Small-particle-size ultra-high-nickel multi-element positive electrode material precursor and preparation method thereof

Abstract

The application provides a small-particle-size super-high-nickel multi-element positive electrode material precursor and a preparation method thereof, and relates to the technical field of lithium ion battery positive electrode materials.The traditional preparation method for maintaining a constant pH value of a reaction system is improved to a pH value gradient self-decrease after the bottom liquid reaches a preset pH value and ammonia concentration, so that the small-particle-size precursor is slowly transitioned from a nucleation process to a growth process, the difference between the nucleation and growth environments is reduced, the coagulation and growth process is shortened, the sphericity and density of the precursor are improved, meanwhile, the failure of a pH meter caused by the blockage of a diaphragm hole under a high solid content system is avoided, the pH value of the reaction system is stabilized, the pH meter does not need to be isolated and cleaned during the reaction process, and the material preparation cost is greatly reduced.The small-particle-size super-high-nickel multi-element positive electrode material precursor prepared by the application has a clear primary particle layered structure, a dense secondary particle, excellent sphericity, a particle size span less than 1.2, an average particle size D 50 of 2-6 mu m, and the primary particle morphology and secondary particle size can be directionally regulated.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material technology, and in particular to a small-particle-size ultra-high nickel multi-element cathode material precursor and its preparation method. Background Technology

[0002] LiNi, an ultra-high nickel ternary cathode material x Co y Mn 1-x-y Ultra-high nickel ternary cathode materials can be formed by removing, adding, and replacing elements based on O2 (x≥0.90). Therefore, ultra-high nickel ternary cathode materials are used as an example for explanation. Ultra-high nickel ternary cathode materials have high theoretical capacity (273mAh / g-285mAh / g) and actual capacity exceeding 220mAh / g, which will directly promote the improvement of battery system energy density. Moreover, the material has low cobalt content, which can minimize costs and promote the industrial application of the material.

[0003] Material preparation methods include co-precipitation, high-temperature solid-state method, sol-gel method, hydrothermal method, and spray pyrolysis method. From a practical production perspective, to improve material yield and batch consistency, the co-precipitation method is often used in laboratories and industry to prepare Ni precursors for ultra-high nickel ternary cathode materials. x Co y Mn 1-x-y (OH)₂ (x≥0.90) was then added, followed by sintering with lithium salt in a pure oxygen atmosphere. This process resulted in a topological transformation of the precursor's layered structure, yielding an ultra-high nickel ternary cathode material. The crystallinity, grain morphology, particle size, and sphericity of the precursor material directly determine the performance of the ternary cathode material. However, the high nickel, low cobalt, and low manganese composition makes the precursor extremely sensitive to changes in the co-precipitation environment. Different chemical compositions, and even precursors with different particle sizes but the same chemical composition, exhibit significant differences in growth parameters, easily resulting in precursors with poor crystallinity, poor sphericity, and porous structure. Therefore, optimizing the co-precipitation reaction parameters is crucial for preparing precursor materials with excellent physicochemical properties.

[0004] Ultra-high nickel ternary cathode materials suffer from rapid performance degradation due to severe surface and interface structural degradation. Single crystallization is a crucial method to improve the stability of the bulk and interfacial structures of the material. It can effectively alleviate stress concentration and crack initiation caused by anisotropic lattice changes during lithium storage, suppress electrolyte penetration into the bulk phase that leads to further surface and interface structural degradation, and significantly improve the capacity retention rate of the material. Studies have shown that single-crystal materials and small-particle-size polycrystalline materials have advantages over conventional polycrystalline materials in terms of compatibility with solid-state battery systems, gas generation, and heat generation.

[0005] Single-crystal materials and small-particle-size polycrystalline materials evolve from small-particle-size precursors through different sintering processes. Preparing small-particle-size ultra-high nickel ternary cathode material precursors requires precise control of the critical equilibrium points of nucleation and growth thermodynamics and kinetics. This involves controlling the secondary particle agglomeration growth size in the early stages of the reaction, followed by rapidly increasing the solid content to end the agglomeration growth process and shift to independent nucleation and surface epitaxy and adsorption growth. However, this process can cause blockage of the diaphragm pores (rings) of the online pH meter, leading to pH instability in the system. Due to the high nickel and low manganese composition of the ultra-high nickel small-particle-size precursor, it is extremely sensitive to changes in the co-precipitation reaction environment during growth. As the precursor particle size increases, the optimal co-precipitation parameters are not constant, and the supersaturation of the precipitate needs to be gradually reduced to meet the requirements of epitaxial growth. Therefore, the traditional method of using constant co-precipitation parameters easily results in poor crystallinity and porous precursors. Furthermore, the traditional method of distinguishing between nucleation and growth process parameters easily causes rapid agglomeration of crystal nuclei in the ultra-high nickel small-particle-size precursor, resulting in precursor particle agglomeration and poor sphericity. Summary of the Invention

[0006] In view of this, the present invention provides a small-particle-size ultra-high nickel multi-element cathode material precursor and its preparation method. The present invention uses a pH self-driven co-precipitation method to prepare the small-particle-size ultra-high nickel multi-element cathode material precursor. During the preparation process, the pH value is slowly reduced, which gradually reduces the supersaturation of the precipitate, and slowly transitions it from the nucleation state to the growth state. This reduces fluctuations in the reaction environment and improves the crystallinity, tap density, and sphericity of the material.

[0007] This invention is achieved using the following technical solution:

[0008] A small-particle-size ultra-high nickel multi-element cathode material precursor, characterized in that the chemical formula of the small-particle-size ultra-high nickel multi-element cathode material precursor is as follows:

[0009] Ni a B b C c D d (OH)2,

[0010] Wherein, B is Fe or Co, C is Mn, and D is one of Al, Na, Mg, K, Ca, Ti, Nb, and Zr;

[0011] 90at.%≤a≤98at.%, 0.1at.%≤b≤10at.%, 0.1at.%≤c≤10at.%, 0at.%≤d≤10at.%, a+b+c+d=1.

[0012] Another objective of this invention is to provide a method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor, comprising the following steps:

[0013] (1) Weigh out nickel salt, B salt, C salt and D salt in proportion, and dissolve them in water to prepare a mixed metal salt solution;

[0014] (2) Add ammonia solution to the reactor as the base liquid, introduce nitrogen gas, set the stirrer speed to 800 r / min-1200 r / min, stir evenly and heat to 50℃-60℃, add alkaline solution to adjust the pH value of the base liquid to 11.0-11.8, and then add the mixed metal salt solution and complexing agent at the same time to carry out precipitation reaction. During the reaction, adjust the feed rate of the alkaline solution and the mixed metal salt solution so that the molar ratio of hydroxide ions to salt entering the reactor per unit time is 2:1. Finally, filter to obtain the precipitate.

[0015] (3) Wash the precipitate obtained in step (2) with deionized water and filter it until the pH value of the filtrate is neutral. Dry it at 90℃-150℃ for 12h-24h, and then sieve it to remove magnetism to obtain the small particle size ultra-high nickel multi-element cathode material precursor.

[0016] Furthermore, the nickel salt includes nickel sulfate, nickel carbonate, nickel oxalate, nickel acetate, and their hydrates.

[0017] Furthermore, the B salt is ferric sulfate, ferric nitrate, ferric chloride, ferrous carbonate, ferric citrate, cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and their hydrates.

[0018] Furthermore, the C salt is manganese sulfate, manganese nitrate, manganese carbonate, manganese chloride, or their hydrates.

[0019] Furthermore, the D salt is a sulfate, carbonate, nitrate, oxalate, or hydrate containing Al, Na, Mg, K, Ca, Ti, Nb, and Zr elements.

[0020] Preferably, the molar concentration of the mixed metal salt solution is 1 mol / L to 4 mol / L.

[0021] Preferably, the base liquid is an ammonia solution with a molar concentration of 0.3 mol / L to 1.1 mol / L.

[0022] Preferably, the volume of the bottom liquid accounts for 1 / 3 to 1 / 2 of the total volume of the reactor.

[0023] Preferably, the alkaline solution is a NaOH solution with a molar concentration of 4 mol / L to 8 mol / L.

[0024] Preferably, the complexing agent is an aqueous ammonia solution with a molar concentration of 4 mol / L to 8 mol / L.

[0025] Furthermore, before the precipitation reaction in step (2), the mixed metal salt solution, the base solution (ammonia solution), and the alkaline solution (NaOH solution) need to be filtered to remove undissolved solid impurities.

[0026] Preferably, the feed rate of the mixed metal salt solution is 0.5 mL / min to 20.0 mL / min.

[0027] Preferably, the feed rate of the alkaline solution is 0.3 mL / min to 40.0 mL / min.

[0028] Preferably, the feeding rate of the complexing agent is 0.2 mL / min to 25.0 mL / min.

[0029] Preferably, the ammonia concentration is maintained at 0.3 mol / L-1.1 mol / L during the precipitation reaction.

[0030] This invention utilizes a pH-driven co-precipitation method to prepare small-particle-size ultra-high nickel ternary cathode material precursors. By adjusting the bottom solution to a preset pH value and ammonia concentration, and determining the salt feed rate, the invention then adjusts the alkaline solution feed rate to ensure that the amount of hydroxide ions entering the reactor per unit time is exactly twice the amount of salt, satisfying the precursor chemical coefficient ratio. This ensures that the salt and alkali entering the reaction system per unit time are completely precipitated. The complexing agent feed rate is then adjusted to maintain a constant ammonia concentration throughout the reaction process, ultimately completing the nucleation and growth of the small-particle-size ultra-high nickel ternary cathode material precursor. The primary particle morphology and secondary particle size are dynamically adjusted through the bottom solution pH value and ammonia concentration.

[0031] The precursor of the small-particle-size ultra-high nickel multi-element cathode material of this invention has a distinct primary particle layer structure, dense secondary particles with excellent sphericity, concentrated particle size distribution, span of less than 1.2, and an average particle size D50 of 2μm-6μm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention uses a pH-driven co-precipitation method to prepare small-particle-size ultra-high nickel multi-element cathode material precursors. During the preparation process, the pH value is slowly reduced, which gradually reduces the supersaturation of the precipitate and slowly transitions it from the nucleation state to the growth state. This reduces fluctuations in the reaction environment and is beneficial to improving the crystallinity, tap density and sphericity of the material.

[0034] 2. Small-particle-size precursors require a high solid content in the reaction system to reduce the precursor particle size growth rate. However, a high solid content system can easily cause the pH meter diaphragm pores (rings) to become clogged, leading to pH meter failure and instability of the reaction system pH value. This invention only needs to control the pH value of the base liquid before the reaction starts so that the pH value reaches the preset value. After the mixed metal salt solution and complexing agent are introduced, it is not necessary to maintain a constant pH value. When the alkaline solution is fed, the pH meter automatically controls the constant rotation speed, thus avoiding pH instability of the reaction system caused by pH meter clogging and failure under a high solid content system.

[0035] 3. Traditional methods require the online pH meter to be isolated and cleaned during the reaction process to maintain a constant pH value in the reaction system. This invention eliminates the need to clean the pH meter during the reaction process, which can significantly reduce the material preparation cost. Attached Figure Description

[0036] Figure 1 Small-particle-size Ni prepared in Example 1 of the present invention 0.92 Co 0.04 Mn 0.04 Scanning electron microscopy (SEM) images of the (OH)2 precursor;

[0037] Figure 2 Small-particle-size Ni prepared in Example 1 of the present invention 0.92 Co 0.04 Mn 0.04 Particle size distribution diagram of (OH)2 precursor;

[0038] Figure 3 Small-particle-size Ni prepared in Example 2 of this invention 0.92 Co 0.04 Mn 0.04 SEM images of (OH)2 precursor;

[0039] Figure 4 Small-particle-size Ni prepared in Example 2 of this invention 0.92 Co 0.04 Mn 0.04 Particle size distribution diagram of (OH)2 precursor;

[0040] Figure 5 Small-particle-size Ni prepared in Example 3 of this invention 0.92 Co 0.04 Mn 0.04 SEM images of (OH)2 precursor;

[0041] Figure 6 Small-particle-size Ni prepared in Example 3 of this invention 0.92 Co 0.04 Mn 0.04 Particle size distribution diagram of (OH)2 precursor;

[0042] Figure 7 Small-particle-size Ni prepared in Example 3 of this invention 0.92 Co 0.04 Mn 0.04 X-ray diffraction (XRD) pattern of (OH)2 precursor;

[0043] Figure 8 Small-particle-size Ni prepared in Example 4 of this invention 0.950 Fe 0.025 Mn 0.025 SEM images of (OH)2 precursor;

[0044] Figure 9 Small-particle-size Ni prepared in Example 4 of this invention 0.950 Fe 0.025 Mn 0.025 Particle size distribution diagram of (OH)2 precursor;

[0045] Figure 10 Small-particle-size Ni prepared in Example 5 of this invention 0.90 Co 0.03 Mn 0.05 Nb 0.02 SEM images of (OH)2 precursor;

[0046] Figure 11 Small-particle-size Ni prepared in Example 5 of this invention 0.90 Co 0.03 Mn 0.05 Nb 0.02 Particle size distribution diagram of (OH)2 precursor.

[0047] Figure 12 Small-particle-size Ni prepared for Comparative Example 1 of this invention 0.92 Co 0.04 Mn 0.04 SEM images of (OH)2 precursor;

[0048] Figure 13 Small-particle-size Ni prepared for Comparative Example 1 of this invention 0.92 Co 0.04 Mn 0.04 Particle size distribution diagram of (OH)2 precursor. Detailed Implementation

[0049] The present invention will be further described below with reference to the embodiments.

[0050] Example 1

[0051] A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps:

[0052] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and manganese sulfate monohydrate (MnSO4·H2O) according to the metal molar ratio of 92:4:4, and prepare a 2 mol / L mixed metal salt solution. Use a 6 mol / L ammonia solution as a complexing agent and a 6 mol / L NaOH solution as an alkaline solution. Filter the above solution to remove solid impurities and precipitates.

[0053] (2) Add a 0.5 mol / L ammonia solution as the base liquid to the reactor. The volume of the base liquid is 1 / 3 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. Stir at 1000 r / min and then heat to 55℃. After the temperature stabilizes, turn on the alkali pump to add NaOH solution to adjust the pH of the base liquid to 11.2. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the feed rate of the alkali pump to 11.63 mL / min, the feed rate of the salt pump to 17.45 mL / min, and the feed rate of the ammonia pump to 5.88 mL / min. React for 30 h.

[0054] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 100°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.92 Co 0.04 Mn 0.04 (OH)2.

[0055] The small-particle-size Ni prepared in Example 1 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 1 As shown, when the concentration of the base solution is 0.5 mol / L, the precursor morphology after pH self-driven growth is spherical secondary particles assembled from layered plate-like primary particles. The material has excellent sphericity and high density.

[0056] The small-particle-size Ni prepared in Example 1 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 2 As shown, when the concentration of the base solution is 0.5 mol / L, the precursor particle size D50 after pH self-driven growth is 2.709 μm, the particle size span is 0.901, and there are no obvious impurity peaks except for the main peak in the particle size distribution diagram. The material has small particle size and concentrated distribution.

[0057] Example 2

[0058] A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps:

[0059] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and manganese sulfate monohydrate (MnSO4·H2O) according to the metal molar ratio of 92:4:4, and prepare a 2 mol / L mixed metal salt solution. Use a 6 mol / L ammonia solution as a complexing agent and a 6 mol / L NaOH solution as an alkaline solution. Filter the above solution to remove solid impurities and precipitates.

[0060] (2) Add a 0.3 mol / L ammonia solution as the base liquid to the reactor. The volume of the base liquid is 1 / 2 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. The stirring speed is 1000 r / min. Then heat the mixture to 55℃. After the temperature stabilizes, turn on the alkali pump to add NaOH solution to adjust the pH of the base liquid to 11.2. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the feed rate of the alkali pump to 11.63 mL / min, the feed rate of the salt pump to 17.45 mL / min, and the feed rate of the ammonia pump to 5.88 mL / min. React for 30 h.

[0061] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 100°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.92 Co 0.04 Mn 0.04 (OH)2.

[0062] The small-particle-size Ni prepared in Example 2 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 3 As shown, when the base solution concentration is 0.3 mol / L, the precursor morphology after pH self-driven growth is spherical secondary particles assembled from layered short sheet-like primary particles. The material has excellent sphericity and high density, and the size of the primary particles is reduced compared with the base solution concentration of 0.5 mol / L.

[0063] The small-particle-size Ni prepared in Example 2 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 4As shown, when the concentration of the base solution is 0.3 mol / L, the precursor particle size D50 after pH self-driven growth is 2.880 μm, and the particle size span is 1.032. Due to the low ammonia concentration in the base solution and the long duration of the nucleation process, small particle size impurities appear in the particle size distribution diagram, and the overall particle size distribution is relatively concentrated.

[0064] Example 3

[0065] A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps:

[0066] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and manganese sulfate monohydrate (MnSO4·H2O) according to the metal molar ratio of 92:4:4, and prepare a 2 mol / L mixed metal salt solution. Use a 6 mol / L ammonia solution as a complexing agent and a 6 mol / L NaOH solution as an alkaline solution. Filter the above solution to remove solid impurities and precipitates.

[0067] (2) Add a 1.1 mol / L ammonia solution as the base liquid to the reactor. The volume of the base liquid is 1 / 3 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. Stir at 1000 r / min and then heat to 55°C. After the temperature stabilizes, turn on the alkali pump to add NaOH solution to adjust the pH of the base liquid to 11.2. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the feed rate of the alkali pump to 11.63 mL / min, the feed rate of the salt pump to 17.45 mL / min, and the feed rate of the ammonia pump to 5.88 mL / min. React for 30 h.

[0068] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 100°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.92 Co 0.04 Mn 0.04 (OH)2.

[0069] The small-particle-size Ni prepared in Example 3 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 5 As shown, when the base solution concentration is 1.1 mol / L, the precursor morphology after pH self-driven growth is spherical secondary particles assembled from layered blocky primary particles. The material has excellent sphericity and high density, and the size of the primary particles is significantly larger compared with the base solution concentration of 0.5 mol / L.

[0070] The small-particle-size Ni prepared in Example 3 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 6 As shown, when the concentration of the base solution is 1.1 mol / L, the precursor particle size D50 after pH self-driven growth is 4.649 μm, and the particle size span is 0.580. The high ammonia concentration in the base solution significantly increases the size of the secondary particles. In the particle size distribution diagram, there are no other impurity peaks except for the main peak. The material has a small particle size and a concentrated distribution.

[0071] The small-particle-size Ni prepared in Example 3 0.92 Co 0.04 Mn 0.04 XRD tests were performed on the (OH)2 precursor (Rigaku SmartLab, Japan). The test patterns are shown below. Figure 7 As shown; the diffraction peaks in the XRD pattern basically correspond to Ni(OH)2, because Ni 2+ Ionic radius greater than Co 2+ and Mn 2+ Therefore, the precursor Ni 0.92 Co 0.04 Mn 0.04 The diffraction peaks of (OH)2 are shifted at higher angles relative to the Ni(OH)2 standard card, and the diffraction pattern is free of impurity peaks, indicating good crystallinity of the material.

[0072] Example 4

[0073] A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps:

[0074] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), ferrous sulfate heptahydrate (FeSO4·7H2O), and manganese sulfate monohydrate (MnSO4·H2O) according to the metal molar ratio of 95:2.5:2.5, and prepare a 2 mol / L mixed metal salt solution. Use a 6 mol / L ammonia solution as a complexing agent and a 6 mol / L NaOH solution as an alkaline solution. Filter the above solutions to remove solid impurities and precipitates.

[0075] (2) Add a 1.1 mol / L ammonia solution as the base liquid to the reactor. The volume of the base liquid is 1 / 3 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. Stir at 1000 r / min and then heat to 55°C. After the temperature stabilizes, turn on the alkali pump to add NaOH solution to adjust the pH of the base liquid to 11.4. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the feed rate of the alkali pump to 3.50 mL / min, the feed rate of the salt pump to 5.24 mL / min, and the feed rate of the ammonia pump to 1.55 mL / min. React for 30 h.

[0076] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 100°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.950 Fe 0.025 Mn 0.025 (OH)2.

[0077] The small-particle-size Ni prepared in Example 4 0.950 Fe 0.025 Mn 0.025 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 8 As shown, the precursor morphology after pH self-driven growth is spherical secondary particles assembled from layered spindle-shaped primary particles, with excellent sphericity and high density.

[0078] The small-particle-size Ni prepared in Example 4 0.950 Fe 0.025 Mn 0.025 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 9 As shown, the precursor particle size D50 after pH self-driven growth is 4.318 μm, the particle size span is 0.592, and there are no other impurity peaks except for the main peak in the particle size distribution diagram. The material has a small particle size and a concentrated distribution, indicating that the pH self-driven co-precipitation method is also suitable for the synthesis of small particle size ultra-high nickel cobalt-free ternary cathode material precursors.

[0079] Example 5

[0080] A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps:

[0081] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), manganese sulfate monohydrate (MnSO4·H2O), and ammonium oxalate hydrate of niobate (C4H4NNbO9·nH2O) according to the metal molar ratio of 90:3:5:2, and prepare a 1 mol / L mixed metal salt solution. Use a 4 mol / L ammonia solution as a complexing agent and a 4 mol / L NaOH solution as an alkaline solution. Filter the above solution to remove solid impurities and precipitates.

[0082] (2) Add a 0.8 mol / L ammonia solution as the base liquid to the reactor. The volume of the base liquid is 1 / 3 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. Stir at 800 r / min and then heat to 57°C. After the temperature stabilizes, turn on the alkali pump to add NaOH solution to adjust the pH of the base liquid to 11.5. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the feed rate of the alkali pump to 1.31 mL / min, the feed rate of the salt pump to 2.62 mL / min, and the feed rate of the ammonia pump to 0.98 mL / min. React for 40 h.

[0083] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 120°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.90 Co 0.03 Mn 0.05 Nb 0.02 (OH)2.

[0084] The small-particle-size Ni prepared in Example 5 0.90 Co 0.03 Mn 0.05 Nb 0.02 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 10 As shown, the precursor of the quaternary material grown by pH self-driving is a spherical secondary particle assembled from short spindle primary particles. The material has excellent sphericity and high density.

[0085] The small-particle-size Ni prepared in Example 5 0.90 Co 0.03 Mn 0.05 Nb 0.02 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 11As shown, when the concentration of the substrate solution is 0.8 mol / L, the precursor particle size D50 after pH self-driven growth is 4.455 μm, the particle size span is 0.584, and the overall particle size distribution is relatively concentrated.

[0086] Comparative Example 1

[0087] Comparative Example 1 maintained a constant pH value throughout the reaction process, and all other parameters were kept the same as in Example 1. Specifically, it included the following steps:

[0088] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and manganese sulfate monohydrate (MnSO4·H2O) according to the metal molar ratio of 92:4:4, and prepare a 2 mol / L mixed metal salt solution. Use a 6 mol / L ammonia solution as a complexing agent and a 6 mol / L NaOH solution as an alkaline solution. Filter the above solutions to remove solid impurities and precipitates.

[0089] (2) Add a 0.5 mol / L ammonia solution as a base liquid to the reactor. The volume of the base liquid is 1 / 3 of the reactor volume. Then, purge the air in the reactor with nitrogen gas and stir until homogeneous. The stirring speed is 1000 r / min. Then, heat the reactor to 55°C. After the temperature stabilizes, turn on the alkali pump to add NaOH solution. Use a PID program control system to control the alkali pump feed rate to control the pH value of the reaction system to 11.2. At the same time, turn on the salt pump and ammonia pump to add mixed metal salt solution and complexing agent. Adjust the salt pump feed rate to 17.45 mL / min and the ammonia pump feed rate to 5.88 mL / min. React for 30 h.

[0090] (3) The product obtained in step (2) was thoroughly washed with deionized water and filtered until the pH of the filtrate was neutral. The filter cake was then dried in a drying oven at 100°C for 24 hours. After sieving and demagnetizing, a small-particle-size ultra-high nickel multi-element cathode material precursor, Ni, was obtained. 0.92 Co 0.04 Mn 0.04 (OH)2.

[0091] The small-particle-size Ni prepared in Comparative Example 1 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor was subjected to SEM testing (FlexSEM1000II), and the test images are shown below. Figure 12 As shown, when a constant pH value is maintained during the reaction, the precipitate has a high degree of supersaturation, and the precursor is always in the nucleation state, resulting in incomplete development of primary particles and missing morphology in the final product. The secondary particles are irregular loose aggregates with low tap density and poor crystallinity and sphericity.

[0092] The small-particle-size Ni prepared in Comparative Example 1 0.92 Co 0.04 Mn 0.04 The (OH)2 precursor underwent particle size analysis (Bettersize 2600), and the particle size distribution is shown in the figure below. Figure 13 As shown, due to the maintenance of a constant pH value, the secondary particles exhibit irregular loose agglomeration, resulting in a large particle size distribution range. Under the cutting action of the stirring paddle, the loosely bound small particles are peeled off from the surface of the secondary particles, and small particle size impurity peaks appear in the particle size distribution diagram.

[0093] Analysis of the results of Example 1 and Comparative Example 1 shows that maintaining a constant pH value cannot simultaneously meet the requirements of nucleation and growth processes of small-particle-size ultra-high nickel multi-element cathode material precursors. However, relying on the increase in liquid phase volume in the reactor to cause a slow decrease in pH value, i.e., the pH self-driven process can slowly transition from the nucleation state to the growth state, reducing fluctuations in the reaction environment, thereby obtaining small-particle-size precursor materials with high tap density, high crystallinity, and excellent sphericity, demonstrating the necessity of pH self-driven processes.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a small-particle-size ultra-high nickel multi-element cathode material precursor, characterized in that, The chemical formula of the small-particle-size ultra-high nickel multi-element cathode material precursor is as follows: Ni a B b C c D d (OH)2, Wherein, B is Fe or Co, C is Mn, and D is one of Al, Na, Mg, K, Ca, Ti, Nb, and Zr; 90at.%≤a≤98at.%, 0.1at.%≤b≤10at.%, 0.1at.%≤c≤10at.%, 0at.%≤d≤10at.%, a+b+c+d=1; The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor includes the following steps: (1) Weigh out nickel salt, B salt, C salt and D salt in proportion, and dissolve them in water to prepare a mixed metal salt solution; (2) Add ammonia solution as the base liquid to the reactor, introduce nitrogen gas, set the stirrer speed to 800 r / min-1200 r / min, stir evenly and heat to 50℃-60℃, add alkaline solution to adjust the pH value of the base liquid to 11.0-11.8, and then add the mixed metal salt solution and complexing agent at the same time to carry out precipitation reaction. During the reaction, adjust the feed rate of the alkaline solution and the mixed metal salt solution so that the molar ratio of hydroxide ions to salt entering the reactor per unit time is 2:

1. The alkaline solution is NaOH solution, and the feed rate of the alkaline solution is 0.3 mL / min-40.0 mL / min; the feed rate of the mixed metal salt solution is 0.5 mL / min-20.0 mL / min. During the preparation process, as the volume of the liquid phase in the reactor increases, the pH value slowly decreases, that is, a pH self-driven process is formed. Finally, filter to obtain the precipitate. (3) Wash the precipitate obtained in step (2) with deionized water and filter it until the pH value of the filtrate is neutral. Dry it at 90℃-150℃ for 12 h-24 h and then sieve it to remove magnetism to obtain the small particle size ultra-high nickel multi-element cathode material precursor. The base liquid is an ammonia solution with a molar concentration of 0.3 mol / L to 1.1 mol / L; the volume of the base liquid occupies 1 / 3 to 1 / 2 of the total volume of the reactor. The average particle size D50 of the small-particle-size ultra-high nickel multi-element cathode material precursor is 2μm-4.649μm.

2. The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor according to claim 1, characterized in that, The nickel salts include nickel sulfate, nickel carbonate, nickel oxalate, nickel acetate, and their hydrates; the B salt is ferric sulfate, ferric nitrate, ferric chloride, ferrous carbonate, ferric citrate, cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and their hydrates; the C salt is manganese sulfate, manganese nitrate, manganese carbonate, manganese chloride, and their hydrates; and the D salt is sulfate, carbonate, nitrate, oxalate, and their hydrates containing Al, Na, Mg, K, Ca, Ti, Nb, and Zr elements.

3. The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor according to claim 1, characterized in that, The molar concentration of the mixed metal salt solution is 1 mol / L to 4 mol / L.

4. The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor according to claim 1, characterized in that, The alkaline solution is a NaOH solution with a molar concentration of 4 mol / L to 8 mol / L; the complexing agent is an ammonia solution with a molar concentration of 4 mol / L to 8 mol / L.

5. The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor according to claim 1, characterized in that, The feeding rate of the complexing agent is 0.2 mL / min to 25.0 mL / min.

6. The method for preparing the small-particle-size ultra-high nickel multi-element cathode material precursor according to claim 1, characterized in that, During the precipitation reaction, the ammonia concentration is maintained at 0.3 mol / L-1.1 mol / L.

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