Preparation method of large-particle-size nickel hydroxide

Abstract

The invention discloses a preparation method of large-particle-size nickel hydroxide in the field of inorganic functional materials. According to the method, particle size control is achieved through a strategy of combining step-by-step parallel flow feeding and guiding agent regulation and control. The method comprises the following steps: firstly, synchronously dropwise adding a nickel salt with relatively high concentration and alkali liquor into a reaction base solution containing ammonia water and the guiding agent, generating a uniform crystal nucleus under a weakly alkaline condition, and ageing; next, nickel salt with relatively low concentration and alkali liquor are dropwise added synchronously, and crystal nucleus epitaxially grows under a slightly strong alkaline condition; and finally, aging, washing and drying to obtain the product. Vanadium pentoxide is activated by hydrogen peroxide and then reacts with cesium carbonate, layered cesium vanadate is prepared through hydrothermal crystallization, and then the layered cesium vanadate is subjected to surface modification by a silane coupling agent to obtain the guiding agent. The heterogeneous nucleation and growth guiding effects of the guiding agent are utilized, and a two-step feeding process is cooperated, so that homogeneous nucleation is effectively inhibited, controllable synthesis of nickel hydroxide with the particle size within a target range is realized, the process is stable, and the repeatability is good.

Description

Technical Field

[0001] This invention relates to the field of inorganic functional materials technology, specifically to a method for preparing large-particle-size nickel hydroxide. Background Technology

[0002] Nickel hydroxide, as an important inorganic functional material, plays an irreplaceable role in the field of alkaline secondary batteries, and is a key component of the positive electrode active materials of nickel-cadmium, nickel-metal hydride, and nickel-zinc batteries. Its physical and chemical properties, especially crystal structure, particle morphology, particle size, and distribution, directly determine the electrode packing density, active material utilization rate, and the overall energy density and cycle life of the battery. Among these, large-particle-size, high-density, and spherical nickel hydroxide can significantly improve the tap density of the electrode, reduce volume during battery assembly, and increase volumetric capacity. It also helps improve electrolyte wettability and charge transport efficiency, thus remaining a key focus of high-performance alkaline battery material research and development. There is a clear market demand for nickel hydroxide products with particle sizes ranging from tens to hundreds of micrometers and concentrated distribution, which places high demands on the preparation process for controllable grain growth and uniform and stable products.

[0003] Currently, the large-scale industrial production of nickel hydroxide mainly employs chemical precipitation, with continuous co-precipitation and its improved processes being the most common. To obtain ideal particle size and morphology, engineers have developed various control strategies. A basic method is single-step co-current precipitation, which influences the crystallization process by controlling macroscopic parameters such as reaction temperature, acid / base concentration, feeding rate, and stirring intensity. However, this method has limited control over the separation of nucleation and growth, and tends to produce products with a wide particle size distribution. A more advanced approach is staged feeding, which first induces the rapid generation of numerous crystal nuclei under specific conditions, then alters the reaction conditions to preferentially deposit and grow new material on the surface of existing nuclei, thereby expanding the particle size. Furthermore, prolonged aging after the reaction, utilizing the Ostwald ripening effect of dissolution-recrystallization, can further refine the particle size distribution. Despite continuous optimization of these traditional methods, some inherent technical bottlenecks remain. For example, it is difficult to completely suppress the continuous occurrence of homogeneous nucleation during the nucleation stage, resulting in the formation of new nuclei during the growth stage, which affects the uniformity of the final particle size; the aging process is time-consuming, usually requiring several hours or even longer, and production efficiency needs to be improved; in order to control performance, it is often necessary to dope other metal elements such as cobalt and zinc during the precipitation process, which increases the cost of raw materials and the complexity of the process. These factors restrict the accuracy, economy and consistency of the preparation of high-performance large-particle-size nickel hydroxide products.

[0004] To address the shortcomings of existing technologies, this invention aims to provide an innovative method for preparing large-particle-size nickel hydroxide. The core of this invention lies in the introduction of a cesium vanadate intercalation directing agent, creatively combining it with a classic two-stage feeding precipitation process. This directing agent does not directly participate in the formation of the final product, but rather acts as a "template" and "regulator" for the crystallization process. Its unique layered structure and surface properties strongly adsorb nickel ions, providing abundant and uniform heterogeneous nucleation sites, thereby effectively controlling the number and position of crystal nuclei from the source and greatly suppressing unnecessary homogeneous nucleation. Based on this guiding effect, a carefully designed two-stage feeding strategy is employed: the first stage generates uniform and dense initial crystal nuclei under a weakly alkaline environment; the second stage, under adjusted alkaline conditions, guides the newly generated nickel hydroxide to directionally coat and epitaxially grow around the crystal nuclei. This method not only reduces sensitivity to fluctuations in traditional process parameters and broadens the process window, but also promises to shorten the necessary aging time. This invention replaces some metal doping with physicochemical regulation, which simplifies the main process and is expected to stably produce large-particle nickel hydroxide products with a clear target particle size range, concentrated distribution, good crystallinity and high tap density, providing a new solution to meet the needs of the high-end market. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing large-particle-size nickel hydroxide, which solves the technical problems of inaccurate particle size and distribution control, long aging time, and dependence on metal doping in existing traditional methods for preparing large-particle-size nickel hydroxide.

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

[0007] A method for preparing large-particle-size nickel hydroxide includes the following steps:

[0008] S1, by weight, add 1500-2500 parts of deionized water to a reactor, heat to 54-56℃, add 0.3-0.7 parts of cesium vanadate intercalation directing agent, add 6.2-8.5 parts of ammonia water, and stir continuously to obtain a mixture;

[0009] S2, add an aqueous solution of 1.4-1.6 mol / L nickel sulfate and an aqueous solution of 2.4-2.6 mol / L sodium hydroxide to the mixture, adjust the pH to 11.2-11.4, stir, and age;

[0010] S3. Add 0.9-1.1 mol / L nickel sulfate aqueous solution and 1.6-2.0 mol / L sodium hydroxide aqueous solution to the reactor, adjust the pH value to 11.5-11.7, stir, and age.

[0011] S4. Maintain the reactor temperature at 54-56℃, stir, and age to obtain a slurry; cool the slurry to room temperature, and use a plate and frame filter press for solid-liquid separation to obtain a filter cake; wash the filter cake with deionized water at 78-82℃, and finally dry it in a vacuum drying oven at 104-106℃.

[0012] In the preparation of nickel hydroxide, the cesium vanadate intercalating directing agent of this invention dominates the entire crystallization kinetic path from nucleation to growth through multiple mechanisms, including physical adsorption, chemical guidance, and interfacial microenvironment regulation. At the beginning of the reaction, the directing agent nanosheets dispersed in an ammoniacal substrate, with their positively charged amino functional groups, efficiently electrostatically adsorb and enrich positively charged tetraammine nickel complex ions in the solution, forming a locally high-concentration region at the solid-liquid interface. When an alkaline solution is added, and the pH of the system rises to the precipitation point, these highly enriched nickel ions rapidly reach supersaturation on the surface of the directing agent and undergo in-situ hydrolysis and precipitation, thereby forming a large number of uniformly distributed initial nickel hydroxide nuclei on the nanosheet surface. This process achieves absolute dominance of heterogeneous nucleation, almost completely suppressing the occurrence of homogeneous nucleation in the bulk solution, ensuring the uniformity and controllability of the number of nuclei from the source. This is a prerequisite for obtaining a narrow-distribution, large-particle-size product. The subsequent first stage of feeding and aging was carried out under slightly lower pH conditions. This condition moderately reduced the precipitation rate, allowing the newly generated nickel hydroxide to be deposited orderly on the existing crystal nuclei, completing the initial consolidation and refinement of the crystal nuclei. Entering the second stage of growth, the pH of the system was increased to appropriately accelerate the precipitation reaction rate, but the presence of the directing agent continued to play a crucial role: firstly, its surface, already covered by the initial crystal nuclei, continued to provide an ideal growth substrate; secondly, the exchangeable cesium ions between its layers underwent slow ion exchange with ammonium ions in the solution, forming a unique dynamic ionic microenvironment near the growth interface. This micro-perturbation promoted the orderly arrangement and deposition of ions along specific crystal planes, which was beneficial for the construction of a dense spherical structure. Under the driving force, the newly formed precipitate preferentially migrated and epitaxially grew on the existing grains, rather than forming new nuclei, thereby achieving a directional increase in grain size. In the final aging stage, under the stable interfacial environment of the directing agent, the Ostwald aging process proceeds more efficiently. A very small amount of unstable fine particles dissolve and redeposit onto the surface of larger particles, further homogenizing the particle size and improving the crystal integrity of the product. In summary, this directing agent, through a multi-level linkage mechanism involving adsorption enrichment, induction of heterogeneous nucleation, stabilization of the growth interface, and regulation of the local chemical environment, synergistically with the stepwise precipitation process, achieves precise control over the nickel hydroxide crystallization process.

[0013] According to a preferred embodiment of the present invention, in step S1, the ammonia concentration in the mixture is 7.8-8.2 g / L.

[0014] According to a preferred embodiment of the present invention, in step S2, the aging time is 30-60 minutes.

[0015] According to a preferred embodiment of the present invention, in step S3, the stirring time is 20-40 min.

[0016] According to a preferred embodiment of the present invention, in step S4, the drying time in a vacuum drying oven at 104-106°C is 12-14 hours.

[0017] According to a preferred embodiment of the present invention, the preparation steps of the cesium vanadate intercalation directing agent include:

[0018] A1, by weight, add 5-7 parts of vanadium pentoxide to 200-400 parts of deionized water, stir to obtain a suspension, and add 15-25 parts of hydrogen peroxide solution dropwise to the suspension while stirring to obtain a mixture. Place the mixture at 68-72℃ and stir continuously to obtain a gel. Wash the gel with deionized water by centrifugation and redisperse it in deionized water to obtain vanadium pentoxide sol.

[0019] A2. While stirring, add dropwise a solution of 3-6 parts cesium carbonate dissolved in 30-60 parts deionized water to vanadium pentoxide sol; adjust the pH to 10-11; after the addition is complete, continue stirring at room temperature to obtain a mixture.

[0020] A3. Transfer the mixture to a high-pressure reactor, seal the reactor, and place it in a forced-air drying oven. Conduct a hydrothermal reaction at 175-185℃. After the reaction is complete, allow it to cool naturally to room temperature. Discard the supernatant from the high-pressure reactor. Wash the lower precipitate from the high-pressure reactor alternately with deionized water and anhydrous ethanol by centrifugation to obtain a clean precipitate. Redisperse the clean precipitate in deionized water and sonicate it under ice-water bath conditions to obtain a nanosheet dispersion.

[0021] A4. Transfer the nanosheet dispersion into a three-necked flask, heat to 58-62℃ under nitrogen protection, add 1.5-2.5 parts of 3-aminopropyltriethoxysilane, stir the reaction to obtain a reaction mixture; centrifuge the reaction mixture to obtain a solid product; wash the solid product with ethanol and freeze-dry.

[0022] In this invention, the preparation of the cesium vanadate intercalation directing agent is a precise structural construction process from macroscopic oxides to functionalized nanosheets. The first step involves the reaction of vanadium pentoxide with hydrogen peroxide under heating conditions. The purpose is not simply dissolution, but rather to utilize the strong oxidizing and intercalation capabilities of hydrogen peroxide to attack and break some of the vanadium-oxygen bonds in the vanadium pentoxide layers. Simultaneously, peroxide and other functional groups are embedded in the interlayer spaces, significantly expanding the interlayer spacing and forming a hydroxyl-rich, loosely structured hydrated vanadium pentoxide gel. This process essentially transforms rigid layered crystals into a reactive precursor sol, creating possibilities for ion exchange and intercalation. The second step, introducing a cesium carbonate solution into the sol, is a crucial transformation step. Cesium carbonate hydrolysis provides cesium ions and a mild alkaline environment. Cesium ions, with their large ionic radius and low charge density, can effectively overcome residual interlayer attraction and diffuse into the expanded interlayer domain of hydrated vanadium pentoxide. Through ion exchange and electrostatic interactions, they remain stably present in the interlayer, partially replacing the original protons or ammonium ions, thus initially forming a vanadium-oxygen layered structure with cesium ion intercalation. Controlling the pH of the system within a weakly alkaline range is crucial, ensuring sufficient carbonate hydrolysis to provide cesium ions while preventing excessive dissolution of the vanadium-oxygen framework or adverse phase transitions in a strongly alkaline environment. The third step, the hydrothermal reaction, is a key stage in crystal engineering. Driven by high temperature and pressure, the disordered structure in the precursor rearranges and crystallizes, resulting in a more ordered positioning of cesium ions in the interlayer, thus forming a well-crystallized cesium vanadate compound with a well-defined layered structure. Subsequent ultrasonic treatment utilizes cavitation energy to further exfoliate the layered crystals, obtaining nanosheets with large lateral dimensions and thin thickness. The final step, surface silanization, is crucial for imparting its guiding function. The silane coupling agent undergoes hydrolysis and condensation on the nanosheet surface, covalently anchoring to the vanadium-oxygen framework. The amino functional groups at its ends give the nanosheet surface a positive charge. This modification not only improves the dispersion stability of the nanosheets in the reaction system, but more importantly, the amino sites on its surface exhibit a strong specific adsorption capacity for nickel-amine cations in the subsequent solution, laying the chemical foundation for guiding the heterogeneous nucleation of nickel hydroxide.

[0023] According to a preferred embodiment of the present invention, in step A1, the mixture is continuously stirred at 68-72°C for 24-30 hours.

[0024] According to a preferred embodiment of the present invention, in step A2, the stirring is continued at room temperature for 12-14 hours.

[0025] According to a preferred embodiment of the present invention, in step A3, the ultrasonic treatment time is 1-2 hours.

[0026] According to a preferred embodiment of the present invention, in step A4, the stirring reaction time is 6-8 hours.

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

[0028] The method for preparing large-particle-size nickel hydroxide based on cesium vanadate intercalation directing agent provided by this invention shows significant progress and advantages in many aspects of technical effect, mainly reflected in the fundamental improvement of the core performance of the product, the substantial optimization of the production process, and the significant improvement of the overall technical and economic efficiency.

[0029] First, the most significant technical advantage of this method lies in its precise and efficient control over the key physicochemical properties of nickel hydroxide products, resulting in high-quality products that are difficult to achieve with traditional processes. By introducing a cesium vanadate intercalation directing agent with a unique layered structure and surface modification, this method achieves revolutionary control from the source of the crystallization process. This directing agent provides a large number of uniform and active heterogeneous nucleation sites, strongly adsorbing nickel ions, transforming the nucleation process from the traditionally uncontrollable homogeneous nucleation to a highly controllable heterogeneous nucleation. This not only ensures the uniformity and consistent distribution of the initial crystal nuclei in principle, but also lays an ideal foundation for subsequent grain growth. Combined with a two-stage feeding strategy, the first stage forms a large number of fine and uniform crystal nuclei on the surface of the directing agent, while the second stage guides the newly formed precipitate to grow almost entirely around these predetermined crystal nuclei, effectively avoiding the random generation of new nuclei during the growth stage. Therefore, the prepared nickel hydroxide product has a particle size that falls precisely within the target range, with an exceptionally narrow particle size distribution range and good particle sphericity, significantly improving the uniformity and consistency of the product. Meanwhile, this method promotes the formation of thermodynamically stable pure-phase nickel hydroxide with a complete crystal structure and no impurity phase interference, and its tap density is greatly improved. These characteristics are crucial for its high volumetric energy density, high utilization rate of active materials and long cycle life as a battery cathode material.

[0030] Secondly, this invention significantly simplifies the production process and improves production stability and efficiency. Traditional two-stage precipitation methods rely heavily on instantaneous and precise control of acid-base concentration, feeding rate, acid-base ratio, and pH value. Even minor fluctuations in any parameter can lead to deviations in nucleation and growth behavior, resulting in batch-to-batch quality variations. In this method, the addition of the cesium vanadate intercalation directing agent acts like a "navigation system" for the crystallization process. Its powerful heterogeneous nucleation and growth guidance capabilities relax the sensitivity requirements for some stringent process parameters, allowing the entire precipitation process to operate within a wider and more stable process window. This increases the tolerance for operational errors and greatly enhances batch stability. Furthermore, the presence of the directing agent significantly suppresses the formation of fine, irregular crystals, effectively shortening the lengthy aging time required in traditional processes to eliminate these fine particles and narrow their distribution. This increases the unit-time capacity of the reaction unit, reduces energy consumption, and improves production efficiency. The entire main synthesis process is clear, the conditions are mild, and all raw materials are commercially available, avoiding the use of special or expensive additives, thus possessing excellent potential for industrial scale-up.

[0031] Finally, the overall technical and economic benefits of this invention are significant. From a technical perspective, this method partially replaces the traditional approach of improving material performance by doping with multiple metal elements through a physicochemical structure-guided mechanism. While ensuring or even improving product performance, it simplifies the raw material system, reduces raw material costs, particularly reducing dependence on precious metals such as cobalt, and alleviates the complexity of subsequent wastewater treatment. From the perspective of the final product value, the obtained high-performance, large-particle-size nickel hydroxide better meets the demands of the high-end alkaline battery market for high energy density, high power output, and long lifespan, thereby increasing the product's added value. In summary, this invention not only provides a method for preparing high-performance nickel hydroxide but also, through innovation in key materials, forms a set of efficient, stable, economical, and environmentally friendly controllable material preparation technology solutions, possessing significant application value and 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 cesium vanadate intercalation directing agent CVID-1

[0035] Step A1: Accurately weigh 6.0 g of vanadium pentoxide powder into a 1 L beaker, add 300 mL of deionized water, place on a magnetic stirrer, and stir at 500 rpm for 30 min to form a uniform orange-red suspension. Using a constant pressure dropping funnel, slowly add 20 mL of 30% hydrogen peroxide solution at a constant rate of 1 mL / min to the continuously stirred suspension. During the addition, observe the system color gradually deepening. After the addition is complete, transfer the resulting mixture to a 70°C constant temperature water bath, maintain a stirring speed of 500 rpm, and continue the reaction for 26 h. After the reaction is complete, a viscous, dark reddish-brown gel is obtained. Transfer this gel to a centrifuge tube and centrifuge at 8000 rpm for 10 min, carefully discarding the supernatant. Add an equal volume of deionized water to the precipitate, use a vortex mixer to redisperse the precipitate, and centrifuge again under the same conditions. Repeat this deionized water washing process three times. The gel-like precipitate after final washing was redispersed in 150 mL of deionized water and dispersed for 10 min using an ultrasonic cleaner at 40 kHz and 200 W to obtain a uniform and stable vanadium pentoxide sol, which was then sealed for later use.

[0036] In step A2, 4.5 g of cesium carbonate powder was accurately weighed into a 100 mL beaker, and 45 mL of deionized water was added. The mixture was stirred magnetically until completely dissolved, yielding a clear, colorless cesium carbonate solution. Under mechanical stirring, the cesium carbonate solution was slowly added dropwise at a rate of 2 mL / min to the vanadium pentoxide sol prepared in step A1. During the addition, the system color gradually changed from reddish-brown to yellowish-green, and the viscosity increased significantly. After the addition was complete, the pH of the entire mixture was finely adjusted to 10.5 using a 0.1 mol / L sodium hydroxide aqueous solution, monitored by a pH meter. Subsequently, the mixture was stirred continuously at room temperature (approximately 25 °C) for 13 hours to obtain the reaction mixture.

[0037] Step A3: Transfer the entire reaction mixture obtained in Step A2 to a 200 mL polytetrafluoroethylene (PTFE) lined container and place it inside a stainless steel high-pressure reactor, ensuring a filling density of approximately 70%. Tighten the reactor lid to ensure a seal. Place the sealed high-pressure reactor in a forced-air drying oven, set the reaction temperature to 180°C, and start the temperature program. Once the temperature reaches 180°C, begin timing and maintain this temperature for 44 hours for hydrothermal crystallization. After the reaction is complete, turn off the oven heating and allow the reactor to cool naturally to room temperature (approximately 25°C). Open the reactor; the product will be separated into layers. Carefully discard the supernatant and collect the lower yellow-green paste-like precipitate. Transfer this precipitate to a centrifuge tube, add 50 mL of deionized water, centrifuge at 8000 rpm for 5 min, and discard the supernatant. Then add 50 mL of anhydrous ethanol and centrifuge under the same conditions for 5 min, discarding the supernatant. Repeat this alternating washing process with deionized water and anhydrous ethanol three times. The washed precipitate was redispersed in 100 mL of deionized water, and the beaker containing the dispersion was placed in an ice-water bath (0 °C). Using an ultrasonic cell disruptor, the operating parameters were set as follows: power 500 W, operating mode 2 s sonication followed by 3 s intermittent sonication. The dispersion was subjected to ultrasonic treatment for a total duration of 1.5 h, resulting in a translucent and uniform nanosheet dispersion.

[0038] Step A4: Transfer the entire nanosheet dispersion obtained in Step A3 into a 250 mL three-necked round-bottom flask. Install a condenser at the middle neck and a nitrogen inlet tube at one neck to ensure the system is airtight. Open the nitrogen cylinder and purge the flask with nitrogen at a flow rate of 50 mL / min for 15 min to displace the air inside the flask and maintain a slightly positive nitrogen protective atmosphere during the subsequent reaction. Place the flask in an oil bath and heat it to stabilize the dispersion temperature at 60 °C. Using a 1 mL syringe, measure 2.0 g of (3-aminopropyl)triethoxysilane (APTES) and slowly inject it into the dispersion in the flask with stirring. Maintain the reaction temperature at 60 °C and a continuous nitrogen atmosphere, and continue the reaction with mechanical stirring at 300 rpm for 7 h. After the reaction is complete, transfer the reaction mixture to a centrifuge tube and centrifuge at 10,000 rpm for 15 min to collect the solid product. Discard the supernatant, add 50 mL of anhydrous ethanol to the solid product, disperse using a vortex mixer, and centrifuge again at 10,000 rpm for 10 min. Repeat this anhydrous ethanol washing process three times. Finally, transfer the washed solid product to a freeze-drying tray, place it in a freeze dryer, and freeze-dry at -50 °C and 10 Pa for 48 h to obtain a dry powder product, which is the cesium vanadate intercalation directing agent, labeled CVID-1.

[0039] Preparation of large-particle-size nickel hydroxide HN-1

[0040] Step S1: Take a 5L jacketed glass reactor equipped with an anchor-type mechanical stirrer, an online pH detection electrode, a temperature sensor, and a constant-temperature circulating water inlet and outlet. Add 2000g of deionized water to the reactor as the base solution. Turn on the stirrer and set the speed to 250rpm. Turn on the circulating water bath and set the target temperature to 55℃, raising the liquid in the reactor to 55℃ and maintaining it stable. Add 0.5g of the CVID-1 directing agent powder prepared above to the reactor. Then, accurately add 7.5g of ammonia water with a mass fraction of 25% using a pipette. Maintain the temperature at 55℃ and the stirring speed at 250rpm, and continue stirring for 30min to ensure that CVID-1 is fully suspended and evenly dispersed. Take a small amount of the base solution using a sampler, dilute it, and use an ammonia nitrogen analyzer to measure the ammonia concentration in the base solution. The concentration is approximately 8.0g / L, resulting in a homogeneous directing agent-ammonia water mixture.

[0041] Step S2: Prepare the first-stage feeding solutions. Solution A1: Accurately weigh 262.5g of nickel sulfate hexahydrate, dissolve it in an appropriate amount of deionized water at 60℃, and after the solution cools to room temperature, transfer it to a 1L volumetric flask. Dilute to the mark with deionized water and mix well to obtain a 1.5mol / L nickel sulfate aqueous solution. 600mL was actually used in this reaction. Solution B1: Accurately weigh 60.0g of sodium hydroxide granules, dissolve them in approximately 800mL of cold deionized water, stir until completely dissolved, and after the solution cools, transfer it to a 1L volumetric flask. Dilute to the mark with deionized water to obtain a 2.5mol / L sodium hydroxide aqueous solution. 600mL was actually used in this reaction. Turn on two high-precision metering pumps. Pump A1 draws solution A1, and pump B1 draws solution B1. Set the flow rate of both pumps to 60mL / min. Simultaneously, two pumps were started to add solutions A1 and B1 dropwise to the mixture prepared in step S1 in a parallel flow. During the dropwise addition, the instantaneous flow rate of pump B1 was automatically fine-tuned based on real-time feedback from the online pH monitoring system to ensure that the pH value of the entire reaction system was precisely stable at 11.3. The total time for adding all solutions was 10 minutes. After stopping the addition, the temperature inside the reactor was maintained at 55°C, and the stirring speed was 250 rpm for aging reaction, which lasted for 45 minutes.

[0042] Step S3: Prepare the second-stage addition solutions. Solution A2: Accurately weigh 105.0 g of nickel sulfate hexahydrate and prepare 400 mL of a 1.0 mol / L nickel sulfate aqueous solution, using the same method as A1. Solution B2: Accurately weigh 28.8 g of sodium hydroxide and prepare 400 mL of a 1.8 mol / L sodium hydroxide aqueous solution, using the same method as B1. Restart the metering pumps, with pump A2 drawing solution A2 and pump B2 drawing solution B2. Set the flow rate of both pumps to 20 mL / min. Simultaneously start both pumps to add solutions A2 and B2 dropwise to the reaction system in a parallel flow. During this addition stage, adjust the flow rate of pump B2 using the pH control system to maintain the pH of the reaction system stably at 11.6. The total time for adding all solutions is approximately 2 hours. After the addition is complete, maintain the temperature at 55°C and stir at 250 rpm for another 20 minutes.

[0043] Step S4: After completing Step S3, adjust the speed of the mechanical agitator to 150 rpm and maintain the circulating water temperature in the reactor jacket at 55°C. Allow the reaction slurry to continue aging under these conditions for 3 hours. After aging, turn off the heating system and agitator. Allow the reaction slurry to cool naturally to room temperature (approximately 25°C) in the reactor. Transfer the cooled slurry to a storage tank and perform solid-liquid separation using a plate and frame filter press to obtain a dark green filter cake. Wash the filter cake with 80°C hot deionized water using a spray method until the conductivity of the outflowing washing liquid measured by a conductivity meter is below 100 µS / cm. Remove the washed, wet filter cake from the filter press, break it into small pieces, and evenly spread it on the tray of a vacuum drying pan. Place the tray in a vacuum drying oven, set the drying temperature to 105°C, turn on the vacuum pump to maintain the pressure inside the oven at -0.09 MPa, and dry for 13 hours. After drying, the material is removed, lightly ground using a mortar and pestle, and then passed through an 80-mesh sieve to obtain the final large-particle-size spherical nickel hydroxide product, labeled as HN-1.

[0044] Example 2

[0045] The specific implementation method is the same as in Example 1, except that the cesium vanadate intercalation directing agent CVID-2 is prepared differently.

[0046] Step A1: Accurately weigh 5.5 g of vanadium pentoxide powder into a 1 L beaker, add 250 mL of deionized water, and stir at 500 rpm for 30 min to form a suspension. Add 18 mL of 30% hydrogen peroxide solution dropwise at a rate of 1 mL / min. Place the mixture in a 69℃ constant temperature water bath, maintain stirring at 500 rpm, and continue the reaction for 24 h to obtain a reddish-brown gel. Transfer the gel to a centrifuge tube, centrifuge at 8000 rpm for 10 min, discard the supernatant, and redisperse the precipitate with deionized water. Repeat this washing process 3 times. Redisperse the final precipitate in 120 mL of deionized water and sonicate for 10 min to obtain a homogeneous vanadium pentoxide sol.

[0047] Step A2: Accurately weigh 3.5 g of cesium carbonate powder and dissolve it in 35 mL of deionized water. While stirring, add this solution dropwise to the above sol at a rate of 2 mL / min. After the addition is complete, adjust the pH of the system to 10.2 with 0.1 mol / L sodium hydroxide solution. Continue stirring at room temperature for 12 h to obtain the reaction mixture.

[0048] Step A3: Transfer the entire mixture from Step A2 into a 200 mL high-pressure reactor lined with polytetrafluoroethylene and seal. Place the reactor in a forced-air drying oven and perform a hydrothermal reaction at 178 °C for 40 h. After naturally cooling to room temperature, discard the supernatant and collect the precipitate. Wash the precipitate three times each with deionized water and anhydrous ethanol by alternating centrifugation. Redisperse the washed precipitate in 90 mL of deionized water and treat it for 1 h in an ice-water bath using an ultrasonic cell disruptor at 500 W power, with a sonication mode of 2 s / interval 3 s, to obtain a nanosheet dispersion.

[0049] Step A4: Transfer the nanosheet dispersion to a 250 mL three-necked flask, purge with nitrogen, and heat to 59 °C. Add 1.8 g of (3-aminopropyl)triethoxysilane, and stir at 300 rpm for 6.5 h at 59 °C under a nitrogen atmosphere. After the reaction is complete, centrifuge to collect the solid, wash three times with anhydrous ethanol, and then freeze-dry to obtain the directing agent powder, labeled CVID-2.

[0050] Preparation of large-particle-size nickel hydroxide HN-2

[0051] Step S1: Add 1800g of deionized water to a 5L reactor, heat to 54℃ and stabilize. Add 0.4g of CVID-2 directing agent and 6.5g of 25% ammonia solution, stir at 250rpm for 30min, and measure the ammonia concentration in the bottom liquid to be approximately 8.0g / L.

[0052] In step S2, 200 mL of a 1.4 mol / L nickel sulfate aqueous solution (adjusted to 200 mL from 78.4 g nickel sulfate hexahydrate) and 200 mL of a 2.4 mol / L sodium hydroxide aqueous solution (adjusted to 200 mL from 19.2 g sodium hydroxide) were simultaneously added dropwise to the reactor in a parallel flow using metering pumps. The total dropping time was controlled to be approximately 15 min, during which the pH of the system was maintained at 11.2 by adjusting the flow rate of the alkali solution. After the addition was complete, the reactor was aged at 54 °C for 30 min.

[0053] In step S3, 300 mL of a 0.95 mol / L nickel sulfate aqueous solution (adjusted to 300 mL from 80.9 g of nickel sulfate hexahydrate) and 300 mL of a 1.7 mol / L sodium hydroxide aqueous solution (adjusted to 300 mL from 20.4 g of sodium hydroxide) were simultaneously added dropwise to the reactor in a parallel flow manner. The total adding time was controlled to be approximately 2.5 h, during which the pH of the system was maintained at 11.55. After the addition was completed, the mixture was stirred at 54 °C for 20 min.

[0054] Step S4: Adjust the stirring speed to 150 rpm, maintain the temperature at 54℃, and age for 2.5 hours. After cooling the slurry to room temperature, filter it and wash the filter cake with hot deionized water at 79℃ until the conductivity of the filtrate is below 100 µS / cm. Dry the filter cake at 104℃ under a vacuum of -0.09 MPa for 12 hours, grind and sieve to obtain the product, labeled as HN-2.

[0055] Example 3

[0056] The specific implementation method is the same as in Example 1, except that the cesium vanadate intercalation directing agent CVID-3 is prepared differently.

[0057] Step A1: Accurately weigh 6.5 g of vanadium pentoxide powder into a 1 L beaker, add 350 mL of deionized water, and stir at 500 rpm for 30 min to form a suspension. Add 22 mL of 30% hydrogen peroxide solution dropwise at a rate of 1 mL / min. Place the mixture in a 71℃ constant temperature water bath, maintain stirring at 500 rpm, and continue the reaction for 28 h to obtain a reddish-brown gel. After centrifuging and washing the gel three times, redisperse it in 180 mL of deionized water and sonicate for 10 min to obtain a uniform vanadium pentoxide sol.

[0058] Step A2: Accurately weigh 5.5 g of cesium carbonate powder and dissolve it in 55 mL of deionized water. While stirring, add this solution dropwise to the above sol at a rate of 2 mL / min. After the addition is complete, adjust the pH of the system to 10.8 with 0.1 mol / L sodium hydroxide solution. Continue stirring at room temperature for 13.5 h to obtain the reaction mixture.

[0059] Step A3: Transfer the entire mixture from Step A2 to a 200 mL high-pressure reactor, seal it, and place it in a forced-air drying oven for hydrothermal reaction at 182 °C for 46 h. After naturally cooling to room temperature, collect the precipitate and wash it alternately with deionized water and anhydrous ethanol three times each. Redisperse the precipitate in 110 mL of deionized water and treat it in an ice-water bath using an ultrasonic cell disruptor at 500 W power, with a 2 s sonication / 3 s intermittent mode for 1.8 h to obtain a nanosheet dispersion.

[0060] Step A4: Transfer the nanosheet dispersion to a 250 mL three-necked flask, purge with nitrogen, and heat to 61 °C. Add 2.3 g of (3-aminopropyl)triethoxysilane, and stir at 300 rpm for 7.5 h at 61 °C under a nitrogen atmosphere. After the reaction is complete, centrifuge to collect the solid, wash three times with anhydrous ethanol, and then freeze-dry to obtain the directing agent powder, labeled CVID-3.

[0061] Preparation of large-particle-size nickel hydroxide HN-3

[0062] Step S1: Add 2200g of deionized water to a 5L reactor, heat to 56℃ and stabilize. Add 0.6g of CVID-3 directing agent and 8.0g of 25% ammonia solution, stir at 250rpm for 30min, and measure the ammonia concentration in the bottom liquid to be approximately 8.0g / L.

[0063] In step S2, 250 mL of a 1.55 mol / L nickel sulfate aqueous solution (adjusted to 250 mL from 108.5 g nickel sulfate hexahydrate) and 250 mL of a 2.55 mol / L sodium hydroxide aqueous solution (adjusted to 250 mL from 25.5 g sodium hydroxide) were simultaneously added dropwise to the reactor in a parallel flow using metering pumps. The total dropping time was controlled to be approximately 12 min, during which the pH of the system was maintained at 11.35 by adjusting the flow rate of the alkali solution. After the addition was complete, the mixture was aged at 56 °C for 50 min.

[0064] In step S3, 350 mL of a 1.05 mol / L nickel sulfate aqueous solution (adjusted to 350 mL from 110.3 g nickel sulfate hexahydrate) and 350 mL of a 1.9 mol / L sodium hydroxide aqueous solution (adjusted to 350 mL from 26.6 g sodium hydroxide) were simultaneously added dropwise to the reactor in a parallel flow manner. The total adding time was controlled to be approximately 2.2 h, during which the pH of the system was maintained at 11.65. After the addition was completed, the mixture was stirred at 56 °C for 20 min.

[0065] Step S4: Adjust the stirring speed to 150 rpm, maintain the temperature at 56℃, and age for 3.5 hours. After cooling the slurry to room temperature, filter it and wash the filter cake with hot deionized water at 81℃ until the conductivity of the filtrate is below 100 µS / cm. Dry the filter cake at 106℃ under a vacuum of -0.09 MPa for 13.5 hours, grind and sieve to obtain the product, labeled as HN-3.

[0066] Comparative Example 1

[0067] The specific implementation method is the same as in Example 1, except that cesium vanadate intercalation directing agent is not added in step S1; only 7.5g of ammonia water with a mass fraction of 25% is added. All operations, material quantities, and process parameters in subsequent steps S2-S4 are exactly the same as in Example 1. The resulting product is labeled C-HN-1.

[0068] Comparative Example 2

[0069] The specific implementation method is the same as in Example 1, except that the cesium vanadate intercalation directing agent used is unmodified cesium vanadate nanosheets. The preparation process includes only steps A1-A3, which are exactly the same as in Example 1. After ultrasonication to obtain the nanosheet dispersion, the silanization reaction in step A4 is not performed; instead, the dispersion is directly freeze-dried to obtain a powdered product, labeled UC-1. In the preparation of nickel hydroxide, step S1 is changed to adding 0.5g of this UC-1 powder. All operations, material amounts, and process parameters in the remaining steps S1-S4 are exactly the same as in Example 1. The resulting product is labeled C-HN-2.

[0070] Comparative Example 3

[0071] The specific implementation method is the same as in Example 1, except that in step S1, 0.5g of sodium carboxymethyl cellulose is used instead of cesium vanadate intercalation directing agent and is added together with ammonia. All operations, material quantities, and process parameters in subsequent steps S2-S4 are exactly the same as in Example 1. The resulting product is labeled C-HN-3.

[0072] Performance testing

[0073] The large-particle-size nickel hydroxide prepared in Examples 1-3 and Comparative Examples 1-3 above was subjected to performance testing according to the following method, which includes the following steps:

[0074] Performance tests were conducted using laser diffraction, tap density, and X-ray diffraction. Particle size analysis was performed using a laser diffraction particle size analyzer. The test procedure was as follows: 0.10 g of the sample to be tested was accurately weighed and placed in a 50 mL beaker. 50 mL of an aqueous solution containing 0.1% (w / w) sodium hexametaphosphate dispersant was added. The beaker was placed in an ultrasonic water bath with an output power of 100 W and dispersed for 3.0 min. Immediately afterwards, the suspension was transferred to the instrument's sample circulation cell. The sample refractive index was set to 2.0, and the background was water. The circulation pump and ultrasonic dispersion were turned on. After the signal stabilized, the measurement was started. The instrument calculated the volumetric particle size distribution based on Mie scattering theory and recorded the median particle size and the particle size distribution span. Each sample was tested in parallel three times, and the arithmetic mean was taken.

[0075] The tap density test was conducted using a tap density meter. The test procedure was as follows: 20.0g of dry sample was carefully poured into a clean and dry 100mL glass graduated cylinder through a funnel. The initial volume was recorded as V0. The graduated cylinder was then securely mounted on the instrument. The vibration amplitude was set to 3.0mm and the vibration frequency to 200 times per minute. The instrument was started, and after a total of 2000 vibrations, the final volume Vf of the sample was read. The tap density was calculated using the formula ρ=m / Vf, where m is the sample mass. Each sample was tested twice, and the average value was taken.

[0076] Phase and crystallinity analysis was performed using an X-ray diffractometer. The testing procedure was as follows: The powder sample was gently pressed into a flat thin sheet on a flat glass plate and then placed in the sample holder. A Cu-Kα X-ray source was used, with the working voltage and current set to 40.0 kV and 40.0 mA, respectively. The scanning range was set to 5.0° to 70.0° (2θ), the scanning step size was 0.02°, and the scanning speed was 2.0° per minute. Angle correction was performed using a silicon standard. The obtained diffraction pattern was compared with the standard β-Ni(OH)2 powder diffraction card. The three strongest diffraction peaks located near 19.3°, 33.1°, and 38.5° were selected, and their average half-width at half-maximum (FWHM) was calculated as the crystallinity index.

[0077] Test results:

[0078] Table 1: Test results of each embodiment and comparative example

[0079] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Median particle size (D50, μm) 152.3 138.7 165.1 85.4 105.6 91.2 Particle size distribution span 0.68 0.72 0.71 1.25 1.08 1.32 Tap density (g / cm³) 2.24 2.19 2.21 1.95 2.05 1.98 β-phase crystallinity index (half-width at half maximum, °) 0.81 0.84 0.83 1.15 0.98 1.10

[0080] As can be seen from Table 1, the nickel hydroxide prepared in Examples 1-3 of this invention, through the introduction of cesium vanadate intercalation directing agent, comprehensively and effectively solves the technical problems of traditional methods in terms of particle size control, process efficiency and material system.

[0081] Specifically, the median particle size of the products in the examples reached 138.7-165.1 μm, and the particle size distribution range remained stable within an extremely narrow range of 0.68-0.72 μm. This directly confirms that highly precise control over the particle size and its distribution has been achieved, completely overcoming the problems of insufficient particle size and excessively wide distribution caused by the lack of an effective guiding mechanism in Comparative Examples 1 and 3. This precise control stems from the heterogeneous nucleation-dominant mechanism provided by the guiding agent, which suppresses random homogeneous nucleation at the source, making the crystal nucleus growth synchronous and uniform.

[0082] In terms of process efficiency, the examples achieved significantly higher tap density (2.19-2.24 g / cm³) and better crystallinity (0.81°-0.84° half-width) with a relatively short aging process, indicating that the directing agent promoted the rapid construction of dense and stable β-phase microcrystals, greatly improving the Ostwald aging efficiency and thus reducing the dependence on the long aging time in the traditional process.

[0083] Most importantly, this invention successfully abandons the traditional approach of relying on co-doping with metals such as cobalt and zinc to improve performance. It achieves multiple performance enhancements, such as large particle size, narrow distribution, high density and high crystallinity, solely through a non-metallic additive, cesium vanadate intercalation directant with physicochemical structure guidance. This provides a new approach for preparing high-performance nickel hydroxide that is free from metal doping, has a wide process window, and is precise and efficient.

[0084] 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 method for preparing large-particle-size nickel hydroxide, characterized in that, Includes the following steps: S1, by weight, add 1500-2500 parts of deionized water to a reactor, heat to 54-56℃, add 0.3-0.7 parts of cesium vanadate intercalation directing agent, add 6.2-8.5 parts of ammonia water, and stir continuously to obtain a mixture; S2, add an aqueous solution of 1.4-1.6 mol / L nickel sulfate and an aqueous solution of 2.4-2.6 mol / L sodium hydroxide to the mixture, adjust the pH to 11.2-11.4, stir, and age; S3. Add 0.9-1.1 mol / L nickel sulfate aqueous solution and 1.6-2.0 mol / L sodium hydroxide aqueous solution to the reactor, adjust the pH value to 11.5-11.7, stir, and age. S4. Maintain the reactor temperature at 54-56℃, stir, and age to obtain a slurry; cool the slurry to room temperature, and use a plate and frame filter press for solid-liquid separation to obtain a filter cake; wash the filter cake with deionized water at 78-82℃, and finally dry it in a vacuum drying oven at 104-106℃.

2. The method for preparing large-particle-size nickel hydroxide according to claim 1, characterized in that, In step S1, the ammonia concentration in the mixture is 7.8-8.2 g / L.

3. The method for preparing large-particle-size nickel hydroxide according to claim 1, characterized in that, In step S2, the aging time is 30-60 minutes.

4. The method for preparing large-particle-size nickel hydroxide according to claim 1, characterized in that, In step S3, the stirring time is 20-40 minutes.

5. The method for preparing large-particle-size nickel hydroxide according to claim 1, characterized in that, In step S4, the drying time in a vacuum drying oven at 104-106℃ is 12-14 hours.

6. The method for preparing large-particle-size nickel hydroxide according to any one of claims 1-5, characterized in that, The preparation steps of the cesium vanadate intercalation directing agent include: A1. By weight, add 5-7 parts of vanadium pentoxide to 200-400 parts of deionized water and stir to obtain a suspension. While stirring, add 15-25 parts of hydrogen peroxide solution to the suspension to obtain a mixture. Place the mixture at 68-72℃ and stir continuously to obtain a gel. Wash the gel with deionized water by centrifugation and redisperse it in deionized water to obtain vanadium pentoxide sol. A2. While stirring, add dropwise a solution of 3-6 parts cesium carbonate dissolved in 30-60 parts deionized water to vanadium pentoxide sol; adjust the pH to 10-11; after the addition is complete, continue stirring at room temperature to obtain a mixture. A3. Transfer the mixture to a high-pressure reactor, seal the reactor, and place it in a forced-air drying oven. Conduct a hydrothermal reaction at 175-185℃. After the reaction is complete, allow it to cool naturally to room temperature. Discard the supernatant from the high-pressure reactor. Wash the lower precipitate from the high-pressure reactor with deionized water and anhydrous ethanol by alternating centrifugation to obtain a clean precipitate. Redisperse the clean precipitate in deionized water and sonicate it under ice-water bath conditions to obtain a nanosheet dispersion. A4. Transfer the nanosheet dispersion into a three-necked flask, heat to 58-62℃ under nitrogen protection, add 1.5-2.5 parts of 3-aminopropyltriethoxysilane, stir the reaction to obtain a reaction mixture; centrifuge the reaction mixture to obtain a solid product; wash the solid product with ethanol and freeze-dry.

7. The method for preparing large-particle-size nickel hydroxide according to claim 6, characterized in that, In step A1, the mixture is placed at 68-72℃ and stirred continuously for 24-30 hours.

8. The method for preparing large-particle-size nickel hydroxide according to claim 6, characterized in that, In step A2, stirring continues at room temperature for 12-14 hours.

9. The method for preparing large-particle-size nickel hydroxide according to claim 6, characterized in that, In step A3, the ultrasonic treatment time is 1-2 hours.

10. The method for preparing large-particle-size nickel hydroxide according to claim 6, characterized in that, In step A4, the stirring reaction time is 6-8 hours.