A nickel-iron-manganese layered oxide precursor, a preparation method and application thereof

Abstract

The application discloses a nickel-iron-manganese layered oxide precursor and a preparation method and application thereof, and relates to the technical field of sodium ion battery materials.The application can control the number of precipitated crystal seeds in the particle size matrix of the whole reaction system, control the precipitation rate, the growth cell sequence direction and the secondary particle morphology, maintain a balanced reaction system, continuously output products with a particle size range meeting the production index requirements, improve the uniformity of the product particle size distribution, obtain a good sphericity morphology, and improve the tap density by adjusting the concentration of a reducing sulfate salt at different stages of particle growth in a reaction system for preparing a nickel-iron-manganese layered oxide precursor by coprecipitation. The process control is relatively simple, the stability is high, and the production cost advantage is obvious.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery materials technology, and more specifically, relates to a nickel-iron-manganese layered oxide precursor, its preparation method, and its application. Background Technology

[0002] Among sodium-ion battery cathode materials, those prepared using layered oxide precursors closely resemble the capacity performance of existing lithium iron phosphate materials, and represent one of the fastest-growing routes for sodium-ion battery cathode materials. The mainstream preparation method for nickel-iron-manganese layered oxide precursors is the liquid-phase synthesis of nickel-iron-manganese ternary layered oxides. This method highly overlaps with the process route for synthesizing lithium-ion battery cathode material precursors, allowing major manufacturers to directly switch to mass production of sodium-ion battery cathode material precursors.

[0003] Co-precipitation synthesis of nickel-iron-manganese ternary layered oxides is widely used, but it has the following drawbacks: In the synthesis of cathode materials with iron as the main material, due to the presence of dissolved oxygen in the liquid, the dissolved oxygen in the water easily destroys the dissolved Fe in the liquid phase during the co-precipitation synthesis of nickel-iron-manganese precursor system. 2+ Iron ions are oxidized to Fe 3+ Valence state, Fe 2+ Oxidation leads to the irregular precipitation of small seed crystals, causing the reaction system to become uncontrolled. This results in a significant deviation between the secondary particle size and the actual requirements, leading to deviations in the physical properties of the finished product. In the co-precipitation preparation of the nickel-iron-manganese precursor, adding a reducing agent can suppress the presence of Fe in the solution. 2+ Iron ions are oxidized to Fe 3+ Valence state, to prevent the precipitation of small crystal seeds, patent CN116986646A adds extra prepared crystal seeds in a co-precipitation reaction system containing reducing agent when the particle size of nickel-iron-manganese layered oxide is close to the target particle size, so that nickel-iron-manganese layered oxide can be continuously produced and the consistency of the finished product particle size can be improved. However, this method still has the following problems in actual industrial applications: (1) The process is relatively complicated: it requires an additional extension of the crystal seed preparation process, and the process equipment requirements are high. (2) The sphericity of the obtained nickel-iron-manganese layered oxide precursor is poor and the tap density is low, which limits the improvement of the electrochemical performance of the cathode material. Summary of the Invention

[0004] To address the problems of poor sphericity and low tap density of particles obtained in the continuous preparation of nickel-iron-manganese precursors with uniform particle size in existing technologies, the primary objective of this invention is to provide a method for preparing nickel-iron-manganese layered oxide precursors. This method enables the regular precipitation of seed crystals and the growth of grains during the reaction process, resulting in controllable particle size, uniform particle size distribution, and improved sphericity and tap density.

[0005] Another object of the present invention is to provide a sodium-ion battery electrode material.

[0006] Another object of the present invention is to provide a sodium-ion battery.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a nickel-iron-manganese layered oxide precursor includes the following steps:

[0009] S1. Under an inert gas atmosphere, a nickel-iron-manganese mixed salt solution, a first precipitant, and ammonia water are added to the base solution. The synthesis reaction continues until the particle size in the system reaches a first particle size value, which is calculated as D5, and is the target particle size D. 50 The numerical values ​​range from 31.5% to 47.5%.

[0010] S2. Continuously add the nickel-iron-manganese mixed salt solution, the second precipitant, and ammonia water, and continue the growth reaction until the particle size in the system reaches the second particle size value; the second particle size value is calculated as D5, which is the target particle size D. 50 The values ​​range from 37.5% to 57.0%.

[0011] S3. Continuously add the nickel-iron-manganese mixed salt solution, the third precipitant, and ammonia water, and continue the reaction until the particle size D5 in the system stabilizes within a specified time. Then replace the third precipitant with the first precipitant and continue the reaction until the particle size in the system reaches the target particle size D. 50 Numerical value;

[0012] S4. Replace the first precipitant with the third precipitant, and continuously add nickel-iron-manganese mixed salt solution and ammonia water until the particle size in the system is smaller than the first particle size value; then replace the third precipitant with the first precipitant and continue the synthesis reaction until the particle size in the system reaches the first particle size value;

[0013] Repeat steps S2 to S4 to continuously produce nickel-iron-manganese layered oxide precursors with the target particle size;

[0014] The concentration of NaOH in the first precipitant is 22-32 wt%, and the concentration of reducing sulfate is 0.008-0.012 wt%.

[0015] The concentration of NaOH in the second precipitant is 22-32 wt%, and the concentration of reducing sulfate is 0.002-0.003 wt%.

[0016] The concentration of NaOH in the third precipitant is 22-32 wt%.

[0017] During processes S1 to S4, the pH of the system is controlled to be 10.5 to 12.5, the NH3 content to be 3 to 6 g / L, and the temperature to be 45 to 65℃.

[0018] It should be noted that:

[0019] In the preparation method of the present invention, a nickel-iron-manganese mixed salt solution, a first precipitant and ammonia water are continuously introduced into the reaction substrate through step S1 to carry out the synthesis reaction, and nickel-iron-manganese co-precipitates to precipitate seed crystals and grow.

[0020] When the particles in the system grow rapidly to the size of the first particle size, the first precipitant is replaced with the second precipitant in step S2, which reduces the concentration of reducing sulfate in the reaction system. This slows down the growth rate of the particles, allowing the grains to grow preferentially in the concave areas of the particles. The orderly growth and stacking of the particles in different directions is beneficial for shaping the spherical morphology of the finished particles. At the same time, the orderly overlap of the particles helps to form a uniform porous structure, control the specific surface area of ​​the particles, and improve their tap density.

[0021] When the particle size in the system reaches the second particle size value, the particle size distribution in the system is uneven. In step S3, the second precipitant is replaced with a third precipitant to adjust the particle size matrix D0 in the synthesis reaction system.

[0022] D5, D 10 The growth trend slows down rapidly, or even shows no signs of increasing. When the particle size D5 stabilizes within a specified time, the third precipitant is replaced with the first precipitant, which can make the particles grow to the target particle size and improve the consistency of the particle size matrix distribution.

[0023] When the particle size in the solution reaches the target particle size, replacing the first precipitant with the third precipitant in step S4 allows for the rapid precipitation of a large number of seed crystals. Once a certain number of seed crystals have precipitated, i.e., when the particle size in the system is smaller than the first particle size value, replacing the third precipitant with the first precipitant again inhibits the precipitation of new seed crystals, causing the particles to grow rapidly. The synthesis reaction continues until the particle size in the system reaches the first particle size value. Steps S2 to S4 are then repeated, cyclically adjusting the concentration of reducing sulfate during the reaction. Ultimately, this results in a stable and continuous production of particles with high sphericity, meeting the target particle size D. 50 Products.

[0024] In a specific implementation, the stability of particle size D5 within a specified time in step S3 means that the change in particle size D5 growth value within the specified time is ≤0.1μm.

[0025] In a specific embodiment, preferably, the target particle size D 50 It is 8–12 μm.

[0026] In a specific embodiment, preferably, the reducing sulfate is Na2S2O3 and / or Na2SO3. By using the aforementioned reducing sulfate, the present invention is compatible with alkaline precipitants, effectively controlling the growth of nickel-iron-manganese layered oxides while avoiding the introduction of impurities, which is beneficial for improving the electrochemical performance of electrode materials prepared from the obtained nickel-iron-manganese layered oxide precursor.

[0027] In a specific embodiment, preferably, the molar ratio of nickel, iron, and manganese in the mixed metal salt solution is (0.2-0.6):(0.1-0.5):(0.1-0.4).

[0028] In a specific embodiment, preferably, the addition rate of the nickel-iron-manganese mixed salt solution is 300–400 L / h. Controlling the addition rate of the nickel-iron-manganese mixed salt within this range is beneficial for ensuring that the precipitated particles in a unit volume sedimentation vessel have sufficient growth and shaping time to reach the preset required balanced particle size range, and to form a stable sedimentation output reaction system that continuously outputs the required slurry product.

[0029] In a specific embodiment, preferably, the total content of nickel, iron, and manganese in the nickel-iron-manganese mixed salt solution is 1–2 mol / L. Controlling the total content of nickel, iron, and manganese in the nickel-iron-manganese mixed salt solution within this range is beneficial for reducing pH fluctuations, and also for promoting uniform particle growth in the precipitation vessel, shaping particle morphology, and improving the crystal phase.

[0030] In a specific embodiment, preferably, the base solution comprises an aqueous solution of reducing sulfate, a first precipitant, and ammonia. More preferably, the base solution contains 3-6 g / L of NH3 and OH... - The content is 1-3 g / L, and the mass percentage of the reducing sulfate in the aqueous solution is 0.005-0.015%.

[0031] In a specific embodiment, the product is washed, dried, sieved for demagnetization, tested, and packaged using conventional procedures in the art, as detailed below:

[0032] (1) Washing and filtration of qualified finished product: Prepare 1-5% NaOH solution to wash some metal impurities and S impurities. The washing temperature range is 40-60℃. Wash Na impurities with deionized water. The washing temperature range is 45-60℃. Use solid-liquid separation equipment to dehydrate and obtain qualified finished product filter cake.

[0033] (2) Drying of qualified finished products: Quantitatively feed the qualified finished product filter cake into the drying equipment, and dry it at a temperature range of 100-150℃. Control the moisture content of the qualified powder after drying to be <0.5%.

[0034] (3) Sieving and demagnetizing qualified finished products: The dried qualified powder is drawn into the transfer silo and sieved quantitatively to remove larger particles and control the particle size D.100 <36μm, after sieving, the powder is demagnetized using an electromagnetic demagnetizer to remove metallic foreign matter, and the content of magnetic foreign matter in the demagnetized powder is controlled to be <50ppb.

[0035] (4) Mixing test: The qualified powder after sieving and demagnetizing is batch mixed to make the particle size matrix uniformly distributed. The batch mixed material is sampled and tested for all performance indicators of the product.

[0036] (5) Finished product packaging: qualified powder materials that have passed all performance indicators inspections are vacuum-packed according to the quantity and requirements, and clearly labeled before being put into storage.

[0037] This invention also specifically protects a nickel-iron-manganese layered oxide precursor prepared by the above-described preparation method.

[0038] Preferably, the tap density of the nickel-iron-manganese layered oxide precursor is ≥2.0 g / cm³. 3 Its specific surface area is 7.5–9.5 m². 2 / g. The nickel-iron-manganese layered oxide precursor has a high tap density, which is beneficial to improving battery performance, with a specific surface area of ​​7.5–9.5 m². 2 Within the range of / g, the high tap density of the material can be guaranteed while improving its electrochemical performance.

[0039] The present invention also specifically protects an electrode material comprising the above-mentioned nickel-iron-manganese layered oxide precursor.

[0040] The present invention also specifically protects a sodium-ion battery comprising the above-mentioned electrode material.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention utilizes the controlled concentration of reducing sulfate at different stages of particle growth in a nickel-iron-manganese layered oxide co-precipitation reaction system. This allows control over both the number of seed crystals in the overall particle size matrix and the precipitation rate during growth, ensuring orderly growth and stacking of primary particles in different directions. This shapes the spherical morphology of secondary particles and maintains a balanced reaction system, enabling the continuous production of nickel-iron-manganese layered oxides with uniform particle size distribution, high sphericity, and high tap density. The tap density of the obtained nickel-iron-manganese layered oxides is ≥2.0 g / cm³. 3 Its specific surface area is 7.5–9.5 m². 2 / g.

[0043] The preparation method of the present invention is simple, requires no additional seed crystal preparation process, has low production cost, and good stability. Attached Figure Description

[0044] Figure 1 This is a microscopic morphology diagram of the nickel-iron-manganese layered oxide precursor obtained in Example 1.

[0045] Figure 2 The image shows the microstructure of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 1.

[0046] Figure 3 The image shows the microstructure of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 2.

[0047] Figure 4 This is a microscopic morphology diagram of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 3. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in this embodiment are conventional reagents, methods and equipment in this technical field.

[0049] Example 1

[0050] A method for preparing a nickel-iron-manganese layered oxide precursor includes the following steps:

[0051] (1) Preparation of nickel-iron-manganese mixed salt solution: Prepare a 2 mol / L mixed salt solution of soluble salts of nickel, iron and manganese, with the molar ratio of nickel, iron and manganese being x, y and z, where x:y:z = 3:4:3;

[0052] (2) Preparation of the first precipitant: Prepare a 25% (w / w) NaOH solution, dissolve Na2S2O3 in the NaOH solution, and the mass percentage of Na2S2O3 in the NaOH solution is 0.01%;

[0053] (3) Preparation of the second precipitant: Prepare a 25% (w / w) NaOH solution, dissolve Na2S2O3 in the NaOH solution, and the mass percentage of Na2S2O3 in the NaOH solution is 0.002%.

[0054] (4) Preparation of the third precipitant: Prepare a 25% (w / w) NaOH solution;

[0055] (5) Preparation of the reaction base solution: Add 2500L of deionized water containing 0.01% Na2S2O3 by mass to a sealed reaction vessel, and simultaneously add a certain amount of the above-mentioned ammonia water and NaOH solution, so that the NH3 content is 4.0±0.5g / L and OH... - The concentration was 1–3 g / L. The reactor temperature was controlled at 50°C, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the replacement synthesis reactor is an inert atmosphere;

[0056] (6) Under an inert gas atmosphere, the above nickel-iron-manganese mixed salt solution, the first precipitant and ammonia water were continuously added to the reaction base liquid until the particle size D5 in the system was 3.8 μm.

[0057] (7) Continue to add nickel-iron-manganese mixed salt solution, second precipitant and ammonia water, and continue the growth reaction until the particle size D5 in the system is 4.5 μm;

[0058] (8) Continue adding nickel-iron-manganese mixed salt solution, the third precipitant, and ammonia water, and continue the reaction until the particle size D5 in the system grows to ≤0.1μm within 4 hours. Then replace the third precipitant with the first precipitant and continue until the particle size in the system reaches the target particle size D. 50 It is 8–12 μm;

[0059] (9) Replace the first precipitant with the third precipitant, and continuously add nickel-iron-manganese mixed salt solution and ammonia water until the particle size D5 in the system is <3.8μm. Then replace the third precipitant with the first precipitant until the particle size D5 in the system is 3.8μm.

[0060] Repeat steps (7) to (9) to continuously produce the target particle size D. 50 The precursor is a nickel-iron-manganese layered oxide with a thickness of 8-12 μm; the pH value of the system is controlled to be 11.50±0.6, the NH3 content is 4.0±0.5 g / L, the temperature is 50℃, and the flow rate of the nickel-iron-manganese mixed salt solution is 350 L / h during the reaction process of steps (6) to (9).

[0061] (10) Washing and filtration of qualified finished product: Prepare a 2% NaOH solution and wash some of the metal impurities and sulfur impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5℃. Wash with deionized water at a temperature range of 50±5℃ to remove the target particle size D. 50 The impurity Na in the nickel-iron-manganese layered oxide precursor with a thickness of 8-12 μm was dehydrated using a solid-liquid separation device to obtain a qualified finished filter cake.

[0062] (11) Drying of qualified finished products: Quantitatively feed the qualified finished product filter cake into the disc dryer, and dry it at a temperature range of 120±5℃. Control the moisture content of the qualified powder after the disc dryer discharge to be <0.5%.

[0063] (12) After drying, qualified powder is pumped into the transfer silo and quantitatively sieved through an upper 400-mesh sieve and a lower 200-mesh sieve to remove larger particles and control the particle size D. 100 <36μm, after sieving, the powder is used to remove metal foreign objects in the powder using an electromagnetic demagnetizer. The demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the content of magnetic foreign objects in the demagnetized powder is controlled to be <50ppb.

[0064] (13) The qualified powder after sieving and demagnetizing is batch-mixed to make the particle size matrix uniformly distributed. The batch-mixed material is sampled and tested for all performance indicators of the product. The electron microscope morphology of the finished product obtained in the example is analyzed.

[0065] Example 2

[0066] The difference between Example 2 and Example 1 is that the mass percentage of Na2S2O3 in the NaOH solution in the second precipitant is 0.0025%.

[0067] Example 3

[0068] The difference between Example 3 and Example 1 is that the mass percentage of Na2S2O3 in the NaOH solution in the second precipitant is 0.003%.

[0069] Comparative Example 1

[0070] A method for preparing a nickel-iron-manganese layered oxide precursor includes the following steps:

[0071] (1) Prepare a 2 mol / L mixed salt solution of soluble salts of nickel, iron and manganese, with the molar ratio of nickel, iron and manganese being x, y and z, where x:y:z = 3:4:3;

[0072] (2) Prepare a 25% NaOH solution and a 25% ammonia solution;

[0073] (3) Add 2500L of deionized water bottom solution to a high-efficiency sealed reaction vessel, along with a certain amount of ammonia and sodium hydroxide solution, so that the NH3 content is 4.0±0.5g / L, the pH of the bottom solution in the vessel is about 12.20±0.05, the temperature of the reaction vessel is controlled at 50±1℃, and nitrogen gas is introduced for more than 2 hours at a flow rate of 4.5±0.5m³. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0074] (4) The above-mentioned nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution, and ammonia water were added to the reactor in a certain proportion to start the reaction. The flow rate of the nickel-iron-manganese mixed salt solution was controlled at 350 L / h. The pH was maintained within the range of 12.20±0.05 for the first hour of the synthesis reaction, and then decreased to the range of 11.50±0.6 after 1 hour. The NH3 content was 4.0±0.5 g / L throughout the reaction. The stirring speed was 210 rpm, and the reactor temperature was controlled at 50±1℃. The particle size of the synthesis reaction grew to D. 50 When the particle size is >7.0 μm, the pH of the reaction in the reactor is increased to the range where seed crystals precipitate to prepare seed crystals. When the amount of seed crystals is sufficient, the pH of the synthesis reaction is decreased to the growth range. The process of increasing and decreasing the pH is repeated to prepare seed crystals and grow them while maintaining the final particle size D of the synthesis reaction.50 Within the range of 10±1μm, collect the overflow qualified nickel-iron-manganese layered oxide precursor slurry.

[0075] (5) Washing and filtration of qualified finished slurry: Prepare a 2% NaOH solution and wash some of the metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5℃. Wash the impurity Na in the nickel-iron-manganese layered oxide precursor with deionized water at a temperature range of 50±5℃. Dehydrate the product using a solid-liquid separation device to obtain a qualified finished filter cake.

[0076] (6) Drying of qualified finished products: Quantitatively feed the qualified finished filter cake into the disc dryer, and dry it at a temperature range of 120±5℃. Control the moisture content of the qualified powder after the disc dryer discharge to be <0.5%.

[0077] (7) The dried qualified powder is drawn into the transfer silo and quantitatively sieved through a 400-mesh sieve in the upper layer and a 200-mesh sieve in the lower layer to remove larger particles and control the particle size D100 < 36μm. After sieving, the powder is demagnetized by an electromagnetic demagnetizer to remove metal foreign matter. The demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the content of magnetic foreign matter in the demagnetized powder is controlled to be < 50ppb.

[0078] (8) The qualified powder after sieving and demagnetizing is batch-mixed to make the particle size matrix uniformly distributed. The batch-mixed material is sampled and tested for all performance indicators of the product.

[0079] (9) The qualified powder materials that have passed the full inspection of various performance indicators are vacuum-packed according to the quantity and requirements, clearly labeled and put into storage. The particle size distribution curve of the process control and the morphology of the finished product are compared and analyzed.

[0080] Comparative Example 2

[0081] A method for preparing a nickel-iron-manganese layered oxide precursor includes the following steps:

[0082] (1) Prepare a 2 mol / L mixed salt solution of soluble salts of nickel, iron and manganese, with the molar ratio of nickel, iron and manganese being x, y and z, where x:y:z = 3:4:3;

[0083] (2) Prepare a 25% NaOH solution by mass fraction, prepare a certain concentration of soluble Na2S2O3 solution and dissolve it in the NaOH solution, the mass percentage of Na2S2O3 in the NaOH solution is 0.002%, and prepare a 25% ammonia solution by mass fraction.

[0084] (3) Add 2500L of deionized water containing 0.01% Na2S2O3 to a high-efficiency sealed reaction vessel. Simultaneously add a certain amount of ammonia and sodium hydroxide solution to achieve an NH3 content of 4.0±0.5g / L. The pH of the bottom solution in the vessel should be approximately 12.20±0.05. Control the reaction vessel temperature at 50±1℃ and purge with nitrogen gas for at least 2 hours at a flow rate of 4.5±0.5m³. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0085] (4) The above-mentioned nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution, and ammonia water were added to the reactor in a certain proportion to start the reaction. The flow rate of the nickel-iron-manganese mixed salt solution was controlled at 350 L / h. The pH was maintained within the range of 12.20±0.05 for the first hour of the synthesis reaction, and then decreased to the range of 11.50±0.6 after 1 hour. The NH3 content was 4.0±0.5 g / L throughout the reaction. The stirring speed was 210 rpm, and the reactor temperature was controlled at 50±1℃. The particle size of the synthesis reaction grew to D. 50 When the particle size is >7.0 μm, the pH of the reaction in the reactor is increased to the range where seed crystals precipitate to prepare seed crystals. When the amount of seed crystals is sufficient, the pH of the synthesis reaction is decreased to the growth range. The process of increasing and decreasing the pH is repeated to prepare seed crystals and grow them while maintaining the final particle size D of the synthesis reaction. 50 Within the range of 10±1μm, collect the overflow qualified nickel-iron-manganese layered oxide precursor slurry.

[0086] (5) Washing and filtration of qualified finished slurry: Prepare a 2% NaOH solution and wash some of the metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5℃. Wash the impurity Na in the nickel-iron-manganese layered oxide precursor with deionized water at a temperature range of 50±5℃. Dehydrate the product using a solid-liquid separation device to obtain a qualified finished filter cake.

[0087] (6) Drying of qualified finished products: Quantitatively feed the qualified finished filter cake into the disc dryer, and dry it at a temperature range of 120±5℃. Control the moisture content of the qualified powder after the disc dryer discharge to be <0.5%.

[0088] (7) After drying, the qualified powder is pumped into the transfer silo and quantitatively sieved through an upper 400-mesh sieve and a lower 200-mesh sieve to remove larger particles and control the particle size D. 100 <36μm, after sieving, the powder is used to remove metal foreign objects in the powder using an electromagnetic demagnetizer. The demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the content of magnetic foreign objects in the demagnetized powder is controlled to be <50ppb.

[0089] (8) The qualified powder after sieving and demagnetizing is batch-mixed to make the particle size matrix uniformly distributed. The batch-mixed material is sampled and tested for all performance indicators of the product.

[0090] (9) The qualified powder materials that have passed the full inspection of various performance indicators are vacuum-packed according to the quantity and requirements, clearly labeled and put into storage. The particle size distribution curve of the process control and the morphology of the finished product are compared and analyzed.

[0091] Comparative Example 3

[0092] A method for preparing a nickel-iron-manganese layered oxide precursor includes the following steps:

[0093] (1) Prepare a 2 mol / L mixed salt solution of soluble salts of nickel, iron and manganese, with the molar ratio of nickel, iron and manganese being x, y and z, where x:y:z = 3:4:3;

[0094] (2) Prepare a 25% mass concentration NaOH solution, dissolve a certain concentration of soluble Na2S2O3 in the NaOH solution, with the mass percentage of Na2S2O3 in the NaOH solution being 0.01%, and prepare a 25% mass concentration ammonia solution.

[0095] (3) Add 2500L of deionized water containing 0.01% Na2S2O3 to a high-efficiency sealed reaction vessel. Simultaneously add a certain amount of ammonia and sodium hydroxide solution to achieve an NH3 content of 4.0±0.5g / L. The pH of the bottom solution in the vessel should be approximately 12.20±0.05. Control the reaction vessel temperature at 50±1℃ and purge with nitrogen gas for at least 2 hours at a flow rate of 4.5±0.5m³ / h. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0096] (4) The above-mentioned nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution, and ammonia water were added to the reactor in a certain proportion to start the reaction. The flow rate of the nickel-iron-manganese mixed sulfate solution was controlled at 350 L / h. The pH was maintained within the range of 12.20±0.05 for the first hour of the synthesis reaction, and then the pH was reduced to the range of 11.50±0.6 after 1 hour. The NH3 content was 4.0±0.5 g / L throughout the reaction. The stirring speed was 210 rpm, and the reactor temperature was controlled at 50±1℃. The particle size of the synthesis reaction grew to D. 50 When the particle size is >7.0 μm, the pH of the reaction in the reactor is increased to the range where seed crystals precipitate to prepare seed crystals. When the amount of seed crystals is sufficient, the pH of the synthesis reaction is decreased to the growth range. The process of increasing and decreasing the pH is repeated to prepare seed crystals and grow them while maintaining the final particle size D of the synthesis reaction. 50 Within the range of 10±1μm, collect the overflow qualified nickel-iron-manganese layered oxide precursor slurry.

[0097] (5) Washing and filtration of qualified finished slurry: Prepare a 2% NaOH solution and wash some of the metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5℃. Wash the impurity Na in the nickel-iron-manganese layered oxide precursor with deionized water at a temperature range of 50±5℃. Dehydrate the product using a solid-liquid separation device to obtain a qualified finished filter cake.

[0098] (6) Drying of qualified finished products: Quantitatively feed the qualified finished filter cake into the disc dryer, and dry it at a temperature range of 120±5℃. Control the moisture content of the qualified powder after the disc dryer discharge to be <0.5%.

[0099] (7) After drying, the qualified powder is pumped into the transfer silo and quantitatively sieved through an upper 400-mesh sieve and a lower 200-mesh sieve to remove larger particles and control the particle size D. 100 <36μm, after sieving, the powder is used to remove metal foreign objects in the powder using an electromagnetic demagnetizer. The demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the content of magnetic foreign objects in the demagnetized powder is controlled to be <50ppb.

[0100] (8) The qualified powder after sieving and demagnetizing is batch-mixed to make the particle size matrix uniformly distributed. The batch-mixed material is sampled and tested for all performance indicators of the product.

[0101] (9) The qualified powder materials that have passed the full inspection of various performance indicators are vacuum-packed according to the quantity and requirements, clearly labeled and put into storage. The particle size distribution curve of the process control and the morphology of the finished product are compared and analyzed.

[0102] Performance testing

[0103] The microstructure of the nickel-iron-manganese layered oxide precursors in the examples and comparative examples was analyzed by scanning electron microscopy. The results are as follows: Figures 1 to 4 As shown. Among them, Figure 1 The microstructure of the product obtained in Example 1 is shown below. Figure 2 The microstructure of the product obtained in Comparative Example 1 is shown. Figure 3 The microstructure of the product obtained in Comparative Example 2 is shown. Figure 4 The microstructure of the product obtained in Comparative Example 3 is shown.

[0104] The specific surface area of ​​the nickel-iron-manganese layered oxide precursors of the examples and comparative examples was determined by N2 adsorption method, and the results are shown in Table 1.

[0105] The tap density of the nickel-iron-manganese layered oxide precursors of the examples and comparative examples was tested using a tap density tester, and the results are shown in Table 1.

[0106] Table 1

[0107] <![CDATA[Tap density (g / cm 3 )]]> <![CDATA[Specific surface area (m 2 / g)]]> Example 1 2.083 7.952 Example 2 2.071 8.021 Example 3 2.066 8.168 Comparative Example 1 1.936 6.638 Comparative Example 2 1.963 10.635 Comparative Example 3 1.901 11.367

[0108] As can be seen from Table 1, the tap density of the nickel-iron-manganese layered oxide precursor prepared by the present invention is relatively high, reaching 2.0 g / cm³. 3 The above have a specific surface area of ​​7.5–9.5 m². 2 Within a certain range (g), a high tap density of the material can be guaranteed while improving its electrochemical performance. If the specific surface area is too small, its porosity will be too low, which is not conducive to the intercalation of metal ions during the subsequent sintering preparation of the cathode material and will reduce the electrochemical performance of the cathode material. If the specific surface area is too large, it will reduce the tap density of the nickel-iron-manganese layered oxide material and thus affect the performance of the battery.

[0109] In Comparative Example 1, a nickel-iron-manganese layered oxide precursor was prepared by continuously using a third precipitant during the reaction process. As can be seen from Example 1 and Comparative Example 1, the nickel-iron-manganese layered oxide precursor prepared by the present invention significantly improved the tap density and specific surface area compared with the product obtained by reaction without the addition of reducing agent Na2S2O3, which is beneficial to improving battery performance.

[0110] Comparative Example 2 continuously used the second precipitant to prepare the nickel-iron-manganese layered oxide precursor during the reaction process, and Comparative Example 3 continuously used the first precipitant to prepare the nickel-iron-manganese layered oxide precursor during the reaction process. It can be seen from the data of Comparative Example 2 and Comparative Example 3 that the nickel-iron-manganese layered oxide precursor obtained by maintaining the same content of Na2S2O3 in the reaction system has too large a specific surface area, which is not conducive to improving the tap density. Its tap density is lower than that of the nickel-iron-manganese layered oxide precursor prepared in Example 1.

[0111] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained in Example 1 ( Figure 1 As can be seen, under 10K magnification electron microscopy, the primary particles exhibit uniform length, width, and thickness, with orderly growth and stacking directions. The secondary particles have high density, which is due to the orderly overlap of the primary particles, resulting in a uniform distribution of porous structures that helps control the specific surface area of ​​the finished particles. The secondary particles also have high sphericity and relatively regular edges and corners, which helps improve the tap density of the finished particles and ensures good compaction performance at the electrode end of the battery material. Under 1K magnification electron microscopy, the overall particle distribution is relatively uniform, with medium-sized particles accounting for a greater proportion than small particles, which in turn accounts for a greater proportion than large particles. This meets the requirements for continuous reaction particle size control of the finished product and corresponds to the particle size matrix distribution, while also enabling stable and continuous production output.

[0112] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained from Comparative Example 1 ( Figure 2 It can be seen that under 10K electron microscopy, the precipitate exhibits significant differences in particle length and thickness polarization after the first stage. After secondary spheroidization, the precipitate morphology shows poor sphericity and prominent end angles. Under 1K electron microscopy, the overall particle size is relatively small, with most particles being fine crystal nuclei that have precipitated but not grown into aggregates. A small proportion of the medium to large secondary spheroids are present, along with Fe formed from oxidation. 3+Ions precipitate seed crystals individually in the synthesis reactor and continuously correlate with each other, causing the particle size of the synthesis reaction to fail to grow to the required range. At the same time, the particle morphology deviates significantly from the actual requirements, affecting the performance of the actual finished product.

[0113] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained from Comparative Example 2 ( Figure 3 It can be seen that under 10K electron microscopy, the primary particles of the precipitate, modified by a stable system of Na2S2O3 with Na2S2O3 injected at 0.002% of the mass of NaOH, exhibit uniform length, reduced thickness deviation, narrowed length, width, and thickness deviation, and improved consistency. However, under 1K electron microscopy, the proportion of large and small particles in the secondary spherical formation index is differentiated at both ends, with a small proportion of medium-sized particles, resulting in poor particle size distribution uniformity of the obtained product.

[0114] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained from Comparative Example 3 ( Figure 4 As can be seen from the 10K electron microscope, the primary Na2S2O3 particles exhibited significant deviations in length and width in a stable system where the injected Na2S2O3 mass was 0.01% of the NaOH mass. The uniformity was poor, and the growth and stacking directions were disorganized. The secondary spheres showed poor morphology and irregularity. Under the 1K electron microscope, the secondary particles were of medium size, with a large proportion being agglomerated particles with poor morphology.

[0115] Therefore, by comparing and verifying with the examples, it was found that using a reaction solution without reducing sulfates to make Fe 2+ Ion oxidation controls the number of new seed crystals formed in the reaction system. By varying the content of reducing sulfate, the growth rate of particles in the system is controlled, inhibiting the formation of new seed crystals. This results in a continuous preparation process with controllable particle size and stable particle morphology, achieving the particle size and morphology requirements of the finished product. Continuous reaction production produces qualified nickel-iron-manganese hydroxide precursors, further improving the plasticity and physical properties of the product particles, and possessing considerable industrial application value.

[0116] The above embodiments are preferred experimental methods of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-iron-manganese layered oxide precursor, characterized in that, Includes the following steps: S1. Under an inert gas atmosphere, a nickel-iron-manganese mixed salt solution, a first precipitant, and ammonia water are added to the base solution. The synthesis reaction continues until the particle size in the system reaches a first particle size value, which is calculated as D5, and is the target particle size D. 50 The value ranges from 31.5% to 47.5%. S2. Continuously add the nickel-iron-manganese mixed salt solution, the second precipitant, and ammonia water, and continue the growth reaction until the particle size in the system reaches the second particle size value; the second particle size value is calculated as D5, which is the target particle size D. 50 The value ranges from 37.5% to 57.0%. S3. Continuously add the nickel-iron-manganese mixed salt solution, the third precipitant, and ammonia water, and continue the reaction until the D5 of the particles in the system stabilizes within a specified time. Then replace the third precipitant with the first precipitant and continue the reaction until the D5 of the particles in the system stabilizes. 50 Size reaches target particle size D 50 Numerical value; S4. Replace the first precipitant with the third precipitant, and continuously add nickel-iron-manganese mixed salt solution and ammonia water until the D5 size of the particles in the system is smaller than the first particle size value; then replace the third precipitant with the first precipitant and continue the synthesis reaction until the D5 size of the particles in the system reaches the first particle size value; Repeat steps S2 to S4 to continuously produce nickel-iron-manganese layered oxide precursors with the target particle size; The concentration of NaOH in the first precipitant is 22~32wt%, and the concentration of reducing sulfate is 0.008~0.012wt%. The concentration of NaOH in the second precipitant is 22-32 wt%, and the concentration of reducing sulfate is 0.002-0.003 wt%. The concentration of NaOH in the third precipitant is 22-32 wt%. During processes S1 to S4, the pH of the system was controlled at 10.5 to 12.5, the NH3 content at 3 to 6 g / L, and the temperature at 45 to 65℃. The target particle size D 50 It is 8~12μm; The reducing sulfate is Na2S2O3 and / or Na2SO3; The stability mentioned in step S3 is defined as the particle size D5 in the system growing to ≤0.1 μm within 4 hours.

2. The preparation method according to claim 1, characterized in that, The molar ratio of nickel, iron, and manganese in the nickel-iron-manganese mixed salt solution is (0.2~0.6):(0.1~0.5):(0.1~0.4).

3. The preparation method according to claim 1, characterized in that, The nickel-iron-manganese mixed salt solution is added at a rate of 300–400 L / h.

4. The preparation method according to claim 1, characterized in that, The base solution contains an aqueous solution of reducing sulfate, a first precipitant, and ammonia.

5. The preparation method according to claim 1, characterized in that, The tap density of the nickel-iron-manganese layered oxide precursor is ≥2.0 g / cm³. 3 Its specific surface area is 7.5~9.5 m². 2 / g.

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