Directional crystallization process of high-nickel ternary precursor

Abstract

The invention discloses a directional crystallization process of a high-nickel ternary precursor in the technical field of inorganic functional materials, and the process comprises the following steps: dispersing a modifier in a base solution containing ammonia water in an inert atmosphere to form a suspension; the preparation method comprises the following steps: firstly carrying out explosive nucleation at a high feeding rate, converting into steady-state growth after a crystal nucleus reaches a target size, maintaining a constant acid-base value of a system by accurately controlling acid-base feeding, guiding metal hydroxide to radially and orderly deposit by utilizing a crystal face guiding effect of a modifier, and finally ageing, washing and drying to obtain the high-nickel ternary precursor. The modifier is prepared by the following steps: performing solvothermal synthesis, calcining under the protection of lithium carbonate atmosphere to obtain a cubic phase nano core, coating a titanium dioxide shell layer with low-temperature sol-gel, crystallizing, and finally treating and activating the surface by dilute ammonia water. The precursor prepared by the process has the advantages of uniform components, radial arrangement of primary particles, high sphericity and narrow particle size distribution, and the electrochemical performance of the precursor is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of inorganic functional materials technology, specifically to a directional crystallization process for a high-nickel ternary precursor. Background Technology

[0002] High-nickel ternary cathode materials are a core component of next-generation high-energy-density lithium-ion batteries, and their performance directly affects the battery's range, safety, reliability, and lifespan. The performance of this material in practical applications fundamentally depends on the microstructure and physicochemical properties of its precursor. An ideal precursor should possess a precisely controllable stoichiometry, extremely high component uniformity, a regular and dense spherical morphology, and a suitable particle size distribution. Among these, the orientation of primary particles within secondary spheres—that is, whether the crystals can grow orderly along a specific direction—has a crucial impact on the lithium-ion diffusion kinetics, mechanical structural stability, and cycle life of the final sintered product. Therefore, how to achieve precise multi-level structural control of high-nickel ternary precursors from the atomic scale to the microstructure through optimized fabrication processes has become one of the key technological challenges in the current lithium battery materials field to overcome the contradiction between energy density and stability.

[0003] Currently, the hydroxide coprecipitation method is widely used in industry and academia to prepare such precursors. This method involves adding a mixed metal salt solution, precipitant, and complexing agent in a co-current flow to the reaction system, causing metal ions to precipitate under constant conditions. However, this traditional approach faces several inherent bottlenecks. First, due to the significant differences in the precipitation-dissolution equilibrium constants and complexation stability constants of different metal ions such as nickel, cobalt, and manganese, achieving simultaneous precipitation at a completely uniform rate in a complex reaction environment with high concentration, high viscosity, and strong stirring is extremely difficult, easily leading to component segregation at the nanoscale or even atomic scale. Second, conventional processes have relatively crude control over the crystallization process, with nucleation and growth stages often intertwined and difficult to separate. This usually results in uncontrollable nucleation numbers and non-uniform nucleus sizes, easily leading to Ostwald ripening in the subsequent growth stage, where small particles dissolve while large particles continue to grow, ultimately resulting in a wider particle size distribution and irregular morphology of the precursor particles. More importantly, traditional methods lack the ability to guide the crystal growth direction, resulting in primary particles that are mostly randomly oriented and stacked. This structure is more prone to anisotropic stress accumulation and microcracks during repeated charging and discharging of the battery, accelerating performance degradation.

[0004] To address the aforementioned issues, researchers have explored various improvement strategies, such as optimizing reactor structure, finely controlling pH and feed rate, and introducing special additives or seed crystals. However, these improvements mostly focus on adjusting macroscopic process parameters or only improve certain single performance indicators. For example, simple additives may affect particle size but do not contribute to component uniformity; complex post-processing increases costs and may damage the structure. In particular, a systematic solution that addresses the three major challenges of component uniformity, morphological regularity, and crystal orientation from the crystallographic origin is lacking. Therefore, developing a novel preparation process that intrinsically guides crystal directional growth, along with a matching high-efficiency modifier, to directly construct precursors with radially ordered microstructures during precipitation through physicochemical means, has become an essential path to overcome existing technological bottlenecks and obtain high-performance products. This will not only enhance the intrinsic properties of materials but also have significant practical implications for promoting the industrialization of high-end lithium-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a directional crystallization process for high-nickel ternary precursors, which solves the technical problems of uneven composition caused by differences in metal ion precipitation rates, wide particle size distribution caused by intertwined nucleation growth processes, and disordered primary particle growth caused by lack of crystal plane guidance in the preparation of existing high-nickel ternary precursors by traditional co-precipitation methods.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A directional crystallization process for a high-nickel ternary precursor includes the following steps:

[0008] S1, by weight, add deionized water to the reactor, stir, and heat to 54.5-55.5℃; introduce nitrogen gas; add lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier, shear and disperse, and pump in concentrated ammonia water to make the ammonia concentration reach 4.0-6.0 g / L to obtain a suspension;

[0009] S2: Start the feed pumps for the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, the sodium hydroxide solution, and ammonia. In the initial 3-5 minutes, increase the feed rate of the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate and the sodium hydroxide solution to 2-4 times the feed rate of the steady-state growth stage, and adjust the feed rate of ammonia to 40-60% of the feed rate of the steady-state growth stage. Monitor the particle size distribution using an online particle size analyzer. When the particle D50 reaches the target value, switch to the next stage.

[0010] S3, the feed rates of the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, the sodium hydroxide solution, and ammonia are adjusted to the steady-state growth stage feed rate, and the automated feedback control system is activated to adjust the pH value to 11.28-11.32, thereby adjusting the feed rates of the alkali solution and ammonia. The lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier added in step S1 guides the metal hydroxide to grow radially ordered along its surface lattice matching.

[0011] S4. Once the target particle size is reached, stop feeding, stir, and age to obtain a slurry. Transfer the slurry to a filtration device and wash it with hot deionized water at 60-80℃. Finally, dry it in a vacuum drying oven at 118-122℃.

[0012] In this invention, the directional crystallization process of the high-nickel ternary precursor is precisely implemented in an aqueous phase system under inert gas protection. The modifier is uniformly dispersed in the base liquid containing the complexing agent through high-speed shearing, forming a stable suspension system. The core of the process adopts a pulse-steady-state dual-stage control strategy: In the initial pulse stage, the feed rate of the metal salt and precipitant is instantaneously increased to create a short-term high supersaturation environment in the reaction micro-region. At this time, the uniformly distributed modifier nanoparticles, with their high specific surface area and surface activity, serve as high-density heterogeneous nucleation sites, inducing the synchronous generation of a massive number of uniformly sized initial crystal nuclei, completely avoiding the particle size dispersion problem caused by homogeneous nucleation. The flow rate of the complexing agent is coordinated to maintain the balance of complexation kinetics of each metal ion, preventing the preferential precipitation of specific metals due to differences in complexation stability. When the crystal nuclei grow to the target size, the process seamlessly transitions to the steady-state growth stage, the feed rate of each reactant is reduced to a low level, and the pH of the system is strictly locked within an optimized narrow range by a high-precision feedback system, so that the supersaturation is maintained in a low and constant ideal state. Under these conditions, the modifier performs a dual core function: surface-regenerated hydroxyl groups selectively adsorb and release metal ammonia complex ions through electrostatic attraction and coordination, balancing the supply rate of various metal ions at the growth interface; simultaneously, the excellent lattice matching characteristics between the core crystal structure and the target hydroxide precursor provide a clear orientation template for crystal epitaxial growth, guiding the metal hydroxide to undergo radially layered ordered deposition. This synergistic mechanism promotes the highly ordered radial arrangement of primary particles, ultimately constructing secondary spherical particles with regular spherical shapes, dense internal structures, and highly uniform distribution of various metal elements. After appropriate aging to improve the crystal structure, thorough washing with warm deionized water to remove impurity ions, and vacuum drying, a high-performance precursor is obtained. This process, through the synergistic effects of the modifier's heterogeneous nucleation, ion buffering, and crystal plane guidance, achieves atomic-level precise control over the number of nuclei, crystal orientation, and elemental distribution, significantly improving the uniformity of the precursor structure and the cycle stability and rate performance of the subsequent cathode material.

[0013] According to a preferred embodiment of the present invention, in step S1, the shearing and dispersion time is 10-15 min.

[0014] According to a preferred embodiment of the present invention, in step S2, the target value is 1.4-1.6 μm.

[0015] According to a preferred embodiment of the present invention, in step S3, the time for guiding the orderly deposition and growth of metal hydroxide along the radial direction is 20-40 hours.

[0016] According to a preferred embodiment of the present invention, in step S4, the drying time in a vacuum drying oven at 118-122°C is 12-14 hours.

[0017] According to a preferred embodiment of the present invention, the preparation steps of the lithium zirconate titanate lanthanum-based heterostructure crystal plane modifier include:

[0018] A1, by weight, lithium nitrate, lanthanum nitrate, zirconium oxychloride, and tantalum ethoxide are dissolved in a mixed solvent of ethylene glycol and anhydrous ethanol and stirred; citric acid is added dropwise, and the pH is adjusted to 8-9 with ammonia; the mixture is transferred to a high-pressure reactor and reacted solvothermically at 218-222℃; after cooling, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and anhydrous ethanol at 60-80℃, and then vacuum dried at 78-82℃ to obtain precursor powder; the precursor powder is spread evenly in a crucible containing lithium carbonate powder, and then calcined at 895-905℃ in an air atmosphere; after cooling, it is ball-milled in an ethanol medium to obtain LLZTO nanoparticles;

[0019] A2. LLZTO nanoparticles were dispersed in anhydrous ethanol and sonicated to obtain an LLZTO ethanol suspension. Tetraisopropyl titanate was added dropwise to a mixture of anhydrous ethanol and glacial acetic acid and stirred to obtain a titanium sol. Under nitrogen protection, at 0-10℃ and with stirring, the LLZTO ethanol suspension was added dropwise to the titanium sol, aged, and centrifuged to obtain a composite powder coated with an amorphous titanium layer. The composite powder coated with the amorphous titanium layer was washed with anhydrous ethanol at 0-10℃ by centrifugation to obtain the washed composite powder.

[0020] A3. The washed composite powder was placed in a muffle furnace and heat-treated at 295-305℃ in air atmosphere, and then heated to 595-605℃ to obtain LLZTO@titanium dioxide composite nanoparticles.

[0021] A4. LLZTO@titanium dioxide composite nanoparticles were dispersed in a dilute ammonia solution, ultrasonicated at 30-40℃, and centrifuged to obtain a solid product. The solid product was washed with water and ethanol and then dried.

[0022] In this invention, the preparation of the lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier begins with the molecular-level dissolution and complexation of lithium, lanthanum, zirconium, and tantalum sources in a polyol mixed solvent. Citric acid, as a multidentate ligand, forms a stable chelate with metal ions. After being controlled in a weakly alkaline environment, a homogeneous precursor precipitate is generated through a solvothermal reaction. The precipitate is thoroughly washed with hot deionized water and anhydrous alcohols until chloride ions are completely removed, and then vacuum dried to obtain a high-purity precursor. The key innovation lies in the calcination process: the precursor is spread evenly in a crucible covered with homologous carbonate powder and heat-treated in an oxidizing atmosphere. The vapor of the active components released by the decomposition of carbonates constructs a dynamically compensated microenvironment, effectively suppressing the volatilization loss of key components at high temperatures, ensuring that the main material forms a high-purity cubic crystal phase structure, and then ball-milling to obtain nanocrystalline nuclei. Subsequently, the precise construction of the titanium dioxide shell was implemented: after the crystal nuclei were dispersed in anhydrous alcohol, they underwent an interfacial reaction with a titanium source precursor stabilized by organic acids in a strictly temperature-controlled low-temperature inert environment. The low temperature precisely suppressed the violent hydrolysis of the titanium source in the bulk solution, promoting the selective anchoring of its hydrolysis-condensation reaction to the active sites on the crystal nuclei surface, forming a uniform amorphous coating layer. The coated product was immediately and thoroughly washed with pre-cooled alcohol to completely remove unreacted substances and alcohol byproducts, eliminating the risk of transesterification side reactions during subsequent heat treatment. After washing, the composite powder underwent gradient heat treatment, first decomposing residual organic matter at low temperature, then raising the temperature to promote the crystallization of the coating layer into anatase phase titanium dioxide, forming a heterogeneous structure with a strong interfacial chemical bond to the core. Finally, after treatment with dilute ammonia water and ultrasound, the chemical bonds on the titanium dioxide surface were selectively hydrolyzed in a weakly alkaline environment, controllably regenerating high-density chemically adsorbed hydroxyl groups. This hydroxyl layer not only endows the particles with excellent aqueous dispersion stability but also serves as an active center for metal ion adsorption, providing a dual functional basis for ion buffering and crystal facet guidance in the co-precipitation system.

[0023] According to a preferred embodiment of the present invention, in step A1, the calcination time at 895-905°C is 6-8 hours.

[0024] According to a preferred embodiment of the present invention, in step A2, the aging time is 12-14 hours.

[0025] According to a preferred embodiment of the present invention, in step A3, the heat treatment time at 595-605°C is 4-6 hours.

[0026] According to a preferred embodiment of the present invention, in step A4, the ultrasonic treatment time at 30-40°C is 30-60 min.

[0027] The beneficial effects of this invention are as follows:

[0028] The technical solution provided by this invention, by introducing original inorganic modified materials and matching directional crystallization control strategies, has achieved a significant improvement in the comprehensive performance of high-nickel ternary precursors at multiple levels, with comprehensive and outstanding technical effects.

[0029] First, this invention achieves a fundamental breakthrough in the core aspect of microstructure control. Through a specially designed lithium zirconate titanate lanthanum-based heterostructure crystal plane modifier, the crystal plane effectively guides the growth of primary metal hydroxide particles along a specific lattice direction on the modifier surface during crystallization, ultimately forming a unique microstructure with significant radially ordered arrangement. This quasi-radial micromorphology allows the precursor and its derived cathode material to better adapt to the periodic changes in lattice parameters during repeated lithium-ion insertion / extraction, uniformly dispersing the internal stress induced by anisotropic volumetric strain, thereby greatly suppressing the generation and propagation of microcracks within the particles. Simultaneously, the modifier, through its regenerated surface active groups, achieves balanced adsorption and buffering of different metal ion ammonia complexes, ensuring ultra-uniform co-precipitation of nickel, cobalt, and manganese at the atomic scale. This fundamentally eliminates component segregation caused by differences in precipitation kinetics of different ions, resulting in a precursor product with highly accurate stoichiometry and consistent distribution.

[0030] Secondly, in terms of process control and product consistency, this invention achieves a leap from "macro-mixing" to "micro-control." By clearly separating the crystallization process into two independent and synergistic stages—"explosive nucleation" and "steady-state directional growth"—and supplementing them with a precise online monitoring and feedback control system, the problem of mutual interference between nucleation and growth in traditional co-precipitation methods is completely overcome. In the initial stage, a controllable high supersaturation environment is created, utilizing uniformly dispersed modifiers as numerous homogeneous heterogeneous nucleation sites, achieving instantaneous and synchronous generation of crystal nuclei, laying a solid foundation for obtaining products with extremely narrow particle size distributions. In the subsequent growth stage, by strictly maintaining the supersaturation at a low and constant level and precisely stabilizing the pH and complexing agent concentration, it is ensured that all crystal nuclei grow synchronously and slowly under almost identical thermodynamic and kinetic conditions, effectively avoiding Ostwald ripening, and ultimately obtaining secondary spherical particles with high sphericity, smooth surfaces, and uniform sizes. This superior process controllability significantly improves the reproducibility between product batches, meeting the stringent requirements of high-end battery manufacturing for the consistency of raw materials.

[0031] Finally, this invention brings comprehensive and significant improvements in overall performance and industrialization value. The high-nickel ternary precursor prepared by this directional crystallization process, thanks to its uniform composition, radially ordered dense structure, and concentrated particle size distribution, exhibits excellent electrochemical performance in the resulting cathode material after subsequent high-temperature sintering. This is manifested in higher first-cycle coulombic efficiency, superior rate performance, and significantly improved cycle life, with more outstanding capacity retention in stringent charge-discharge tests. Furthermore, the modifiers used in this process are all common commercially available chemicals, the main crystallization process steps are simple, the control logic is clear, and it is easy to scale up production. While improving the high-end performance of the product, it also possesses good process feasibility and cost control potential, providing a reliable and efficient solution for overcoming key technological bottlenecks in high-energy-density lithium-ion battery cathode materials and enhancing product market competitiveness. Detailed Implementation

[0032] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0033] Example 1

[0034] Preparation of lanthanum-based heterostructure crystal plane modifier for lithium zirconate titanate:

[0035] A1: Accurately weigh 4.78g lithium nitrate, 8.67g lanthanum nitrate, 2.94g zirconium oxychloride, and 2.56g tantalum ethoxide. Dissolve the above raw materials together in a mixed solvent of 40mL ethylene glycol and 40mL anhydrous ethanol, stirring at 500rpm until completely dissolved to form a clear solution. Add 12.0g citric acid dropwise to this solution, then adjust the pH of the mixture to 8.5 using a 25% ammonia solution. Transfer the pH-adjusted solution to a 100mL polytetrafluoroethylene-lined high-pressure reactor. Place the reactor in an oven and conduct a solvothermal reaction at 220℃ for a strictly controlled reaction time of 24 hours. After the reaction, allow the reactor to cool naturally to room temperature (approximately 25℃). Centrifuge to collect the white precipitate formed at the bottom of the reactor, and wash the precipitate alternately with 70℃ hot deionized water and room temperature anhydrous ethanol, three times each. The washed precipitate was transferred to a vacuum drying oven and dried at 80℃ for 12 hours to obtain a dry white precursor powder. 2.0 g of this precursor powder was weighed and evenly spread in an alumina crucible containing 2.0 g of lithium carbonate powder. The crucible was placed in a box-type muffle furnace and heated to 900℃ at a programmed rate of 5℃ / min under air atmosphere, and then calcined at this temperature for 6 hours, followed by a programmed cooling to room temperature. The calcined bulk material was placed in a ball mill jar with zirconia grinding balls at a mass ratio of 1:10, and an appropriate amount of anhydrous ethanol was added as a dispersion medium. High-energy ball milling was performed at 300 rpm for 48 hours. After ball milling, cubic lithium zirconate titanate (LLZTO) nanoparticles with a particle size distribution of 20-50 nm were obtained.

[0036] A2: Accurately weigh 1.0 g of LLZTO nanoparticles obtained in step A1, disperse them in 50 mL of anhydrous ethanol, and sonicate for 30 min to form a homogeneous and stable LLZTO ethanol suspension. In another container, measure 1.2 mL of tetraisopropyl titanate and slowly add it dropwise to a solution premixed with 45 mL of anhydrous ethanol and 1.5 mL of glacial acetic acid under vigorous stirring (800 rpm), continuing stirring for 30 min to obtain a completely transparent titanium sol. In a reaction apparatus equipped with cooling and inert gas protection, nitrogen gas is introduced, and the temperature of the reaction system is precisely maintained at 5 °C. Under continuous stirring (500 rpm) and nitrogen protection, the above LLZTO ethanol suspension is slowly and uniformly added dropwise to the titanium sol at a rate of 1.5 mL / min using a constant flow pump. After the addition is complete, the system is kept at 5 °C and aged for 12 h with stirring. After aging, the mixture is centrifuged, and the solid precipitate is collected. The solid precipitate was washed three times by centrifugation with pre-cooled anhydrous ethanol at 5°C to obtain LLZTO / amorphous titanium composite powder coated with an amorphous titanium layer.

[0037] A3: The composite powder obtained after washing in step A2 was transferred to an alumina ceramic boat and then placed in a muffle furnace. Under air atmosphere, the temperature was first increased to 300℃ at a rate of 5℃ / min and heat-treated at this temperature for 2 hours; subsequently, the temperature was further increased to 600℃ at a rate of 3℃ / min and heat-treated at this final temperature for 4 hours. This process caused the amorphous titanium layer to completely crystallize and transform into anatase phase titanium dioxide, ultimately yielding LLZTO@TiO2 composite nanoparticles with a clear core-shell structure.

[0038] A4: Accurately weigh 0.5 g of the LLZTO@TiO2 composite nanoparticles prepared in step A3 and disperse them in 50 mL of a 2% (w / w) dilute ammonia solution. Place the mixture in a constant temperature water bath at 35°C and simultaneously sonicate for 30 min. After treatment, centrifuge the mixture and collect the solid product. Wash the solid product once each with deionized water and anhydrous ethanol. Finally, place the washed solid in a vacuum drying oven and dry at 60°C for 6 h to obtain the final lithium zirconate titanate lanthanum-based heterostructure crystal facet modifier suitable for directional crystallization.

[0039] Directed crystallization process of high-nickel ternary precursors:

[0040] S1: Add 1000g of deionized water as the reaction base liquid to a 5L jacketed stainless steel reactor. Turn on the reactor's agitator and set the initial stirring speed to 300rpm. Simultaneously, turn on the external circulating water bath system to precisely stabilize the temperature of the material inside the reactor at 55.0℃. Continuously purify high-purity nitrogen gas into the reactor to replace and isolate it from air. Weigh 1.5g of the modifier prepared above and add it to the reactor. Start a high-speed shear disperser and shear disperse the mixture at 10000rpm for 12min to ensure that the modifier nanoparticles are fully and uniformly dispersed in the water. Subsequently, use a metering pump to pump 25% concentrated ammonia solution into the reactor. Through real-time monitoring and calculation, precisely adjust the initial ammonia concentration in the reaction system to 5.0g / L to obtain a uniform and stable modifier suspension.

[0041] S2: Activate and control three precision feed pumps to pump three solutions into the reactor: the first is a mixed metal salt solution of nickel sulfate, cobalt sulfate, and manganese sulfate, with a total metal ion concentration of 2.0 mol / L and a molar ratio of nickel, cobalt, and manganese of 8:1:1; the second is a sodium hydroxide precipitant solution with a concentration of 4.0 mol / L; and the third is an ammonia solution with a concentration of 2.0 mol / L, used as a supplementary complexing agent. During the first 5 minutes of feeding, a pulse feeding mode is implemented: the instantaneous feed rates of the metal salt solution and sodium hydroxide solution are increased to 3.0 times the preset feed rates for the subsequent steady-state growth stage, specifically 60 mL / min for the metal salt solution and 45 mL / min for the sodium hydroxide solution; simultaneously, the feed rate of the supplementary ammonia solution is adjusted to 50% of the steady-state growth stage feed rate, i.e., 10 mL / min. The particle size changes within the reactor are monitored in real time using an online laser particle size analyzer installed on the reactor's circulation pipeline. When the D50 value of the particle group reaches 1.5 μm, the system will automatically switch to the next growth stage.

[0042] S3: The feed rates of the metal salt solution, sodium hydroxide solution, and ammonia solution are synchronously and smoothly reduced to preset steady-state values ​​of 20 mL / min, 15 mL / min, and 20 mL / min, respectively. An automated feedback control system, centered on a high-precision pH electrode and controller, is activated. This system monitors the pH value inside the reactor in real time and fine-tunes the instantaneous feed rates of the sodium hydroxide and ammonia solutions through a PID algorithm, precisely and stably controlling the pH value of the reaction system at 11.30, with fluctuations not exceeding ±0.02. Under these stringent steady-state control conditions, the modifier added in step S1 exerts its crystal plane guiding effect, guiding the metal hydroxide crystals to undergo ordered deposition and epitaxial growth along a radial direction matching its surface lattice. This steady-state growth process continues for 30 hours.

[0043] S4: Once the online particle size analyzer displays the D50 value of the secondary particles reaching the preset target particle size of 11.0 μm, immediately stop all feed pumps. Maintain stirring (300 rpm) and reaction temperature (55.0℃) to allow the slurry to continue aging in the reactor for 2 hours. After aging, transfer all the slurry to a vacuum filtration device for solid-liquid separation. Repeatedly wash the filter cake with 70℃ hot deionized water until the conductivity of the washing filtrate decreases and stabilizes below 20 μS / cm. Transfer the qualified wet filter cake to a vacuum drying oven and dry at 120℃ for 12 hours. After drying, crush and sieve to obtain the final high-nickel ternary precursor NCM811 product.

[0044] Example 2

[0045] The specific implementation method is the same as in Example 1, except for the preparation of the lithium zirconate titanate lanthanum-based heterostructure crystal plane modifier:

[0046] A1: Accurately weigh 4.70 g of lithium nitrate, 8.52 g of lanthanum nitrate, 2.89 g of zirconium oxychloride, and 2.51 g of tantalum ethoxide. Dissolve the above raw materials together in a mixed solvent of 38 mL ethylene glycol and 38 mL anhydrous ethanol, stirring at 480 rpm until completely dissolved. Add 11.8 g of citric acid dropwise to the solution, and then adjust the pH of the mixture to 8.2 using a 25% ammonia solution. Transfer the solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor. Place the reactor in an oven and carry out a solvothermal reaction at 219 °C for 24 h. After the reaction, allow it to cool naturally to room temperature. Collect the precipitate by centrifugation, and wash the precipitate alternately with hot deionized water at 65 °C and anhydrous ethanol at room temperature, three times each. Dry the washed precipitate in a vacuum drying oven at 79 °C for 12 h to obtain the precursor powder. Weigh 1.8g of the precursor powder and spread it evenly in an alumina crucible already containing 1.8g of lithium carbonate powder. Place the crucible in a muffle furnace and heat to 898℃ at 5℃ / min in air atmosphere, calcine at this temperature for 6 hours, and then cool down using a programmed temperature control. Place the calcined block and zirconia grinding balls in a ball milling jar at a mass ratio of 1:10, add anhydrous ethanol, and ball mill at 300 rpm for 48 hours to obtain LLZTO nanoparticles.

[0047] A2: Accurately weigh 0.9 g of LLZTO nanoparticles and disperse them in 45 mL of anhydrous ethanol. Sonicate for 30 min to obtain a suspension. Measure 1.0 mL of tetraisopropyl titanate and add it dropwise to a mixture of 42 mL of anhydrous ethanol and 1.3 mL of glacial acetic acid while stirring (800 rpm). Stir for 30 min to obtain a titanium sol. Under nitrogen protection and at 2 °C, add the suspension dropwise to the titanium sol while continuously stirring (500 rpm). After the addition is complete, age the mixture at 2 °C for 12 h with stirring. Collect the precipitate by centrifugation and wash it three times with anhydrous ethanol at 2 °C to obtain the composite powder.

[0048] A3: The composite powder was placed in a muffle furnace and heat-treated at 298°C for 2 hours at a rate of 5°C / min in air atmosphere, and then heat-treated at 598°C for 4 hours at a rate of 3°C / min to obtain LLZTO@TiO2 composite nanoparticles.

[0049] A4: Accurately weigh 0.45g of LLZTO@TiO2 composite nanoparticles and disperse them in 45mL of 1% (w / w) dilute ammonia solution. Sonicate the mixture in a 32℃ constant temperature water bath for 30min. After centrifugation, wash the solid product once with deionized water and once with anhydrous ethanol, and finally vacuum dry at 60℃ for 6h to obtain the modifier.

[0050] Directed crystallization process of high-nickel ternary precursors:

[0051] S1: Add 800g of deionized water to a 5L reactor. Start the stirrer and set the speed to 300rpm. Turn on the circulating water bath and stabilize the temperature at 54.7℃. Purge with nitrogen for protection. Add 0.8g of modifier and disperse at 10000rpm for 10min. Pump in concentrated ammonia water to adjust the initial ammonia concentration to 4.5g / L.

[0052] S2: Start the feed pump and pump in a mixed salt solution of NCM811 with a total metal concentration of 2.0 mol / L, a sodium hydroxide solution of 4.0 mol / L, and ammonia solution of 2.0 mol / L. For the first 4 minutes, increase the feed rates of the salt and alkali solutions to 2.5 times the steady-state rate (50 mL / min for salt solution, 37.5 mL / min for alkali solution), and adjust the ammonia feed rate to 45% of the steady-state rate (9 mL / min). Use an online particle size analyzer to monitor the particle size distribution; switch to the next step when the D50 reaches 1.4 μm.

[0053] S3: Adjust all feed rates to steady-state values ​​(salt solution 20 mL / min, alkali solution 15 mL / min, ammonia 20 mL / min). Activate automatic pH control to precisely stabilize the system pH at 11.29. Grow under these conditions for 25 hours.

[0054] S4: When the secondary particle D50 reaches 10.2 μm, stop feeding and age at 54.7℃ for 2 hours. Filter the slurry and wash it with 70℃ hot water until the conductivity of the filtrate is below 20 μS / cm. Dry the wet filter cake in a vacuum drying oven at 119℃ for 12 hours to obtain the precursor product.

[0055] Example 3

[0056] The specific implementation method is the same as in Example 1, except for the preparation of the lithium zirconate titanate lanthanum-based heterostructure crystal plane modifier:

[0057] A1: Accurately weigh 4.85 g of lithium nitrate, 8.80 g of lanthanum nitrate, 2.99 g of zirconium oxychloride, and 2.62 g of tantalum ethoxide. Dissolve the above raw materials together in a mixed solvent of 42 mL of ethylene glycol and 42 mL of anhydrous ethanol, stirring at 520 rpm until completely dissolved. Add 12.2 g of citric acid dropwise to the solution, and then adjust the pH of the mixture to 8.8 using a 25% ammonia solution. Transfer the solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor. Place the reactor in an oven and carry out a solvothermal reaction at 221 °C for 24 h. After the reaction, allow it to cool naturally to room temperature. Collect the precipitate by centrifugation, and wash the precipitate alternately with hot deionized water at 75 °C and anhydrous ethanol at room temperature, three times each. Dry the washed precipitate in a vacuum drying oven at 81 °C for 12 h to obtain the precursor powder. Weigh 2.2g of the precursor powder and evenly spread it in an alumina crucible already containing 2.2g of lithium carbonate powder. Place the crucible in a muffle furnace and heat to 902℃ at 5℃ / min under air atmosphere, calcine at this temperature for 7h, and then cool down using a programmed temperature control. Place the calcined block and zirconia grinding balls in a ball milling jar at a mass ratio of 1:10, add anhydrous ethanol, and ball mill at 300rpm for 48h to obtain LLZTO nanoparticles.

[0058] A2: Accurately weigh 1.1 g of LLZTO nanoparticles and disperse them in 55 mL of anhydrous ethanol. Sonicate for 30 min to obtain a suspension. Measure 1.4 mL of tetraisopropyl titanate and add it dropwise to a mixture of 48 mL of anhydrous ethanol and 1.7 mL of glacial acetic acid while stirring (800 rpm). Stir for 30 min to obtain a titanium sol. Under nitrogen protection and at 8°C, add the suspension dropwise to the titanium sol while continuously stirring (500 rpm). After the addition is complete, age the mixture at 8°C with stirring for 13 h. Collect the precipitate by centrifugation and wash it three times with anhydrous ethanol at 8°C to obtain the composite powder.

[0059] A3: The composite powder was placed in a muffle furnace and heat-treated at 302℃ for 2 hours in air atmosphere at a rate of 5℃ / min, and then heat-treated at 603℃ for 5 hours at a rate of 3℃ / min to obtain LLZTO@TiO2 composite nanoparticles.

[0060] A4: Accurately weigh 0.55g of LLZTO@TiO2 composite nanoparticles and disperse them in 55mL of 4% (w / w) dilute ammonia solution. Sonicate the mixture in a 38℃ constant temperature water bath for 50min. After centrifugation, wash the solid product once with deionized water and once with anhydrous ethanol, and finally vacuum dry at 60℃ for 6h to obtain the modifier.

[0061] Directed crystallization process of high-nickel ternary precursors:

[0062] S1: Add 1200g of deionized water to a 5L reactor. Start the stirrer and set the speed to 300rpm. Turn on the circulating water bath and stabilize the temperature at 55.3℃. Purge with nitrogen for protection. Add 2.2g of modifier and disperse at 10000rpm for 15min. Pump in concentrated ammonia water to adjust the initial ammonia concentration to 5.5g / L.

[0063] S2: Start the feed pump and pump in a 2.0 mol / L NCM811 mixed salt solution, a 4.0 mol / L sodium hydroxide solution, and a 2.0 mol / L ammonia solution. For the first 3 minutes, increase the feed rates of the salt and alkali solutions to 3.5 times the steady-state rate (70 mL / min for salt solution, 52.5 mL / min for alkali solution), and adjust the ammonia feed rate to 55% of the steady-state rate (11 mL / min). Use an online particle size analyzer to monitor the particle size distribution; switch to the next step when the D50 reaches 1.6 μm.

[0064] S3: Adjust all feed rates to steady-state values ​​(salt solution 20 mL / min, alkali solution 15 mL / min, ammonia 20 mL / min). Activate automatic pH control to precisely stabilize the system pH at 11.31. Grow under these conditions for 38 hours.

[0065] S4: When the secondary particle D50 reaches 11.8 μm, stop feeding and age at 55.3℃ for 2 hours. Filter the slurry and wash it with 70℃ hot water until the conductivity of the filtrate is below 20 μS / cm. Dry the wet filter cake in a vacuum drying oven at 121℃ for 13 hours to obtain the precursor product.

[0066] Comparative Example 1

[0067] The specific implementation method is the same as in Example 1, except that in step S1 of the directional crystallization process of the high-nickel ternary precursor, no lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier is added. Only deionized water is added to the reactor, the ammonia concentration is adjusted, and subsequent steps are performed. All other process parameters and operating conditions, such as the reactor feeding, temperature, feed program, pH control, growth time, washing, and drying, are completely consistent with those in Example 1.

[0068] Comparative Example 2

[0069] The specific implementation method is the same as in Example 1, except that the preparation of the lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier is only carried out up to step A3 in Example 1. That is, LLZTO@TiO2 composite nanoparticles obtained after heat treatment at 600℃ are used, but step A4 (ultrasonic treatment with dilute ammonia solution and subsequent washing and drying) is not performed. This composite nanoparticle without surface hydroxylation functionalization treatment is used as an additive. In the directional crystallization process of the high-nickel ternary precursor, the amount of this additive used (1.5g) and all other process parameters and operating conditions from S1 to S4 are completely consistent with those in Example 1.

[0070] Comparative Example 3

[0071] The specific implementation method is the same as in Example 1, except that the preparation method of the lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier is changed as follows: Step A1 is completely replaced by accurately weighing 1.0 g of silica nanoparticles (particle size approximately 20 nm) prepared by the gas phase method as the core material. Step A2: Disperse this 1.0 g silica nanoparticles in 50 mL of anhydrous ethanol and sonicate for 30 min to form a suspension. The preparation method of titanium sol is the same as Step A2 in Example 1 (1.2 mL tetraisopropyl titanate, 45 mL anhydrous ethanol, 1.5 mL glacial acetic acid). The subsequent coating reaction conditions (nitrogen protection, 5 °C, dropwise addition and aging), washing (washing 3 times with anhydrous ethanol at 5 °C), and the heat treatment procedure of Step A3 (300 °C for 2 h, 600 °C for 4 h) are all exactly the same as in Example 1, finally obtaining SiO2@TiO2 composite nanoparticles. The surface treatment of Step A4 (2% ammonia water, sonication at 35 °C for 30 min, washing and drying) is also exactly the same as in Example 1. Using this surface-hydroxylated SiO2@TiO2 composite nanoparticle as an additive, in the directional crystallization process of the high-nickel ternary precursor, its usage (1.5g) and all other process parameters and operating conditions from S1 to S4 are completely consistent with those in Example 1.

[0072] Performance testing

[0073] The high-nickel ternary precursors prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing according to the following method, which included the following steps:

[0074] Elemental quantitative analysis was performed using inductively coupled plasma atomic emission spectrometry (ICP-AES). Specifically, 0.1000g of the precursor sample was accurately weighed, digested with aqua regia, and brought to a final volume before being tested on the instrument. The actual molar percentages of nickel, cobalt, and manganese were obtained by comparing with the standard curve. The absolute deviations from the theoretical ratios were calculated, and the arithmetic mean was obtained. The result was reported as the mean absolute deviation, expressed as a molar percentage.

[0075] The microstructure of the sample was observed using a field emission scanning electron microscope. Specifically, a small amount of powder sample was uniformly dispersed on a conductive adhesive and sputtered with gold. The morphology of the secondary particles and the arrangement characteristics of the primary particles were observed under an accelerating voltage of 15.0 kV. The cross-section of a single secondary particle was scanned using an X-ray energy dispersive spectrometer at a voltage of 10.0 kV to qualitatively evaluate the uniformity of the distribution of nickel, cobalt, and manganese.

[0076] The crystal structure of the sample was analyzed using an X-ray diffractometer. Specifically, a copper target Kα-ray source was used, with a scanning range of 10° to 80°, a step size of 0.02°, and a scanning speed of 10° per minute. After obtaining the diffraction pattern, the characteristic diffraction peak located at approximately 19° was fitted using the instrument's software, and its full width at half maximum (FWHM) was calculated in degrees.

[0077] The particle size distribution of the sample was measured using a laser particle size analyzer. Specifically, about 0.1g of sample was dispersed in an aqueous solution containing 0.5% sodium hexametaphosphate, ultrasonically dispersed for 3 minutes, and then tested. The median particle size and particle size distribution span on a volume basis were reported.

[0078] The tap density of the sample was measured using a powder tap density meter. Specifically, 5.000g of powder was poured into a 25mL graduated cylinder and vibrated 1500 times at a vibration frequency of 250 times per minute and an amplitude of 3mm. The volume of the powder after tapping was recorded and the density was calculated, expressed in grams per cubic centimeter.

[0079] The precursor was prepared as a positive electrode material and electrochemical tests were performed. Specifically, the precursor was uniformly mixed with lithium hydroxide at a molar ratio of 1:1.05, calcined at 480℃ for 5 hours in an oxygen atmosphere, and then calcined at 750℃ for 12 hours to obtain the positive electrode material. Active material, conductive carbon black, and polyvinylidene fluoride were mixed at a mass ratio of 92:4:4 to form a slurry, which was then coated onto aluminum foil. After vacuum drying at 120℃ for 12 hours, the slurry was cut into electrode sheets. A lithium metal sheet was used as the counter electrode, and 1.0 mol / L lithium hexafluorophosphate was added. Using ethylene carbonate and diethyl carbonate solutions as electrolytes, CR2032 coin cells were assembled in an argon glove box. A Blue Battery testing system was used to perform a two-week charge-discharge activation at 0.1C within a voltage range of 2.8 to 4.3V. Subsequently, a constant current charge-discharge cycle test was conducted at 1.0C at 25°C. The discharge specific capacity and coulombic efficiency of the first cycle were recorded, and the percentage of discharge capacity retained relative to the discharge capacity of the third cycle was calculated at the 100th cycle.

[0080] Test results:

[0081] Table 1: Test results of each embodiment and comparative example

[0082] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Elemental homogeneity (mean absolute deviation, mol%) 0.02 0.04 0.02 0.15 0.08 0.17 Microscopic morphology (primary particle arrangement) Clear radial arrangement radial arrangement radial arrangement Random unordered stack Weak radial trend No obvious orientation Elemental distribution (EDS surface scan) uniform height uniform uniform Local segregation Relatively uniform Significant cobalt enrichment Crystal structure (101) crystal plane diffraction peak full width at half maximum (FWHM), °) 0.98 1.02 1.05 1.35 1.21 1.28 Median particle size D50 (μm) 11.2 10.3 11.9 10.8 11.1 10.5 Particle size distribution span 0.43 0.47 0.45 0.68 0.59 0.62 Tap density (g / cm³) 2.15 2.11 2.13 1.92 2.03 1.98 Initial discharge specific capacity (mAh / g) 212.5 210.8 211.9 205.3 208.6 203.7 First Coulomb efficiency (%) 93.2 92.8 92.9 90.1 91.5 89.4 1C cycle 100-cycle capacity retention (%) 96.5 95.8 96.0 87.2 91.0 84.5

[0083] As can be seen from Table 1, Examples 1-3, compared with Comparative Examples 1-3, comprehensively and systematically solved the three major technical problems faced by the traditional co-precipitation method in preparing high-nickel ternary precursors.

[0084] First, to address the issue of component inhomogeneity caused by differences in metal ion precipitation rates, the examples employed a lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier. The regenerated active hydroxyl groups on its surface can uniformly adsorb different metal ammonium complex ions, playing an effective ion buffering role. This resulted in an average absolute deviation of only 0.02-0.04 mol% in the sample, significantly lower than that of Comparative Example 1 without the modifier and Comparative Example 3 using an ineffective core modifier. This demonstrates that the modifier fundamentally achieves uniform co-precipitation at the atomic scale.

[0085] Secondly, to address the issue of wide particle size distribution caused by the intertwining of nucleation and growth processes, the example precisely controls the process through two stages: "explosive nucleation" and "steady-state directional growth." It also utilizes uniformly dispersed modifiers as numerous homogeneous heterogeneous nucleation sites to achieve instantaneous synchronous generation of crystal nuclei, thereby obtaining a product with a narrow particle size distribution spanning only 0.43-0.47, which is far superior to the 0.68 of Comparative Example 1. At the same time, the higher tap density also confirms the compactness and uniformity of particle growth.

[0086] Finally, addressing the issue of disordered primary particle growth due to the lack of crystal plane guidance, the modifier in the examples successfully guided the orderly radial deposition of hydroxide crystals through its specific lattice-matching interface. Scanning electron microscopy and sharper diffraction peaks confirmed that the primary particles exhibited a clear radial arrangement, forming structurally stable secondary spherical particles. This microstructure directly translates into excellent electrochemical performance, resulting in a capacity retention rate of 95.8-96.5% in long-cycle testing, far exceeding that of all comparative examples.

[0087] In summary, this invention, through innovative modifier design and process control, synergistically solves the challenges of component, morphology, and structure regulation, significantly improving the overall performance of the precursor and its derived cathode materials.

[0088] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A directional crystallization process for a high-nickel ternary precursor, characterized in that, Includes the following steps: S1, by weight, add deionized water to the reactor, stir, and heat to 54.5-55.5℃; introduce nitrogen gas; add lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier, shear and disperse, and pump in concentrated ammonia water to make the ammonia concentration reach 4.0-6.0 g / L to obtain a suspension; S2: Start the feed pumps for the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, the sodium hydroxide solution, and ammonia. In the initial 3-5 minutes, increase the feed rate of the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate and the sodium hydroxide solution to 2-4 times the feed rate of the steady-state growth stage, and adjust the feed rate of ammonia to 40-60% of the feed rate of the steady-state growth stage. Monitor the particle size distribution using an online particle size analyzer. When the particle D50 reaches the target value, switch to the next stage. S3, the feed rates of the metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, the sodium hydroxide solution, and ammonia are adjusted to the steady-state growth stage feed rate, and the automated feedback control system is activated to adjust the pH value to 11.28-11.32, thereby adjusting the feed rates of the alkali solution and ammonia. The lithium zirconate titanate lanthanum-based heterostructure crystal surface modifier added in step S1 guides the metal hydroxide to grow radially ordered along its surface lattice matching. S4. Once the target particle size is reached, stop feeding, stir, and age to obtain a slurry. Transfer the slurry to a filtration device and wash it with hot deionized water at 60-80℃. Finally, dry it in a vacuum drying oven at 118-122℃.

2. The directional crystallization process for the high-nickel ternary precursor according to claim 1, characterized in that, In step S1, the shear dispersion time is 10-15 min.

3. The directional crystallization process for the high-nickel ternary precursor according to claim 1, characterized in that, In step S2, the target value is 1.4-1.6 μm.

4. The directional crystallization process for the high-nickel ternary precursor according to claim 1, characterized in that, In step S3, the time for guiding the radially ordered deposition and growth of metal hydroxide is 20-40 hours.

5. The directional crystallization process for the high-nickel ternary precursor according to claim 1, characterized in that, In step S4, the drying time in a vacuum drying oven at 118-122℃ is 12-14 hours.

6. The directional crystallization process for the high-nickel ternary precursor according to any one of claims 1-5, characterized in that, The preparation steps of the lithium zirconate titanate lanthanum-based heterostructure crystal plane modifier include: A1, by weight, lithium nitrate, lanthanum nitrate, zirconium oxychloride, and tantalum ethoxide are dissolved in a mixed solvent of ethylene glycol and anhydrous ethanol and stirred; citric acid is added dropwise, and the pH is adjusted to 8-9 with ammonia; the mixture is transferred to a high-pressure reactor and reacted solvothermically at 218-222℃; after cooling, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and anhydrous ethanol at 60-80℃, and then vacuum dried at 78-82℃ to obtain precursor powder; the precursor powder is spread evenly in a crucible containing lithium carbonate powder, and then calcined at 895-905℃ in an air atmosphere; after cooling, it is ball-milled in an ethanol medium to obtain LLZTO nanoparticles; A2. LLZTO nanoparticles were dispersed in anhydrous ethanol and sonicated to obtain an LLZTO ethanol suspension. Tetraisopropyl titanate was added dropwise to a mixture of anhydrous ethanol and glacial acetic acid and stirred to obtain a titanium sol. Under nitrogen protection, at 0-10℃ and with stirring, the LLZTO ethanol suspension was added dropwise to the titanium sol, aged, and centrifuged to obtain a composite powder coated with an amorphous titanium layer. The composite powder coated with the amorphous titanium layer was washed with anhydrous ethanol at 0-10℃ by centrifugation to obtain the washed composite powder. A3. The washed composite powder was placed in a muffle furnace and heat-treated at 295-305℃ in air atmosphere, and then heated to 595-605℃ to obtain LLZTO@titanium dioxide composite nanoparticles. A4. LLZTO@titanium dioxide composite nanoparticles were dispersed in a dilute ammonia solution, ultrasonicated at 30-40℃, and centrifuged to obtain a solid product. The solid product was washed with water and ethanol and then dried.

7. The directional crystallization process for the high-nickel ternary precursor according to claim 6, characterized in that, In step A1, the calcination time at 895-905℃ is 6-8 hours.

8. The directional crystallization process for the high-nickel ternary precursor according to claim 6, characterized in that, In step A2, the aging time is 12-14 hours.

9. The directional crystallization process for the high-nickel ternary precursor according to claim 6, characterized in that, In step A3, the heat treatment time is 4-6 hours at a temperature of 595-605℃.

10. The directional crystallization process for the high-nickel ternary precursor according to claim 6, characterized in that, In step A4, the ultrasonic treatment at 30-40℃ takes 30-60 minutes.