Preparation method of positive electrode material precursor

Abstract

The invention relates to the technical field of preparation of positive electrode materials, and discloses a preparation method of a positive electrode material precursor, the method lays a foundation through raw material treatment and intelligent regulation and control of a reaction system, adopts a sectional type coprecipitation and ultrasonic-magnetic field double-field coupling synergistic technology, scatters free fine grains in a particle nucleation stage, and guides directional development in a growth stage, so as to obtain the positive electrode material precursor. Feeding and settling processes are synchronously optimized, and accurate control over morphology and particle size uniformity of the spheroidic particles is achieved; subsequent multi-stage washing, screening magnetic separation and vacuum drying are performed to strengthen the purification effect, and multi-stage crystallization treatment under nitrogen is matched, so that complete growth of a crystal structure is promoted, impurity residues are greatly reduced, and the crystallization order degree of a product is improved; by means of process coordination and innovative regulation and control means, the product has high purity, excellent flowability and balanced structural performance, the large-scale production requirement of the power battery is met, the energy density, the cycling stability and the safety performance of a subsequent positive electrode material can be effectively improved, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of cathode material preparation technology, specifically to a method for preparing a cathode material precursor. Background Technology

[0002] Ni-Co-Mn hydroxide precursor is a core raw material for preparing ternary cathode materials. Its quality directly determines the energy density, cycle stability, and safety performance of power batteries. Its uniform spherical morphology can improve the tap density of cathode materials, its narrow particle size distribution can optimize lithium-ion diffusion channels, and its low impurity content can reduce side reactions during battery cycling. Therefore, high-purity precursors with excellent morphology are key to supporting the upgrading of power batteries to high specific capacity. Currently, the mainstream industrial method for preparing this precursor is the co-precipitation method, but the existing process has significant bottlenecks: First, the reaction parameters are poorly controlled, and a single pH and ammonia concentration are used in the nucleation and growth stages, which leads to defects such as easy crystal nucleus agglomeration and particle size CV values ​​often exceeding 8%; Second, the material mixing method is outdated, and direct feeding of metal salts and precipitants can easily form local concentration gradients, causing uneven crystal nucleus size. To address these issues, we propose a method for preparing cathode material precursors that can control the reaction process and enhance the uniformity of material mixing. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a cathode material precursor to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a cathode material precursor, comprising the following steps: S1: Raw material pretreatment: Select metal salt components, precipitant components, and complexing agent components. After drying, sieving, and concentration calibration, the metal salt components are nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in a ratio of 5:2:3. These are then dissolved in deionized water with a mass ratio of 8:1 for deionized water to nickel sulfate hexahydrate, 18.2:1 for deionized water to cobalt sulfate heptahydrate, and 20:1 for deionized water to manganese sulfate monohydrate. The precipitant component is prepared with a sodium hydroxide to deionized water solid-liquid mass ratio of 1:5. The complexing agent component is prepared with a concentrated ammonia solution to deionized water volume ratio of 1:1. S2: Reaction system construction: Add deionized water to the reactor, and add concentrated ammonia and sodium hydroxide at a volume ratio of 50:1 for deionized water and 125:1 for deionized water and 4.0-5.0 mol / L sodium hydroxide solution to prepare the base solution. Purge the air with nitrogen, and adjust the temperature, pH value, ammonia concentration and stirring rate to the preset state. Build a real-time monitoring and feedback system. S3: Segmented co-precipitation reaction: Using a co-feeding system, the nucleation reaction is first carried out with a low feed flow rate, high stirring rate and pH value of 10.5±0.1. After the particles grow to 60%-80% of the target particle size, the ultrasonic-magnetic dual-field coupling system is activated for auxiliary control, and the co-feeding system is simultaneously switched to a high feed flow rate, low stirring rate and pH value of 9.5±0.1 to continue growth. The sedimentation and drainage generate a spherical precursor slurry. S4: Precursor post-processing and purification: After slurry aging, solid-liquid separation is performed, followed by multi-stage washing, sieving, magnetic separation to remove iron, and vacuum drying to constant quality to obtain precursor powder. S5: Crystallization treatment: The powder is placed in a tube furnace, and nitrogen is added for multi-stage heating, holding and cooling to promote the complete growth of crystals and obtain the cathode material precursor.

[0005] Preferably, in step S1, an inductively coupled plasma mass spectrometer is used to detect the metal salt components. The content of a single impurity element, Fe, Ca, Cu, Pb, or Zn, is ≤5 ppm, and the total impurity content is ≤20 ppm. The purity of sodium hydroxide is ≥99.5%, and the water-insoluble matter is ≤0.05%, of which the sodium carbonate impurity content is ≤0.1%. The mass fraction of concentrated ammonia is stable at 25%-28%, and the concentration deviation calibrated by acid-base titration is ≤0.2%, with a carbonate content ≤0.1%. The conductivity of deionized water is ≤10 μS / cm, and the resistivity is ≥100 MΩ·cm.

[0006] Preferably, in step S1, the raw material pretreatment specifically includes: drying treatment: vacuum drying of the metal salt components at 80±5℃ and -0.08~-0.09MPa vacuum for 4±0.5h, recording the material mass once per hour, and determining that the drying standard is met when the difference between two consecutive mass values ​​is ≤0.1%, removing the crystal water and surface adsorbed water from the crystals; sieving and impurity removal: the dried metal salt components are passed through a 120-mesh standard inspection sieve, assisted by negative pressure suction sieving, and the residue is collected and treated separately, with the residue mass ratio ≤0.1% to ensure that the material is free of agglomerated impurities; concentration calibration: ammonia water is calibrated for concentration using an automatic potentiometric titrator, calibrated 3 times per batch, and the average value is taken as the actual concentration value, with a calibration error ≤0.05mol / L; sodium hydroxide solid is dried at a constant temperature and then calibrated by titration using potassium hydrogen phthalate as a reference to ensure the accuracy of the subsequent solution concentration.

[0007] Preferably, in step S2, the reaction system is constructed as follows: 10L of deionized water is added to the reaction vessel; 200-280mL of concentrated ammonia solution with a mass fraction of 25%-28% is added at a volume ratio of deionized water to concentrated ammonia solution of 50:1, and the mixture is stirred for 5 minutes until uniformly dispersed; then, a mixture of deionized water and 4.0-5.0mol / L sodium hydroxide solution is added... Add 80-100 mL of sodium hydroxide solution dropwise at a volume ratio of 125:1, while simultaneously monitoring the pH using an online pH meter, until the pH of the base solution stabilizes at 10.5 ± 0.1. Add deionized water to bring the total volume of the base solution to 10.5-11 L. Raise the temperature of the base solution to 55 ± 2 °C using a constant temperature water bath circulation system, with a temperature control accuracy of ± 0.5 °C. Introduce nitrogen gas with a purity ≥ 99.99% into the reactor at a flow rate of 50 ± 5 mL / min through a ring gas distributor at the bottom of the reactor to replace the air for 30 minutes, stopping when the oxygen content detector shows ≤ 0.1%. Adjust the stirring speed to 400 ± 20 rpm to form a stable vortex with a depth of 1 / 5 to 1 / 4 of the liquid level. After the pH value remains stable for 30 minutes without fluctuation, the reaction system is complete.

[0008] Preferably, in step S3, the segmented co-precipitation reaction is as follows: Nucleation stage: The feed flow rate of the mixed solution of metal salt components is set to 10±1 mL / min, the feed flow rate of sodium hydroxide solution is dynamically adjusted according to the feedback of the online pH meter to maintain the pH value in the reactor at 10.5±0.1, the feed flow rate of ammonia is set to 5±0.5 mL / min to maintain the ammonia concentration in the reactor at 6±0.5 g / L, and the stirring speed is maintained at 400 rpm. This stage continues until the particle size D50 reaches 7±0.5 μm, which is about 70% of the target particle size. The particle size distribution is detected every 30 minutes by an online laser particle size analyzer; Growth stage: After the particles reach the preset particle size, the metal salt... The flow rate of the mixed solution of the components was increased to 20±1 mL / min, the stirring rate was reduced to 250±20 rpm, the pH value was adjusted to 9.5±0.1, and the flow rate of ammonia water was kept constant. Slurry samples were taken through the sampling port every 15 min, and the particle morphology was observed by scanning electron microscopy. When the particles were uniformly spherical and the particle size D50 reached 10±0.5 μm, the feeding of the mixed solution of metal salt components, sodium hydroxide solution, and ammonia water was stopped, and stirring was continued for 30 min to allow the residual metal ions to fully precipitate. Process drainage: During the growth stage, 10% of the supernatant was drained through the bottom drain valve every 1 h, and an equal amount of deionized water was added at the same time to maintain the stability of the liquid level in the reactor and improve the particle density.

[0009] Preferably, in step S3, the co-feeding system is specifically a microfluidic co-feeding system: the mixed solution of metal salt components, sodium hydroxide solution, and ammonia water are respectively delivered by three constant flow drip pumps; the mixed solution of metal salt components and sodium hydroxide solution are pre-mixed by a cross-shaped microchannel mixer before entering the reactor, with a mixing time of <0.1s to ensure uniform local concentration; the feed inlet is set 10cm above the stirrer to form convective mixing with the liquid in the reactor and reduce the concentration gradient; at the same time, an online concentration monitor is installed on the feed pipeline to monitor the concentration of metal ions and OH⁻ in real time, and when the concentration fluctuation is >0.01mol / L, the flow rate of the drip pump is automatically adjusted to ensure the stability of the reaction.

[0010] Preferably, in step S3, the ultrasonic-magnetic field dual-field coupling system is specifically configured as follows: Ultrasonic system: Four sets of ultrasonic transducers are uniformly arranged on the inner wall of the reactor. The ultrasonic frequency is set to 20±1kHz, and the ultrasonic power is dynamically adjusted according to the particle growth stage. The power is 150±10W in the nucleation stage to disperse free fine crystals; the power is reduced to 80±10W in the growth stage. Magnetic field system: A ring electromagnet is fitted outside the reactor, generating a magnetic field strength of 0.5±0.05T. The magnetic field direction is consistent with the stirring direction, guiding the particles to grow directionally along the magnetic field direction and reducing agglomeration. Linkage control: The dual-field coupling system is linked with the online laser particle size analyzer and the Zeta potential analyzer. When the particle size CV value is detected to be >5%, the ultrasonic power is automatically increased by 10%-20%. When the absolute value of the Zeta potential is <20mV, the magnetic field strength is increased by 0.05-0.1T to ensure particle dispersion and sphericity.

[0011] Preferably, in step S4, the solid-liquid separation and washing process in the precursor post-processing purification is as follows: aging treatment: the precursor slurry in the reactor is transferred to an aging tank and aged in a sealed environment at 50±5℃ for 12±1h to promote regular particle crystal formation. During the aging process, the mixture is stirred for 10min every 2h; pressure filtration separation: a plate and frame filter press is used for solid-liquid separation at a pressure of 0.3±0.05MPa. Filtration is stopped when the moisture content of the filter cake is ≤60%. The filtrate is collected and treated with a nanofiltration membrane to recover ammonia; gradient washing: the filter cake is first washed three times with deionized water at 80±5℃, with each washing solution being twice the mass of the filter cake. After soaking for 5min, the filter cake is then filtered; then it is washed twice with a 50% (v / v) ethanol aqueous solution to remove residual sulfate ions. The washing endpoint is determined by the conductivity of the washing solution being ≤100μS / cm, and the sulfate ion content in the washing solution is detected by ion chromatography to be ≤500ppm.

[0012] Preferably, in step S4, the drying and impurity removal process is as follows: Vacuum drying: The washed filter cake is transferred to a vacuum drying oven, spread out to a thickness ≤1cm, and dried for 14±1h under a vacuum of -0.09~-0.095MPa and a temperature of 90±5℃. The material quality is recorded every 2h. When the difference between two consecutive quality values ​​is ≤0.1%, it is determined that the drying meets the standard. Screening and impurity removal: The dried powder is screened through a 100-mesh standard sieve to remove large particles and lumps. The undersized material enters a magnetic separator for iron removal. The magnetic field strength of the magnetic separator is 1.2±0.1T. The iron impurity content in the powder after treatment is ≤50ppm.

[0013] Preferably, in step S5, the specific crystallization process is as follows: Sample preparation: The dried precursor powder is evenly spread in a crucible with a powder thickness ≤2cm, and the crucible is placed in the constant temperature zone of a tube furnace; Atmosphere control: Nitrogen gas with a purity ≥99.99% is introduced into the tube furnace at a flow rate of 100±10mL / min to replace the air in the furnace for 60min, ensuring that the oxygen content is ≤0.1%; Heating program: A two-stage heating process is adopted. The first stage is to raise the temperature from room temperature to 300±5℃ at a rate of 5±1℃ / min and hold for 2±0.5h to remove residual moisture and ammonia in the powder; the second stage is to raise the temperature from 300℃ to 650±5℃ at a rate of 3±1℃ / min and hold for 5±0.5h to promote the complete growth of the crystal structure; Cooling control: After the holding period, the heating system is turned off, and nitrogen gas is kept flowing until the tube furnace cools down naturally to room temperature.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention systematically solves the core problems of traditional processes, such as coarse parameter control, uneven material mixing, and difficulty in removing impurities, through a synergistic process of segmented co-precipitation, ultrasonic-magnetic dual-field coupling, microfluidic feeding, and precise purification. This achieves a dual improvement in precursor quality and preparation efficiency. Addressing the issue of coarse parameter control in traditional processes, this invention employs a segmented co-precipitation strategy, precisely matching pH values ​​for the nucleation and particle growth stages respectively. Combined with ultrasonic-magnetic dual-field coupling technology, this not only disperses free fine crystals generated during the reaction but also guides the directional development of crystals, ultimately resulting in a precursor with a uniform, near-spherical morphology and concentrated particle size distribution, significantly improving the agglomeration defects common in traditional processes. Regarding the problem of uneven material mixing, a microfluidic feeding system enables rapid pre-mixing of raw materials, eliminating local concentration gradients at the source and ensuring uniform crystal nucleus size. All process parameters can be controlled in real time, ensuring stability for large-scale production. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the steps involved in preparing a cathode material precursor. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 As shown, the present invention provides a technical solution: a method for preparing a cathode material precursor, comprising the following steps: S1: Raw material pretreatment: Select metal salt components, precipitant components, and complexing agent components. After drying, sieving, and concentration calibration, the metal salt components are nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in a ratio of 5:2:3. These are then dissolved in deionized water with a mass ratio of 8:1 for deionized water to nickel sulfate hexahydrate, 18.2:1 for deionized water to cobalt sulfate heptahydrate, and 20:1 for deionized water to manganese sulfate monohydrate. The precipitant component is prepared with a sodium hydroxide to deionized water solid-liquid mass ratio of 1:5. The complexing agent component is prepared with a concentrated ammonia solution to deionized water volume ratio of 1:1. S2: Reaction system construction: Add deionized water to the reactor, and add concentrated ammonia and sodium hydroxide at a volume ratio of deionized water to concentrated ammonia water = 50:1 and a volume ratio of deionized water to 4.0-5.0 mol / L sodium hydroxide solution = 125:1 to prepare the base solution. Purge the air with nitrogen, and adjust the temperature, pH value, ammonia concentration and stirring rate to the preset state. Build a real-time monitoring and feedback system. S3: Segmented co-precipitation reaction: Using a co-feeding system, the nucleation reaction is first carried out with a low feed flow rate, high stirring rate and pH value of 10.5±0.1. After the particles grow to 60%-80% of the target particle size, the ultrasonic-magnetic dual-field coupling system is activated for auxiliary control, and the co-feeding system is simultaneously switched to a high feed flow rate, low stirring rate and pH value of 9.5±0.1 to continue growth. The sedimentation and drainage generate a spherical precursor slurry. S4: Precursor post-processing and purification: After slurry aging, solid-liquid separation is performed, followed by multi-stage washing, sieving, magnetic separation to remove iron, and vacuum drying to constant quality to obtain precursor powder. S5: Crystallization treatment: The powder is placed in a tube furnace, and nitrogen is added for multi-stage heating, holding and cooling to promote the complete growth of crystals and obtain the cathode material precursor.

[0018] Further, in step S1: Inductively coupled plasma mass spectrometry (ICP-MS) is used to detect the metal salt components. The content of single impurity elements Fe, Ca, Cu, Pb, and Zn is ≤5 ppm, and the total impurity content is ≤20 ppm; the purity of sodium hydroxide is ≥99.5%, the water-insoluble matter is ≤0.05%, and the sodium carbonate impurity content is ≤0.1%; the mass fraction of concentrated ammonia is stable at 25%-28%, the concentration deviation after acid-base titration is ≤0.2%, and the carbonate content is ≤0.1%; the conductivity of deionized water is ≤10 μS / cm, and the resistivity is ≥100 MΩ·cm. The rationality of the proportions in this invention was verified through three sets of comparative experiments. The table below uses D50, CV value, tap density, total impurity content, and corresponding cathode cycle retention rate as key performance indicators for evaluation. The invention is compared with three common formulations, demonstrating the advantages of the proportions in this invention in improving precursor quality and corresponding cathode performance. Specific data and implementation details are as follows: This invention comprises nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in a molar ratio of 5:2:3; deionized water to nickel sulfate hexahydrate in a mass ratio of 8:1; deionized water to cobalt sulfate heptahydrate in a mass ratio of 18.2:1; deionized water to manganese sulfate monohydrate in a mass ratio of 20:1; sodium hydroxide to deionized water in a mass ratio of 1:5; and concentrated ammonia to deionized water in a volume ratio of 1:1. Comparison Group 1: Nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate, in a molar ratio of 6:1:3; deionized water to nickel sulfate hexahydrate mass ratio of 8:1; deionized water to cobalt sulfate heptahydrate mass ratio of 18.2:1; deionized water to manganese sulfate monohydrate mass ratio of 20:1; sodium hydroxide to deionized water mass ratio of 1:5; concentrated ammonia to deionized water volume ratio of 1:1. Comparison Group 2: Nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate, in a molar ratio of 6:1:3; the mass ratio of deionized water to nickel sulfate hexahydrate is 5:1; the mass ratio of deionized water to cobalt sulfate heptahydrate is 18.2:1; the mass ratio of deionized water to manganese sulfate monohydrate is 20:1; the mass ratio of sodium hydroxide to deionized water is 1:5; and the volume ratio of concentrated ammonia to deionized water is 1:1. Comparison Group 3: Nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate, in a molar ratio of 6:1:3; the mass ratio of deionized water to nickel sulfate hexahydrate is 8:1; the mass ratio of deionized water to cobalt sulfate heptahydrate is 18.2:1; the mass ratio of deionized water to manganese sulfate monohydrate is 20:1; the mass ratio of sodium hydroxide to deionized water is 1:3; and the volume ratio of concentrated ammonia to deionized water is 1:1. Comparative experiment D50 (μm) CV value (%) Tap density (g / cm³) Total impurities (ppm) Corresponding positive electrode cycle retention rate (100 cycles) This invention 10.2 4.8 2.15 18 92.5% Control group 1 9.8 7.2 1.82 20 83.1% Control group 2 8.5 8.5 1.76 35 81.3% Control group 3 11.6 9.1 1.90 22 85.7% By comparing control group 1, it was found that the high specific capacity advantage of Ni element and the stabilizing effect of Co and Mn crystals formed a synergistic effect, resulting in a 9.4 percentage point increase in the positive electrode cycle retention rate. By comparing control group 2, it was found that the metal salt components were completely dissolved, avoiding the introduction of impurities by undissolved particles, reducing the total impurity content from 35 ppm to 18 ppm and increasing the tap density by 22.2%. By comparing control group 3, it was found that the 1:5 sodium hydroxide:deionized water mass ratio ensured that the pH response deviation during addition was ≤0.05, avoiding a sudden increase in local pH, reducing the CV value from 9.1% to 4.8%, and effectively inhibiting the agglomeration of crystal nuclei.

[0019] Further, step S1, the raw material pretreatment specifically includes: drying treatment: the metal salt components are vacuum dried at 80±5℃ and -0.08~-0.09MPa for 4±0.5h, and the material mass is recorded once per hour. When the difference between two consecutive mass values ​​is ≤0.1%, it is determined that the drying meets the standard, removing the crystal water and surface adsorbed water from the crystals; sieving and impurity removal: the dried metal salt components are passed through a 120-mesh standard inspection sieve, and sieving is assisted by negative pressure suction sieving. The residue is collected and treated separately, and the mass ratio of the residue is ≤0.1% to ensure that the material is free of agglomerated impurities; concentration calibration: the ammonia water is calibrated using an automatic potentiometric titrator, calibrated 3 times per batch, and the average value is taken as the actual concentration value, with a calibration error ≤0.05mol / L; after the sodium hydroxide solid is dried at a constant temperature, it is calibrated by titration using potassium hydrogen phthalate as a reference to ensure the accuracy of the subsequent solution concentration.

[0020] Further, in step S2, the reaction system is constructed as follows: 10L of deionized water is added to the reaction vessel; the ratio of deionized water to concentrated ammonia is 50:1. Add 200-280 mL of concentrated ammonia solution (25%-28% by mass) at a volume ratio of [volume ratio missing], and stir for 5 minutes until uniformly dispersed. Then, slowly add 80-100 mL of sodium hydroxide solution at a volume ratio of deionized water to 4.0-5.0 mol / L sodium hydroxide solution (125:1), simultaneously monitoring with an online pH meter, until the pH of the bottom solution stabilizes at 10.5±0.1. Add deionized water to bring the total volume of the bottom solution to 10.5-11 L. Raise the temperature of the bottom solution to 55±2℃ using a constant temperature water bath circulation system, with a temperature control accuracy of ±0.5℃. Introduce nitrogen gas with a purity ≥99.99% into the reactor at a flow rate of 50±5 mL / min through a ring gas distributor at the bottom of the reactor, replacing the air for 30 minutes, stopping when the oxygen content detector shows ≤0.1%. Adjust the stirring speed to 400±20 rpm to form a stable vortex with a depth of 1 / 5 to 1 / 4 of the liquid surface height. After the value remained stable for 30 minutes without fluctuation, the reaction system was successfully constructed. The underlying solution affects reaction stability; its initial ammonia concentration and pH stability directly determine nucleation efficiency and particle morphology. The table below, through two sets of control experiments, uses initial ammonia concentration, stable pH value, nucleation time, particle sphericity, and specific surface area as core indicators to demonstrate the superiority of the present invention in constructing a stable reaction environment using a deionized water:concentrated ammonia solution volume ratio of 50:1 and a deionized water:4.0 mol / L sodium hydroxide volume ratio of 125:1. Specific data are as follows: This invention uses a deionized water to concentrated ammonia solution at a volume ratio of 50:1 and a deionized water to 4.0-5.0 mol / L sodium hydroxide solution at a volume ratio of 125:1. Comparative Group A: Deionized water to concentrated ammonia solution = 30:1 volume ratio, deionized water to 4.0-5.0 mol / L sodium hydroxide solution = 125:1 volume ratio; Control group B: Deionized water to concentrated ammonia solution = 50:1 volume ratio, deionized water to 4.0-5.0 mol / L sodium hydroxide solution = 200:1 volume ratio; Comparative experiment Initial ammonia concentration (g / L) Stable pH value Nucleation time (min) Particle sphericity (%) Specific surface area (m² / g) This invention 6.2 10.5±0.1 45 93 15.8 Control group A 10.3 10.8±0.2 72 82 12.1 Control group B 6.1 9.8±0.3 38 75 20.3 Compared to control group A with excessive concentrated ammonia, this invention controls the initial ammonia concentration within the optimal range of 6.2 g / L, avoiding the inhibitory effect of excessive ammonia on nucleation. The nucleation time is shortened from 72 min to 45 min, the particle sphericity is increased from 82% to 93%, and the fluctuation range of specific surface area is reduced by 66%. Compared to control group B with insufficient NaOH, this invention ensures that the pH of the bottom solution is stable at 10.5 ± 0.1, avoiding particle growth disorder caused by pH runaway. This results in a 24% increase in particle sphericity and a decrease in specific surface area from 20.3 m² / g to 15.8 m² / g, which remains stable.

[0021] Further, in step S3, the segmented co-precipitation reaction is as follows: Nucleation stage: The feed flow rate of the mixed solution of metal salt components is set to 10±1 mL / min, the feed flow rate of sodium hydroxide solution is dynamically adjusted according to the feedback of the online pH meter to maintain the pH value in the reactor at 10.5±0.1, the feed flow rate of ammonia is set to 5±0.5 mL / min to maintain the ammonia concentration in the reactor at 6±0.5 g / L, and the stirring speed is maintained at 400 rpm. This stage continues until the particle size D50 reaches 7±0.5 μm, which is about 70% of the target particle size. The particle size distribution is detected every 30 minutes using an online laser particle size analyzer; Growth stage: After the particles reach the preset particle size, the metal salt components... The flow rate of the mixed solution was increased to 20±1 mL / min, the stirring rate was reduced to 250±20 rpm, the pH value was adjusted to 9.5±0.1, and the ammonia flow rate remained unchanged. Slurry samples were taken through the sampling port every 15 min, and the particle morphology was observed using a scanning electron microscope. When the particles showed a uniform spherical shape and the particle size D50 reached 10±0.5 μm, the feeding of the mixed solution of metal salt components, sodium hydroxide solution, and ammonia was stopped, and stirring was continued for 30 min to allow the residual metal ions to fully precipitate. Process drainage: During the growth stage, 10% of the supernatant was drained through the bottom drain valve every 1 h, while an equal amount of deionized water was added to maintain a stable liquid level in the reactor and improve particle density.

[0022] Further, in step S3, the co-feeding system is specifically a microfluidic co-feeding system: the mixed solution of metal salt components, sodium hydroxide solution, and ammonia water are delivered by three constant flow drip pumps respectively; the mixed solution of metal salt components and sodium hydroxide solution are pre-mixed by a cross-shaped microchannel mixer before entering the reactor, with a mixing time of <0.1s to ensure uniform local concentration; the feed inlet is set 10cm above the agitator to form convective mixing with the liquid in the reactor and reduce the concentration gradient; at the same time, an online concentration monitor is installed on the feed pipeline to monitor the concentration of metal ions and OH⁻ in real time. When the concentration fluctuation is >0.01mol / L, the flow rate of the drip pump is automatically adjusted to ensure the stability of the reaction; The microfluidic synergistic feeding system shortens the diffusion distance through "forced convection mixing," achieving millisecond-level uniform mixing of raw materials. Three constant-flow drip pumps with a flow accuracy of ±0.1 mL / min are used to deliver the mixed solution of the metal salt component, sodium hydroxide solution, and ammonia water, respectively. The mixed solution of the metal salt component and the sodium hydroxide solution first pass through a cross-shaped microchannel mixer with an inner diameter of 1 mm and a Reynolds number of Re=500, forming turbulent mixing with a mixing time of <0.1 s. Then, together with the ammonia water, it is injected into the reactor through an inlet 10 cm above the stirrer, where secondary mixing is enhanced by a stirring vortex. During the nucleation stage, the flow rate of the mixed solution of the metal salt component is 10 mL / min. The sodium hydroxide solution flow rate is 3 mL / min to ensure that the molar ratio of OH⁻ to Ni²⁺, Co²⁺, and Mn²⁺ is stable at 2.05:1, avoiding crystal distortion caused by excessive OH⁻. During the growth stage, the flow rate is increased proportionally to 20:6 mL / min to maintain a stable ratio until D50 reaches 10 μm. An online ion concentration monitor is installed on the feed line to monitor the concentrations of Ni²⁺, Co²⁺, and Mn²⁺ in the mixed solution of metal salt components and the concentration of OH⁻ in the sodium hydroxide solution in real time. When the concentration fluctuation is >0.01 mol / L, the corresponding drip pump flow rate is automatically adjusted through the PID control system, with a response time of <2s. Further, in step S3, the specific settings of the ultrasonic-magnetic field dual-field coupling system are as follows: Ultrasonic system: Four sets of ultrasonic transducers are evenly arranged on the inner wall of the reactor. The ultrasonic frequency is set to 20±1kHz, and the ultrasonic power is dynamically adjusted according to the particle growth stage. The power is 150±10W in the nucleation stage to disperse free fine crystals; the power is reduced to 80±10W in the growth stage. Magnetic field system: A ring electromagnet is fitted outside the reactor, generating a magnetic field strength of 0.5±0.05T. The magnetic field direction is consistent with the stirring direction, guiding the particles to grow directionally along the magnetic field direction and reducing agglomeration. Linkage control: The dual-field coupling system is linked with the online laser particle size analyzer and Zeta potential analyzer. When the particle size CV value is detected to be >5%, the ultrasonic power is automatically increased by 10%-20%; when the absolute value of the Zeta potential is <20mV, the magnetic field strength is increased by 0.05-0.1T to ensure particle dispersion and sphericity. The synergistic mechanism of the ultrasonic-magnetic field dual-field coupling system is that the cavitation effect of ultrasound and the directional guiding effect of the magnetic field complement each other. Specifically, the microjets generated by ultrasonic cavitation can disperse particle agglomerates, while the magnetic field generates Lorentz force on paramagnetic crystals containing Ni, Co, and Mn, guiding crystal growth along the magnetic field direction. These two mechanisms synergistically resolve the contradiction between particle dispersion and morphological regularity. Four sets of 20kHz ultrasonic transducers with adjustable power (50-200W) are uniformly arranged on the inner wall of the reactor. A ring electromagnet with adjustable magnetic field strength (0.3-0.8T) is installed outside the reactor. Both the ultrasonic and magnetic field systems are linked to an online laser particle size analyzer and a Zeta potentiometer. During the nucleation stage, the ultrasonic power is 150W, and the strong cavitation effect disperses free fine crystals, reducing the proportion of fine crystals with a diameter <0.5μm from 12% to 3%. During the growth stage, the power is reduced to 80W, and the weak cavitation effect further reduces the proportion of fine crystals with a diameter <0.5μm from 12% to 3%. It can prevent particle adhesion and avoid damaging the already grown crystal structure. A magnetic field strength of 0.5T can increase the crystal orientation growth index to 0.85, compared with 0.42 for crystals without a magnetic field, which is a significant improvement. When the laser particle size analyzer detects a CV value > 5%, the system automatically increases the ultrasonic power by 10%-20% to enhance the cavitation dispersion effect. When the Zeta potential analyzer detects an absolute value < 20mV, the magnetic field strength is automatically increased by 0.05-0.1T, which improves the particle dispersion stability through magnetic dipole interaction. Without this system, the particle agglomeration rate is 12.5%, and the specific surface area fluctuates between 12-21m² / g. After the system is activated, the agglomeration rate drops to 1.8%, and the specific surface area stabilizes at 15-16m² / g, with the fluctuation range reduced by 72%, demonstrating that the dual-field synergy can precisely control the particle dispersion and morphology.

[0023] Further, in step S4, the solid-liquid separation and washing process in the precursor post-processing purification is as follows: aging treatment: the precursor slurry in the reactor is transferred to an aging tank and aged in a sealed manner at 50±5℃ for 12±1h to promote the regularity of particle crystals. During the aging process, the mixture is stirred for 10min every 2h; pressure filtration separation: a plate and frame filter press is used for solid-liquid separation. The pressure filtration pressure is 0.3±0.05MPa. Filtration is stopped when the moisture content of the filter cake is ≤60%. The filtrate is collected and treated by nanofiltration membrane to recover ammonia water; gradient washing: the filter cake is first washed 3 times with deionized water at 80±5℃, with the washing liquid volume being twice the mass of the filter cake each time. After soaking for 5min, the filter cake is then filtered; then it is washed 2 times with a 50% ethanol aqueous solution to remove residual sulfate ions; the washing endpoint is determined by the conductivity of the washing liquid being ≤100μS / cm, and the sulfate ion content in the washing liquid is detected by ion chromatography to be ≤500ppm.

[0024] Further, step S4, the drying and impurity removal process is as follows: Vacuum drying: The washed filter cake is transferred to a vacuum drying oven, spread out to a thickness ≤1cm, and dried at a vacuum degree of -0.09~-0.095MPa and a temperature of 90±5℃ for 14±1h. The material quality is recorded every 2h. When the difference between two consecutive quality values ​​is ≤0.1%, it is determined that the drying meets the standard. Screening and impurity removal: The dried powder is screened through a 100-mesh standard sieve to remove large particles and lumps. The undersized material enters a magnetic separator for iron removal. The magnetic field strength of the magnetic separator is 1.2±0.1T. The iron impurity content in the powder after treatment is ≤50ppm.

[0025] Further, in step S5, the specific process of crystallization is as follows: Sample preparation: The dried precursor powder is evenly spread in the crucible, with a powder thickness ≤2cm, and the crucible is placed in the constant temperature zone of the tube furnace; Atmosphere control: Nitrogen gas with a purity ≥99.99% is introduced into the tube furnace at a flow rate of 100±10mL / min to replace the air in the furnace for 60min, ensuring that the oxygen content is ≤0.1%; Heating program: A two-stage heating method is adopted. The first stage is to raise the temperature from room temperature to 300±5℃ at a rate of 5±1℃ / min and hold for 2±0.5h to remove residual moisture and ammonia in the powder; the second stage is to raise the temperature from 300℃ to 650±5℃ at a rate of 3±1℃ / min and hold for 5±0.5h to promote the complete growth of the crystal structure; Cooling control: After the holding period, the heating system is turned off, and nitrogen gas is kept flowing until the tube furnace cools down naturally to room temperature.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a cathode material precursor, characterized in that, Includes the following steps: S1: Raw material pretreatment: Select metal salt components, precipitant components, and complexing agent components. After drying, sieving, and concentration calibration, the metal salt components are nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in a ratio of 5:2:

3. These are then dissolved in deionized water with a mass ratio of 8:1 for deionized water to nickel sulfate hexahydrate, 18.2:1 for deionized water to cobalt sulfate heptahydrate, and 20:1 for deionized water to manganese sulfate monohydrate. The precipitant component is prepared with a sodium hydroxide to deionized water solid-liquid mass ratio of 1:

5. The complexing agent component is prepared with a concentrated ammonia solution to deionized water volume ratio of 1:

1. S2: Construction of reaction system: Add deionized water to the reaction vessel, add concentrated ammonia and sodium hydroxide at a volume ratio of 50:1 for deionized water and 125:1 for deionized water and 4.0-5.0 mol / L sodium hydroxide solution to prepare the base solution, purge the air with nitrogen, adjust the temperature, pH value, ammonia concentration and stirring rate to the preset state, and build a real-time monitoring and feedback system; S3: Segmented co-precipitation reaction: Using a co-feeding system, the nucleation reaction is first carried out with a low feed flow rate, high stirring rate and pH value of 10.5±0.

1. After the particles grow to 60%-80% of the target particle size, the ultrasonic-magnetic dual-field coupling system is activated for auxiliary control, and the co-feeding system is simultaneously switched to a high feed flow rate, low stirring rate and pH value of 9.5±0.1 to continue growth. The sedimentation and drainage generate a spherical precursor slurry. S4: Precursor post-processing and purification: After slurry aging, solid-liquid separation is performed, followed by multi-stage washing, sieving, magnetic separation to remove iron, and vacuum drying to constant quality to obtain precursor powder. S5: Crystallization treatment: The powder is placed in a tube furnace, and nitrogen is added for multi-stage heating, holding and cooling to promote the complete growth of crystals and obtain the cathode material precursor.

2. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S1, inductively coupled plasma mass spectrometry is used to detect the metal salt components. The content of a single impurity element, Fe, Ca, Cu, Pb, or Zn, is ≤5 ppm, and the total impurity content is ≤20 ppm. The purity of sodium hydroxide is ≥99.5%, and the water-insoluble matter is ≤0.05%, of which the sodium carbonate impurity content is ≤0.1%. The mass fraction of concentrated ammonia is stable at 25%-28%, and the concentration deviation calibrated by acid-base titration is ≤0.2%, with a carbonate content ≤0.1%. The conductivity of deionized water is ≤10 μS / cm, and the resistivity is ≥100 MΩ·cm.

3. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S1, the raw material pretreatment specifically includes: drying: vacuum drying of the metal salt components at 80±5℃ and -0.08~-0.09MPa for 4±0.5h, recording the material mass every hour, and determining that the drying standard is met when the difference between two consecutive mass values ​​is ≤0.1%, thus removing the crystal water and surface adsorbed water from the crystals; sieving and impurity removal: the dried metal salt components are passed through a 120-mesh standard inspection sieve, assisted by negative pressure suction sieving, and the residue is collected and treated separately, with the residue mass ratio ≤0.1% to ensure that the material is free of agglomerated impurities; concentration calibration: ammonia water is calibrated using an automatic potentiometric titrator, calibrated 3 times per batch, and the average value is taken as the actual concentration value, with a calibration error ≤0.05mol / L; sodium hydroxide solid is dried at a constant temperature and then calibrated by titration using potassium hydrogen phthalate as a reference to ensure the accuracy of the subsequent solution concentration.

4. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S2, the reaction system is constructed as follows: 10L of deionized water is added to the reaction vessel; 200-280mL of concentrated ammonia solution with a mass fraction of 25%-28% is added at a volume ratio of deionized water to concentrated ammonia solution of 50:1, and stirred for 5 minutes until uniformly dispersed; then 80-100mL of sodium hydroxide solution is slowly added dropwise at a volume ratio of deionized water to 4.0-5.0mol / L sodium hydroxide solution of 125:1, while simultaneously monitoring the pH using an online pH meter, until the pH of the bottom solution stabilizes at 10.5±0.1, and then deionized water is added to bring the total volume of the bottom solution to [missing value]. The volume is 10.5-11L. The temperature of the bottom liquid is raised to 55±2℃ using a constant temperature water bath circulation system with a temperature control accuracy of ±0.5℃. Nitrogen gas with a purity of ≥99.99% is introduced into the reactor through a ring gas distributor at a flow rate of 50±5mL / min to replace the air for 30min. The process is stopped when the oxygen content detector shows ≤0.1%. The stirring speed is adjusted to 400±20rpm to form a stable vortex with a depth of 1 / 5 to 1 / 4 of the liquid level. After the pH value remains stable for 30min without fluctuation, the reaction system is complete.

5. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S3, the segmented co-precipitation reaction is as follows: Nucleation stage: The feed flow rate of the mixed solution of metal salt components is set to 10±1 mL / min, the feed flow rate of sodium hydroxide solution is dynamically adjusted according to the feedback of the online pH meter to maintain the pH value in the reactor at 10.5±0.1, the feed flow rate of ammonia is set to 5±0.5 mL / min to maintain the ammonia concentration in the reactor at 6±0.5 g / L, and the stirring speed is maintained at 400 rpm. This stage continues until the particle size D50 reaches 7±0.5 μm, which is about 70% of the target particle size. The particle size distribution is detected every 30 minutes by an online laser particle size analyzer; Growth stage: After the particles reach the preset particle size, the metal salt components... The flow rate of the mixed solution was increased to 20±1 mL / min, the stirring rate was reduced to 250±20 rpm, the pH value was adjusted to 9.5±0.1, and the flow rate of ammonia water was kept constant. Slurry samples were taken through the sampling port every 15 min, and the particle morphology was observed using scanning electron microscopy. When the particles showed a uniform spherical shape and the particle size D50 reached 10±0.5 μm, the feeding of the mixed solution of metal salt components, sodium hydroxide solution, and ammonia water was stopped, and stirring was continued for 30 min to allow the residual metal ions to fully precipitate. Process drainage: During the growth stage, 10% of the supernatant was drained through the bottom drain valve every 1 h, and an equal amount of deionized water was added at the same time to maintain the stability of the liquid level in the reactor and improve the particle density.

6. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S3, the co-feeding system is specifically a microfluidic co-feeding system: the mixed solution of metal salt components, sodium hydroxide solution, and ammonia water are delivered by three constant flow drip pumps; the mixed solution of metal salt components and sodium hydroxide solution are pre-mixed by a cross-shaped microchannel mixer before entering the reactor, with a mixing time of <0.1s to ensure uniform local concentration; the feed inlet is set 10cm above the stirrer to form convective mixing with the liquid in the reactor and reduce the concentration gradient; at the same time, an online concentration monitor is installed on the feed pipeline to monitor the concentration of metal ions and OH⁻ in real time. When the concentration fluctuation is >0.01mol / L, the flow rate of the drip pump is automatically adjusted to ensure the stability of the reaction.

7. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S3, the specific configuration of the ultrasonic-magnetic dual-field coupling system is as follows: Ultrasonic system: Four sets of ultrasonic transducers are uniformly arranged on the inner wall of the reactor. The ultrasonic frequency is set to 20±1kHz, and the ultrasonic power is dynamically adjusted according to the particle growth stage. The power is 150±10W in the nucleation stage to disperse free fine crystals; the power is reduced to 80±10W in the growth stage. Magnetic field system: A ring electromagnet is fitted outside the reactor, generating a magnetic field strength of 0.5±0.05T. The magnetic field direction is consistent with the stirring direction, guiding the particles to grow directionally along the magnetic field direction and reducing agglomeration. Linkage control: The dual-field coupling system is linked with the online laser particle size analyzer and the Zeta potential analyzer. When the particle size CV value is detected to be >5%, the ultrasonic power is automatically increased by 10%-20%. When the absolute value of the Zeta potential is <20mV, the magnetic field strength is increased by 0.05-0.1T to ensure particle dispersion and sphericity.

8. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S4, the solid-liquid separation and washing process in the precursor post-processing purification is as follows: aging treatment: the precursor slurry in the reactor is transferred to an aging tank and aged in a sealed environment at 50±5℃ for 12±1h to promote regular particle crystal formation. During aging, the mixture is stirred for 10min every 2h; pressure filtration separation: a plate and frame filter press is used for solid-liquid separation at a pressure of 0.3±0.05MPa. Filtration is stopped when the moisture content of the filter cake is ≤60%. The filtrate is collected and treated with a nanofiltration membrane to recover ammonia; gradient washing: the filter cake is first washed three times with deionized water at 80±5℃, with each washing solution being twice the mass of the filter cake. After soaking for 5min, the filter cake is then filtered; then it is washed twice with a 50% (v / v) ethanol aqueous solution to remove residual sulfate ions. The washing endpoint is determined by the conductivity of the washing solution being ≤100μS / cm, and the sulfate ion content in the washing solution is detected by ion chromatography to be ≤500ppm.

9. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S4, the drying and impurity removal process is as follows: Vacuum drying: The washed filter cake is transferred to a vacuum drying oven, spread out to a thickness ≤1cm, and dried for 14±1h under a vacuum of -0.09~-0.095MPa and 90±5℃. The material quality is recorded every 2h. When the difference between two consecutive quality values ​​is ≤0.1%, it is determined that the drying meets the standard. Screening and impurity removal: The dried powder is screened through a 100-mesh standard sieve to remove large particles and lumps. The undersized material enters a magnetic separator for iron removal. The magnetic field strength of the magnetic separator is 1.2±0.1T. The iron impurity content in the powder after treatment is ≤50ppm.

10. The method for preparing a cathode material precursor according to claim 1, characterized in that: In step S5, the specific crystallization process is as follows: Sample preparation: The dried precursor powder is evenly spread in a crucible with a powder thickness ≤2cm, and the crucible is placed in the constant temperature zone of a tube furnace; Atmosphere control: Nitrogen gas with a purity ≥99.99% is introduced into the tube furnace at a flow rate of 100±10mL / min to replace the air in the furnace for 60min, ensuring that the oxygen content is ≤0.1%; Heating program: A two-stage heating process is adopted. The first stage is to raise the temperature from room temperature to 300±5℃ at a rate of 5±1℃ / min and hold for 2±0.5h to remove residual moisture and ammonia in the powder; the second stage is to raise the temperature from 300℃ to 650±5℃ at a rate of 3±1℃ / min and hold for 5±0.5h to promote the complete growth of the crystal structure; Cooling control: After the holding period, the heating system is turned off, and nitrogen gas is kept flowing until the tube furnace cools down to room temperature naturally.

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