Preparation Method of Precursor for Cathode Material of Lithium-Ion Battery and Draft Tube-Type Synthesis Kettle

Abstract

The present invention discloses a method for preparing a precursor of a cathode material for a lithium-ion battery and a draft-tube type synthesis kettle. The draft-tube type synthesis kettle includes a kettle body, a driving mechanism installed on the kettle body, a stirrer arranged in the kettle body and linked with the driving mechanism, a draft tube fixedly connected in the kettle body, a lifting mechanism further installed on the kettle body, and a lifting tube arranged in the draft tube and linked with the lifting mechanism; the draft tube is circumferentially provided with a plurality of windows for material circulation, the lifting tube cooperates with the windows, and the lower edge height of the material channel formed by the windows is adjusted by lifting. The preparation method is based on the draft-tube type synthesis kettle and combines the method of regulating with an energy factor and unit volume power. The present invention can solve the problems that in the draft-tube type synthesis kettle, since the distance between the window and the liquid level cannot be adjusted according to the liquid level, a good circulating flow cannot be formed, easily leading to the agglomeration of crystal particles and the blockage of the membrane tube, as well as the problems of relatively wide particle size distribution and poor product quality.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium production, and particularly to a method for preparing a precursor of a cathode material for a lithium-ion battery and a draft-tube type synthesis kettle. Background Art

[0002] The rapid growth of the electric vehicle market has promoted the development and research of high-performance cathode materials.

[0003] At present, ternary cathode materials are being upgraded towards high nickel, high voltage and single crystalization. While bringing high energy density, improved safety performance and cost reduction, they also increase the process difficulty of material production, posing higher requirements for precursor synthesis, doping, coating and understanding of the material system. As ternary cathodes develop towards single crystal and high nickel, the corresponding precursors are also developing towards small particle size and narrow distribution. Their synthesis is more difficult to control in terms of morphology and particle size due to the short particle growth cycle, and higher requirements are put forward for synthesis equipment.

[0004] The precursor production process can be divided into two types: batch method and continuous method. The batch method produces precursors with an extremely narrow particle size distribution, while the continuous method has higher production capacity. In the batch method, the residence time of the material in the reaction kettle is relatively uniform, and the produced precursor has a narrower particle size distribution, which is suitable for producing high-end products such as high nickel and single crystal type precursor products; however, it has the disadvantages of poor production continuity and poor batch stability. The continuous method has a higher production rate. The production capacity of the continuous method in a reaction kettle with the same volume is about twice that of the batch method, and the batch stability is good; but due to feeding and discharging at the same time, the residence time distribution of the material in the reaction kettle is wider, and the produced precursor has a wider particle size distribution. In particular, there are some particles with too small particle size, which will cause overburning during the cathode sintering process, thus affecting the cathode quality. Currently, it is mainly used for producing medium and low-end precursor products.

[0005] Draft-tube type synthesis kettles are widely used for producing high nickel and single crystal type precursor products because they can form a relatively good uniform flow field. First, windows need to be opened in the draft tube. The size and number of the windows and the liquid level difference between the lower edge of the window and the material level determine whether a relatively good circulating flow can be formed. If the lower edge of the window is too high, since the liquid level difference between the lower edge of the window and the material level is relatively small, the material does not have enough circulation channels, resulting in a decrease in the overall circulating flow. A lot of aggregated particles will form at the lower edge of the window, seriously affecting the product quality and leading to low efficiency of the reaction kettle. If the lower edge of the window is too low, local circulation will be formed, and local backflow will occur. Most of the material returns from the lower edge of the window, and a good overall large circulation cannot be formed. In addition, for a reaction kettle with a membrane tube (internal concentration enhancement), due to the inability to form a relatively good circulating flow, the flow velocity near the membrane tube is low, and particles agglomerate on the membrane tube, which further leads to membrane tube blockage.

[0006] For external concentration synthesis equipment, improper distances between the overflow port and the lower edge of the window will cause the above problems. Additionally, during the batch operation of a reaction kettle with membrane tubes, the material liquid level will fluctuate. Currently, in the case of a draft-tube type synthesis, since it is unable to adjust the distance between the window and the liquid level according to the liquid level, a good circulating flow cannot be formed, easily leading to agglomeration of crystal particles and blockage of the membrane tubes, as well as a wide particle size distribution and poor product quality. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for preparing a precursor of a lithium-ion battery cathode material and a draft-tube type synthesis kettle, to solve the problems that in the draft-tube type synthesis kettle, since it is unable to adjust the distance between the window and the liquid level according to the liquid level, a good circulating flow cannot be formed, easily leading to agglomeration of crystal particles and blockage of the membrane tubes, as well as a wide particle size distribution and poor product quality.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A draft-tube type synthesis kettle for preparing a precursor of a lithium-ion battery cathode material, including a kettle body, a driving mechanism installed on the kettle body, and a stirrer arranged in the kettle body and linked with the driving mechanism. A draft tube is fixedly connected inside the kettle body, and a lifting mechanism is also installed on the kettle body. A lifting cylinder linked with the lifting mechanism is arranged inside the draft tube. The draft tube is circumferentially provided with a plurality of windows for material circulation. The lifting cylinder cooperates with the windows and adjusts the height of the lower edge of the material channel formed by the windows through lifting.

[0009] In this solution, the lifting cylinder cooperates with the windows on the draft tube. Since the draft tube is fixedly connected, its position will not change, and similarly, the position of the windows will not change either. The provided windows can form a channel for the material to pass through and form a cycle. At this time, through the lifting action of the lifting cylinder, the size of the channel can be changed by using the upper edge of the lifting cylinder to block the windows. The change in this size is achieved by adjusting the height of the lower edge of the channel through the upper edge of the lifting cylinder blocking the windows. Since the height of the lower edge of the channel changes, the material liquid level during the preparation process can be adapted, so that there is a certain height difference between the material liquid level and the upper edge of the lifting cylinder, thereby achieving a better material circulation effect. Based on this adjustable method, the lower edge of the channel will not be too high or too low, and the existing problems in the background technology will not occur, and the quality of the prepared product can be better.

[0010] As a further improvement of the present invention, the lifting mechanism is connected to the lifting cylinder through a connecting rod, and the lifting cylinder cooperates with the windows through its upper edge to block and adjust the height of the lower edge of the material channel formed by the windows.

[0011] The way of connecting the lifting mechanism through a connecting rod has a simple structure, is easy to implement, and has a low assembly cost.

[0012] In a further setting, a liquid level sensor for detecting the liquid level of the material is arranged in the kettle body. The liquid level sensor is connected to a control unit, and the control unit is also connected to the lifting mechanism to control the lifting mechanism to drive the lifting cylinder to lift according to the liquid level information transmitted by the liquid level sensor, so as to adjust the window size.

[0013] Through the setting of the liquid level sensor, the detection and feedback of the internal liquid level can be realized. The control unit is used to control the lifting mechanism to achieve adaptive adjustment. This detection and feedback can be real-time to achieve real-time adjustment.

[0014] In addition, as a further optimization, the following improvement can also be made. A displacement sensor for detecting the position of the lifting cylinder is also arranged in the kettle body. The displacement sensor is connected to the control unit to feedback the position information of the lifting cylinder to the control unit.

[0015] By setting the position sensor to feedback the current position of the lifting cylinder, errors can be avoided, the position control of the lifting cylinder can be made more accurate, and then the height between the lifting cylinder and the liquid level can be made more stable and accurate, which helps to maintain better product quality control.

[0016] Preferably, the control unit controls the lifting cylinder to lift according to the position information and liquid level information of the displacement sensor and the liquid level sensor, so as to keep the height difference between the material liquid level and the upper edge of the lifting cylinder as ΔH = 300 mm to 500 mm, preferably 400 mm.

[0017] Based on the settings of the displacement sensor and the liquid level sensor, this height difference can maintain a more suitable material circulation and make the product quality better.

[0018] In addition, since the lifting cylinder and the flow guide cylinder move relatively up and down and block each other, in order to reduce the scratching between the two, preferably, the surface of the lifting cylinder corresponding to the flow guide cylinder is sprayed with polytetrafluoroethylene.

[0019] The flow guide cylinder is a cylinder, and the shape of the lifting cylinder is adapted to that of the flow guide cylinder. The setting of the cylinder can make the guiding effect better and is more suitable for the stirrer to carry out material circulation, and the material circulation effect is better.

[0020] Preferably, there are four windows, which are evenly distributed on the side wall of the flow guide cylinder. This setting is beneficial to material circulation. Through the discharge circulation of the four windows, the material circulation and mixing effect can be good.

[0021] In addition, the agitator includes an upper agitator and a lower agitator. The upper agitator uses an axial-flow agitator paddle, the angle of its blades with the horizontal is 15 to 55 degrees, and the number of blades is 3 to 6; the ratio of the diameter of the upper agitator to the diameter of the kettle body is 0.25 to 0.35; the lower agitator uses a disk turbine agitator paddle, the angle of its blades with the disk is 45 to 90 degrees, the number of blades is 4 to 8, and the ratio of the outer contour diameter of the blades to the diameter of the kettle body is 0.3 to 0.4. Based on the setting of this agitator, the shear force required for preparing small particles and a relatively good circulation ability can be satisfied, and it can be adapted to the height difference ΔH set above to form a better circulation effect.

[0022] In addition, a method for preparing a precursor of a lithium-ion battery cathode material is provided, which is characterized by including the following steps:

[0023] S1. Configure the concentration of the nickel-cobalt-manganese metal salt solution to be 1.5 to 2.5 mol / L; the concentration of ammonia water to be 8 to 12 mol / L, and the concentration of the lye to be the concentration of sodium hydroxide solution to be 5.0 to 7.0 mol / L; the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn z (OH)2, where 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.3, and x + y + z = 1;

[0024] S2. Add pure water to the kettle body of the above improvement scheme to submerge the lower edge of the draft tube window, and introduce a protective gas for 1 to 2 h; then add the prepared metal mixed salt solution, precipitant solution, and complexing agent solution to the kettle body;

[0025] S3. Start stirring, monitor the torque, motor current, rotation speed, and liquid level, and control the energy factor E to be 9.0 to 15.0 m 2 / s 2 ; the energy factor E = N 2 D 2 , N is the stirring speed, and D is the blade diameter; during the continuous rise of the material liquid level, the control unit sets a suitable height difference ΔH between the material liquid level and the upper edge of the lifting cylinder to be 300 mm to 500 mm. When the material liquid level is higher than the upper edge of the lifting cylinder by ΔH, the control unit starts the lifting mechanism for upward operation until the height difference between the upper edge of the lifting cylinder and the material liquid level reaches ΔH and then stops;

[0026] S4. Control the flow rate of the solution entering the kettle body, the reaction temperature is 45 to 55 ± 0.2 °C, the pH value is 11.0 to 12.5 ± 0.1, and the ammonia concentration is 7.5 to 10.0 ± 0.5 g / L; when the feed liquid reaches the overflow liquid level, perform membrane tube pump extraction of the mother liquor for concentration, and control the energy factor to be 9.0 to 15.0 m 2 / s 2, the power per unit volume is 6.0 - 8.0 kW / m 3 , when the particulate solid content reaches 200 g / L, control the energy factor to be 7.5 - 12.5 m 2 / s 2 , the power per unit volume is 7.0 - 9.0 kW / m 3 ; when the particulate solid content reaches 600 g / L, control the energy factor to be 5.5 - 8.5 m 2 / s 2 , the power per unit volume is 4.0 - 6.0 kW / m 3 ; during the process, continue to control the pH, ammonia concentration and temperature in the reaction process well. Stop the reaction when the D50 particle size of the particles is 2.0 - 5.0 ± 0.1 μm; when discharging, when the material liquid level is ΔH = 300 mm - 500 mm lower than the upper edge of the lifting cylinder, the control unit starts the lifting mechanism for a descending operation until the height difference between the upper edge of the lifting cylinder and the material liquid level reaches ΔH and then stops. During this period, continue to control the energy factor to be 5.5 - 8.5 m 2 / s 2 ;

[0027] S5. After the precursor slurry obtained after the reaction ends undergoes solid-liquid separation, washing, drying, and screening, small-particle high-nickel ternary precursors for lithium-ion battery cathodes are obtained.

[0028] The preparation using the combination regulation of the energy factor and the power per unit volume, its principle of action is that the energy factor regulates the dispersive force of the collision and contact between the alkali inlet and the metal slurry for precipitation reaction. A sufficiently large dispersive force is to obtain smaller primary crystal nuclei. The gradual decrease of the energy factor during the preparation process is to reduce the fragmentation of the existing crystalline particles by the dispersive force. The power per unit volume and the size of the guide cylinder window regulate the overall circulation force of the slurry. A good circulation force is to obtain uniformly growing crystalline particles. It can finally prepare a precursor Ni x Co y Mn z (OH)2 product, without obvious agglomeration of crystalline particles and no blockage of the membrane tube.

[0029] The beneficial effects of the present invention are that it can adjust the distance between the window and the liquid level according to the liquid level to form a good overall circulation flow. In addition, it can also cooperate with the preparation method using the combination regulation of the energy factor and the power per unit volume to obtain ternary precursors with small particles, narrow particle size distribution, and good product quality. It solves problems such as agglomeration of crystalline particles and blockage of the membrane tube. Brief Description of the Drawings

[0030] Figure 1 is a schematic cross-sectional structure diagram of the present invention;

[0031] Figure 2 It is a schematic structural diagram of the lifting mechanism of the present invention;

[0032] Figure 3 It is a schematic cross-sectional structural diagram of the prior art adopted in Comparative Example 1 of the present invention;

[0033] Reference numerals in the attached drawings: 1, driving mechanism; 2, coupling; 3, frame; 4, shaft seal; 5, stirring shaft; 6, upper stirrer; 7, lower stirrer; 8, draft tube; 82, window; 83, tie rod; 9, baffle; 10, membrane tube; 11, kettle body; 12, liquid level sensor; 13, feed pipe; 131, metal mixed slurry inlet; 132, ammonia inlet; 133, alkali solution inlet; 14, lifting mechanism; 141, servo motor; 142, transmission gear; 143, lifting rod; 144, displacement sensor; 146, lifting cylinder; 15, control unit. Detailed implementation manners

[0034] The present invention will be further described in detail below with reference to the embodiments given in the attached drawings.

[0035] Referring to Figure 1-2 as shown,

[0036] As an embodiment of the liquid level self-adaptive draft tube 8 type synthesis kettle for preparing the precursor of the lithium ion battery cathode material, it includes a driving mechanism 1, a coupling 2, a frame 3, a shaft seal 4, a stirring shaft 5 extending into the kettle body 11, an upper stirrer 6 and a lower stirrer 7 installed on the stirring shaft 5, a draft tube 8, a baffle 9, a membrane tube 10, a kettle body 11, a liquid level sensor 12, a feed pipe 13, a lifting mechanism 14, and a control unit 15 at the upper part. The frame 3 is installed and positioned on the channel steel of the kettle body 11, and the shaft seal 4 is installed on the top plate of the kettle body 11 to achieve the sealing of materials and prevent leakage. The shaft seal 4 selects liquid seal.

[0037] Draft tube 8: circular, with four windows 82 opened, and is hung on the top plate of the kettle body 11 through tie rods 83.

[0038] Lifting mechanism 14: includes a servo motor 141, a transmission gear 142, a lifting rod 143, a displacement sensor 144, a shaft seal 4 and a lifting cylinder 146. The upper part of the lifting rod 143 is a gear, which meshes with the transmission gear 142. The servo motor 141 is controlled to control the lifting and lowering of the lifting rod 143. The displacement sensor 144 is installed at the top end of the lifting rod 143. The shaft seal 4 is installed on the top of the kettle body 11 to achieve the sealing of materials and prevent leakage. Two connecting rods are welded on the upper part of the lifting cylinder 146, and the lifting cylinder 146 is connected to the lifting rod 143 of the lifting mechanism 14 through the connecting rods. The material of the main body of the lifting cylinder 146 is a stainless steel cylinder, and the surface is sprayed with polytetrafluoroethylene. The surface treatment is mainly to prevent the lifting cylinder 146 from scratching the draft tube 8 during the lifting process.

[0039] The position of the lifting cylinder 146 is obtained by the displacement sensor 144, and the liquid level of the material is obtained by the liquid level sensor 12. Initially, the upper edge of the lifting cylinder 146 is flush with the lower edge of the window 82 of the draft tube 8. During the continuous rise of the material liquid level, the control unit 15 sets a suitable height difference ΔH = 400 mm between the material liquid level and the upper edge of the lifting cylinder 146. The applicable range is 300 mm to 500 mm. In the following embodiments, 400 mm is taken as an example for illustration. Of course, any parameter within the range of 300 mm to 500 mm can also be implemented. When the material liquid level is higher than the upper edge of the lifting cylinder 146 by ΔH, the control unit 15 starts the lifting mechanism 14 to perform the rising operation until the height difference between the upper edge of the lifting cylinder 146 and the material liquid level reaches ΔH and then stops. On the contrary, when the material liquid level is lower than the upper edge of the lifting cylinder 146 by ΔH, the control unit 15 starts the lifting mechanism 14 to perform the descending operation until the height difference between the upper edge of the lifting cylinder 146 and the material liquid level reaches ΔH and then stops.

[0040] The upper stirrer 6 adopts an axial-flow stirring paddle, which is composed of a hub and blades. The angle between the blades and the horizontal is 35 degrees, and the number of blades is 4. The ratio of the stirrer diameter to the diameter of the kettle body 11 is 0.3.

[0041] The lower stirrer 7 adopts a disk turbine stirring paddle. It is composed of a hub, a disk and blades. The angle between the blades and the disk is 70 degrees, and the number of blades is 6, which can not only meet the shear force required for preparing small particles and have a good circulation ability. The ratio of the paddle diameter to the diameter of the kettle body 11 is 0.35.

[0042] The beneficial effect of the present invention is that the draft tube 8 type synthesis kettle can adjust the distance between the window 82 and the liquid level according to the liquid level, form a good overall circulation flow, and obtain a ternary precursor with a narrow particle size distribution and good product quality. It solves the problems of crystallization particle agglomeration and blockage of the membrane tube 10, etc.

[0043] Using the liquid level adaptive draft tube 8 type synthesis kettle prepared by the precursor of the positive electrode material of the lithium ion battery in this embodiment to prepare a precursor of the positive electrode material of a lithium ion battery, the method is as follows:

[0044] (1) Configure the concentration of the nickel-cobalt-manganese metal salt solution to be 2 mol / L, and the optional range is 1.5 to 2.5 mol / L (nickel, cobalt, manganese molar ratio 8:1:1), the concentration of ammonia water is 10 mol / L, and the optional range is 8 to 12 mol / L, and the concentration of the alkali solution is the concentration of sodium hydroxide solution is 6 mol / L, and the optional range is 5.0 to 7.0 mol / L; the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn z (OH)2, where 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.3, x + y + z = 1;

[0045] (2) Add pure water into the sealed kettle body 11 until it submerges the lower edge of the window 82 of the draft tube 8, and introduce a protective gas for 1 - 2 hours; then use a pump to add the three solutions of the prepared metal mixed salt solution, precipitant solution, and complexing agent solution into the kettle body 11 through their respective liquid inlet pipes, the ammonia inlet 132, the metal mixed slurry inlet 131, and the alkali liquor inlet 133. Start stirring, monitor the torque, motor current, rotation speed, and liquid level, and control the energy factor E to be 12.5 m 2 / s 2 , and the optional range is 9.0 - 15.0 m 2 / s 2 . During the continuous rise of the material liquid level, the control unit 15 sets a suitable height difference ΔH between the material liquid level and the upper edge of the lifting cylinder 146 to be 400 mm. When the material liquid level is higher than the upper edge of the lifting cylinder 146 by ΔH, the control unit 15 starts the lifting mechanism 14 for upward operation until the height difference between the upper edge of the lifting cylinder 146 and the material liquid level reaches ΔH and then stops. The lifting mechanism 14 stops when the lifting rod 143 triggers the maximum stroke.

[0046] (3) Control the flow rate of the solution entering the kettle body 11, the reaction temperature is 50 ± 0.2 °C, and the optional range is 45 - 55 ± 0.2 °C, the pH value is 12.1 ± 0.1, and the optional range is 11.0 - 12.5 ± 0.1, the ammonia concentration is 8.9 ± 0.5 g / L, and the optional range is 7.5 - 10.0 ± 0.5 g / L; when the feed liquid reaches the overflow liquid level, perform membrane tube 10 pump extraction to concentrate the mother liquor, and control the energy factor to be 12.5 m 2 / s 2 , and the optional range is 9.0 - 15.0 m 2 / s 2 , the unit volume power is about 6.5 kW / m 3 , and the optional range is 6.0 - 8.0 kW / m 3 . When the particle solid content reaches 200 g / L, control the energy factor to be 10.0 m 2 / s 2 , and the optional range is 7.5 - 12.5 m 2 / s 2 , the unit volume power is about 7.5 kW / m 3 , and the optional range is 7.0 - 9.0 kW / m 3 , when the particle solid content reaches 600 g / L, control the energy factor to 8.0 m 2 / s 2 , and the optional range is 5.5 - 8.5 m 2 / s 2 , the unit volume power is about 5.0 kW / m 3, the optional range is 4.0 - 6.0 kW / m 3 . During the process, continue to control the pH, ammonia concentration and temperature in the reaction process. When the particle D50 particle size is 3.0 ± 0.1 μm (the optional range is 2.0 - 5.0 ± 0.1 μm), stop the reaction. When discharging, when the material liquid level is ΔH = 400 mm lower than the upper edge of the lifting cylinder 146, the control unit 15 starts the lifting mechanism 14 for a descending operation until the height difference between the upper edge of the lifting cylinder 146 and the material liquid level reaches ΔH and then stops. The lifting mechanism 14 stops when the lifting rod 143 triggers the lowest stroke. During this period, continue to control the energy factor of 8.0 m 2 / s 2 (the optional range is 5.5 - 8.5 m 2 / s 2 ).

[0047] (4) After the precursor slurry obtained after the reaction ends undergoes solid-liquid separation, washing, drying, and screening, small-particle high-nickel ternary precursors for lithium-ion battery cathode materials are obtained. Finally, a precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 product with a D50 of 3.02 μm and a slurry diameter distance of 0.82 is prepared, without obvious agglomeration of crystalline particles and no blockage of the membrane tube 10.

[0048] Comparative Example 1:

[0049] Figure 3 It is a schematic structural diagram of a precursor reaction kettle in the prior art. The difference is that there is no lifting mechanism 14 and lifting cylinder 146, and the energy factor and unit volume power are not regulated.

[0050] Use Figure 3 in the reaction kettle to prepare a precursor for lithium-ion battery cathode materials:

[0051] (1) Configure the nickel-cobalt-manganese metal salt solution concentration to be 2 mol / L (nickel, cobalt, manganese molar ratio 8:1:1), the ammonia water concentration to be 10 mol / L, and the alkali solution concentration to be 6 mol / L for sodium hydroxide solution; the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn z (OH)2, where 0.5 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.3, and x + y + z = 1;

[0052] (2) Add pure water into the sealed kettle body 11 until it submerges the lower edge of the window 82 of the draft tube 8. Start stirring and introduce a protective gas for 1 - 2 hours. Then, use a pump to add the three solutions of the prepared metal mixed salt solution, precipitant solution, and complexing agent solution into the kettle body 11 through their respective liquid inlet pipes, the ammonia inlet 132, the metal mixed slurry inlet 131, and the alkali solution inlet 133.

[0053] (3) Control the flow rate of the solution entering the kettle body 11. The reaction temperature is 50 ± 0.2 °C, the pH value is 12.1 ± 0.1, and the ammonia concentration is 8.9 ± 0.5 g / L. When the liquid level of the feed liquid reaches the overflow level, pump the mother liquor through the membrane tube 10 for concentration. During the process, continue to control the pH, ammonia concentration, and temperature in the reaction process. Stop the reaction when the particle D50 particle size is 3.0 ± 0.1 μm.

[0054] (4) After the reaction is completed, the obtained precursor slurry is subjected to solid-liquid separation, washing, drying, and screening to obtain small-particle high-nickel ternary precursors for lithium-ion battery cathodes. Finally, a precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 product is obtained, with obvious agglomeration of crystalline particles and blockage of the membrane tube 10.

[0055] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A draft tube type synthesis kettle for preparing a cathode material precursor of a lithium ion battery, comprising a kettle body, a driving mechanism installed on the kettle body, and a stirrer arranged in the kettle body and linked with the driving mechanism, characterized in that, A flow guide cylinder is fixedly connected inside the kettle body. A lifting mechanism is also installed on the kettle body. A lifting cylinder linked to the lifting mechanism is arranged inside the flow guide cylinder. The flow guide cylinder is circumferentially provided with a plurality of windows for material circulation. The lifting cylinder cooperates with the windows and adjusts the height of the lower edge of the material channel formed by the windows through lifting. A liquid level sensor for detecting the liquid level of the material is arranged inside the kettle body. The liquid level sensor is connected to a control unit, and the control unit is also connected to the lifting mechanism to control the lifting mechanism to drive the lifting cylinder to lift according to the liquid level information transmitted by the liquid level sensor and adjust the size of the windows.

2. The draft tube type synthesis kettle for preparing the precursor of the lithium ion battery cathode material according to claim 1, wherein, The lifting mechanism is connected to the lifting cylinder through a connecting rod. The lifting cylinder cooperates with the windows through its upper edge to block and adjust the height of the lower edge of the material channel formed by the windows.

3. The draft tube type synthesis kettle for preparing the precursor of the cathode material of the lithium ion battery according to claim 1, characterized in that, A displacement sensor for detecting the position of the lifting cylinder is also arranged inside the kettle body. The displacement sensor is connected to the control unit to feed back the position information of the lifting cylinder to the control unit.

4. The draft tube type synthesis kettle for preparing the precursor of the cathode material of the lithium ion battery according to claim 3, characterized in that, The control unit controls the lifting of the lifting cylinder according to the position information and liquid level information of the displacement sensor and the liquid level sensor to keep the height difference between the material liquid level and the upper edge of the lifting cylinder at ΔH = 300 - 500 mm.

5. The draft tube type synthesis kettle for preparing the precursor of the cathode material of the lithium ion battery according to claim 1, wherein, The surface of the lifting cylinder corresponding to the flow guide cylinder is sprayed with polytetrafluoroethylene.

6. The draft tube type synthesis kettle for preparing the precursor of the cathode material of the lithium ion battery according to claim 1, characterized in that, The flow guide cylinder is a cylinder, and the shape of the lifting cylinder matches that of the flow guide cylinder.

7. The draft tube type synthesis kettle for preparing the precursor of the positive electrode material of the lithium ion battery according to claim 1, characterized in that, There are four windows, which are evenly distributed on the side wall of the flow guide cylinder.

8. The draft tube type synthesis kettle for preparing the precursor of the cathode material of the lithium ion battery according to claim 1, wherein, The stirrer includes an upper layer stirrer and a lower layer stirrer. Among them, the upper layer stirrer adopts an axial flow stirring paddle, the angle between its blades and the horizontal is 15 - 55 degrees, and the number of blades is 3 - 6; the ratio of the diameter of the upper layer stirrer to the diameter of the kettle body is 0.25 - 0.35; among them, the lower layer stirrer adopts a disk turbine stirring paddle, the angle between its blades and the disk is 45 - 90 degrees, the number of blades is 4 - 8, and the ratio of the outer contour diameter of the blades to the diameter of the kettle body is 0.3 - 0.

4.

9. A method for preparing a precursor of a cathode material for a lithium-ion battery, characterized in that, It includes the following steps: S1. Configure the concentration of the nickel-cobalt-manganese metal salt solution to be 1.5 - 2.5 mol / L; the concentration of ammonia water to be 8 - 12 mol / L, and the concentration of the lye to be the concentration of sodium hydroxide solution to be 5.0 - 7.0 mol / L; the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn z (OH)2, where 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.3, and x + y + z = 1; S2. Add pure water to the kettle body of the flow guide cylinder type synthesis kettle for preparing the precursor of the lithium-ion battery cathode material according to any one of claims 1 - 7 until it submerges the lower edge of the flow guide cylinder window, and introduce a protective gas for 1 - 2 h; then add the prepared metal mixed salt solution, precipitant solution, and complexing agent solution to the kettle body; S3. Start stirring, monitor torque, motor current, rotation speed, and liquid level, and control the energy factor E to be 9.0 - 15.0 m 2 / s 2 ; The energy factor E = N 2 D 2 , where N is the stirring speed and D is the blade diameter; During the continuous rise of the material liquid level, the control unit sets a suitable height difference ΔH between the material liquid level and the upper edge of the lifting cylinder to be 300 mm - 500 mm. When the material liquid level is higher than the upper edge of the lifting cylinder by ΔH, the control unit starts the lifting mechanism for upward operation and stops until the height difference between the upper edge of the lifting cylinder and the material liquid level reaches ΔH; S4. Control the flow rate of the solution into the kettle body. The reaction temperature is 45 - 55 ± 0.2 °C, the pH value is 11.0 - 12.5 ± 0.1, and the ammonia concentration is 7.5 - 10.0 ± 0.5 g / L. When the feed liquid reaches the overflow level, use a membrane tube pump to pump the mother liquor for concentration. Control the energy factor to be 9.0 - 15.0 m 2 / s 2 , and the power per unit volume is 6.0 - 8.0 kW / m 3 . When the particle solid content reaches 200 g / L, control the energy factor to be 7.5 - 12.5 m 2 / s 2 , and the power per unit volume is 7.0 - 9.0 kW / m 3 ; when the particle solid content reaches 600 g / L, control the energy factor to be 5.5 - 8.5 m 2 / s 2 , and the power per unit volume is 4.0 - 6.0 kW / m 3 ; during the process, continue to control the pH, ammonia concentration, and temperature in the reaction process. Stop the reaction when the D50 particle size is 2.0 - 5.0 ± 0.1 μm. When discharging, when the material liquid level is ΔH = 300 mm - 500 mm lower than the upper edge of the lifting cylinder, the control unit starts the lifting mechanism for downward operation until the height difference between the upper edge of the lifting cylinder and the material liquid level reaches ΔH and then stops. During this period, continue to control the energy factor to be 5.5 - 8.5 m 2 / s 2 ; S5. After the reaction, the obtained precursor slurry is subjected to solid-liquid separation, washing, drying, and screening to obtain small-particle high-nickel ternary precursor of the lithium-ion battery cathode material.

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