Washing method for reducing impurities of high-power ternary precursor

Abstract

The invention discloses a washing method for reducing impurities of a high-power ternary precursor. The washing method comprises the following steps: transferring a high-power ternary precursor material after reaction into washing and filtering equipment for purging; pure water is injected for pulpifying, washing is carried out, and purging is carried out after washing; preparing an ammonium salt solution; injecting an ammonium salt solution while stirring, and starting washing; blowing is started after washing; repeating for 2-5 times; pure water is injected, washing is started, and purging is carried out after washing; and repeating for 1-3 times, and finishing washing when the water content reaches 10-50%, the Na index is reduced to 60 ppm or below, and the S index is reduced to 350 ppm or below. The washing efficiency is high, Na < + > in the product can be greatly reduced, and the effect of removing SO4 < 2-> is more obvious. The liquid obtained after third washing of the ammonium salt and the liquid obtained after washing of the pure water in the fourth step can be prepared into an ammonium salt solution or subjected to secondary washing and can be reused due to no enrichment of metal ions, and energy loss and wastewater generation are greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of ternary precursor battery materials, and in particular to a washing method for reducing impurities in a high-power ternary precursor. Background Art

[0002] Ternary lithium-ion batteries have become one of the important choices for electric vehicle batteries due to their high energy density, long battery life and long life. The main material of ternary lithium-ion batteries is ternary precursors, so the impurity content in lithium-ion batteries mainly inherits the impurity content in the ternary precursors.

[0003] At present, the mainstream production method of ternary precursors is liquid phase co-precipitation crystallization. The main raw and auxiliary materials of this method are sulfates, caustic soda is used as a precipitant, and a large amount of Na and S impurities are introduced. Sodium ions are larger than lithium ions and may enter the layered structure of lithium, causing lattice distortion, which in turn affects the diffusion rate of lithium ions and the electrochemical properties of the material. That is, the incorporation of sodium ions may interfere with the orderly arrangement of lithium ions, reduce the electronic and ionic conductivity of the material, and thus affect the rate performance and cycle stability of the battery. Sulfur may introduce lattice defects during the synthesis of the material, which will change the structural stability of the material, affect the insertion and deinsertion process of lithium ions, and thus reduce the electrochemical performance of the battery. Especially under high temperature or overcharge conditions, sodium and sulfide may participate in adverse chemical reactions and increase the risk of thermal runaway.

[0004] For sodium and sulfur in the ternary precursor, which account for 70% of all impurities, washing is required to improve the purity of the precursor. When it comes to raw materials for manufacturing high-performance positive or negative electrode materials, purity has a significant impact on the performance of the battery. Improving purity and reducing impurities make it more suitable for high-power applications. Especially for high-power products, the battery needs to release or absorb a large amount of energy in a short period of time. Therefore, high-power products with low impurities can increase the proportion of active substances, thereby increasing the energy density of the battery, and are more helpful to increase the charge and discharge rate of the battery. In addition, pure ternary precursors help to extend the cycle life of the battery, reduce the self-discharge rate, and extend the storage time of the battery. Therefore, in order to obtain higher performance batteries, it is crucial to reduce impurities in high-power ternary precursors.

[0005] In the traditional process, the method of removing impurity S from the ternary precursor is alkali washing, but a large amount of Na ions will be introduced during washing, and a large amount of pure water is required to wash and remove metal impurities, resulting in a large consumption of energy. Since the material characteristics of high-power ternary precursors are mainly loose and porous, with a large specific surface area, washing is difficult. The difficulty is increased compared to conventional ternary precursors, and the cost is increased.

[0006] Therefore, how to solve the above-mentioned deficiencies in the prior art has become a subject to be studied and solved by the present invention. Summary of the invention

[0007] The object of the present invention is to provide a washing method for reducing impurities in a high-power ternary precursor.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A washing method for reducing impurities in a high-power ternary precursor, comprising:

[0010] Step 1: transfer the high-power ternary precursor material after the reaction to a transfer tank, and then transfer it to a washing and filtering device through a pump body, and purge it with air flow for 100 to 200 seconds at a purge pressure of 4 to 9 kg;

[0011] Step 2: inject pure water at a temperature of 80-100°C for slurrying, set the stirring shaft frequency to 10-40Hz, wash, wash for 10-50min, then purge for 100-200s, and the purge pressure is 4-9kg;

[0012] Step 3, prepare an ammonium salt solution with a concentration of 2-10 mol / L and a temperature of 20-80° C.;

[0013] The stirring shaft frequency is set to 10-40 Hz, the ammonium salt solution is injected, and the washing is started for 30-120 minutes; the amount of the ammonium salt solution added is 2-5 times the volume of the high-power ternary precursor material;

[0014] Start the purge again, purge for 100-200 seconds, the purge pressure is 4-9 kg, and the material-liquid separation is carried out;

[0015] Repeat step 3 2 to 5 times;

[0016] Step 4: inject pure water at a temperature of 80-100°C and start washing. After washing for 10-20 minutes, purge for 200-300 seconds at a purge pressure of 6-10 kg.

[0017] Repeat step 4 1 to 3 times. When the moisture content reaches 10 to 50%, the Na index is reduced to below 60 ppm, and the S index is reduced to below 350 ppm, the washing is completed.

[0018] In the above scheme, in step one, the "high-power ternary precursor material after the reaction is completed" is now in a solid-liquid mixed state.

[0019] In the above scheme, in step 2, the washing method is: mix the solid dried in step 1 with pure water, start stirring to allow the pure water and the solid to fully contact to form a solution, and allow the impurity ions stored in the solid to enter the solution.

[0020] In the above scheme, the washing and filtering equipment can adopt the existing washing and filtering equipment, which is well known to those skilled in the art. Since it is not the invention point of this case, it will not be described in detail in this case.

[0021] In the above scheme, the purpose of the purging is to separate the solids in the material by purging and discharge the liquid separated from the material.

[0022] According to a further technical solution, in step one, step two and step three, the compressed gas purging pressure is 4-7 kg, and in step four, the moisture content of the material after purging is 10-50%.

[0023] According to a further technical solution, in step 2 and step 4, the volume of pure water added is 1.2 to 3.0 times of the volume of the material; in step 3, the volume of ammonium salt solution added is 2.0 to 5.0 times of the volume of the material, and the temperature is 20 to 50°C.

[0024] In a further technical solution, in step 3, the ammonium salt is a combination of one or more of ammonium carbonate, ammonium bicarbonate, and ammonium nitrate, preferably ammonium carbonate and ammonium bicarbonate.

[0025] According to a further technical solution, when the number of times step three is repeated is less than or equal to two times, the liquid after the two washes and two purges is discharged into a wastewater storage tank;

[0026] When step three is repeated more than twice, the liquid after the first two washings and purges is discharged into a wastewater storage tank, and starting from the third washing and purge, the liquid after washing and purge is discharged into a reuse storage tank.

[0027] According to a further technical solution, in step 4, the washed liquid is discharged into a reuse storage tank.

[0028] According to a further technical solution, in step 2, pure water at a temperature of 80 to 100° C. or the effluent from the reuse storage tank is injected for slurrying.

[0029] According to a further technical solution, in step three, the ammonium salt solution is prepared by using the effluent from the reuse storage tank.

[0030] The terms “include,” “including,” “have,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The terms used herein generally have the ordinary meanings of each term used in the art, in the context of the present invention, and in the specific context, unless otherwise noted. Certain terms used to describe the present invention will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of the present invention.

[0032] The invention provides a washing method for reducing the impurity sodium and sulfur in a high-power ternary precursor, aiming to reduce the impurity sodium and sulfur content in a high-power product with low tap compaction and large specific surface area.

[0033] Compared with the prior art, the working principle and advantages of the present invention are as follows:

[0034] 1. Since the surface of high-power ternary precursor is loose and porous and has a large specific surface area, it is usually washed with alkali to remove SO4 2- Over a long period of time, not only the introduction of Na + , and at high temperatures, Na + It is easier to adsorb on the surface of high-power precursor, making water washing more difficult and even causing abnormal Na index of the product. The present invention uses ammonium carbonate, ammonium bicarbonate or ammonium nitrate instead of alkali solution for washing. + No more introduction, which can significantly reduce the Na in the product + .

[0035] 2. The present invention is to prevent Na + Embedded into the high-power material particles, causing the product indicators to exceed the standard, no alkali solution soaking was performed before washing, but the washing time of ammonium salt was innovatively set, which not only achieved the washing effect, but also achieved the soaking effect, removing SO4 2- The effect is more obvious.

[0036] 3. The liquid after the ammonium salt is washed three times and after the pure water washing in step 4 can be used to prepare an ammonium salt solution or washed twice because there is no enrichment of metal ions, and can be reused, which greatly reduces energy loss and wastewater generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Attached Figure 1 This is a scanning electron microscope image of a high-power material product according to an embodiment of the present invention;

[0038] Attached Figure 2 The figure is a flow chart of a washing method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0040] The present invention will be clearly described below with drawings and detailed descriptions. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention.

[0041] The terms used herein are only for describing specific embodiments and are not intended to be limiting of the present invention. Singular forms such as "a", "this", "here", "this" and "the" as used herein also include plural forms.

[0042] Example 1

[0043] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0044] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0045] Step 3: Use pure water to prepare 2.5 mol / L ammonium bicarbonate solution, heat to 25°C, inject 14m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25Hz, start the secondary washing program, wash for 50min, start the secondary purge, pressure 4kg, purge for 130s.

[0046] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0047] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3 The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 6kg, and the purge time is 220s.

[0048] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0049] After washing, the water content, impurities Na and S are tested.

[0050] Example 2

[0051] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0052] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0053] Step 3: Use pure water to prepare 4 mol / L ammonium bicarbonate solution, heat to 25°C, inject 14m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25Hz, start the secondary washing program, wash for 50min, start the secondary purge, pressure 4kg, purge for 130s.

[0054] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0055] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3 The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 6kg, and the purge time is 220s.

[0056] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0057] After washing, the water content, impurities Na and S are tested.

[0058] Example 3

[0059] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0060] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0061] Step 3: Prepare 4 mol / L ammonium bicarbonate solution from the recovered solutions of Example 1 and Example 2, heat to 25°C, inject 14 m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25 Hz, start the secondary washing program, wash for 50 min, start the secondary purge, pressure 4 kg, purge for 130 s.

[0062] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0063] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 6kg, and the purge time is 220s.

[0064] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0065] After washing, the water content, impurities Na and S are tested.

[0066] Example 4

[0067] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0068] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0069] Step 3: Prepare 4 mol / L ammonium bicarbonate solution from the recovered solutions of Example 1 and Example 2, heat to 25°C, inject 14 m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25 Hz, start the secondary washing program, wash for 80 min, start the secondary purge, pressure 4 kg, purge for 130 s.

[0070] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0071] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3 The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 6kg, and the purge time is 220s.

[0072] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0073] After washing, the water content, impurities Na and S are tested.

[0074] Example 5

[0075] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0076] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0077] Step 3: Prepare 4 mol / L ammonium bicarbonate solution from the recovered solutions of Example 1 and Example 2, heat to 25°C, inject 14 m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25 Hz, start the secondary washing program, wash for 80 min, start the secondary purge, pressure 4 kg, purge for 130 s.

[0078] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0079] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3 The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 8kg, and the purge time is 220s.

[0080] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0081] After washing, the water content, impurities Na and S are tested.

[0082] Example 6

[0083] Step 1: Set the volume to 7m 3 The high-power material is added to the washing and filtering equipment, the purge pressure is 4kg, the purge is 120s, and the mother liquor is discharged into the wastewater storage tank.

[0084] Step 2: 8.4m 3 Pure water at a temperature of 85°C is added to the washing and filtering equipment, the stirring frequency is adjusted to 15Hz, the first-level washing is started, the time is set to 15min, the first-level purge is started, the pressure is 4kg, the purge is 130s, and the washing liquid is discharged into the wastewater storage tank.

[0085] Step 3: Prepare 4 mol / L ammonium bicarbonate solution from the recovered solutions of Example 1 and Example 2, heat to 25°C, inject 14 m3 of ammonium salt solution into the washing and filtering equipment, set the stirring to 25 Hz, start the secondary washing program, wash for 80 min, start the secondary purge, pressure 4 kg, purge for 130 s.

[0086] Repeat step 3 3 times, the first and second washing liquids are discharged into the wastewater storage tank, and the third washing liquid is discharged into the reuse storage tank. The first and second purge liquids are discharged into the wastewater storage tank, and the third purge liquid is discharged into the reuse storage tank.

[0087] Step 4: Inject 8.4m3 of water into the washing and filtering equipment 3 The temperature is 85℃ pure water, the stirring frequency is set to 15Hz, the three-stage washing program is started, the washing time is 12min, and the three-stage purge is started, the pressure is 8kg, and the purge time is 280s.

[0088] Repeat step 4 twice, and each time the washing liquid and the purge liquid are recovered to the reuse tank.

[0089] After washing, the water content, impurities Na and S are tested.

[0090] Comparative Example 1

[0091] Step 1: Set the volume to 7m 3 The high-power material is injected into the filter press for washing. The compressed air purging pressure is 5kg and the purging time is 80s. The mother liquor after purging is discharged into the wastewater storage tank.

[0092] Step 2: Prepare 2.5 mol / L alkali solution, raise the temperature to 40°C, and perform alkali washing for 50 minutes. Use compressed air to blow, and after blowing, discharge the alkali washing solution into the wastewater tank.

[0093] Step 3: Inject pure water at 40°C into the filter press. The pure water washing volume is 16.8m 3 , use compressed air to blow and discharge the washed liquid into the wastewater storage tank.

[0094] The above steps are not repeated.

[0095] After washing, the water content, impurities Na and S are tested.

[0096] Table 1 Impurities in high power ternary precursor materials after washing

[0097]

[0098]

[0099] From the test results of each embodiment and comparative example in Table 1, it can be seen that ammonium salt washing of high-power ternary precursor materials has a significant effect, no Na ions are introduced in the desulfurization stage, and the Na ions are reduced by an average of 95ppm. Since there is no dead corner in washing, the average S index is reduced by 618ppm, and the washing effect of ammonium salt is better than that of alkali solution. It should be emphasized that the present invention only reduces the impurities Na and S in the high-power product, does not cause high moisture, and is consistent with the washing effect of the filter press.

[0100] Comparing Example 1 with Example 2, when the concentration of ammonium salt increases, it can be seen from Table 1 that the S index decreases to 150 ppm, indicating that the concentration of ammonium salt has a significant effect on the washing S.

[0101] By comparing Example 2 with Example 3, it can be seen that the liquid recovered from washing is reused to prepare ammonium salt without causing an increase in impurities Na and S, and can be reused.

[0102] By comparing Example 3 with Example 4, it can be seen that extending the ammonium salt washing time helps to reduce the impurity S in the high-power product, but has no effect on the Na index.

[0103] By comparing Example 4 with Example 5, it can be seen that the purge pressure has a greater impact on the moisture content. The greater the purge pressure, the lower the moisture content.

[0104] By comparing Example 5 and Example 6, it can be seen that the purge time has little effect on moisture.

[0105] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A washing method for reducing impurities in a high-power ternary precursor, characterized in that: include: Step 1: transfer the high-power ternary precursor material after the reaction to a washing and filtering device, and purge it with air flow for 100-200 seconds at a purge pressure of 4-9 kg; Step 2: inject pure water at a temperature of 80-100°C for slurrying, set the stirring shaft frequency to 10-40 Hz, wash, wash for 10-50 minutes, then purge for 100-200 seconds at a purge pressure of 4-9 kg; Step 3, prepare an ammonium salt solution with a concentration of 2-10 mol / L and a temperature of 20-80°C; The stirring shaft frequency is set to 10-40 Hz, the ammonium salt solution is injected, and the washing is started for 30-120 min; the amount of the ammonium salt solution added is 2-5 times the volume of the high-power ternary precursor material; Start the purge again, purge for 100-200 seconds, the purge pressure is 4-9 kg, and the material-liquid separation is carried out; Repeat step 3 2 to 5 times; Step 4: inject pure water at a temperature of 80-100°C and start washing. After washing for 10-20 minutes, purge for 200-300 seconds at a purge pressure of 6-10 kg. Repeat step 4 1 to 3 times. When the moisture content reaches 10-50%, the Na index drops below 60ppm, and the S index drops below 350ppm, the washing is completed.

2. A washing method for reducing impurities in a high-power ternary precursor according to claim 1, characterized in that: In step 1, step 2 and step 3, the compressed gas purging pressure is 4-7 kg, and in step 4, the moisture content of the material after purging is 10-50%.

3. A washing method for reducing impurities in a high-power ternary precursor according to claim 1, characterized in that: In step 2 and step 4, the volume of pure water added is 1.2 to 3.0 times of the material volume; in step 3, the volume of ammonium salt solution added is 2.0 to 5.0 times of the material volume, and the temperature is 20 to 50°C.

4. A washing method for reducing impurities in a high-power ternary precursor according to claim 1, characterized in that: In step 3, the ammonium salt is a combination of one or more of ammonium carbonate, ammonium bicarbonate and ammonium nitrate.

5. The washing method for reducing impurities in a high-power ternary precursor according to claim 1, characterized in that: When the number of times step 3 is repeated is less than or equal to two times, the liquid after the two washes and two purges is discharged into a wastewater storage tank; When step three is repeated more than twice, the liquid after the first two washings and purges is discharged into a wastewater storage tank, and starting from the third washing and purge, the liquid after washing and purge is discharged into a reuse storage tank.

6. The method for washing high-power ternary precursors to reduce impurities according to claim 1, characterized in that: In step 4, the washed liquid is discharged into a reuse storage tank.

7. A washing method for reducing impurities in a high-power ternary precursor according to claim 5 or 6, characterized in that: In step 2, pure water at a temperature of 80-100° C. or the effluent from the reuse storage tank is injected for slurrying.

8. A washing method for reducing impurities in a high-power ternary precursor according to claim 5 or 6, characterized in that: In step three, the ammonium salt solution is prepared by using the effluent from the reuse storage tank.

Images