A binary precursor and preparation method thereof

Abstract

The invention discloses a binary precursor and a preparation method thereof, comprising: preparing a solution; injecting water into a synthesis reactor to increase the temperature, and injecting ammonia water; introducing NaOH solution into a crystal nucleus synthesis reactor to adjust the pH value; introducing a nickel-cobalt mixed salt solution, a NaOH solution, and ammonia water for nucleation; reducing the system pH value, and concentrating, and controlling the particle growth rate by increasing the flow rate of the nickel-cobalt mixed salt solution until the target particle size is reached and the feeding is stopped to obtain a crystal nucleus; pumping the crystal nucleus into a growth synthesis reactor, and simultaneously introducing a nickel-cobalt mixed salt solution, a NaOH solution, and ammonia water for reaction, and concentrating, and after D50 grows to the target value, adjusting the temperature and pH value, and increasing the system ammonia concentration, and then increasing the temperature, ammonia concentration, and pH value for each 1 μm growth of D50 until the target particle size is reached and the reaction is stopped. The binary precursor prepared by the method of the invention has a narrow particle size distribution, good sphericity, different structures of the inner core and the outer shell, no cracks on the particle surface, and strong product consistency.

Description

Technical Field

[0001] The present invention relates to the technical field of precursor preparation, and in particular to a binary precursor and a preparation method thereof. Background Art

[0002] At present, the lithium-ion battery industry is developing rapidly. Ternary lithium-ion batteries have become mainstream products in the mid-to-high-end market with their high battery capacity, good rate performance, and excellent cycle performance. The performance of ternary positive electrode materials mainly depends on the ternary precursors. The requirements of high capacity, high voltage, and excellent cycle performance make nickel-cobalt-aluminum ternary precursors more advantageous than nickel-cobalt-manganese ternary precursors. However, the synthesis process of nickel-cobalt-aluminum ternary precursors is difficult. Aluminum salts require a separate feeding system and cannot be mixed with nickel and cobalt. In addition, ammonia water has a poor complexing effect with aluminum ions, and it is extremely difficult to control the precipitation reaction. The current method is mainly to synthesize high-nickel binary precursors from nickel-cobalt raw materials, but the nickel-cobalt binary precursors synthesized by traditional processes have a wide particle size distribution, the primary particles are thick and large, the secondary particles have obvious ball cracking, the control is unstable, the batch consistency is poor, the tap density is large, the reaction time is limited, and the particle size grows to a certain range, and the ball breaking phenomenon will occur. Summary of the invention

[0003] The present invention is based on the inventors' discovery and understanding of the following facts and problems: At present, the production process of nickel-cobalt binary precursors is mainly a continuous method or a pure discontinuous method. The continuous method has poor control stability, a wide product particle size distribution, poor batch consistency, a relatively large tap density, thick and large primary particles, and irregular secondary particle morphology. The pure discontinuous method is difficult to control the growth rate. If the growth rate is too fast, the product particle size distribution is wide, the sphericity is poor, and various physical properties deviate significantly from the required values; if the growth rate is too slow, the growth particle size is limited. When D50 reaches about 10μm, the secondary particles have obvious ball cracking, and the tap density of the obtained product is too large and the specific surface area is too small, resulting in obvious ball breakage during the sintering process, affecting the battery capacity and cycle performance.

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, an embodiment of the present invention proposes a method for preparing a binary precursor, which adopts a double-concentration quantitative nucleation process to reduce the particle size distribution, improve the control stability and product consistency, change the particle growth mode and morphology, and thus improve the process indicators such as tap density and specific surface area, and prepare a binary precursor with narrow particle size distribution, good sphericity, different structures of the inner core and the outer shell, no cracks on the particle surface, strong product consistency, and less control difficulty.

[0005] A method for preparing a binary precursor according to an embodiment of the present invention comprises the following steps:

[0006] (1) preparing a nickel-cobalt mixed salt solution by taking NiSO4 and CoSO4, preparing a NaOH solution as a precipitant, and preparing an ammonia solution as a complexing agent;

[0007] (2) respectively injecting water into the crystal nucleus synthesis reactor and the growth synthesis reactor, raising the temperature, respectively injecting ammonia solution into the crystal nucleus synthesis reactor and the growth synthesis reactor to prepare a bottom liquid, and introducing nitrogen;

[0008] (3) introducing NaOH solution into the nucleation reactor to adjust the pH value; simultaneously introducing nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution to form nuclei, and controlling the pH value and ammonia concentration of the system;

[0009] (4) After the nucleation is completed, the pH value of the system is lowered. After the pH value is stable, the material is pumped into the concentrator. After the concentrator has finished pumping the material, the concentration is started. The supernatant is discharged through the concentrator, and the flow rate of the nickel-cobalt mixed salt solution is increased to control the particle growth rate, the pH value and ammonia concentration of the system are controlled, and the feeding is stopped when the particle size grows to the target particle size to obtain the crystal nucleus;

[0010] (5) pumping the material in the crystal nucleus synthesis reactor obtained in step (4) into the growth synthesis reactor, adjusting the homogenization speed of the system, and simultaneously introducing a nickel-cobalt mixed salt solution, a NaOH solution, and an ammonia solution to react, and then pumping the material to the concentrator, and starting to concentrate after the concentrator has finished pumping the material, and discharging the supernatant through the concentrator to control the pH value and ammonia concentration of the system;

[0011] (6) After the D50 of the material in the growth reactor grows to the target value, the temperature and pH value are adjusted, and the ammonia concentration of the system is increased; thereafter, the temperature, ammonia concentration and pH value are increased every time the D50 grows by 1 μm, and the reaction is stopped when the particle size grows to the target particle size. After aging, alkali washing, water washing and drying, a binary precursor is obtained.

[0012] The advantages and technical effects brought by the preparation method of the binary precursor of the embodiment of the present invention have changed the traditional continuous and discontinuous processes, and adopted a double concentration and fixed crystal nucleus amount nucleation process, which is mainly divided into two steps: (1) The first step is to prepare the crystal nucleus. The surface of the secondary particles of the crystal nucleus is loose and porous, the particle size distribution is narrow, the particle consistency is high, the number of twin balls is small, and the specific surface area is large. After the crystal nucleus synthesis kettle prepares the bottom liquid, it starts to feed. After feeding, a certain seeding time is controlled, and then the concentration growth is carried out. After adjusting various process control indicators to reach the target particle size, the reaction is stopped to obtain the crystal nucleus. (2) The second step is to prepare the binary precursor, which has a large particle size, good sphericity, a narrower particle size distribution, no cracks on the surface, different structures of the inner core and the outer shell, and strong product consistency. The production process is a pure discontinuous method. The base liquid is prepared in the growth synthesis kettle, and the required amount of crystal nuclei is calculated by the equivalent spherical theory. The crystal nuclei of the target volume are pumped in. After completion, a concentration reaction is carried out. After D50 grows to the target value, the pH value, alkalinity and temperature are adjusted to change the growth mode and thickness of the primary particles, so that the proportion of fine particles on the surface of the secondary particles increases, the diameter gaps become more, the sphericity is good, and cracks are not easy to occur. The reaction is stopped when the particle size reaches the target particle size.

[0013] In some embodiments, in step (1), the concentration of the nickel-cobalt mixed salt is 1.8-2.4 mol / L; NiSO4 and CoSO4 are taken according to the molar ratio of X:Y to prepare a nickel-cobalt mixed salt solution, wherein X+Y=1, 0.8<X<1, 0<Y<0.2; the concentration of the NaOH solution is 6-12 mol / L; the concentration of the ammonia solution is 4-10 mol / L.

[0014] In some embodiments, in the step (2), the volume of water injected into the nucleus synthesis reactor and the growth synthesis reactor is 75%-80% of the reactor volume; and / or, the temperature is raised to 60-70°C; and / or, the ammonia concentration in the bottom liquid is 1-5g / L; and / or, the flow rate of nitrogen is 10-30L / h; and / or, the homogenization speed of the system is 700-800rpm.

[0015] In some embodiments, in the step (3), NaOH solution is introduced into the crystal nucleus synthesis reactor to adjust the pH value to 11.6-11.8; and / or the flow rate of the nickel-cobalt mixed salt solution introduced per hour is 2%-4% of the volume of the crystal nucleus synthesis reactor; and / or the pH value of the system is controlled to be 11.6-11.8; and / or the ammonia concentration of the system is controlled to be 1-5 g / L; and / or the nucleation stage is completed after the nickel-cobalt mixed salt solution, NaOH solution and ammonia solution are introduced for 10-20 minutes.

[0016] In some embodiments, in the step (4), the pH value of the system is lowered to 11.0-11.2; and / or, the hourly flow rate of the nickel-cobalt mixed salt solution is increased to 6%-8% of the volume of the crystal nucleus synthesis reactor; and / or, the pH value of the system is controlled to be 11.0-11.2; and / or, the ammonia concentration of the system is controlled to be 1-5g / L; and / or, the target particle size is 5-6μm; and / or, the primary particles of the obtained crystal nuclei are plate-shaped, and the secondary particles are porous.

[0017] In some embodiments, in the step (5), the volume of the material in the crystal nucleus synthesis reactor obtained in step (4) pumped into the growth synthesis reactor is 10%-20% of the volume of the growth synthesis reactor; and / or the system homogenization speed is adjusted to 500-600rpm; and / or the hourly flow rate of the nickel-cobalt mixed salt solution is 8%-12% of the volume of the growth synthesis reactor; and / or the pH value of the system is controlled to be 11.4-11.6; and / or the ammonia concentration of the system is controlled to be 1-5g / L; and / or the material is pumped into the concentrator after the reaction is carried out for 0.5-2h.

[0018] In some embodiments, in step (6), the target value of D50 is 11-12 μm; and / or the temperature is adjusted to 70-75° C.; and / or the pH value is adjusted to 11.2-11.4; and / or the ammonia concentration of the system is increased to 6-8 g / L.

[0019] In some embodiments, in step (6), for every 1 μm growth of D50, the temperature increases by 0.5-1°C, the ammonia concentration increases by 0.5-1 g / L, and the pH value increases by 0.05-0.1; the target particle size is 16-20 μm.

[0020] A binary precursor of an embodiment of the present invention is prepared by the preparation method of the above embodiment. In the embodiment of the present invention, the binary precursor has a narrow particle size distribution, good sphericity, different structures of the core and the shell, no cracks on the particle surface, strong product consistency, and low control difficulty.

[0021] In some embodiments, the secondary particles of the binary precursor have no cracks on their surfaces; the specific surface area of ​​the binary precursor is 7±2 m 2 / g, tap density is 2±0.2g / cm 3 , bulk density is 1.6±0.2g / cm 3 , particle size distribution diameter is 0.42±0.05, sodium content is <320ppm, sulfur content is <1800ppm, and D50 is 18±2μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0023] Figure 2 This is the SEM image of the binary precursor prepared in Example 1.

[0024] Figure 3 This is the SEM image of the binary precursor prepared in Example 2.

[0025] Figure 4 This is the SEM image of the binary precursor prepared in Example 3.

[0026] Figure 5 This is the SEM image of the crystal nuclei prepared in the crystal nucleus synthesis reactor in Example 1. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0028] like Figure 1 As shown, a method for preparing a binary precursor according to an embodiment of the present invention comprises the following steps:

[0029] (1) preparing a nickel-cobalt mixed salt solution by taking NiSO4 and CoSO4, preparing a NaOH solution as a precipitant, and preparing an ammonia solution as a complexing agent;

[0030] (2) respectively injecting water into the crystal nucleus synthesis reactor and the growth synthesis reactor, raising the temperature, respectively injecting ammonia solution into the crystal nucleus synthesis reactor and the growth synthesis reactor to prepare a bottom liquid, and introducing nitrogen;

[0031] (3) introducing NaOH solution into the nucleation reactor to adjust the pH value; simultaneously introducing nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution to form nuclei, and controlling the pH value and ammonia concentration of the system;

[0032] (4) After the nucleation is completed, the pH value of the system is lowered. After the pH value is stable, the material is pumped into the concentrator. After the concentrator has finished pumping the material, the concentration is started. The supernatant is discharged through the concentrator, and the flow rate of the nickel-cobalt mixed salt solution is increased to control the particle growth rate, the pH value and ammonia concentration of the system are controlled, and the feeding is stopped when the particle size grows to the target particle size to obtain the crystal nucleus;

[0033] (5) pumping the material in the crystal nucleus synthesis reactor obtained in step (4) into the growth synthesis reactor, adjusting the homogenization speed of the system, and simultaneously introducing a nickel-cobalt mixed salt solution, a NaOH solution, and an ammonia solution to react, and then pumping the material to the concentrator, and starting to concentrate after the concentrator has finished pumping the material, and discharging the supernatant through the concentrator to control the pH value and ammonia concentration of the system;

[0034] (6) After the D50 of the material in the growth reactor grows to the target value, the temperature and pH value are adjusted, and the ammonia concentration of the system is increased; thereafter, the temperature, ammonia concentration and pH value are increased every time the D50 grows by 1 μm, and the reaction is stopped when the particle size grows to the target particle size. After aging, alkali washing, water washing and drying, a binary precursor is obtained.

[0035] The method for preparing the binary precursor of the embodiment of the present invention changes the traditional continuous method and discontinuous method, and adopts a double concentration and fixed crystal nucleus amount nucleation process, which is mainly divided into two steps: (1) The first step is to prepare the crystal nucleus, the surface of the secondary particles of the crystal nucleus is loose and porous, the particle size distribution is narrow, the particle consistency is high, the number of twin balls is small, and the specific surface area is large. After the crystal nucleus synthesis kettle prepares the bottom liquid, it starts to feed. After feeding, a certain seeding time is controlled, and then the concentration growth is carried out. After the target particle size is reached by adjusting various process control indicators, the reaction is stopped to obtain the crystal nucleus. (2) The second step is to prepare the binary precursor, which has a large particle size, good sphericity, a narrower particle size distribution, no cracks on the surface, different structures of the inner core and the outer shell, and strong product consistency. The production process is a pure discontinuous method. The base liquid is prepared in the growth synthesis kettle, and the required amount of crystal nuclei is calculated by the equivalent spherical theory. The crystal nuclei of the target volume are pumped in. After completion, a concentration reaction is carried out. After D50 grows to the target value, the pH value, alkalinity and temperature are adjusted to change the growth mode and thickness of the primary particles, so that the proportion of fine particles on the surface of the secondary particles increases, the diameter gaps become more, the sphericity is good, and cracks are not easy to occur. The reaction is stopped when the particle size reaches the target particle size.

[0036] In some embodiments, in step (1), the concentration of the nickel-cobalt mixed salt is 1.8-2.4 mol / L, specifically, for example, 1.8 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L; NiSO4 and CoSO4 are prepared into a nickel-cobalt mixed salt solution according to a molar ratio of X:Y, wherein X+Y=1, 0.8<X<1, 0<Y<0.2, specifically, for example, X is 0.85, 0.9, 0.95, Y is 0.15, 0.1, 0.05; the concentration of the NaOH solution is 6-12mol / L, specifically, for example, 6mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L, 12mol / L; the concentration of the ammonia solution is 4-10mol / L, specifically, for example, 4mol / L, 5mol / L, 6mol / L, 8mol / L, 10mol / L. In the embodiment of the present invention, X+Y=1, 0.8<X<1, 0<Y<0.2, and a high-nickel binary precursor is prepared. In the embodiment of the present invention, the concentration of the nickel-cobalt mixed salt, the concentration of the NaOH solution and the concentration of the ammonia solution are further optimized. When the concentration of the nickel-cobalt mixed salt is too low, the production efficiency is low; when it is too high, the reaction rate is too fast and the growth is abnormal. When the concentration of NaOH solution is too low, the concentration effect is poor and the particle size distribution is wide; when it is too high, the primary particles are too dense and the secondary particles are prone to ball cracking. When the concentration of ammonia solution is too low, the complexing effect is not obvious and uniform coprecipitation cannot be achieved; when it is too high, there are too many complexed metal ions, the reaction is incomplete, and the primary particles are thick.

[0037] In some embodiments, in the step (2), the volume of water injected into the nucleus synthesis reactor and the growth synthesis reactor is 75%-80% of the reactor volume, specifically, for example, 75%, 77%, 80%,; and / or, the temperature is raised to 60-70°C, specifically, for example, 60°C, 63°C, 65°C, 70°C; and / or, the ammonia concentration in the bottom liquid is 1-5g / L, specifically, for example, 1g / L, 2g / L, 3g / L, 4g / L, 5g / L; and / or, the flow rate of nitrogen is 10-30L / h, preferably, 20L / h; and / or, the homogenization speed of the system is 700-800rpm, specifically, for example, 700rpm, 750rpm, 780rpm, 800rpm. In the embodiment of the present invention, the ammonia concentration in the bottom liquid is optimized, which can better complex nickel and cobalt ions, orderly control particle growth, and achieve a coprecipitation effect.

[0038] In some embodiments, in the step (3), NaOH solution is introduced into the crystal nucleus synthesis reactor to adjust the pH value to 11.6-11.8, specifically, for example, 11.6, 11.7, 11.8; and / or, the flow rate of the nickel-cobalt mixed salt solution introduced per hour is 2%-4% of the volume of the crystal nucleus synthesis reactor, specifically, for example, 2%, 2.5%, 3%, 3.5%, 4%; and / or, the pH value of the system is controlled to be 11.6-11.8, specifically, for example, 11.6, 11.7, 11.8; and / or, the ammonia concentration of the system is controlled to be 1-5 g / L; and / or, the nucleation stage is completed after 10-20 minutes of introducing the nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution, specifically, for example, 10 minutes, 15 minutes, 20 minutes. In the embodiment of the present invention, the nickel-cobalt mixed salt solution, NaOH solution and ammonia solution are introduced for 10-20 minutes, that is, the discharge is stopped after 10-20 minutes of feeding, and the nucleation stage is completed. This refers to the reaction time under high pH conditions. If the feeding time is too long, the particles grow slowly and the particle morphology is too thick; if the feeding time is too short, the particles grow too fast, the particle morphology is loose, and the particle size distribution is wide. Controlling the appropriate nucleation time can produce products with narrow particle size distribution and good sphericity.

[0039] In some embodiments, in the step (4), the pH value of the system is lowered to 11.0-11.2, specifically, for example, 11.0, 11.1, 11.2; and / or, the hourly flow rate of the nickel-cobalt mixed salt solution is increased to 6%-8% of the volume of the crystal nucleus synthesis reactor, specifically, 6%, 7%, 8%; and / or, the pH value of the system is controlled to be 11.0-11.2, specifically, for example, 11.0, 11.1, 11.2; and / or, the ammonia concentration of the system is controlled to be 1-5g / L, specifically, for example, 1g / L, 2g / L, 3g / L, 4g / L, 5g / L; and / or, the target particle size is 5-6μm, specifically, for example, 5μm, 5.5μm, 6μm; and / or, the primary particles of the obtained crystal nuclei are plate-like, and the secondary particles are porous. In the embodiment of the present invention, lowering the pH value of the system to 11.0-11.2 can stop the system from producing seeds, and the particles tend to grow. After starting to concentrate, increasing the flow rate of the nickel-cobalt mixed salt solution can control the particle growth rate, and further preferably increasing it to 6-8% is conducive to uniform particle growth. In the embodiment of the present invention, the target particle size of the crystal nucleus is 5-6μm, and the obtained crystal nucleus primary particles are moderately thick and plate-like, and the secondary particles are porous.

[0040] In some embodiments, in the step (5), the volume of the material in the crystal nucleus synthesis reactor obtained in step (4) pumped into the growth synthesis reactor is 10%-20% of the volume of the growth synthesis reactor, specifically, for example, 10%, 12%, 15%, 18%, 20%. In a specific embodiment, the pumping volume is 15-20L, specifically, for example, 15L, 16L, 17L, 18L, 19L, 20L; and / or, the system homogenization speed is adjusted to 500-600rpm, specifically, for example, 500rpm, 550rpm, 600rpm; and / or, the nickel-cobalt mixed salt The flow rate of the solution per hour is 8%-12% of the volume of the growth synthesis reactor, specifically, for example, 8%, 9%, 10%, 11%, 12%; and / or, the pH value of the control system is 11.4-11.6, specifically, for example, 11.4, 11.45, 11.5, 11.55, 11.6; and / or, the ammonia concentration of the control system is 1-5g / L, specifically, for example, 1g / L, 2g / L, 3g / L, 4g / L, 5g / L; and / or, the reaction is carried out for 0.5-2h before the concentrator is pumped, specifically, for example, 0.5h, 1h, 1.5h, 2h. In the embodiment of the present invention, the growth synthesis reactor is prepared with the bottom liquid, and the required amount of crystal nuclei is calculated, and the crystal nuclei of the target volume are pumped in, which is conducive to the appropriate reaction time and growth to the target particle size. The pumped volume is further preferably selected so that the reaction time is within a controllable range. In the embodiment of the present invention, the flow rate of the nickel-cobalt mixed salt solution is further optimized to increase the early reaction speed and reduce the density between particles.

[0041] In some embodiments, in step (6), the target value of D50 is 11-12 μm, specifically, for example, 11 μm, 11.3 μm, 11.5 μm, 11.7 μm, 12 μm; and / or, the temperature is adjusted to 70-75°C, specifically, for example, 70°C, 72°C, 75°C; and / or, the pH value is adjusted to 11.2-11.4, specifically, for example, 11.2, 11.3, 11.4; and / or, the ammonia concentration of the system is increased to 6-8 g / L, specifically, for example, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L. In the embodiment of the present invention, the target value of D50 is further preferred, which is conducive to avoiding the ball cracking phenomenon. In the embodiment of the present invention, after the D50 of the material in the growing synthesis reactor grows to the target value, the temperature is adjusted, the pH value is adjusted, and the ammonia concentration of the system is increased, the purpose of which is to change the growth mode of the particles; by further optimizing the adjustment of the temperature, the pH value, and the increase of the ammonia concentration of the system, the growth mode of the particles can be changed, while ensuring that no new nuclei are produced in the system.

[0042] In some embodiments, in step (6), the temperature is increased by 0.5-1°C for each 1 μm growth of D50, specifically, for example, 0.5°C, 0.6°C, 0.7°C, 0.8°C, 0.9°C, 1°C; the ammonia concentration is increased by 0.5-1g / L, specifically, for example, 0.5g / L, 0.6g / L, 0.7g / L, 0.8g / L, 0.9g / L, 1g / L; the pH value is increased by 0.05-0.1, specifically, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1; the target particle size is 16-20μm, specifically, for example, 16μm, 17μm, 18μm, 19μm, 20μm. In the embodiment of the present invention, the temperature, ammonia concentration and pH value are increased for each 1μm growth of D50, so as to refine the primary particles. By preferably increasing the temperature by 0.5-1°C, the ammonia concentration by 0.5-1g / L, and the pH value by 0.05-0.1, the primary particles can be uniformly changed. When the rate of increase of the temperature, ammonia concentration, and pH value is too fast, the reaction system changes significantly and the reaction is uncontrollable; when it is too slow, the primary particle morphology is not significantly refined.

[0043] A binary precursor of an embodiment of the present invention is prepared by the preparation method of the above embodiment. In the embodiment of the present invention, the binary precursor has a narrow particle size distribution, good sphericity, different structures of the core and the shell, no cracks on the particle surface, strong product consistency, and low control difficulty.

[0044] In some embodiments, the secondary particles of the binary precursor have no cracks on their surfaces; the specific surface area of ​​the binary precursor is 7±2 m 2 / g, tap density is 2±0.2g / cm 3 , bulk density is 1.6±0.2g / cm 3 , particle size distribution diameter is 0.42±0.05, sodium content is less than 320ppm, sulfur content is less than 1800ppm, and D50 is 18±2μm. In the embodiment of the present invention, the binary precursor prepared has a larger specific surface area, a more uniform particle size distribution, and a lower impurity content.

[0045] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0046] Example 1

[0047] (1) A 2.1 mol / L nickel-cobalt mixed salt solution was prepared by mixing NiSO4 and CoSO4 at a molar ratio of 0.95:0.05, and a 10 mol / L NaOH solution was used as a precipitant and a 6 mol / L ammonia solution was used as a complexing agent.

[0048] (2) Water was injected into the nucleus synthesis reactor and the growth synthesis reactor respectively. The volume of the nucleus synthesis reactor was 100 L, and the volume of the growth synthesis reactor was 100 L. The volume of the water injected was 80% of the reactor volume. Then, stirring was performed and the jacket water of the synthesis reactor was heated to 65°C. Ammonia solution was injected into the synthesis reactor to prepare the bottom liquid before grooving. The ammonia concentration of the system was controlled at 4 g / L. The flow rate of nitrogen was 20 L / h to ensure that the synthesis reactor was in a nitrogen atmosphere. The homogenization speed of the system was adjusted to 800 rpm.

[0049] (3) First, NaOH solution was introduced into the crystal nucleus synthesis reactor to control the pH value at 11.8. At the same time, the salt pump, alkali pump, and ammonia water pump were turned on to introduce nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution to carry out a co-precipitation reaction. The flow rate of the nickel-cobalt mixed salt solution was controlled to be 4 L / h. After the liquid was introduced, the pH value was stably controlled to be 11.75, and the ammonia concentration was 3 g / L. The nucleation stage was completed 15 minutes after the feeding.

[0050] (4) Then, the concentration growth stage is carried out, the pH value of the system is lowered to 11.0, and the material is pumped into the concentrator after the pH value stabilizes. After the concentrator has finished pumping the material, the concentration is started, the supernatant is discharged through the concentrator, and the flow rate of the nickel-cobalt mixed salt solution is increased to 6 L / h. The pH value of the system is controlled to be 11.15, and the ammonia concentration is 3 g / L. When the particle size grows to 6 μm, the feeding is stopped. The sample obtained is a crystal nucleus with a primary particle thickness of moderate plate-like shape and a secondary particle of porous shape. The SEM image of the crystal nucleus is shown in FIG. Figure 5 .

[0051] (5) The material in the crystal nucleus synthesis reactor was pumped into the growth synthesis reactor. The calculated pumping amount was 15 L (15% of the volume of the growth synthesis reactor). The homogenization speed of the system was adjusted to 600 rpm. The salt pump, alkali pump, and ammonia water pump were simultaneously turned on to introduce the nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution. The flow rate of the nickel-cobalt mixed salt solution was controlled to be 12 L / h. After reacting for 1 hour, the material was pumped into the concentrator. After the concentrator had finished pumping the material, the material was concentrated. The supernatant was discharged through the concentrator. The pH value of the system was controlled to be 11.5 and the ammonia concentration was 4 g / L.

[0052] (6) After the material D50 in the growth synthesis reactor grows to 12 μm, the temperature is adjusted to 70°C, the pH value is adjusted to 11.2, and the ammonia concentration of the system is increased to 6 g / L; thereafter, for every 1 μm growth of D50, the temperature is increased by 0.5°C, the ammonia concentration is increased by 0.5 g / L, and the pH value is increased by 0.05. The reaction is stopped when the particle size grows to 18 μm; the output product is subjected to aging, clear liquid discharge, alkali washing, water washing, and drying to obtain a binary precursor.

[0053] from Figure 2It can be seen that the binary precursor has good sphericity, narrow particle size distribution, and no cracks on the surface of the secondary particles. The physical properties of the binary precursor are: specific surface area 6.72m 2 / g, tap density is 2.08g / cm 3 , bulk density is 1.67g / cm 3 , particle size distribution diameter distance is 0.43, sodium content is 300ppm, sulfur content is 1637ppm.

[0054] Example 2

[0055] The preparation method is the same as that of Example 1, except that step (6) is different:

[0056] (6) After the material D50 in the growth synthesis reactor grows to 12 μm, the temperature is adjusted to 70°C, the pH value is adjusted to 11.2, and the ammonia concentration of the system is increased by 6 g / L; thereafter, for every 1 μm growth of D50, the temperature is increased by 0.7°C, the ammonia concentration is increased by 0.7 g / L, and the pH value is increased by 0.07. When the particle size grows to 18 μm, the reaction is stopped, and the output product is subjected to aging, alkali washing, water washing, and drying to obtain a binary precursor.

[0057] from Figure 3 It can be seen that the binary precursor has good sphericity, narrow particle size distribution, and no cracks on the surface of the secondary particles. The physical properties of the binary precursor are: specific surface area 7.13m 2 / g, tap density is 2.05g / cm 3 , bulk density is 1.65g / cm 3 The particle size distribution diameter is 0.40, the sodium content is 291ppm, and the sulfur content is 1596ppm.

[0058] Example 3

[0059] The preparation method of Example 3 is the same as that of Example 1, except that step (6) is different:

[0060] (6) After the material D50 in the growth synthesis reactor grows to 12 μm, the temperature is adjusted to 70°C, the pH value is adjusted to 11.2, and the ammonia concentration of the system is increased to 6 g / L; thereafter, for every 1 μm growth of D50, the temperature is increased by 1°C, the ammonia concentration is increased by 1 g / L, and the pH value is increased by 0.1. When the particle size grows to 18 μm, the reaction is stopped, and the output product is subjected to aging, alkali washing, water washing, and drying to obtain a binary precursor.

[0061] from Figure 4 It can be seen that the binary precursor has good sphericity, narrow particle size distribution, and no cracks on the surface of the secondary particles. The physical properties of the binary precursor are: specific surface area 7.67m 2 / g, tap density is 2.01g / cm 3, bulk density is 1.63g / cm 3 The particle size distribution diameter is 0.45, the sodium content is 272ppm, and the sulfur content is 1432ppm.

[0062] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0063] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing a binary precursor, characterized in that: The following steps are involved: (1) preparing a nickel-cobalt mixed salt solution by taking NiSO4 and CoSO4, preparing a NaOH solution as a precipitant, and preparing an ammonia solution as a complexing agent; (2) respectively injecting water into the crystal nucleus synthesis reactor and the growth synthesis reactor, raising the temperature, respectively injecting ammonia solution into the crystal nucleus synthesis reactor and the growth synthesis reactor to prepare a bottom liquid, and introducing nitrogen; (3) introducing NaOH solution into the nucleation reactor to adjust the pH value; simultaneously introducing nickel-cobalt mixed salt solution, NaOH solution, and ammonia solution to form nuclei, and controlling the pH value and ammonia concentration of the system; and controlling the pH value of the system to be 11.6-11.8; (4) After the nucleation is completed, the pH value of the system is lowered. After the pH value is stable, the material is pumped into the concentrator. After the concentrator has finished pumping the material, the concentration is started. The supernatant is discharged through the concentrator, and the flow rate of the nickel-cobalt mixed salt solution is increased to control the particle growth rate, the pH value and ammonia concentration of the system are controlled, and the feeding is stopped when the particle size grows to the target particle size to obtain the crystal nucleus; the pH value of the system is controlled to be 11.0-11.2; (5) pumping the material in the crystal nucleus synthesis reactor obtained in step (4) into the growth synthesis reactor, adjusting the homogenization speed of the system, and simultaneously introducing a nickel-cobalt mixed salt solution, a NaOH solution, and an ammonia solution to react, and then pumping the material to the concentrator, and starting to concentrate after the concentrator has finished pumping the material, and discharging the supernatant through the concentrator to control the pH value and ammonia concentration of the system; the pH value of the system is controlled to be 11.4-11.6; (6) After the D50 of the material in the growth reactor grows to the target value, the temperature and pH value are adjusted to 11.2-11.4, and the ammonia concentration of the system is increased; thereafter, the temperature, ammonia concentration and pH value are increased for each 1 μm growth of D50, and the reaction is stopped when the particle size grows to the target particle size. After aging, alkali washing, water washing and drying, a binary precursor is obtained.

2. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (1), the concentration of the nickel-cobalt mixed salt is 1.8-2.4 mol / L; NiSO4 and CoSO4 are taken according to the molar ratio X:Y to prepare a nickel-cobalt mixed salt solution, wherein X+Y=1, 0.8<X<1, 0<Y<0.2; the concentration of the NaOH solution is 6-12 mol / L; the concentration of the ammonia solution is 4-10 mol / L.

3. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (2), the volume of water injected into the nucleus synthesis reactor and the growth synthesis reactor is 75%-80% of the reactor volume; and / or, the temperature is raised to 60-70°C; and / or, the ammonia concentration in the bottom liquid is 1-5g / L; and / or, the flow rate of the nitrogen introduced is 10-30L / h; and / or, the homogenization speed of the system is 700-800rpm.

4. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (3), NaOH solution is introduced into the crystal nucleus synthesis reactor to adjust the pH value to 11.6-11.8; and / or the flow rate of the nickel-cobalt mixed salt solution introduced per hour is 2%-4% of the volume of the crystal nucleus synthesis reactor; and / or the ammonia concentration of the system is controlled to be 1-5 g / L; and / or the nucleation stage is completed after the nickel-cobalt mixed salt solution, NaOH solution and ammonia solution are introduced for 10-20 minutes.

5. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (4), the pH value of the system is lowered to 11.0-11.2; and / or the hourly flow rate of the nickel-cobalt mixed salt solution is increased to 6%-8% of the volume of the crystal nucleus synthesis reactor; and / or the ammonia concentration of the system is controlled to be 1-5 g / L; and / or the target particle size is 5-6 μm; and / or the primary particles of the obtained crystal nuclei are in the form of plates and the secondary particles are in the form of porous particles.

6. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (5), the volume of the material in the crystal nucleus synthesis reactor obtained in the step (4) pumped into the growth synthesis reactor is 10%-20% of the volume of the growth synthesis reactor; and / or the system homogenization speed is adjusted to 500-600rpm; and / or the hourly flow rate of the nickel-cobalt mixed salt solution is 8%-12% of the volume of the growth synthesis reactor; and / or the ammonia concentration of the system is controlled to be 1-5g / L; and / or the material is pumped into the concentrator after the reaction is carried out for 0.5-2h.

7. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (6), the target value of D50 is 11-12 μm; and / or the temperature is adjusted to 70-75° C.; and / or the ammonia concentration of the system is increased to 6-8 g / L.

8. The method for preparing a binary precursor according to claim 1, characterized in that: In the step (6), for every 1 μm growth of D50, the temperature is increased by 0.5-1°C, the ammonia concentration is increased by 0.5-1 g / L, and the pH value is increased by 0.05-0.1; the target particle size is 16-20 μm.

9. A binary precursor, characterized in that The compound is prepared by the preparation method according to any one of claims 1 to 8.

10. The binary precursor according to claim 9, characterized in that The secondary particles of the binary precursor have no cracks on their surface; the specific surface area of ​​the binary precursor is 7±2m 2 / g, tap density is 2±0.2g / cm 3 , bulk density is 1.6±0.2g / cm 3 , particle size distribution diameter is 0.42±0.05, sodium content is <320ppm, sulfur content is <1800ppm, and D50 is 18±2μm.

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