co-precipitation process. However, since the particles are always in the nucleation stage, there are still many small particles in the system, and the particle size distribution is still not concentrated, which will also lead to the phenomenon of mixing single crystals and polycrystals in the subsequent sintering. In addition, the primary grains of the ultra-small particle precursors obtained by this method are relatively thin, which is also not conducive to sintering single crystals.

[0006] CN114408988A discloses a method for synthesizing a precursor of a ternary cathode material. The precursor synthesis process includes three stages. The first stage is the rapid nucleation stage, the second stage is the intermediate uniform growth stage, and the third stage is the slow growth stage. By adjusting the pH value, the flow rate of the mixed salt solution, the flow rate of the oxidizing gas, and the rotation speed in different stages, the morphology and properties of the precursor are controlled. By adjusting the pH value and the flow rate of the mixed salt solution, the particle size of the precursor during the growth stage can be controlled; by adjusting the flow rate of the oxidizing gas and the rotation speed, the primary particles can be refined and the agglomeration phenomenon of the primary particles can be improved. By controlling the ammonia concentration at a low level, the sphericity of the precursor can be improved, and a precursor with a loose and porous structure and high sphericity can be obtained.

[0007] CN117208977A discloses a precursor of a high-capacity cathode material, its preparation method and application. During the coprecipitation process, there is no need to continuously introduce ammonia water as a complexing agent, and it is not required that the reaction atmosphere is a protective atmosphere. A normal atmospheric environment is sufficient. By only adding an appropriate amount of complexing agent ammonia water solution to the bottom liquid of the reaction kettle, and by controlling the different pH values in the nucleation stage and the growth stage and the different flow rates of the transition metal salt solution, a precursor with a loose inner core, a dense surface, a specific surface area ≥ 20 m2 / g, and a tap density ≥ 1.55 g / cm3 is realized. The cathode material obtained by mixing and sintering the precursor with lithium has a high capacity.

[0008] The preparation methods of ultra-small particle high-nickel precursors disclosed in the prior art all have certain defects, and there are problems such as relatively thin primary grains of the prepared precursor and non-concentrated particle size distribution. Therefore, it is crucial to develop and design a new type of ultra-small particle high-nickel precursor, its preparation method, small-size single crystal and application. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an ultra-small particle high-nickel precursor, its preparation method, small-size single crystal and application. In the preparation method provided by the present invention, by controlling the addition flow rate of the metal salt solution during the nucleation period, a sufficient number of crystal nuclei are formed at a relatively large flow rate; then, by controlling the addition flow rate of the metal salt solution during the transition period, the growth of the precursor particles by absorbing solutes is inhibited; then, by controlling the addition flow rate of the metal salt solution during the growth period, while ensuring the preparation efficiency, the larger particles in the precursor are promoted to grow continuously by absorbing smaller particles; the preparation method of the present invention obtains an ultra-small particle high-nickel precursor with relatively thick primary grains, and the particle size concentration of the ultra-small particle high-nickel precursor is good, which is convenient for subsequent sintering of the single crystal cathode material.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a method for preparing an ultra-small particle high-nickel precursor, and the preparation method includes:

[0012] (1) Nucleation stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added to the reaction bottom liquid in a co-current manner to carry out a coprecipitation reaction to obtain a solution containing crystal nuclei; the addition flow rate of the metal salt solution is the first flow rate;

[0013] (2) Transition stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added to the solution containing crystal nuclei obtained in step (1) in a co-current manner to carry out a coprecipitation reaction, and the pH is controlled to decrease during the coprecipitation reaction to obtain a solution containing transitional crystal nuclei; the addition flow rate of the metal salt solution is the second flow rate;

[0014] (3) Growth stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added to the solution containing transitional crystal nuclei obtained in step (2) in a co-current manner to carry out a coprecipitation reaction to obtain an ultra-small particle high-nickel precursor; the addition flow rate of the metal salt solution is the third flow rate;

[0015] The second flow rate in step (2) < the third flow rate in step (3) < the first flow rate in step (1).

[0016] The growth mode of the precursor particles is mainly divided into two modes. The first growth mode is that the particles continuously grow by absorbing solutes; the second growth mode is that the larger particles continuously grow by absorbing the smaller particles.

[0017] There are two methods for preparing ultra-small particle high-nickel precursors in the prior art; the first method is the traditional large-scale production method of ternary precursors in the background technology. The disadvantage of this method is that due to the action of the first growth mode, during the switching process between the nucleation stage and the growth stage, a large amount of particle agglomeration will occur, resulting in a non-concentrated particle size distribution of the precursor; the second method is a common method for preparing ultra-small particles in the background technology. In this method, it is necessary to control the growth conditions to always remain in the nucleation stage. However, since the reaction process is always in the nucleation stage, both the first growth mode and the second growth mode are inhibited, resulting in the existence of more fine particles, which will also lead to a non-concentrated particle size distribution of the precursor. Moreover, this method is carried out at a high pH, and the primary grains of the crystal tend to Ostwald ripening more, forming nano-sheets that preferentially grow in the (001) plane. Therefore, the primary grains of the precursor prepared are relatively thin, which is not conducive to sintering to obtain single crystals.

[0018] Therefore, in order to obtain an ultra-small particle high-nickel precursor with a relatively thick primary grain and a good particle size concentration in the present invention, a preparation method of an ultra-small particle high-nickel precursor is provided; in the preparation method provided by the present invention, the second flow rate described in step (2) < the third flow rate described in step (3) < the first flow rate described in step (1); that is, by controlling the addition flow rate of the metal salt solution in the nucleation period, a sufficient number of crystal nuclei are formed at a relatively large flow rate; then, by controlling the addition flow rate of the metal salt solution in the transition period, the growth of the precursor in growth mode 1 (the particles absorb solutes and continuously grow) is inhibited; and then, by controlling the addition flow rate of the metal salt solution in the growth period, while ensuring the preparation efficiency, the growth of the precursor in growth mode 2 (the larger particles continuously grow by absorbing the smaller particles) is promoted; in summary, the method described in the present application inhibits growth mode 1 while promoting growth mode 2, obtaining an ultra-small particle high-nickel precursor with a good particle size concentration, and moreover, both the transition period and the growth period in the preparation method provided by the present invention are carried out at a low pH, and the primary grains are more inclined to grow in a mode of oriented attachment, thereby obtaining an ultra-small particle high-nickel precursor with a relatively thick primary grain that is convenient for sintering single crystals.

[0019] In the present invention, the relatively thick primary grain of the precursor means that the thickness of the primary grain exceeds 100 nm; the reason why the preparation method of the present invention can obtain an ultra-small particle high-nickel precursor with relatively thick primary grains is that both the transition period and the growth period are carried out at a low pH, and the primary grains are more inclined to stack growth, obtaining a relatively thick flaky structure.

[0020] Preferably, the ratio of the first flow rate described in step (1), the second flow rate described in step (2), and the third flow rate described in step (3) is (1.5 - 2.5):(0.05 - 0.15):1. For example, it can be 1.5:0.05:1, 1.6:0.06:1, 1.7:0.07:1, 1.8:0.08:1, 1.9:0.09:1, 2.0:0.10:1, 2.1:0.11:1, 2.2:0.12:1, 2.3:0.13:1, 2.4:0.14:1, or 2.5:0.15:1, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0021] Preferably, the first flow rate described in step (1) is 4 - 200 L / h. For example, it can be 4 L / h, 20 L / h, 50 L / h, 80 L / h, 100 L / h, 120 L / h, 150 L / h, 180 L / h, or 200 L / h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] Preferably, the second flow rate in step (2) is 0.2 - 10 L / h. For example, it can be 0.2 L / h, 0.5 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h, or 10 L / h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0023] Preferably, the third flow rate in step (3) is 2 - 100 L / h. For example, it can be 2 L / h, 10 L / h, 20 L / h, 30 L / h, 40 L / h, 50 L / h, 60 L / h, 70 L / h, 80 L / h, 90 L / h, or 100 L / h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0024] Preferably, the pH of the reaction bottom liquid in step (1) is 11 - 13, and the concentration of the complexing agent is 0.2 - 1 mol / L.

[0025] In the present invention, the pH of the reaction bottom liquid in step (1) is 11 - 13. For example, it can be 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, or 13.0. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0026] In the present invention, the concentration of the complexing agent in the reaction bottom liquid in step (1) is 0.2 - 1 mol / L. For example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1.0 mol / L. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0027] Preferably, the coprecipitation reactions in step (1), step (2), and step (3) are all carried out in a protective atmosphere.

[0028] Preferably, the protective atmosphere includes nitrogen and / or inert gas.

[0029] Preferably, the inert gas includes nitrogen and / or argon.

[0030] Preferably, the flow rate of the protective gas introduced in the coprecipitation reactions in steps (1), (2) and (3) is independently 2 to 25 L / min, for example, it can be 2 L / min, 5 L / min, 8 L / min, 10 L / min, 12 L / min, 15 L / min, 18 L / min, 20 L / min, 22 L / min or 25 L / min, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0031] Preferably, the temperatures of the coprecipitation reactions in steps (1), (2) and (3) are independently 20 to 95 °C, for example, it can be 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C or 95 °C, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0032] Preferably, the coprecipitation reactions in steps (1), (2) and (3) are all carried out in a reaction kettle, and the volume of the reaction kettle is 100 to 1000 L, for example, it can be 100 L, 200 L, 300 L, 400 L, 500 L, 600 L, 700 L, 800 L, 900 L or 1000 L, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0033] Preferably, in the coprecipitation reactions in steps (1), (2) and (3), the liquid accounts for 10 to 80% of the volume of the reaction kettle, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80%, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0034] Preferably, the total concentration of metal ions in the metal salt solutions in steps (1), (2) and (3) is independently 1 to 3 mol / L, for example, it can be 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3.0 mol / L, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0035] Preferably, the total concentration of metal ions in the metal salt solutions in steps (1), (2) and (3) is the same.

[0036] Preferably, the precipitants in the precipitant solutions in steps (1), (2) and (3) independently include any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate.

[0037] Preferably, the concentrations of the precipitants in the precipitant solutions in steps (1), (2) and (3) are independently 1 to 10 mol / L. For example, they can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but are not limited to the listed values, and other unlisted values within this range are equally applicable.

[0038] Preferably, the complexing agents in the complexing agent solutions in steps (1), (2) and (3) independently include any one or a combination of at least two of ammonia, ammonium bicarbonate, ammonium sulfate, oxalic acid, sodium oxalate, citric acid, sodium citrate, ethylenediaminetetraacetic acid, tartaric acid, sodium tartrate or sodium hexametaphosphate. Typical but non-limiting combinations include the combination of ammonia and ammonium bicarbonate, the combination of oxalic acid and citric acid, the combination of sodium citrate and ethylenediaminetetraacetic acid, the combination of tartaric acid and sodium tartrate, or the combination of ammonia, oxalic acid and citric acid.

[0039] Preferably, the concentrations of the complexing agents in the complexing agent solutions in steps (1), (2) and (3) are independently 1 to 10 mol / L. For example, they can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but are not limited to the listed values, and other unlisted values within this range are equally applicable.

[0040] Preferably, during the coprecipitation reaction in step (1), the pH is controlled to be 11 to 13, the complexing agent concentration is 0.2 to 1 mol / L, and the time is 6 to 12 h.

[0041] During the coprecipitation reaction in step (1) of the present invention, the pH is controlled to be 11 to 13. For example, it can be 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8 or 13.0, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0042] In the co-precipitation reaction in step (1) of the present invention, the concentration of the complexing agent is controlled to be 0.2 to 1 mol / L. For example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0043] In the co-precipitation reaction in step (1) of the present invention, the reaction time is 6 to 12 h. For example, it can be 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0044] Preferably, during the co-precipitation reaction in step (2), the pH is controlled to decrease at a rate of 0.1 to 0.5 per hour until it reaches 8 to 10, and the concentration of the complexing agent is controlled to be 0.2 to 1 mol / L.

[0045] During the co-precipitation reaction in step (2) of the present invention, the pH is controlled to decrease at a rate of 0.1 to 0.5 per hour. For example, it can be a decrease of 0.1, 0.2, 0.3, 0.4 or 0.5 per hour. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0046] During the co-precipitation reaction in step (2) of the present invention, the pH is controlled to decrease to 8 to 10. For example, it can be 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8 or 10.0. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0047] During the co-precipitation reaction in step (2) of the present invention, the concentration of the complexing agent is controlled to be 0.2 to 1 mol / L. For example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0048] Preferably, in the coprecipitation reaction in step (2), the transition period ends after the pH is reduced to 8-10. The pH at the end of the transition period can be, for example, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8 or 10.0, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0049] Preferably, during the coprecipitation reaction in step (3), the pH is controlled to be 8-10, and the complexing agent concentration is 0.07-1 mol / L.

[0050] During the coprecipitation reaction in step (3) of the present invention, the pH is controlled to be 8-10. It can be, for example, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8 or 10.0, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0051] During the coprecipitation reaction in step (3) of the present invention, the complexing agent concentration is controlled to be 0.07-1 mol / L. It can be, for example, 0.07 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0052] As a preferred technical solution of the preparation method of the present invention, the preparation method includes:

[0053] (1) Nucleation period: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1-3 mol / L, a precipitant solution with a concentration of 1-10 mol / L, and a complexing agent solution with a concentration of 1-10 mol / L are added in parallel to a reaction bottom solution with a pH of 11-13 and a complexing agent concentration of 0.2-1 mol / L, and a coprecipitation reaction is carried out for 6-12 h. During the coprecipitation reaction, the temperature is controlled to be 20-95 °C, the pH is 11-13, and the complexing agent concentration is 0.2-1 mol / L to obtain a solution containing crystal nuclei; wherein, the addition flow rate of the metal salt solution is the first flow rate;

[0054] (2) Transition period: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1 - 3 mol / L, a precipitant solution with a concentration of 1 - 10 mol / L, and a complexing agent solution with a concentration of 1 - 10 mol / L are added to the solution containing crystal nuclei obtained in step (1) in a concurrent flow manner to carry out a coprecipitation reaction. During the coprecipitation reaction, the temperature is controlled at 20 - 95 °C, the complexing agent concentration is controlled at 0.2 - 1 mol / L, and the pH is controlled to decrease at a rate of 0.1 - 0.5 per hour until it reaches 8 - 10. After the pH in the coprecipitation reaction decreases to 8 - 10, the transition period ends, and a solution containing transitional crystal nuclei is obtained; wherein, the addition flow rate of the metal salt solution is the second flow rate;

[0055] (3) Growth period: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1 - 3 mol / L, a precipitant solution with a concentration of 1 - 10 mol / L, and a complexing agent solution with a concentration of 1 - 10 mol / L are added to the solution containing transitional crystal nuclei obtained in step (2) in a concurrent flow manner, and a coprecipitation reaction is carried out at 20 - 95 °C. During the coprecipitation reaction, the pH is controlled at 8 - 10 and the complexing agent concentration is controlled at 0.07 - 1 mol / L to obtain an ultra-small particle high-nickel precursor; wherein, the addition flow rate of the metal salt solution is the third flow rate;

[0056] The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is (1.5 - 2.5):(0.05 - 0.15):1;

[0057] The first flow rate in step (1) is 4 - 200 L / h, the second flow rate in step (2) is 0.2 - 10 L / h, and the third flow rate in step (3) is 2 - 100 L / h.

[0058] In the second aspect, the present invention provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method described in the first aspect.

[0059] Preferably, the D50 particle size of the ultra-small particle high-nickel precursor is 1.5 - 2.5 μm, and the particle size distribution width SPAN value is 0.5 - 0.7.

[0060] In the present invention, the D50 particle size of the ultra-small particle high-nickel precursor is 1.5 - 2.5 μm, for example, it can be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm or 2.5 μm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0061] In the present invention, the SPAN value of the particle size distribution width of the ultra-small particle high-nickel precursor is 0.5 to 0.7, and can be, for example, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68 or 0.70, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0062] Preferably, the tap density of the ultra-small particle high-nickel precursor is 1.7 to 2.0 g / cm 3 , and can be, for example, 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 , 1.9 g / cm 3 , 1.95 g / cm 3 or 2.0 g / cm 3 , but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0063] Preferably, the specific surface area of the ultra-small particle high-nickel precursor is 5 to 15 m 2 / g, and can be, for example, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g or 15 m 2 / g, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0064] Preferably, the chemical formula of the ultra-small particle high-nickel precursor includes Ni a Co b Mn c Al d (OH)2; where a + b + c + d = 1, 0.8 ≤ a < 0.98, 0 ≤ b < 0.1, 0 ≤ c < 0.1 and 0 ≤ d < 0.1.

[0065] In the present invention, 0.8 ≤ a < 0.98, and the value of a can be, for example, 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96 or 0.98, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0066] In the present invention, 0 ≤ b < 0.1. The value of b can be, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0067] In the present invention, 0 ≤ c < 0.1. The value of c can be, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0068] In the present invention, 0 ≤ d < 0.1. The value of d can be, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0069] In a third aspect, the present invention provides a small-sized single crystal, which is obtained by sintering the ultra-small particle high-nickel precursor with lithium doping as described in the second aspect.

[0070] The lithium doping sintering in the present invention includes: mixing the ultra-small particle high-nickel precursor and a lithium source to obtain a mixture, and sintering the obtained mixture.

[0071] Preferably, the D50 particle size of the small-sized single crystal is 1.5 - 2.5 μm. It can be, for example, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm or 2.5 μm, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0072] In a fourth aspect, the present invention provides a solid-state battery, which includes the small-sized single crystal described in the third aspect.

[0073] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] In the present invention, in order to obtain an ultra-small particle high-nickel precursor with a relatively thick primary grain and a good particle size concentration, a preparation method of an ultra-small particle high-nickel precursor is provided. In the preparation method provided by the present invention, it is controlled that the second flow rate described in step (2) < the third flow rate described in step (3) < the first flow rate described in step (1); that is, by controlling the addition flow rate of the metal salt solution in the nucleation period, sufficient crystal nuclei are formed at a relatively large flow rate; then, by controlling the addition flow rate of the metal salt solution in the transition period, the growth of the precursor in growth mode 1 (the particles absorb solutes and continuously grow) is inhibited; then, by controlling the addition flow rate of the metal salt solution in the growth period, while ensuring the preparation efficiency, the growth of the precursor in growth mode 2 (the larger particles continuously grow by absorbing the smaller particles) is promoted. In summary, the method described in the present application inhibits growth mode 1 while promoting growth mode 2, and obtains an ultra-small particle high-nickel precursor with a good particle size concentration. Moreover, both the transition period and the growth period in the preparation method provided by the present invention are carried out at a low pH, and the primary grains tend to grow in a mode of oriented attachment, so as to obtain an ultra-small particle high-nickel precursor with relatively thick primary grains that is convenient for sintering single crystals. Detailed Embodiments

[0076] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0077] Example 1

[0078] This example provides a preparation method of an ultra-small particle high-nickel precursor, and the preparation method includes:

[0079] (1) Nucleation period: In a protective atmosphere (composed of nitrogen and argon with a volume ratio of 1:1), into a reaction bottom solution with a pH of 12.7 (the pH is adjusted by adding a precipitant, that is, LiOH and NaCO3 with a molar ratio of 1:1) and a complexing agent concentration of 0.9 mol / L (the complexing agent is composed of sodium oxalate and tartaric acid with a molar ratio of 1:1) (the solvent of the reaction bottom solution is water), a metal salt aqueous solution with a total metal ion concentration of 1.7 mol / L (the molar ratio of Ni ions, Mn ions and Co ions is 0.96:0.02:0.02), a precipitant aqueous solution with a concentration of 8 mol / L (composed of LiOH and NaCO3 with a molar ratio of 1:1) and a complexing agent aqueous solution with a concentration of 5 mol / L (composed of sodium oxalate and tartaric acid with a molar ratio of 1:1) are added in parallel, and a coprecipitation reaction is carried out for 7 h. During the coprecipitation reaction, the temperature is controlled at 45 °C, the pH is 12.7, and the complexing agent concentration is 0.9 mol / L to obtain a solution containing crystal nuclei; wherein, the addition flow rate of the metal salt aqueous solution is the first flow rate;

[0080] (2) Transition period: In a protective atmosphere (composed of nitrogen and argon with a volume ratio of 1:1), an aqueous metal salt solution with a total metal ion concentration of 1.7 mol / L (the molar ratio of Ni ions, Mn ions, and Co ions is 0.96:0.02:0.02), an aqueous precipitant solution with a concentration of 8 mol / L (composed of LiOH and NaCO3 with a molar ratio of 1:1), and an aqueous complexing agent solution with a concentration of 5 mol / L (composed of sodium oxalate and tartaric acid with a molar ratio of 1:1) are added to the solution containing crystal nuclei obtained in step (1) in a co-current manner to carry out a coprecipitation reaction. During the coprecipitation reaction, the temperature is controlled at 45 °C, the concentration of the complexing agent is 0.9 mol / L, and the pH is controlled to decrease to 8.7 at a rate of 0.2 per hour. After the pH decreases to 8.7 in the coprecipitation reaction, the transition period ends, and a solution containing transitional crystal nuclei is obtained; wherein, the addition flow rate of the aqueous metal salt solution is the second flow rate;

[0081] (3) Growth period: In a protective atmosphere (composed of nitrogen and argon with a volume ratio of 1:1), an aqueous metal salt solution with a total metal ion concentration of 1.7 mol / L (the molar ratio of Ni ions, Mn ions, and Co ions is 0.96:0.02:0.02), an aqueous precipitant solution with a concentration of 8 mol / L (composed of LiOH and NaCO3 with a molar ratio of 1:1), and an aqueous complexing agent solution with a concentration of 5 mol / L (composed of sodium oxalate and tartaric acid with a molar ratio of 1:1) are added to the solution containing transitional crystal nuclei obtained in step (2) in a co-current manner, and a coprecipitation reaction is carried out at 45 °C. During the coprecipitation reaction, the pH is controlled at 8.7 and the concentration of the complexing agent is 0.9 mol / L to obtain an ultra-small particle high-nickel precursor with a D50 particle size of 2.0 μm; wherein, the addition flow rate of the aqueous metal salt solution is the third flow rate;

[0082] The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 2:0.1:1;

[0083] The first flow rate in step (1) is 60 L / h, the second flow rate in step (2) is 3 L / h, and the third flow rate in step (3) is 30 L / h.

[0084] This example also provides an ultra-small particle high-nickel precursor, and the ultra-small particle high-nickel precursor is obtained by the preparation method provided in this example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2.

[0085] Example 2

[0086] This embodiment provides a method for preparing an ultra-small particle high-nickel precursor, and the preparation method includes:

[0087] (1) Nucleation stage: In a nitrogen atmosphere, into a reaction bottom solution with a pH of 11 (the pH is adjusted by adding sodium hydroxide) and an ammonia concentration of 1 mol / L (the solvent of the reaction bottom solution is water), a metal salt aqueous solution with a total metal ion concentration of 3 mol / L (the molar ratio of Ni ions, Mn ions, and Co ions is 0.96:0.02:0.02), a sodium hydroxide aqueous solution with a concentration of 1 mol / L, and ammonia water with a concentration of 10 mol / L are added in parallel flow, and a coprecipitation reaction is carried out for 12 h. During the coprecipitation reaction, the temperature is controlled at 20 °C, the pH is 11, and the ammonia concentration is 1 mol / L to obtain a solution containing crystal nuclei; wherein, the addition flow rate of the metal salt aqueous solution is the first flow rate;

[0088] (2) Transition stage: In a nitrogen atmosphere, into the solution containing crystal nuclei obtained in step (1), a metal salt solution with a total metal ion concentration of 3 mol / L (the molar ratio of Ni ions, Mn ions, and Co ions is 0.96:0.02:0.02), a sodium hydroxide aqueous solution with a concentration of 1 mol / L, and ammonia water with a concentration of 10 mol / L are added in parallel flow, and a coprecipitation reaction is carried out. During the coprecipitation reaction, the temperature is controlled at 20 °C and the ammonia concentration is 1 mol / L, and the pH is controlled to decrease to 8 at a rate of 0.5 per hour. After the pH decreases to 8 in the coprecipitation reaction, the transition stage ends, and a solution containing transitional crystal nuclei is obtained; wherein, the addition flow rate of the metal salt aqueous solution is the second flow rate;

[0089] (3) Growth stage: In a nitrogen atmosphere, into the solution containing transitional crystal nuclei obtained in step (2), a metal salt solution with a total metal ion concentration of 3 mol / L (the molar ratio of Ni ions, Mn ions, and Co ions is 0.96:0.02:0.02), a sodium hydroxide aqueous solution with a concentration of 1 mol / L, and ammonia water with a concentration of 10 mol / L are added in parallel flow, and a coprecipitation reaction is carried out at 20 °C. During the coprecipitation reaction, the pH is controlled at 8 and the ammonia concentration is 1 mol / L to obtain an ultra-small particle high-nickel precursor with a D50 particle size of 1.6 μm; wherein, the addition flow rate of the metal salt aqueous solution is the third flow rate;

[0090] The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 1.5:0.05:1;

[0091] The first flow rate in step (1) is 15 L / h, the second flow rate in step (2) is 0.5 L / h, and the third flow rate in step (3) is 10 L / h.

[0092] This embodiment also provides a super-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the super-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2.

[0093] Example 3

[0094] This embodiment provides a preparation method of a super-small particle high-nickel precursor, and the preparation method includes:

[0095] (1) Nucleation stage: In an argon atmosphere, into a reaction bottom solution with a pH of 13 (the pH is adjusted by adding potassium hydroxide) and an ammonium sulfate concentration of 0.2 mol / L (the solvent of the reaction bottom solution is water), an aqueous metal salt solution with a total metal ion concentration of 1 mol / L (the molar ratio of Ni ions, Mn ions to Co ions is 0.96:0.02:0.02), an aqueous potassium hydroxide solution with a concentration of 10 mol / L and an aqueous ammonium sulfate solution with a concentration of 1 mol / L are added in parallel flow, and a coprecipitation reaction is carried out for 6 h. During the coprecipitation reaction process, the temperature is controlled at 60 °C, the pH is 13, and the ammonium sulfate concentration is 0.2 mol / L to obtain a solution containing crystal nuclei; wherein, the addition flow rate of the aqueous metal salt solution is the first flow rate;

[0096] (2) Transition stage: In an argon atmosphere, into the solution containing crystal nuclei obtained in step (1), an aqueous metal salt solution with a total metal ion concentration of 1 mol / L (the molar ratio of Ni ions, Mn ions to Co ions is 0.96:0.02:0.02), an aqueous potassium hydroxide solution with a concentration of 10 mol / L and an aqueous ammonium sulfate solution with a concentration of 1 mol / L are added in parallel flow, and a coprecipitation reaction is carried out. During the coprecipitation reaction process, the temperature is controlled at 60 °C, the ammonium sulfate concentration is 0.2 mol / L, and the pH is controlled to decrease to 10 at a rate of 0.1 per hour. After the pH decreases to 10 in the coprecipitation reaction, the transition stage ends, and a solution containing transition crystal nuclei is obtained; wherein, the addition flow rate of the aqueous metal salt solution is the second flow rate;

[0097] (3) Growth period: In a protective atmosphere, an aqueous metal salt solution with a total metal ion concentration of 1 mol / L (the molar ratio of Ni ions, Mn ions, Co ions, and Al ions is 0.96:0.15:0.15:0.1), an aqueous potassium hydroxide solution with a concentration of 10 mol / L, and an aqueous ammonium sulfate solution with a concentration of 1 mol / L are added in a co-current manner to the solution containing transitional crystal nuclei obtained in step (2). A co-precipitation reaction is carried out at 60 °C. During the co-precipitation reaction process, the pH is controlled at 10 and the ammonium sulfate concentration is controlled at 0.07 mol / L to obtain an ultra-small particle high-nickel precursor with a D50 particle size of 2.5 μm. Among them, the addition flow rate of the aqueous metal salt solution is the third flow rate;

[0098] The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 2.5:0.15:1;

[0099] The first flow rate in step (1) is 250 L / h, the second flow rate in step (2) is 15 L / h, and the third flow rate in step (3) is 100 L / h.

[0100] This embodiment also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2.

[0101] Example 4

[0102] This embodiment provides a preparation method of an ultra-small particle high-nickel precursor. Except that the aqueous metal salt solutions in step (1), step (2), and step (3) are all replaced with an aqueous metal salt solution with a total metal ion concentration of 1.7 mol / L, which is composed of Ni ions, Mn ions, Co ions, and Al ions with a molar ratio of 0.96:0.015:0.015:0.1, the rest are the same as those in Example 1.

[0103] This embodiment also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.015 Mn 0.015 Al 0.01 (OH)2.

[0104] Example 5

[0105] This embodiment provides a method for preparing ultra-small particle high-nickel precursor. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2) and the third flow rate in step (3) is 1.2:0.1:1;

[0106] The first flow rate in step (1) is 36 L / h, the second flow rate in step (2) is 3 L / h, and the third flow rate in step (3) is 30 L / h. The rest are the same as those in Embodiment 1.

[0107] This embodiment also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2.

[0108] Embodiment 6

[0109] This embodiment provides a method for preparing ultra-small particle high-nickel precursor. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2) and the third flow rate in step (3) is 3:0.1:1;

[0110] The first flow rate in step (1) is 90 L / h, the second flow rate in step (2) is 3 L / h, and the third flow rate in step (3) is 30 L / h. The rest are the same as those in Embodiment 1.

[0111] This embodiment also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2.

[0112] Embodiment 7

[0113] This embodiment provides a method for preparing ultra-small particle high-nickel precursor. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2) and the third flow rate in step (3) is 2:0.02:1;

[0114] The first flow rate in step (1) is 60 L / h, the second flow rate in step (2) is 0.6 L / h, and the third flow rate in step (3) is 30 L / h. The rest are the same as those in Embodiment 1.

[0115] This embodiment also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this embodiment; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02Mn 0.02 (OH)2。

[0116] Example 8

[0117] This example provides a method for preparing ultra-small particle high-nickel precursors. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 2:0.2:1;

[0118] The first flow rate in step (1) is 60 L / h, the second flow rate in step (2) is 6 L / h, and the third flow rate in step (3) is 30 L / h. The rest are the same as in Example 1.

[0119] This example also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.02 Mn 0.02 (OH)2。

[0120] Example 9

[0121] This example provides a method for preparing ultra-small particle high-nickel precursors. Except that the transition period ends after the pH in the co-precipitation reaction in step (2) is reduced to 7.5, and the pH is controlled at 7.5 during the co-precipitation reaction in step (3), the rest are the same as in Example 1.

[0122] This example also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.2 Mn 0.2 (OH)2。

[0123] Example 10

[0124] This example provides a method for preparing ultra-small particle high-nickel precursors. Except that the transition period ends after the pH in the co-precipitation reaction in step (2) is reduced to 11, and the pH is controlled at 11 during the co-precipitation reaction in step (3), the rest are the same as in Example 1.

[0125] This example also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.2 Mn 0.2 (OH)2。

[0126] Comparative Example 1

[0127] This comparative example provides a method for preparing an ultra-small particle high-nickel precursor. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 2:2:1;

[0128] the first flow rate in step (1) is 60 L / h, the second flow rate in step (2) is 60 L / h, and the third flow rate in step (3) is 30 L / h, the rest are the same as in Example 1.

[0129] This comparative example also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this comparative example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.2 Mn 0.2 (OH)2.

[0130] Comparative Example 2

[0131] This comparative example provides a method for preparing an ultra-small particle high-nickel precursor. Except that the ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is 1:1:1;

[0132] the first flow rate in step (1) is 30 L / h, the second flow rate in step (2) is 30 L / h, and the third flow rate in step (3) is 30 L / h, the rest are the same as in Example 1.

[0133] This comparative example also provides an ultra-small particle high-nickel precursor, which is obtained by the preparation method provided in this comparative example; the chemical formula of the ultra-small particle high-nickel precursor includes Ni 0.96 Co 0.2 Mn 0.2 (OH)2.

[0134] The tap density of the ultra-small particle high-nickel precursor provided in the examples and comparative examples was measured using a tap density meter, and the tap density of the ultra-small particle high-nickel precursor obtained by the measurement is shown in Table 1.

[0135] The specific surface area of the ultra-small particle high-nickel precursor provided in the examples and comparative examples was measured using a specific surface area analyzer, and the specific surface area of the ultra-small particle high-nickel precursor obtained by the measurement is shown in Table 1.

[0136] The particle size of the ultra-small particle high-nickel precursor provided in the examples and comparative examples was tested using a laser particle size analyzer. The D10 particle size, D50 particle size, and D90 particle size of the ultra-small particle high-nickel precursor are shown in Table 2. The SPAN value of the particle size distribution was calculated as shown in Table 2, and the calculation formula is: SPAN value of particle size distribution = (D90 particle size - D10 particle size) / D50 particle size.

[0137] The ultra-small particle high-nickel precursor provided in the examples and comparative examples was mixed with lithium hydroxide to obtain a mixture, and the obtained mixture was kept at 900 °C for 12 h to obtain a small-size single-crystal cathode material; the obtained small-size single-crystal cathode material was used to prepare a CR2025-type button cell (it is well known to those skilled in the art that in order to conveniently and quickly test the performance of the small-size single-crystal cathode material, a CR2025-type button cell is usually prepared for testing. When the performance of the CR2025-type button cell obtained by testing is excellent, the solid-state battery prepared from the small-size single-crystal cathode material also has excellent performance).

[0138] Production process of the cathode sheet: First, the synthesized small-size single-crystal cathode material was made into a slurry and coated. The cathode material, Super P, and polyvinylidene fluoride (PVDF) were mixed evenly in N-methylpyrrolidone according to a mass ratio of 8:1:1 to make a slurry, and the slurry was coated on the aluminum foil with a gap of 150 - 250 μm on a coater. Then, the aluminum foil was placed in a vacuum drying oven and vacuum-dried at 120 °C for 12 h. After cooling, the aluminum foil was punched into a cathode sheet with a diameter of 14 mm using a cathode material punching machine. The punched cathode sheet was subjected to double-roll rolling to obtain the cathode sheet for assembling the battery.

[0139] All electrochemical performance tests were carried out on CR2025-type button cells. The CR2025 button cells were assembled in an oxygen-free and water-vapor-free environment in a glove box. The obtained cathode sheet was placed in the CR2025 button cell case, 0.2 mL of lithium hexafluorophosphate electrolyte was dropped in, a separator was covered, 0.1 mL of electrolyte was dropped at the exact center of the separator on the cathode sheet, and then the lithium sheet, current collector, and spring washer were placed on the exact center of the separator in sequence from bottom to top. Finally, the CR2025 button cell cover was covered, and the button cell was sealed with a button cell sealer; the sealed CR2025-type button cells were horizontally static for 12 h and then subjected to electrochemical performance tests. The first-cycle discharge capacity of the material (the test conditions for the first-cycle discharge capacity were 0.1C 2.7 - 4.3V) and the capacity retention rate after 100 cycles at 1C are shown in Table 3.

[0140] Table 1

[0141]

[0142] Table 2

[0143]

[0144]

[0145] Table 3

[0146]

[0147]

[0148] It can be obtained from Tables 1 to 3 that:

[0149] (1) The ultra-small particle high-nickel precursor prepared by the preparation methods provided in Examples 1 to 4 has a relatively high tap density, a relatively small specific surface area, a relatively small particle size, and a relatively good particle size concentration; the solid-state battery prepared from the obtained ultra-small particle high-nickel precursor has a relatively high first-cycle capacity and excellent cycle stability;

[0150] (2) By comparing Example 1 with Examples 5 to 8, it can be seen that the ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) in the present invention affects the electrochemical performance of the ultra-small particle high-nickel precursor and the cathode material; when the ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is (1.5 to 2.5):(0.05 to 0.15):1, both the ultra-small particle high-nickel precursor and the small-size single-crystal cathode material exhibit relatively good performance. This is because a relatively small first flow rate will result in insufficient nucleation in the early stage, too fast growth in the middle stage, fewer nuclei, and easy occurrence of small particles due to mismatched flow rates in the later stage, leading to non-concentrated particle distribution and a mixture of single crystals and polycrystals during the sintering stage, ultimately affecting the electrochemical stability of the cathode material; while an overly large first flow rate will cause particle agglomeration during the nucleation period, resulting in non-concentrated particle distribution and ultimately affecting the electrochemical stability of the cathode material; an overly small second flow rate will lead to growth stagnation during the transition period, and the particles still maintain highly active nuclei and enter the growth period, resulting in particle agglomeration; an overly large second flow rate will cause particle agglomeration during the process of the particles transitioning from the nucleation period to the growth period, resulting in non-concentrated particle distribution, and ultimately affecting the electrochemical performance of the cathode material;

[0151] (3) By comparing Example 1 with Examples 9 and 10, it can be seen that the end pH after the pH reduction in step (2) and the pH during the coprecipitation reaction in step (3) in the present invention affect the performance of the ultra-small particle high-nickel precursor and the solid-state battery; when the end pH after the pH reduction in step (2) and the pH during the coprecipitation reaction in step (3) are 8 to 10, the small-size single-crystal cathode material exhibits relatively good performance. This is because the pH can regulate the thickness of the primary crystal grains to facilitate single-crystal sintering. The transition period and the growth period are both carried out at a low pH, and a precursor with relatively thick primary crystal grains can be obtained. However, if the pH is too low, the precursor will dissolve and the performance indicators will deteriorate;

[0152] (4) By comparing Example 1 with Comparative Examples 1-2, it can be seen that in the present invention, in order to obtain an ultra-small particle high-nickel precursor with good particle size concentration, a preparation method of an ultra-small particle high-nickel precursor is provided; in the preparation method provided by the present invention, the second flow rate described in step (2) < the third flow rate described in step (3) < the first flow rate described in step (1); that is, by controlling the addition flow rate of the metal salt solution in the nucleation period, sufficient crystal nuclei are formed at a relatively large flow rate; then, by controlling the addition flow rate of the metal salt solution in the transition period, the growth of the precursor in growth mode 1 (the particles absorb solutes and continuously grow) is inhibited; then, by controlling the addition flow rate of the metal salt solution in the growth period, while ensuring the preparation efficiency, the growth of the precursor in growth mode 2 (the larger particles continuously grow by absorbing the smaller particles) is promoted; in summary, the method described in the present application inhibits growth mode 1 while promoting growth mode 2, and obtains an ultra-small particle high-nickel precursor with good particle size concentration; moreover, both the transition period and the growth period in the preparation method provided by the present invention are carried out at a low pH, and the primary grains tend to grow in a mode of oriented attachment, so as to obtain an ultra-small particle high-nickel precursor with thick primary grains, which is convenient for sintering single crystals.

[0153] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of an ultra-small particle high-nickel precursor, characterized in that, The preparation method includes: (1) Nucleation stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added in parallel to the reaction bottom liquid for coprecipitation reaction to obtain a solution containing crystal nuclei; the feeding flow rate of the metal salt solution is the first flow rate; (2) Transition stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added in parallel to the solution containing crystal nuclei obtained in step (1) for coprecipitation reaction, and the pH is controlled to decrease during the coprecipitation reaction to obtain a solution containing transitional crystal nuclei; the feeding flow rate of the metal salt solution is the second flow rate; (3) Growth stage: A metal salt solution, a precipitant solution, and a complexing agent solution are added in parallel to the solution containing transitional crystal nuclei obtained in step (2) for coprecipitation reaction to obtain an ultra-small particle high-nickel precursor; the feeding flow rate of the metal salt solution is the third flow rate; The second flow rate in step (2) < the third flow rate in step (3) < the first flow rate in step (1).

2. The preparation method according to claim 1, characterized in that, The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is (1.5 - 2.5):(0.05 - 0.15):

1.

3. The preparation method according to claim 1 or 2, characterized in that The first flow rate in step (1) is 4 - 200 L / h; Preferably, the second flow rate in step (2) is 0.2 - 10 L / h; Preferably, the third flow rate in step (3) is 2 - 100 L / h.

4. The preparation method according to claim 1, wherein, The pH of the reaction bottom liquid in step (1) is 11 - 13, and the complexing agent concentration is 0.2 - 1 mol / L; Preferably, the coprecipitation reactions in step (1), step (2), and step (3) are all carried out in a protective atmosphere; Preferably, the temperatures of the coprecipitation reactions in step (1), step (2), and step (3) are independently 20 - 95 °C; Preferably, the total concentration of metal ions in the metal salt solution in step (1), step (2), and step (3) is independently 1 - 3 mol / L; Preferably, the total concentration of metal ions in the metal salt solution in step (1), step (2), and step (3) is the same; Preferably, the concentration of the precipitant in the precipitant solution in step (1), step (2), and step (3) is independently 1 - 10 mol / L; Preferably, the concentration of the complexing agent in the complexing agent solution in step (1), step (2), and step (3) is independently 1 - 10 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that, During the coprecipitation reaction in step (1), the pH is controlled to be 11 - 13, the complexing agent concentration is 0.2 - 1 mol / L, and the time is 6 - 12 h; Preferably, during the coprecipitation reaction in step (2), the pH is controlled to decrease at a rate of 0.1 - 0.5 per hour to 8 - 10, and the complexing agent concentration is controlled to be 0.2 - 1 mol / L; Preferably, the transition stage ends after the pH in the coprecipitation reaction in step (2) decreases to 8 - 10; Preferably, during the coprecipitation reaction in step (3), the pH is controlled to be 8 - 10, and the complexing agent concentration is 0.07 - 1 mol / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method includes: (1) Nucleation stage: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1 - 3 mol / L, a precipitant solution with a concentration of 1 - 10 mol / L, and a complexing agent solution with a concentration of 1 - 10 mol / L are added in parallel to a reaction bottom solution with a pH of 11 - 13 and a complexing agent concentration of 0.2 - 1 mol / L, and a coprecipitation reaction is carried out for 6 - 12 h. During the coprecipitation reaction, the temperature is controlled at 20 - 95°C, the pH is 11 - 13, and the complexing agent concentration is 0.2 - 1 mol / L to obtain a solution containing crystal nuclei; wherein, the addition flow rate of the metal salt solution is the first flow rate; (2) Transition stage: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1 - 3 mol / L, a precipitant solution with a concentration of 1 - 10 mol / L, and a complexing agent solution with a concentration of 1 - 10 mol / L are added in parallel to the solution containing crystal nuclei obtained in step (1), and a coprecipitation reaction is carried out. During the coprecipitation reaction, the temperature is controlled at 20 - 95°C and the complexing agent concentration is 0.2 - 1 mol / L, and the pH is controlled to decrease at a rate of 0.1 - 0.5 per hour to 8 - 10. After the pH in the coprecipitation reaction decreases to 8 - 10, the transition stage ends, and a solution containing transitional crystal nuclei is obtained; wherein, the addition flow rate of the metal salt solution is the second flow rate; (3) Growth stage: In a protective atmosphere, a metal salt solution with a total metal ion concentration of 1 - 3 mol / L, a precipitant solution with a concentration of 1 - 10 mol / L, and a complexing agent solution with a concentration of 1 - 10 mol / L are added in parallel to the solution containing transitional crystal nuclei obtained in step (2), and a coprecipitation reaction is carried out at 20 - 95°C. During the coprecipitation reaction, the pH is controlled at 8 - 10 and the complexing agent concentration is 0.07 - 1 mol / L to obtain an ultra-small particle high-nickel precursor; wherein, the addition flow rate of the metal salt solution is the third flow rate; The ratio of the first flow rate in step (1), the second flow rate in step (2), and the third flow rate in step (3) is (1.5 - 2.5):(0.05 - 0.15):1; The first flow rate in step (1) is 4 - 200 L / h, the second flow rate in step (2) is 0.2 - 10 L / h, and the third flow rate in step (3) is 2 - 100 L / h.

7. A super-small particle high-nickel precursor, characterized in that, The ultra-small particle high-nickel precursor is obtained by the preparation method according to any one of claims 1 - 6.

8. The ultra-small particle high-nickel precursor according to claim 7, characterized in that, The D50 particle size of the ultra-small particle high-nickel precursor is 1.5 - 2.5 μm, and the particle size distribution width SPAN value is 0.5 - 0.7; Preferably, the tap density of the ultra-small particle high-nickel precursor is 1.7-2.0 g / cm 3 ; Preferably, the specific surface area of the ultra-small particle high-nickel precursor is 5 to 15 m 2 / g.

9. The ultra-small particle high-nickel precursor according to claim 7 or 8, characterized in that, The chemical formula of the ultra-small particle high-nickel precursor includes Ni a Co b Mn c Al d (OH)2; where a + b + c + d = 1, 0.8 ≤ a < 0.98, 0 ≤ b < 0.1, 0 ≤ c < 0.1 and 0 ≤ d < 0.

1.

10. A small-sized single crystal, characterized in that, The small-sized single crystal is obtained by lithium doping and sintering of the ultra-small particle high-nickel precursor according to any one of claims 7 - 9.

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