Nickel-iron-manganese layered oxide precursor as well as preparation method and application thereof

Abstract

The invention discloses a nickel-iron-manganese layered oxide precursor as well as a preparation method and application thereof, and relates to the technical field of sodium-ion battery materials. In a reaction system for preparing the nickel-iron-manganese layered oxide precursor through coprecipitation, the concentration of reducing sulfate is regulated and controlled from particle growth to different stages, so that the quantity of precipitated crystal seeds in a particle size matrix of the whole reaction system can be controlled, and the precipitation rate, the growth unit cell sequence direction and the secondary particle morphology in the growth process can be controlled; a balanced reaction system is maintained, products with the particle size range meeting production index requirements are continuously produced, the particle size distribution uniformity of the products is improved, good sphericity morphology is obtained, and the tap density is improved. The process is relatively simple to control, high in stability and obvious in production cost advantage.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery materials, and more specifically, relates to a nickel-iron-manganese layered oxide precursor and a preparation method and application thereof. Background Art

[0002] Among the positive electrode materials for sodium-ion batteries, the sodium-ion positive electrode materials prepared using layered oxide precursors are closer to the capacity performance of existing lithium iron phosphate materials, and are also a route for the rapid development of positive electrode materials for sodium-ion batteries today. The mainstream preparation method for nickel-iron-manganese layered oxide precursors is the nickel-iron-manganese ternary layered oxide liquid phase synthesis method, which is highly consistent with the process route for synthesizing lithium-ion battery positive electrode material precursors. Mainstream manufacturers can basically switch directly to quantitative production of sodium-ion battery positive electrode material precursors.

[0003] The co-precipitation synthesis process for preparing nickel-iron-manganese ternary layered oxides is widely used, but there are the following defects in the synthesis process: in the positive electrode material synthesized with iron as the main material, due to the presence of dissolved oxygen in the liquid, in the liquid phase co-precipitation synthesis of nickel-iron-manganese precursor system, the dissolved oxygen in the water easily dissolves the Fe 2+ Iron ions are oxidized to Fe 3+ Valence, Fe 2+ After oxidation, small crystals will be precipitated irregularly, causing the reaction system to lose control, resulting in a large deviation between the secondary particle size and the actual requirements, and a deviation in the physical properties of the finished product. In the process of preparing nickel-iron-manganese precursors by coprecipitation, adding a reducing agent can inhibit the Fe 2+ Iron ions are oxidized to Fe 3+ The patent CN116986646A adds additional prepared seeds in a coprecipitation reaction system containing a reducing agent when the particle size of the nickel-iron-manganese layered oxide grows close to the target particle size, which can make the nickel-iron-manganese layered oxide continue to be produced and improve the consistency of the finished product particle size. However, this method still has the following problems in actual industrial application: (1) The process is relatively complicated: it is necessary to extend the seed preparation process and the process equipment requirements are high. (2) The obtained nickel-iron-manganese layered oxide precursor has poor sphericity and low tap density, which limits the improvement of the electrochemical performance of the positive electrode material. Summary of the invention

[0004] In order to solve the problem that in the prior art, the sphericity of the obtained particles is poor and the tap density is small during the continuous preparation of nickel-iron-manganese precursors with uniform particle size, the primary purpose of the present invention is to provide a method for preparing a nickel-iron-manganese layered oxide precursor, so that the precipitation of seeds and the growth of grains are carried out regularly during the reaction system, so that the particle size of the synthesized particles is controllable, the particle size distribution of the obtained particles is uniform, and the sphericity and tap density are improved.

[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 purpose of the present invention is achieved through the following technical solutions:

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

[0009] S1. Adding a nickel-iron-manganese mixed salt solution, a first precipitant and ammonia water to the bottom liquid under an inert gas atmosphere, and performing a synthesis reaction until the particle size in the system reaches a first particle size value, wherein the first particle size value is D 5 Numerical calculation, which is the target particle size D 50 31.5-47.5% of the value;

[0010] S2. Continue to add nickel-iron-manganese mixed salt solution, the second precipitant and ammonia water, and continue to grow the reaction until the particle size in the system reaches the second particle size value; the second particle size value is D 5 Numerical calculation, which is the target particle size D 50 37.5-57.0% of the value;

[0011] S3. Continue to add nickel-iron-manganese mixed salt solution, the third precipitant and ammonia water, and continue to react until the particle size D in the system 5 After stabilization within a specified time, the third precipitant is replaced by the first precipitant, and the reaction is continued until the particle size in the system reaches the target particle size D 50 Numeric value;

[0012] S4. The first precipitant is replaced by a third precipitant, and the nickel-iron-manganese mixed salt solution and ammonia are continuously added to react until the particle size in the system is less than the first particle size value; and then the third precipitant is replaced by the first precipitant, and the synthesis reaction is performed until the particle size in the system reaches the first particle size value;

[0013] Repeating steps S2 to S4 to continuously produce a nickel-iron-manganese layered oxide precursor having a target particle size;

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

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

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

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

[0018] Among them, it should be noted that:

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

[0020] When the particles in the system grow rapidly to a particle size that reaches a first particle size value, the first precipitant is replaced with a second precipitant through step S2, that is, the concentration of reducing sulfate in the reaction system is reduced to slow down the growth rate of the particles, so that the grains can grow preferentially in the concave parts of the particles. The particles grow and stack in an orderly manner in different directions, which is beneficial to shaping the spherical morphology of the finished particles. At the same time, the orderly overlapping of the particles is beneficial to forming a uniform porous structure, controlling the specific surface area of ​​the particles, and improving 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. The second precipitant is replaced by the third precipitant in step S3 to make the particle size matrix D in the synthesis reaction system 0 ,

[0022] D 5 , D 10 The growth trend slowed down rapidly, and there was even no sign of growth. 5 When the particles are stable within a specified time, the third precipitant is replaced by the first precipitant, so that the particles can grow to meet the target particle size and improve the consistency of the particle size matrix distribution.

[0023] When the particle size of the particles in the solution reaches the target particle size, the first precipitant is replaced by the third precipitant through step S4 to quickly precipitate a large number of seed crystals. When a certain number of seed crystals are precipitated, that is, when the particle size in the system is smaller than the first particle size value, the third precipitant is replaced by the first precipitant, which can inhibit the precipitation of new seed crystals and make the particles grow rapidly. The synthesis reaction is carried out until the particle size in the system reaches the first particle size value, and then the cycle steps S2 to S4 are repeated, that is, the concentration of the reducing sulfate in the reaction process is cyclically adjusted, and finally a high sphericity and target particle size D can be stably and continuously produced. 50 products.

[0024] In a specific embodiment, the particle size D in step S3 is 5 Stability within a specified time refers to the particle size D within a specified time. 5 The growth value changes ≤0.1μm.

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

[0026] In a specific embodiment, preferably, the reducing sulfate is Na 2 S 2 O 3 and / or Na 2 SO 3 The present invention can be compatible with the alkaline precipitant by using the reducing sulfate, effectively controlling the growth of nickel-iron-manganese layered oxide while avoiding the introduction of impurities, which is beneficial to improving the electrochemical performance of the electrode material 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 conducive to having sufficient growth and shaping time for the precipitated particles in the unit volume precipitation kettle, reaching the preset required equilibrium particle size range, and forming a stable precipitation output reaction system to continuously output the required slurry product.

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

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

[0031] In a specific embodiment, the product is washed, dried, sieved, demagnetized, tested and packaged using conventional operations in the art, and the specific operations can be referred to as follows:

[0032] (1) Qualified finished product washing and filter pressing: 1-5% NaOH solution is prepared to wash some metal impurities and S impurities, and the washing temperature range is 40-60°C; impurity Na is washed with deionized water, and the washing temperature range is 45-60°C, and the qualified finished product filter cake is dehydrated by solid-liquid separation equipment;

[0033] (2) Drying of qualified finished products: quantitatively put qualified finished product filter cakes into drying equipment, the drying temperature range is 100-150°C, and the moisture content of the qualified powder after drying is controlled to be less than 0.5%;

[0034] (3) Screening and demagnetization of qualified finished products: The dried qualified powder is pumped into the transfer bin for quantitative screening to remove larger particles and control the particle size D 100 <36μm, the powder after screening is used to remove metal foreign matter in the powder using an electromagnetic demagnetizer, and the magnetic foreign matter content of the powder after demagnetization is controlled to be <50ppb.

[0035] (4) Mixing test: The qualified powder materials after screening and demagnetization are batch mixed to make the particle size matrix uniformly distributed. The materials after batch mixing are sampled and fully tested for various performance indicators of the product;

[0036] (5) Finished product packaging: Qualified powders that have passed the full inspection of various performance indicators are vacuum-packed according to the quantity and requirements and are clearly labeled before storage.

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

[0038] Preferably, the tap density of the nickel-iron-manganese layered oxide precursor is ≥2.0 g / cm 3 , with a specific surface area of ​​7.5 to 9.5 m 2 / g. The tap density of the nickel-iron-manganese layered oxide precursor is high, which is beneficial to improving the performance of the battery. The specific surface area is 7.5 to 9.5 m 2 / g range, the high tap density of the material can be ensured 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 electrode material.

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

[0042] The present invention regulates the concentration of reducing sulfate at different stages of particle growth in the nickel-iron-manganese layered oxide co-precipitation reaction system, thereby controlling the number of precipitated crystal seeds in the particle size matrix of the entire reaction system and the precipitation rate during the growth process, so that the primary particles grow and stack in an orderly manner in different directions, shape the sphericity morphology of the secondary particles, maintain a balanced reaction system, and continuously produce nickel-iron-manganese layered oxides with uniform particle size distribution, high sphericity and tap density. The tap density of the obtained nickel-iron-manganese layered oxide is ≥2.0 g / cm 3 , with a specific surface area of ​​7.5 to 9.5 m 2 / g.

[0043] The preparation method of the present invention has simple process, does not need to use an additional crystal seed preparation process, has low production cost and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0045] Figure 2 This is the microscopic morphology of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 1.

[0046] Figure 3 This is the microscopic morphology of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 2.

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

[0048] The content of the present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. 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 the present embodiment are conventional reagents, methods and equipment in the art.

[0049] Example 1

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

[0051] (1) preparing a nickel-iron-manganese mixed salt solution: preparing soluble salts of nickel, iron and manganese into a 2 mol / L mixed salt solution, wherein the molar ratio of nickel, iron and manganese is x, y and z, wherein x:y:z=3:4:3;

[0052] (2) Preparation of the first precipitant: Prepare a 25% mass concentration NaOH solution, 2 S 2 O 3 Dissolved in NaOH solution, Na 2 S 2 O 3 The mass percentage in NaOH solution is 0.01%;

[0053] (3) Preparation of the second precipitant: Prepare a 25% mass concentration NaOH solution and add Na 2 S 2 O 3 Dissolved in NaOH solution, Na 2 S 2 O 3The mass proportion in the NaOH solution is 0.002%.

[0054] (4) preparing the third precipitant: preparing a 25% mass concentration NaOH solution;

[0055] (5) Preparation of reaction base liquid: Add 2500L of Na-containing 2 S 2 O 3 Deionized water accounts for 0.01% by weight, and a certain amount of the above ammonia and NaOH solution are added to make NH 3 The content is 4.0±0.5g / L, OH - The content is 1-3 g / L, the temperature of the reactor is controlled at 50°C, nitrogen is introduced for 2 hours, and the nitrogen flow rate is 4.5±0.5m 3 / h, the reaction atmosphere in the displacement synthesis reactor is inert atmosphere conditions;

[0056] (6) In an inert gas atmosphere, the nickel-iron-manganese mixed salt solution, the first precipitant and ammonia water are continuously added to the reaction base liquid to perform a synthesis reaction until the particle size D in the system reaches 5 3.8μm;

[0057] (7) Continue to add nickel-iron-manganese mixed salt solution, the second precipitant and ammonia water, and continue the growth reaction until the particle size D in the system is 5 4.5μm;

[0058] (8) Continue to add nickel-iron-manganese mixed salt solution, the third precipitant and ammonia water, and continue to react until the particle size D in the system is 5 When the growth value is ≤0.1 μm within 4 hours, the third precipitant is replaced by the first precipitant, and the process continues until the particle size in the system reaches the target particle size D 50 8~12μm;

[0059] (9) The first precipitant is replaced with a third precipitant, and the nickel-iron-manganese mixed salt solution and ammonia water are continuously added to react until the particle size D in the system is 5 <3.8μm, then replace the third precipitant with the first precipitant, and react until the particle size D 5 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 having a diameter of 8 to 12 μm; the pH value of the system during the reaction of steps (6) to (9) is controlled to be 11.50±0.6, and NH 3 The content is 4.0±0.5g / L, the temperature is 50°C, and the flow rate of the nickel-iron-manganese mixed salt solution is 350L / h.

[0061] (10) Qualified finished product washing and filtration: Prepare 2% NaOH solution, wash some metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5°C, and use deionized water to wash the target particle size D at a temperature range of 50±5°C. 50 The impurity Na in the nickel-iron-manganese layered oxide precursor of 8 to 12 μm is dehydrated by solid-liquid separation equipment to obtain a qualified finished product filter cake;

[0062] (11) Drying of qualified finished products: quantitatively put the qualified finished filter cake into the disc dryer, the drying temperature range is 120±5℃, and the moisture content of the qualified powder after the disc dryer is controlled to be less than 0.5%;

[0063] (12) The dried qualified powder is pumped into the transfer bin for quantitative screening, and the upper layer is 400 mesh and the lower layer is 200 mesh to remove the larger particles and control the particle size D 100 <36μm, the powder after screening is removed by electromagnetic demagnetizer to remove metal foreign matter in the powder, the demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the magnetic foreign matter content of the powder after demagnetization is controlled to be <50ppb;

[0064] (13) The qualified powder materials after screening and demagnetization are batch mixed to make the particle size matrix uniformly distributed. The materials after batch mixing are sampled for full inspection of various performance indicators of the product, and the electron microscopy morphology of the finished product obtained in the embodiment is analyzed.

[0065] Example 2

[0066] The difference between Example 2 and Example 1 is that Na 2 S 2 O 3 The mass proportion in the NaOH solution is 0.0025%.

[0067] Example 3

[0068] The difference between Example 3 and Example 1 is that the Na 2 S 2 O 3 The mass proportion in the NaOH solution is 0.003%.

[0069] Comparative Example 1

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

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

[0072] (2) preparing a 25% mass fraction NaOH solution and a 25% mass concentration ammonia solution;

[0073] (3) Add 2500L of deionized water to a high-efficiency closed synthesis reactor, and add a certain amount of ammonia water and sodium hydroxide solution so that NH 3 The content is 4.0±0.5g / L, the pH of the bottom liquid in the kettle is about 12.20±0.05, the temperature of the reactor is controlled at 50±1℃, nitrogen is introduced for more than 2h, and the nitrogen flow rate is 4.5±0.5m 3 / h, and the reaction atmosphere in the replacement synthesis reactor is inert atmosphere conditions.

[0074] (4) Controlling the nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution, and ammonia water to be added to a reactor in a certain proportion to start the reaction, wherein the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, the pH value within 1 hour before the synthesis reaction is within the range of 12.20±0.05, and the pH value of the synthesis reaction is reduced to 11.50±0.6 after 1 hour, and the whole reaction NH 3 The content was 4.0±0.5g / L, the stirring speed was 210rpm, the reactor temperature was controlled at 50±1℃, and the particle size of the synthetic reaction grew to D 50 When the pH value is greater than 7.0 μm, the reaction pH in the reactor is raised to the pH range for precipitating crystal seeds to prepare crystal seeds. When the amount of crystal seeds is sufficient, the synthesis reaction pH is lowered to the growth range. The pH is repeatedly raised and lowered to prepare crystal seeds and grow to maintain the terminal synthesis reaction particle size D 50 : In the range of 10±1μm, the overflow qualified nickel-iron-manganese layered oxide precursor finished slurry is collected.

[0075] (5) Qualified finished product slurry washing and filtration: prepare 2% NaOH solution, wash some metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5°C, use deionized water to wash the impurity Na in the nickel-iron-manganese layered oxide precursor at a temperature range of 50±5°C, and dehydrate with solid-liquid separation equipment to obtain a qualified finished product filter cake;

[0076] (6) Drying of qualified finished products: quantitatively put qualified finished product filter cakes into the disc dryer, the drying temperature range is 120±5℃, and the moisture content of qualified powder after the disc dryer is controlled to be less than 0.5%;

[0077] (7) The dried qualified powder is pumped into the transfer bin for quantitative screening, and is screened through the upper 400 mesh and lower 200 mesh sieves to remove larger particles, and the particle size D100 is controlled to be less than 36 μm. The sieved powder is removed by an electromagnetic demagnetizer to remove metal foreign matter in the powder. The demagnetization intensity of the electromagnetic demagnetizer is 10000-13000 GS, and the magnetic foreign matter content of the demagnetized powder is controlled to be less than 50 ppb;

[0078] (8) The qualified powder materials after screening and demagnetization are batch mixed to make the particle size matrix uniformly distributed, and the materials after batch mixing are sampled for full inspection of various performance indicators of the products;

[0079] (9) The qualified powders 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, and the particle size distribution curve of the proportional process control and the electron microscopy 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 comprises the following steps:

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

[0083] (2) Prepare a 25% mass fraction of NaOH solution and a certain concentration of soluble Na 2 S 2 O 3 The solution is dissolved in NaOH solution, Na 2 S 2 O 3 The mass proportion of the NaOH solution is 0.002%, and a 25% mass concentration of ammonia solution is prepared;

[0084] (3) Add 2500L of Na-containing 2 S 2 O 3 The mass percentage of deionized water is 0.01%, and a certain amount of ammonia and sodium hydroxide solution are added to make NH 3 The content is 4.0±0.5g / L, the pH of the bottom liquid in the kettle is about 12.20±0.05, the temperature of the reactor is controlled at 50±1℃, nitrogen is introduced for more than 2h, and the nitrogen flow rate is 4.5±0.5m 3 / h, and the reaction atmosphere in the replacement synthesis reactor is inert atmosphere conditions.

[0085] (4) Controlling the nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution, and ammonia water to be added to a reactor in a certain proportion to start the reaction, wherein the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, the pH value within 1 hour before the synthesis reaction is within the range of 12.20±0.05, and the pH value of the synthesis reaction is reduced to 11.50±0.6 after 1 hour, and the whole reaction NH 3 The content was 4.0±0.5g / L, the stirring speed was 210rpm, the reactor temperature was controlled at 50±1℃, and the particle size of the synthetic reaction grew to D 50When the pH value is greater than 7.0 μm, the reaction pH in the reactor is raised to the pH range for precipitating crystal seeds to prepare crystal seeds. When the amount of crystal seeds is sufficient, the synthesis reaction pH is lowered to the growth range. The pH is repeatedly raised and lowered to prepare crystal seeds and grow to maintain the terminal synthesis reaction particle size D 50 : In the range of 10±1μm, the overflow qualified nickel-iron-manganese layered oxide precursor finished slurry is collected.

[0086] (5) Qualified finished product slurry washing and filtration: prepare 2% NaOH solution, wash some metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5°C, use deionized water to wash the impurity Na in the nickel-iron-manganese layered oxide precursor at a temperature range of 50±5°C, and dehydrate with solid-liquid separation equipment to obtain a qualified finished product filter cake;

[0087] (6) Drying of qualified finished products: quantitatively put qualified finished product filter cakes into the disc dryer, the drying temperature range is 120±5℃, and the moisture content of qualified powder after the disc dryer is controlled to be less than 0.5%;

[0088] (7) The dried qualified powder is pumped into the transfer bin for quantitative screening, and the upper layer is 400 mesh and the lower layer is 200 mesh to remove the larger particles and control the particle size D 100 <36μm, the powder after screening is removed by electromagnetic demagnetizer to remove metal foreign matter in the powder, the demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the magnetic foreign matter content of the powder after demagnetization is controlled to be <50ppb;

[0089] (8) The qualified powder materials after screening and demagnetization are batch mixed to make the particle size matrix uniformly distributed, and the materials after batch mixing are sampled for full inspection of various performance indicators of the products;

[0090] (9) The qualified powders 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, and the particle size distribution curve of the proportional process control and the electron microscopy 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 comprises the following steps:

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

[0094] (2) Prepare a 25% mass concentration NaOH solution and a certain concentration of soluble Na 2 S 2 O 3 Dissolved in NaOH solution, Na 2 S 2 O3 The mass proportion of the NaOH solution is 0.01%, and a 25% mass concentration of ammonia solution is prepared;

[0095] (3) Add 2500L of Na-containing 2 S 2 O 3 A certain amount of ammonia and sodium hydroxide solution were added to the deionized water base solution with a proportion of 0.01%. 3 The content is 4.0±0.5g / L, the pH of the bottom liquid in the kettle is about 12.20±0.05, the temperature of the reactor is controlled at 50±1℃, nitrogen is introduced for more than 2h, and the nitrogen flow rate is 4.5±0.5m 3 / h, and the reaction atmosphere in the replacement synthesis reactor is inert atmosphere conditions.

[0096] (4) Add the nickel-iron-manganese mixed sulfate solution, sodium hydroxide solution and ammonia water into a reactor in a certain proportion to start the reaction, wherein the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, the pH value within 1 hour before the synthesis reaction is within the range of 12.20±0.05, and the pH value of the synthesis reaction is reduced to 11.50±0.6 after 1 hour, and the whole reaction NH 3 The content was 4.0±0.5g / L, the stirring speed was 210rpm, the reactor temperature was controlled at 50±1℃, and the particle size of the synthetic reaction grew to D 50 When the pH value is greater than 7.0 μm, the reaction pH in the reactor is raised to the pH range for precipitating crystal seeds to prepare crystal seeds. When the amount of crystal seeds is sufficient, the synthesis reaction pH is lowered to the growth range. The pH is repeatedly raised and lowered to prepare crystal seeds and grow to maintain the terminal synthesis reaction particle size D 50 : In the range of 10±1μm, the overflow qualified nickel-iron-manganese layered oxide precursor finished slurry is collected.

[0097] (5) Qualified finished product slurry washing and filtration: prepare 2% NaOH solution, wash some metal impurities and S impurities in the obtained nickel-iron-manganese layered oxide precursor product at a temperature range of 50±5°C, use deionized water to wash the impurity Na in the nickel-iron-manganese layered oxide precursor at a temperature range of 50±5°C, and dehydrate with solid-liquid separation equipment to obtain a qualified finished product filter cake;

[0098] (6) Drying of qualified finished products: quantitatively put qualified finished product filter cakes into the disc dryer, the drying temperature range is 120±5℃, and the moisture content of qualified powder after the disc dryer is controlled to be less than 0.5%;

[0099] (7) The dried qualified powder is pumped into the transfer bin for quantitative screening, and the upper layer is 400 mesh and the lower layer is 200 mesh to remove the larger particles and control the particle size D 100<36μm, the powder after screening is removed by electromagnetic demagnetizer to remove metal foreign matter in the powder, the demagnetization intensity of the electromagnetic demagnetizer is 10000~13000GS, and the magnetic foreign matter content of the powder after demagnetization is controlled to be <50ppb;

[0100] (8) The qualified powder materials after screening and demagnetization are batch mixed to make the particle size matrix uniformly distributed, and the materials after batch mixing are sampled for full inspection of various performance indicators of the products;

[0101] (9) The qualified powders 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, and the particle size distribution curve of the proportional process control and the electron microscopy morphology of the finished product are compared and analyzed.

[0102] Performance Testing

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

[0104] Using N 2 The specific surface areas of the nickel-iron-manganese layered oxide precursors of the examples and comparative examples were measured by adsorption method. The results are shown in Table 1.

[0105] The tap density tester was used to test the tap density of the nickel-iron-manganese layered oxide precursors of the embodiment and the comparative example. 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] It can be seen from Table 1 that the tap density of the nickel-iron-manganese layered oxide precursor prepared by the present invention is relatively high, which can reach 2.0 g / cm 3 Above, the specific surface area is 7.5~9.5m 2 / g range, the 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 embedding of metal ions in the subsequent sintering process to prepare the positive electrode material, thereby reducing the electrochemical performance of the positive electrode material. If the specific surface area is too large, the tap density of the nickel-iron-manganese layered oxide material will be reduced, thereby affecting the performance of the battery.

[0109] Comparative Example 1: In the reaction process, the third precipitant is continuously used to prepare the nickel-iron-manganese layered oxide precursor. It can be seen from Example 1 and Comparative Example 1 that the nickel-iron-manganese layered oxide precursor prepared by the present invention is different from the layered oxide precursor without adding the reducing agent Na 2 S 2 O 3 Compared with the products obtained by the reaction, the tap density and specific surface area are significantly improved, which is beneficial to improving battery performance.

[0110] In Comparative Example 2, the second precipitant is continuously used during the reaction to prepare the nickel-iron-manganese layered oxide precursor, and in Comparative Example 3, the first precipitant is continuously used during the reaction to prepare the nickel-iron-manganese layered oxide precursor. It can be seen from the data of Comparative Example 2 and Comparative Example 3 that the same content of Na in the reaction system is maintained. 2 S 2 O 3 The specific surface area of ​​the obtained nickel-iron-manganese layered oxide precursor is too large, which is not conducive to the improvement of 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 ) It can be seen that under the electron microscope magnification of 10K, the length, width and thickness of the primary particles of the precipitation indicators are uniform, the growth and stacking direction is orderly, the secondary particles have a high density, and the porous gaps formed by the orderly overlapping of the primary particles are evenly distributed, which is beneficial to controlling the specific surface area of ​​the finished particles. The secondary particles have high sphericity and relatively regular edges and corners, which is beneficial to improving the tap density of the finished particles and is beneficial to having good compaction performance indicators at the electrode end of the battery material. Under the electron microscope magnification of 1K, the overall particle distribution is relatively uniform, with the proportion of medium particles > small particles > large particles, which meets the requirements of the particle size control indicators of the finished continuous reaction, corresponds to the particle size matrix distribution, and can complete stable and continuous production output.

[0112] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 1 ( Figure 2 ) It can be seen that under the electron microscope at a magnification of 10K, the precipitation index varies greatly after the length and thickness polarization of the primary particles. After the secondary balling, the sphericity of the precipitation morphology is poor, and the end corners are prominent. Under the electron microscope at 1K, the overall particle size is small, most of which are agglomerates that have not grown after the precipitation of small crystal nuclei. Some medium and large secondary spherical particles account for a small proportion, which is related to the Fe 3+ The ions precipitate as seeds separately in the synthesis reactor and continuously react with each other, which causes the particle size of the synthesis reaction to be unable to grow to the required range. At the same time, the particle morphology deviates greatly from the actual requirements, affecting the actual performance of the finished product.

[0113] Electron microscopic image of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 2 ( Figure 3 ) It can be seen that under the electron microscope at 10K magnification, the precipitation index primary particles are in Na2 S 2 O 3 , Na 2 S 2 O 3 Under the modification of a stable system with an injected mass of 0.002% of NaOH, the length of the primary particles is uniform, the thickness deviation is reduced, the length, width and thickness deviation indicators of the primary particles are narrowed, and the consistency is improved; but under an electron microscope 1K, the proportion of large and small particles under the secondary spherical index is differentiated at both ends, the proportion of medium-sized spherical particles is small, and the particle size distribution uniformity of the obtained product is poor.

[0114] Electron micrograph of the nickel-iron-manganese layered oxide precursor obtained in Comparative Example 3 ( Figure 4 ) It can be seen that under the electron microscope at 10K magnification, the precipitation index primary particle Na 2 S 2 O 3 , Na 2 S 2 O 3 In a stable system with an injected mass of 0.01% of the mass of NaOH, the primary particles showed length deviations, large deviations in length and width, poor uniformity, no sequence in the growth stacking direction, and poor and irregular morphology of the secondary spheroidization. Under an electron microscope at 1K, the secondary particle distribution was dominated by medium-sized particles, and most of them were agglomerated particles with poor morphology.

[0115] Therefore, by comparing the comparative examples with the examples, it is verified that the Fe 2+ Ion oxidation controls the number of new crystal seeds formed in the reaction system, controls the growth rate of particles in the system by changing the content of reducing sulfate, inhibits the formation of new crystal seeds, and forms a continuous preparation process with controllable synthetic particle size and controllable and stable particle morphology, achieving the technical particle size and technical morphology requirements of the finished product end, and continuous reaction production to produce qualified nickel-iron-manganese hydroxide precursors, further improving the plasticity and physical properties of the product particles, and has considerable industrial application value.

[0116] The above embodiments are preferred experimental methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a nickel-iron-manganese layered oxide precursor, characterized in that: The steps include: S1. Adding a nickel-iron-manganese mixed salt solution, a first precipitant and ammonia water to the bottom liquid under an inert gas atmosphere, and performing a synthesis reaction until the particle size in the system reaches a first particle size value, wherein the first particle size value is calculated as D5 value, which is the target particle size D 50 31.5-47.5% of the value; S2. Continue to add nickel-iron-manganese mixed salt solution, the second precipitant and ammonia water, and continue to grow the reaction until the particle size in the system reaches the second particle size value; the second particle size value is calculated as D5 value, which is the target particle size D 50 37.5-57.0% of the value; S3. Continue to add nickel-iron-manganese mixed salt solution, the third precipitant and ammonia water, and continue to react until the particle size D5 in the system is stable within a specified time, then replace the third precipitant with the first precipitant, and continue to react until the particle size in the system reaches the target particle size D 50 Numeric value; S4. The first precipitant is replaced by a third precipitant, and the nickel-iron-manganese mixed salt solution and ammonia are continuously added to react until the particle size in the system is less than the first particle size value; and then the third precipitant is replaced by the first precipitant, and the synthesis reaction is performed until the particle size in the system reaches the first particle size value; Repeating steps S2 to S4 to continuously produce a nickel-iron-manganese layered oxide precursor having a target particle size; The concentration of NaOH in the first precipitant is 22-32 wt %, and the concentration of the reducing sulfate is 0.008-0.012 wt %; The concentration of NaOH in the second precipitant is 22-32 wt %, and the concentration of the reducing sulfate is 0.002-0.003 wt %; The concentration of NaOH in the third precipitant is 22-32 wt %; During the process of S1 to S4, the pH value of the system is controlled to be 10.5 to 12.5, the NH3 content is 3 to 6 g / L, and the temperature is 45 to 65°C.

2. The preparation method according to claim 1, characterized in that: The target particle size D 50 8~12μm.

3. The preparation method according to claim 1, characterized in that: The reducing sulfate is Na2S2O3 and / or Na2SO3.

4. The preparation method according to claim 1, characterized in that: 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).

5. The preparation method according to claim 1, characterized in that: The addition rate of the nickel-iron-manganese mixed salt solution is 300-400 L / h.

6. The preparation method according to claim 1, characterized in that: The base liquid comprises an aqueous solution of reducing sulfate, a first precipitant and ammonia water.

7. A nickel-iron-manganese layered oxide precursor prepared by the preparation method according to any one of claims 1 to 6.

8. The nickel-iron-manganese layered oxide precursor according to claim 7, characterized in that: The tap density of the nickel-iron-manganese layered oxide precursor is ≥2.0 g / cm 3 , with a specific surface area of ​​7.5 to 9.5 m 2 / g.

9. An electrode material, characterized in that: Contains the nickel-iron-manganese layered oxide precursor as described in claim 7 or 8.

10. A sodium ion battery, characterized in that: Contains the electrode material according to claim 9.

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