A modified reactor for producing ternary precursors

Abstract

The invention belongs to the technical field of lithium battery material production equipment, and specifically is a modified reactor for producing ternary precursors, comprising a reactor body, a salt inlet pipe arranged on the reactor body, an air inlet pipe, a stirrer for stirring materials and a driving motor for driving the stirrer to rotate, the stirrer comprising a stirring rod and a stirring paddle arranged on the stirring rod, the stirring paddle is three-layered, the stirring paddles of the upper and lower layers of the stirrer are four-leaf stirring paddles, the stirring paddle in the middle is a two-leaf stirring paddle, the inner diameter of the salt inlet pipe outlet is smaller than the inner diameter at the feed inlet; the salt inlet pipe outlet extends between the middle and lower layers of stirring paddles, the lower end of the salt inlet pipe is arc-shaped, the outlet faces the stirring rod, and the tangent of the arc-shaped end of the salt inlet pipe is perpendicular to the stirring rod; the invention reduces the inner diameter of the salt inlet pipe outlet and increases the material flow rate at the salt inlet pipe outlet, thereby avoiding excessive local concentration and causing a large number of nucleations, better controlling the particle size, and making the particle size distribution more uniform.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery material production equipment, in particular to a modified reaction kettle for producing ternary precursors. Background Art

[0002] Since the advent of lithium-ion batteries, people have been trying to design and explore new electrode materials with good electrochemical properties to meet the application requirements of electric vehicles with high energy and high power density and the development needs of large-scale energy. As the core materials of lithium-ion batteries, the main commercial cathode materials are LiMn2O4, LiCoO2, LiFePO4 and ternary cathode Li(NixCoyMnz)O2 (LNCM) materials. Among them, ternary cathode materials have the highest energy density, especially nickel-rich ternary cathode materials (Ni molar ratio>0.6), which have attracted widespread attention in the lithium-ion battery industry.

[0003] The influence of ternary precursors on the performance of ternary cathode materials is very important, because the physicochemical indicators of the precursors, such as morphology, particle size, particle size distribution, specific surface area, impurity content, tap density, etc., directly determine the physicochemical indicators of the final ternary cathode materials. The most commonly used ternary precursor synthesis method is the controlled crystallization co-precipitation method, in which the reactor is the most core equipment in the production of ternary precursors. The existing ternary precursor reactor has a low flow rate at the outlet of the salt inlet pipe when producing ternary precursor products, resulting in excessive local concentrations and a large amount of nucleation, and the particle size is difficult to control, which reduces the product quality. The stirring paddle is three-layer, and each layer has four-blade stirring paddles. The stirring convection in the reactor is not strong enough, resulting in poor mixing effect, excessive local concentration, a large amount of nucleation, and poor particle size control, which reduces the product quality. Therefore, a new technical solution is needed to solve the above technical problems. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a modified reaction kettle for producing ternary precursors.

[0005] The present invention is achieved through the following technical solutions:

[0006] A modified reactor for producing a ternary precursor comprises a reactor body, a salt inlet pipe arranged on the reactor body, an air inlet pipe, a stirrer for stirring materials and a drive motor for driving the stirrer to rotate, the stirrer comprises a stirring rod and a stirring paddle arranged on the stirring rod, the stirring paddle is three-layered, the stirring paddles on the upper and lower layers of the stirrer are four-blade stirring paddles, the stirring paddle in the middle is a two-blade stirring paddle, the inner diameter of the salt inlet pipe outlet is smaller than the inner diameter at the feed inlet; the salt inlet pipe outlet extends between the middle and lower layers of stirring paddles, the lower end of the salt inlet pipe is arc-shaped, the outlet faces the stirring rod, and the tangent of the arc-shaped end of the salt inlet pipe is perpendicular to the stirring rod.

[0007] Furthermore, the distance from the outlet of the salt inlet pipe to the stirring rod is equal to the radius of the lowest stirring paddle.

[0008] Furthermore, the diameter of the stirring paddle is 0.35-0.38 of the diameter of the reactor.

[0009] Furthermore, the height from the lowest stirring paddle to the bottom of the inner cavity of the kettle body is 0.12-0.15 of the maximum effective depth of the kettle body, and the spacing between adjacent layers of stirring paddles is 0.2-0.3 of the maximum effective depth of the kettle body.

[0010] Preferably, the driving motor is a reduction motor.

[0011] Preferably, the inner diameter of the salt inlet pipe gradually decreases from the feed inlet to the discharge outlet.

[0012] Preferably, the ratio of the inner diameters of the inlet and outlet of the salt inlet pipe is 8:5.

[0013] The beneficial effects of the present invention are:

[0014] The present invention reduces the inner diameter of the salt inlet pipe outlet and increases the material flow rate at the salt inlet pipe outlet, thereby avoiding excessive local concentration and causing a large amount of nucleation, better controlling the particle size, making the particle size distribution more uniform, and improving the quality of the ternary precursor; and by changing the number of blades of the middle-layer stirring paddle on the stirring rod from the original four blades to a two-blade stirring paddle, the fluid convection is strengthened, the mixing effect is enhanced, the local concentration is avoided to be too high and causing a large amount of nucleation, and the particle size is better controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Attached Figure 1 It is a structural schematic diagram of the present invention.

[0017] Main component symbols

[0018] Kettle body-1; salt inlet pipe-2; stirrer-3; drive motor-4; air inlet pipe-5; stirring rod-31; stirring paddle-32. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0021] Reference Figure 1 A modified reactor for producing ternary precursors comprises a reactor body 1, a salt inlet pipe 2 arranged on the reactor body 1, an air inlet pipe 5, a stirrer 3 for stirring materials and a driving motor 4 for driving the stirrer 3 to rotate, wherein the driving motor 4 is a reduction motor, and the reactor body 1 is also provided with an ammonia inlet pipe and an alkali inlet pipe (not shown in the figure); the stirrer 3 comprises a stirring rod 31 and a stirring paddle 32 arranged on the stirring rod 31, the stirring paddle 32 is three-layered, the stirring paddles of the upper and lower layers of the stirrer 3 are four-blade stirring paddles, and the stirring paddle 32 in the middle is a two-blade stirring paddle, the inner diameter of the discharge port of the salt inlet pipe 2 is smaller than the inner diameter at the feed port, and the inner diameter ratio of the inlet and discharge ports of the salt inlet pipe is 8:5 The inner diameter of the discharge port of the salt inlet pipe 2 is reduced from the original 32mm (the size of the salt inlet pipe 2 is also 32mm) to 20mm; the discharge port of the salt inlet pipe 2 extends to between the middle and lower layers of stirring paddles. The shear force on the liquid between the middle and lower layers of stirring paddles is the largest. Extending the discharge port of the salt inlet pipe 2 to this point is conducive to the mixing of materials; the lower end of the salt inlet pipe 2 is arc-shaped, and its discharge port faces the stirring rod 31. The tangent of the arc-shaped end of the salt inlet pipe 2 is perpendicular to the stirring rod 31, so that the liquid coming out of the discharge port can rush into the middle and lower layers of stirring paddles in a horizontal direction, avoiding the longitudinal velocity component. At the same flow rate, the liquid can rush to a position closer to the stirring rod 31, which is conducive to the full mixing of the solution.

[0022] Furthermore, the inner diameter of the salt inlet pipe 2 gradually decreases from the feed inlet to the discharge outlet.

[0023] Furthermore, the distance from the outlet of the salt inlet pipe 2 to the stirring rod 31 is equal to the radius of the lowest stirring paddle; this facilitates the liquid flowing out of the outlet of the salt inlet pipe 2 to enter the longitudinal convection between the middle and lower stirring paddles, which is beneficial to the mixing of materials.

[0024] Furthermore, the diameter of the stirring paddle 32 is 0.35-0.38 of the reactor diameter; if the diameter of the stirring paddle 32 is too small, the materials cannot be fully mixed. If the diameter of the stirring paddle 32 is too large, the mixing effect can be improved but the energy consumption of the motor will increase. Therefore, it is preferred that the diameter of the paddle be 0.35-0.38 of the reactor diameter.

[0025] Furthermore, the height from the bottom stirring paddle to the bottom of the inner cavity of the kettle body 1 is 0.12-0.15 of the maximum effective depth of the kettle body 1, and the spacing between adjacent stirring paddles is 0.2-0.3 of the maximum effective depth of the kettle body 1. As a further improvement, the distance from the outlet of the salt inlet pipe 2 to the top surface of the bottom stirring paddle is 0.10-0.12 of the spacing between adjacent stirring paddles; the particle size distribution of the ternary precursor synthesized at different spacings is tested.

[0026] The synthesis method of the ternary precursor is as follows:

[0027] S1: According to Ni 0.65 Co 0.07 Mn 0.28 A soluble mixed salt solution with a molar concentration of 1.6 mol / L of metal ions is prepared according to the molar ratio of the metal elements in the (OH)2 chemical formula, with water as the solvent; at the same time, a 32% by mass sodium hydroxide solution and a 22% by mass ammonia solution are prepared.

[0028] S2: Add 2 / 3 of the maximum effective volume of the reactor into the reactor with pure water, add ammonia water, and control the ammonia concentration at 7.0 g / L, and then add sodium hydroxide solution to adjust the pH of the mixed solution to 11.9-12.5.

[0029] S3: nitrogen was introduced into the reactor at a flow rate of 0.5 L / min, and the reactor stirrer was turned on at a motor frequency of 10 Hz.

[0030] S4: Adjust the motor frequency of the reactor to 50Hz, and use a precision metering pump to uniformly flow the metal salt solution, sodium hydroxide solution, and ammonia solution prepared in S1 into the reactor, and control the pH of the mixed system in the reactor to 11.9-12.5, the reaction temperature to 60°C, and after 2 hours of nucleation, reduce the pH to 11.5-11.9 to complete the nucleation stage.

[0031] S5: Adjust the motor frequency of the reactor to 45 Hz, and continue to use the precision metering pump to uniformly flow the metal salt solution, sodium hydroxide solution, and ammonia solution prepared in S1 into the reactor for co-precipitation reaction. The reaction pH is controlled at 11.5-11.9, the reaction temperature is 60°C, and crystal nucleus growth is carried out.

[0032] S6: The particle size of the small crystal nucleus continues to grow and the sphericity gradually improves as the feed liquid continues to enter. After the solution reaches the maximum effective volume of the reactor, the excess mother liquor is discharged out of the reactor by standing to drain the supernatant or using a precision filter. Then the feed is continuously fed, and the solid small particles of ternary hydroxide generated by co-precipitation remain in the reactor to continue to develop and grow.

[0033] S7: When the particle size test value of the precursor in the reactor reaches 3.5-4.5um, stop feeding, reduce the motor frequency of the reactor to 20Hz, and continue stirring and aging for 4 hours.

[0034] S8: After aging, the mother liquor is removed by a centrifuge to obtain a solid material of a precursor of a ternary positive electrode material. The solid material of the precursor is added to a 0.8 mol / L sodium hydroxide solution at a temperature of 50-75°C, and circulated and stirred for 15-60 minutes to obtain a slurry.

[0035] S9: Dehydrate the slurry obtained in S8 by using a centrifuge, and wash it with pure water at a temperature of 50-70° C. until the sodium content in the material is ≤100 ppm, then stop washing and perform centrifugal dehydration.

[0036] S10: The dehydrated solid material is dried at 120° C. for 10 hours to obtain a ternary precursor.

[0037] The particle size distribution of the ternary precursors synthesized at different spacings was tested, and the test results are shown in the following table:

[0038]

[0039]

[0040] It can be seen from the above table that when the distance from the outlet of the salt inlet pipe 2 to the upper surface of the bottom stirring paddle is 0.10-0.12 of the spacing between adjacent stirring paddles, the particle size distribution of the obtained ternary precursor is more uniform, that is, the particle size distribution of the ternary precursor is narrower; the main reason for the above situation is that when the distance from the outlet of the salt inlet pipe 2 to the upper surface of the bottom stirring paddle is less than 0.10 of the spacing between adjacent stirring paddles, the outlet of the salt inlet pipe 2 is too close to the bottom stirring paddle, and the rotation of the stirring paddle is easy to cause the liquid flowing out of the outlet of the salt inlet pipe 2 to The body is thrown out in the horizontal direction, which is not conducive to the longitudinal convection of the liquid and weakens the mixing effect of the liquid. Therefore, the particle size distribution of the ternary precursor is wider; when the distance from the outlet of the salt inlet pipe 2 to the upper surface of the lowest stirring paddle is greater than 0.12 of the distance between adjacent stirring paddles, since the outlet of the salt inlet pipe 2 is far away from the lowest stirring paddle, the liquid flowing out of the outlet of the salt inlet pipe 2 is subjected to a weaker longitudinal thrust, and the longitudinal convection of the liquid in the reactor is weak, which is not conducive to uniform mixing of the liquid. Therefore, the particle size distribution of the ternary precursor will be wider.

[0041] Working principle:

[0042] During the production process, a nickel-cobalt-manganese salt solution, an alkali solution of a certain concentration and an ammonia water of a certain concentration configured in a certain proportion are added into the reactor through a salt inlet pipe 2, an alkali inlet pipe and an ammonia inlet pipe respectively through a metering pump, and nitrogen is continuously introduced when the reaction liquid is injected, and the stirring is carried out through the stirring paddle 32 on the stirring rod 31 to carry out the reaction; the upper and lower stirring paddles 32 on the stirrer 3 are four-blade stirring paddles, and the middle stirring paddle 32 is a two-blade stirring paddle, which enhances the up and down convection, and the fluid inside the reactor is mixed evenly. The ammonia-alkali salt solution enters the reactor through the modified salt inlet pipe 2. The reduction of the discharge port of the salt inlet pipe 2 increases the flow rate of the solution at the outlet of the salt inlet pipe, and the shear force between the middle and lower stirring paddles is relatively large. The discharge port of the salt inlet pipe 2 extends to between the middle and lower stirring paddles and is closer to the intense mixing area, which is beneficial to the mixing of the materials, avoids the situation of excessive local concentration during the mixing process, and makes the particle size grow stably and the particle size distribution more uniform.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A modified reactor for producing a ternary precursor, comprising a reactor body (1), a salt inlet pipe (2) arranged on the reactor body (1), an air inlet pipe (5), a stirrer (3) for stirring materials, and a drive motor (4) for driving the stirrer (3) to rotate, wherein the stirrer (3) comprises a stirring rod (31) and a stirring paddle (32) arranged on the stirring rod (31), wherein the stirring paddle (32) is three-layered, and characterized in that: The stirring paddles of the upper and lower layers of the stirrer (3) are four-blade stirring paddles, the stirring paddle (32) in the middle is a two-blade stirring paddle, the inner diameter of the discharge port of the salt inlet pipe (2) is smaller than the inner diameter of the feed port; the discharge port of the salt inlet pipe (2) extends between the middle and lower layers of stirring paddles, the lower end of the salt inlet pipe (2) is arc-shaped, the discharge port faces the stirring rod (31), and the tangent of the arc-shaped end of the salt inlet pipe (2) is perpendicular to the stirring rod (31); The height from the bottom stirring paddle to the bottom of the inner cavity of the kettle body (1) is 0.12-0.15 of the maximum effective depth of the kettle body (1), and the spacing between adjacent stirring paddles is 0.2-0.3 of the maximum effective depth of the kettle body (1); the distance from the outlet of the salt inlet pipe (2) to the top surface of the bottom stirring paddle is 0.10-0.12 of the spacing between adjacent stirring paddles.

2. The modified reactor for producing ternary precursors according to claim 1, characterized in that: The distance from the outlet of the salt inlet pipe (2) to the stirring rod (31) is equal to the radius of the stirring paddle at the bottom layer.

3. The modified reactor for producing ternary precursors according to claim 1, characterized in that: The diameter of the stirring paddle (32) is 0.35-0.38 of the diameter of the reactor.

4. The modified reactor for producing ternary precursors according to claim 1, characterized in that: The driving motor (4) is a reduction motor.

5. The modified reactor for producing ternary precursors according to claim 1, characterized in that: The diameter of the salt inlet pipe (2) gradually decreases from the feed inlet to the discharge outlet.

6. The modified reactor for producing ternary precursors according to claim 1 or 5, characterized in that: The ratio of the inner diameters of the inlet and outlet ports of the salt inlet pipe (2) is 8:5.

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