Method for reducing number of magnetic particles of ternary positive electrode material precursor

Abstract

The invention discloses a method for reducing the number of magnetic particles of a ternary positive electrode material precursor. A reaction device comprises a reaction kettle and an electromagnetic iron remover; the method comprises the following steps: preparing a mixed solution of Ni, Co and Mn, and preparing a precipitator and a complexing agent; adding pure water, a precipitator and a complexing agent into a reaction kettle to prepare a base solution; stirring of the reaction kettle is kept, and the mixed solution, the precipitant and the complexing agent are added into the kettle for a co-precipitation reaction; when the reaction is started, carrying out magnetic particle enrichment on the slurry in the reaction process through an electromagnetic iron remover; enriching for a certain time, enabling the reaction kettle to perform self-circulation, washing the electromagnetic iron remover, and discharging magnetic particles; and carrying out filter pressing, washing, drying, sieving and iron removal on the coprecipitation product to obtain the ternary positive electrode material precursor. According to the method, the problem that part of magnetic metal particles enter gaps among primary particles of the precursor and are difficult to remove is solved, and the number of the magnetic particles of the finally obtained product is lower than 10 / kg.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for lithium-ion batteries, and particularly to a method for reducing the number of magnetic particles in the precursor of ternary cathode materials. Background Art

[0002] The number of magnetic particles in the precursor of ternary cathode materials has a significant impact on the performance of ternary cathode materials. Inside the battery, magnetic particles will react with lithium ions, releasing substances such as iron oxide, triggering battery self-discharge, and thus shortening the battery life. At the same time, magnetic particles will adsorb the electrode materials and electrolytes inside the battery, interfering with the ion movement inside the battery and reducing the reaction rate and charging efficiency. If magnetic particles remain in the positive and negative electrode materials, there is also a possibility of piercing the separator, causing short circuits and self-discharge, seriously threatening the safety of the battery.

[0003] To reduce the number of magnetic particles in the precursor of ternary cathode materials, manufacturers usually implement iron removal measures on the precursor of ternary cathode materials, including iron removal of raw and auxiliary materials and iron removal before finished product packaging. Patent CN115432747A discloses a method and equipment for reducing magnetic foreign matters in ternary precursors. This patent proposes to remove iron from raw and auxiliary materials at the front end of the material production process and remove iron from the slurry after the reaction to reduce magnetic foreign matters. The iron removal method disclosed in this patent has certain effects in reducing magnetic foreign matters in ternary precursors, but the effect on reducing the number of magnetic particles in ternary precursors is relatively limited. This is mainly because when preparing ternary precursors, some magnetic metal particles will embed in the gaps between the primary particles of the precursor, making it extremely difficult to remove, resulting in a high number of magnetic particles in the finished product and not meeting the usage requirements.

[0004] Therefore, how to solve the deficiencies of the above-mentioned existing technologies has become the research topic of the present invention. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for reducing the number of magnetic particles in the precursor of ternary cathode materials.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for reducing the number of magnetic particles in the precursor of ternary cathode materials is realized through a reaction device, and the reaction device includes a reaction kettle and an electromagnetic iron remover;

[0008] The discharge of the reaction kettle is connected to the inlet of the electromagnetic iron remover through a first pipeline and is connected to its own reflux through a second pipeline;

[0009] The discharge of the electromagnetic iron remover is connected to the reflux of the reaction kettle through a third pipeline; the water inlet of the electromagnetic iron remover is connected to a flushing pipeline, and the drainage is connected to a discharge pipeline;

[0010] The method includes:

[0011] Step 1: Prepare a mixed solution of Ni, Co, and Mn, where the total molar concentration of Ni, Co, and Mn is 1.8 - 2.2 mol / L;

[0012] Prepare a sodium hydroxide or potassium hydroxide solution with a molar concentration of 6 - 10 mol / L as a precipitant;

[0013] Prepare an ammonia water solution with a molar concentration of 2 - 3 mol / L as a complexing agent;

[0014] Step 2: Add pure water, the precipitant, and the complexing agent to the reaction kettle to form a bottom liquid; keep the stirring of the reaction kettle on, introduce nitrogen or an inert gas, and add the mixed solution, the precipitant, and the complexing agent to the reaction kettle separately and simultaneously for coprecipitation reaction;

[0015] Enrichment stage of magnetic particles: At the same time as the reaction starts, keep the first pipeline and the third pipeline unblocked, close the other pipelines, and turn on the electromagnetic iron remover to enrich the magnetic particles in the slurry during the reaction process;

[0016] Discharge stage of magnetic particles: When enriched for a set time, close the first pipeline and the third pipeline, open the second pipeline, and make the reaction kettle in a self - circulation state; at the same time, turn off the electromagnetic iron remover, open the flushing pipeline and the discharge pipeline, flush the electromagnetic iron remover, and discharge the magnetic particles;

[0017] Step 3: Subject the coprecipitation product obtained in Step 2 to pressure filtration, washing, drying, sieving, and iron removal to obtain a ternary cathode material precursor.

[0018] Further technical solution, the reaction device further includes a high - magnetic waste material tank, and the drainage of the electromagnetic iron remover is connected to the high - magnetic waste material tank through the drainage pipeline.

[0019] In the above solution, the third pipeline serves as a reflux pipeline, and the flushing pipeline can be a pure - water flushing pipeline. With this design, the slurry after iron removal by the electromagnetic iron remover can enter the reaction kettle again through the reflux pipeline for growth. Through the setting of the flushing pipeline, the electromagnetic iron remover can be flushed when discharging high - magnetic materials, and the magnetic particles are flushed and discharged into the high - magnetic waste material tank. The flushing liquid is collected by the high - magnetic waste material tank. Since the flushing liquid is mixed with ternary precursors and enriched magnetic particles, it can be dissolved with acid and reused after impurity removal.

[0020] Further technical solution: In the reaction device, solenoid valves are connected in series on the first pipeline, the second pipeline, the third pipeline, the flushing pipeline and the discharge pipeline. The solenoid valve on the first pipeline is the first solenoid valve, the solenoid valve on the second pipeline is the second solenoid valve, the solenoid valve on the third pipeline is the third solenoid valve, the solenoid valve on the flushing pipeline is the fourth solenoid valve, and the solenoid valve on the discharge pipeline is the fifth solenoid valve.

[0021] Further technical solution: In the reaction device, a centrifugal pump is connected in series on the first pipeline. The centrifugal pump is located at one end close to the discharge port of the reaction kettle, and the second solenoid valve is located at one end close to the feed port of the electromagnetic separator. During the preparation of the ternary precursor, the slurry in the reaction kettle is transported to the electromagnetic separator by the centrifugal pump for wet iron removal to remove the magnetic particles in the slurry and prevent them from entering the gaps between the primary particles during the formation of the ternary precursor. When the electromagnetic separator discharges the high-magnetic material, it is necessary to pause the feeding of the material to the electromagnetic separator, and the material flows back to the reaction kettle through another pipeline, avoiding frequent shutdowns of the centrifugal pump.

[0022] Further technical solution: In the reaction device, the second pipeline can be used as a branch of the first pipeline, and its inlet end is connected to the position between the centrifugal pump and the first solenoid valve on the first pipeline.

[0023] Further technical solution: In the reaction device, an observation window for the turbidity of the discharged liquid is provided on the discharge pipeline. The observation window can be used to observe whether the electromagnetic separator is washed clean, ensure that all the high-magnetic material in the electromagnetic separator is transferred to the high-magnetic waste tank, and avoid magnetic particles from entering the reaction system again. When the discharged liquid is clear, the enrichment stage of the magnetic particles can be switched back.

[0024] Further technical solution: The volume of the slurry transferred by the centrifugal pump per hour is 2 to 4 times the effective volume of the reaction kettle. On the one hand, in order to improve the enrichment efficiency of magnetic particles, the slurry in the reaction kettle needs to pass through the electromagnetic separator for iron removal in a short time, so the volume of the slurry transferred by the centrifugal pump per hour should be large enough; on the other hand, if the flow rate of the centrifugal pump is too high, the impact force of the slurry in the pipeline will also increase, resulting in the magnetic particles adsorbed on the electromagnetic separator being washed back into the reaction kettle again, reducing the iron removal effect. Therefore, the volume of the slurry transferred by the centrifugal pump per hour is controlled at 2 to 4 times the effective volume of the reaction kettle.

[0025] A further technical solution is that the frequency of discharging the magnetic particles is 1 time per 3 hours, that is, the set time is 3 hours. As the iron removal time increases, the number of magnetic particles adsorbed by the electromagnetic iron remover also increases. It is necessary to discharge the magnetic particles in time to prevent them from being washed back into the reaction kettle again. The above purpose can be achieved by setting the frequency of discharging the magnetic particles to 1 time per 3 hours. If the frequency is lower than this value, some magnetic particles will be washed back into the reaction kettle again, resulting in a decrease in the iron removal effect; if the frequency is higher than this value, it will cause excessive discharge of high-magnetic materials, increase the material loss, and increase the cost.

[0026] In the above solution, in the second step, when the material grows to the target particle size (D50 is 1.5 - 30 μm), the reaction is stopped.

[0027] A further technical solution is that in the third step, the chemical formula of the ternary cathode material precursor is Ni x Co y Mn z (OH)2; where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1, and the number of magnetic particles is less than 10 per kg.

[0028] Regarding the use of "first", "second", etc. in this article, it does not particularly refer to the order or sequence, nor is it used to limit this case. It is only used to distinguish components or operations described with the same technical terms.

[0029] Regarding the use of "connected" or "positioned" in this article, it can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other. It can also refer to two or more components or devices operating or acting on each other.

[0030] Regarding the use of "comprising", "including", "having", etc. in this article, they are all open-ended terms, that is, they mean including but not limited to.

[0031] Regarding the terms used in this article, unless otherwise specified, they usually have their ordinary meanings in this field, in the context of this case, and in the special context. Some terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of this case.

[0032] The working principle and advantages of the present invention are as follows:

[0033] 1. In the process of preparing the ternary cathode material precursor of the present invention, the magnetic particles in the ternary precursor are enriched and discharged by the method of a wet electromagnetic iron remover. Compared with dry iron removal, the wet iron removal effect is better, mainly because the ternary precursor has better dispersibility in water, which is beneficial to the separation of magnetic particles.

[0034] 2. The present invention provides a method for reducing the number of magnetic particles in the ternary cathode material precursor. By enriching and discharging magnetic particles during the preparation of the ternary cathode material precursor, the problem that some magnetic metal particles are difficult to remove because they enter the gaps between the primary particles of the precursor is solved. Finally, the number of magnetic particles in the obtained product is less than 10 per kg.

[0035] 3. Compared with the prior art, the method provided by the present invention is simple and easy to operate, reduces the number of magnetic particles in the ternary precursor product, and improves the quality of the product.

[0036] 4. Further, the present invention uses a centrifugal pump in the reaction device to transport the slurry in the reaction kettle to an electromagnetic iron remover for wet iron removal. After iron removal, the slurry of the ternary cathode material precursor returns to the reaction kettle through a reflux pipeline to continue growing. The enriched high-magnetic material enters the high-magnetic waste tank through the flushing of pure water. By adjusting the opening degree of the solenoid valve, continuous iron removal is achieved throughout the reaction process, effectively reducing the number of magnetic particles in the ternary precursor product. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Attached Figure 1 is a schematic structural diagram of the reaction device in the embodiment of the present invention;

[0038] Attached Figure 2 is a flow chart of the method in the embodiment of the present invention.

[0039] In the above drawings: 1. Reaction kettle; 2. Electromagnetic iron remover; 3. High-magnetic waste tank; 4. First pipeline; 5. Second pipeline; 6. Third pipeline; 7. Flushing pipeline; 8. Discharge pipeline; 9. First solenoid valve; 10. Second solenoid valve; 11. Third solenoid valve; 12. Fourth solenoid valve; 13. Fifth solenoid valve; 14. Centrifugal pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be further described below with reference to the drawings and embodiments:

[0041] The following will clearly illustrate the present case with diagrams and detailed descriptions. After understanding the embodiments of the present case, any person skilled in the art can make changes and modifications based on the techniques taught by the present case, which do not depart from the spirit and scope of the present case.

[0042] The terms used in this article are only for describing specific embodiments and are not intended to limit the present case. Singular forms such as "a", "this", "this", "the present", and "the" also include plural forms as used herein.

[0043] Embodiment: Refer to Attached Figure 1As shown in the figure, a method for reducing the number of magnetic particles in a ternary cathode material precursor is realized through a reaction device, and the reaction device includes a reaction kettle, an electromagnetic iron remover, and a high-magnetic waste tank.

[0044] The discharge of the reaction kettle is connected to the feed of the electromagnetic iron remover through a first pipeline and is connected to its own reflux through a second pipeline.

[0045] The discharge of the electromagnetic iron remover is connected to the reflux of the reaction kettle through a third pipeline (reflux pipeline); the water inlet of the electromagnetic iron remover is connected to a pure water flushing pipeline, and the drainage is connected to the high-magnetic waste tank through a discharge pipeline.

[0046] Among them, a first solenoid valve is connected in series on the first pipeline, a second solenoid valve is connected in series on the second pipeline, a third solenoid valve is connected in series on the third pipeline, a fourth solenoid valve is connected in series on the flushing pipeline, and a fifth solenoid valve is connected in series on the discharge pipeline.

[0047] A centrifugal pump is connected in series on the first pipeline, and the centrifugal pump is located at one end close to the discharge port of the reaction kettle, and the second solenoid valve is located at one end close to the feed port of the electromagnetic iron remover.

[0048] The second pipeline is a branch of the first pipeline, and its inlet end is connected to the position between the centrifugal pump and the first solenoid valve.

[0049] An observation window (not shown in the figure) for discharging liquid turbidity is provided on the discharge pipeline.

[0050] As Figure 2 shown, the method of this embodiment includes:

[0051] Step 1: Prepare a mixed solution of Ni, Co, and Mn, where the total molar concentration of Ni, Co, and Mn is 2.0 mol / L, and the ratio of Ni, Co, and Mn is 94:4:2;

[0052] Prepare a sodium hydroxide solution with a molar concentration of 8 mol / L as a precipitant;

[0053] Prepare an ammonia water solution with a molar concentration of 2.5 mol / L as a complexing agent.

[0054] Step 2: Add pure water, the precipitant, and the complexing agent into the reactor to prepare the bottom liquid; the pH value of the bottom liquid is maintained at 12.2 - 12.6, and the temperature is maintained at 50 - 70°C; keep the stirring of the reactor on, introduce nitrogen or inert gas, and add the mixed solution, the precipitant, and the complexing agent into the reactor separately and simultaneously for coprecipitation reaction. The volume of the mixed solution entering the reactor per hour is 1 - 10% of the effective volume of the reactor. The pH value during the reaction is maintained at 11.6 - 12.6, and the synthesis temperature is maintained at 50 - 70°C;

[0055] Enrichment stage of magnetic particles: At the same time as the reaction starts, open the first solenoid valve and the third solenoid valve to keep the first pipeline and the third pipeline unblocked, and close the second solenoid valve, the fourth solenoid valve, and the fifth solenoid valve, that is, keep the remaining pipelines shut off. Turn on the electromagnetic separator to enrich the magnetic particles in the slurry during the reaction. The volume of the slurry pumped out by the centrifugal pump per hour is 3 times the effective volume of the reactor.

[0056] Discharge stage of magnetic particles: When the enrichment lasts for 3 hours, close the first solenoid valve and the third solenoid valve, that is, shut off the first pipeline and the third pipeline. Open the second solenoid valve to make the second pipeline unblocked. At this time, the reactor is in a self-circulation state. At the same time, turn off the electromagnetic separator, open the fourth solenoid valve and the fifth solenoid valve to make the flushing pipeline and the discharge pipeline unblocked. Flush the electromagnetic separator with pure water and discharge the magnetic particles to the high-magnetic waste tank until the discharge pipeline discharges clear liquid. At this time, it can be switched back to the enrichment stage of magnetic particles.

[0057] Step 3: Subject the coprecipitation product obtained in Step 2 to pressure filtration, washing, drying, sieving, and iron removal to obtain the ternary cathode material precursor with the chemical formula Ni 0.94 Co 0.04 Mn 0.02 (OH)2, with the number of magnetic particles less than 10 per kg. The relevant data are shown in Table 1.

[0058] Comparative Example 1:

[0059] The difference from the example is that the volume of the slurry pumped out by the centrifugal pump per hour in Step 2 is different. In this comparative example, the volume of the slurry pumped out by the centrifugal pump per hour is 1 times the effective volume of the reactor, and the rest is exactly the same as the example. The relevant data of the precursor obtained by pressure filtration, washing, drying, sieving, and iron removal are shown in Table 1.

[0060] Comparative Example 2:

[0061] The difference from the example lies in that the volume of the slurry discharged by the centrifugal pump per hour in step two is different. In this comparative example, the volume of the slurry discharged by the centrifugal pump per hour is 5 times the effective volume of the reaction kettle, and the rest is exactly the same as the example. The precursor obtained by pressure filtration, washing, drying, sieving, and iron removal, and the relevant data are shown in Table 1.

[0062] Comparative Example 3:

[0063] The difference from the example lies in that the frequency of discharging magnetic particles in step two is different. In this comparative example, the frequency of discharging magnetic particles is 1 time per 4 hours, and the rest is exactly the same as the example. The precursor obtained by pressure filtration, washing, drying, sieving, and iron removal, and the relevant data are shown in Table 1.

[0064]

[0065] It can be seen from the above table that when the volume of the slurry discharged by the centrifugal pump per hour is too low (Comparative Example 1), the corresponding iron removal effect decreases, resulting in too many magnetic particles in the product; when the volume of the slurry discharged by the centrifugal pump per hour is too high (Comparative Example 2), the impact force of the slurry in the corresponding pipeline also increases, causing the magnetic particles adsorbed on the electromagnetic iron remover to be washed back into the reaction kettle again, reducing the iron removal effect, and finally the number of magnetic particles in the product is also at a relatively high level. In addition, as the frequency of discharging magnetic particles decreases (Comparative Example 3), some magnetic particles are washed back into the reaction kettle again, the iron removal effect decreases, and the number of magnetic particles in the corresponding product is much higher than that of the example.

[0066] The present invention provides a method for reducing the number of magnetic particles in the precursor of ternary cathode materials. By enriching and discharging magnetic particles during the preparation of the precursor of ternary cathode materials, the problem that some magnetic metal particles are difficult to remove because they enter the gaps between the primary particles of the precursor is solved, and finally the number of magnetic particles in the obtained product is less than 10 per kg.

[0067] The above examples are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for reducing the number of magnetic particles in a ternary cathode material precursor, characterized in that: It is achieved by a reaction device, which includes a reaction kettle and an electromagnetic iron remover; The discharge of the reactor is connected to the feed of the electromagnetic iron remover through a first pipeline, and is connected to its own reflux through a second pipeline; The discharge of the electromagnetic iron remover is connected to the reflux of the reactor through a third pipeline; the water inlet of the electromagnetic iron remover is connected to a flushing pipeline, and the water discharge is connected to a discharge pipeline; Methods include: Step 1, preparing a mixed solution of Ni, Co and Mn, wherein the total molar concentration of Ni, Co and Mn is 1.8-2.2 mol / L; Prepare a sodium hydroxide or potassium hydroxide solution with a molar concentration of 6-10 mol / L as a precipitant; Prepare an ammonia solution with a molar concentration of 2-3 mol / L as a complexing agent; Step 2: adding pure water, the precipitant and the complexing agent into the reactor to prepare a base solution; keeping the stirring of the reactor on, introducing nitrogen or an inert gas, and adding the mixed solution, the precipitant and the complexing agent into the reactor separately and simultaneously to carry out a coprecipitation reaction; Magnetic particle enrichment stage: while the reaction is started, the first pipeline and the third pipeline are kept unobstructed, the remaining pipelines are closed, and the electromagnetic iron remover is turned on to enrich the slurry in the reaction process with magnetic particles; Discharge stage of magnetic particles: when the enrichment reaches a set time, the first pipeline and the third pipeline are closed, and the second pipeline is opened, so that the reactor is in a self-circulating state; at the same time, the electromagnetic iron remover is closed, and the flushing pipeline and the discharge pipeline are opened to flush the electromagnetic iron remover and discharge the magnetic particles; Step three: filter the coprecipitated product obtained in step two, wash, dry, screen and remove iron to obtain a ternary positive electrode material precursor.

2. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: The reaction device also includes a high-magnetic waste tank, and the drainage of the electromagnetic iron remover is connected to the high-magnetic waste tank through the drainage pipeline.

3. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: In the reaction device, the first pipeline, the second pipeline, the third pipeline, the flushing pipeline, and the discharge pipeline are all connected in series with electromagnetic valves.

4. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: In the reaction device, a centrifugal pump is connected in series to the first pipeline.

5. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 4, characterized in that: In the reaction device, a first solenoid valve is connected in series to the first pipeline; The second pipeline serves as a branch of the first pipeline, and an inlet end of the second pipeline is connected to a position between the centrifugal pump and the first solenoid valve in the first pipeline.

6. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: In the reaction device, the discharge pipeline is provided with an observation window for the turbidity of the discharge liquid; when the discharge liquid becomes clear, the phase is switched back to the enrichment phase of the magnetic particles.

7. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 4, characterized in that: The volume of slurry transferred out by the centrifugal pump per hour is 2 to 4 times the effective volume of the reactor.

8. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: The frequency of the magnetic particles being discharged is once every three hours.

9. The method for reducing the number of magnetic particles in a ternary cathode material precursor according to claim 1, characterized in that: In step 3, the chemical formula of the ternary cathode material precursor is Ni x Co y Mn z (OH)2; Among them, 0<x<1, 0<y<1, 0<z<1, x+y+z=1, and the number of magnetic particles is less than 10 / kg.

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