Water washing system and water washing method

Abstract

This invention relates to the field of lithium battery cathode material production technology, and discloses a washing system and washing method. The washing system includes a washing device, which comprises a washing drum and a stirring assembly. The washing drum has a stirring chamber inside, and is equipped with a material inlet and a material outlet communicating with the stirring chamber. The material inlet continuously introduces the material to be washed and the washing solution, while the material outlet continuously discharges the mixture of washed material and washing solution. The stirring assembly includes two spiral shafts rotatably disposed within the washing drum, with their spiral edges staggered and rotating in the same direction. Based on the washing system provided by this invention, the washing process of the material to be washed can be ensured to be continuous, reducing interruptions and improving production efficiency; at the same time, it ensures the uniformity of the material to be washed, avoiding over-washing or under-washing, and guaranteeing product consistency.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material production technology, specifically to a water washing system and water washing method. Background Technology

[0002] Ternary lithium-ion battery materials (NCA or NCM) are widely used cathode materials in power batteries due to their high specific capacity. The specific capacity of the material is directly proportional to the Ni content, but higher Ni content also leads to higher residual alkali content. In the battery, residual alkali reacts with the electrolyte to produce large amounts of gas, potentially causing a series of safety issues. Furthermore, excessive residual alkali can generate inactive substances on the material surface, affecting the material's rate performance and capacity. Therefore, reducing residual alkali in high-nickel ternary materials through modification is a challenge.

[0003] Currently, the main solution for reducing residual alkali on the surface of high-nickel materials is water washing. Water washing can effectively reduce residual alkali on the surface of ternary materials. However, traditional water washing often uses a stirred tank as the washing equipment. During the water washing process, it is necessary to continuously stir to suspend the ternary material in order to achieve sufficient contact with water. Therefore, the water-to-material ratio in general industry is controlled at about 1:1, which requires a large amount of water resources. Water washing with a large amount of water will cause some loss of capacity and deterioration of cycle performance of high-nickel ternary cathode materials.

[0004] In addition, using the existing stirred tank for water washing can only ensure the metered addition of ternary cathode materials. In industrial production, even if a standardized feeding procedure is followed, when faced with a large volume of materials to be washed, there are still differences in the timing of the same batch of materials entering the stirred tank, resulting in over-washing or under-washing of some materials, causing uneven washing and thus reducing the washing effect. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, or at least partially solve the above-mentioned technical problems, the present invention provides a water washing system and a water washing method.

[0006] This invention provides a water washing system, including a water washing device, the water washing device comprising:

[0007] A washing drum has an internal stirring chamber. The washing drum is provided with a material inlet and a material outlet that communicate with the stirring chamber. The material inlet is used to continuously introduce the material to be washed and the washing solution, and the material outlet is used to continuously discharge the mixture of the washed material and the washing solution.

[0008] The stirring assembly includes two spiral shafts rotatably disposed inside the washing drum, the spiral edges of the two spiral shafts being staggered, and the two spiral shafts rotating in the same direction.

[0009] Optionally, the material inlet includes a feed port and a liquid inlet located above the washing drum and in a pipe communicating with the stirring chamber. The feed port is used to introduce the material to be washed, and the liquid inlet is used to introduce the washing solution. The distance between the liquid inlet and the feed port and the end of the washing drum is the same.

[0010] Optionally, the distance between the helical edge of the spiral shaft and the inner wall of the washing drum is no more than 2 mm;

[0011] And / or, the feed inlet is used to connect to a powder feeder, which is capable of supplying the material to be washed toward the washing drum at a preset conveying speed;

[0012] The liquid inlet is used to connect to a liquid feeder, which can supply the washing solution to the washing drum at a preset conveying speed.

[0013] Optionally, the washing device further includes a seasoning assembly for adjusting the discharge amount of the material outlet. The seasoning assembly includes a pressure detection element disposed at the material outlet for detecting the discharge pressure of the mixture and a regulating valve for adjusting the opening of the material outlet. The regulating valve is signal-connected to the pressure detection element and is configured to adjust the opening of the material outlet according to the material pressure information fed back by the pressure detection element.

[0014] Optionally, the spiral groove of the spiral shaft is an asymmetric spline, the pitch of the spiral shaft is S, the outer diameter of the spiral shaft is Ds, and the length of the screw is L, where S = (0.8-1)Ds and L = (22-28)Ds.

[0015] Optionally, the washing system further includes a separation device, which includes an intermediate tank, a transfer pump, and a solid-liquid separator. The intermediate tank is used to receive the mixture discharged through the material outlet, and the transfer pump is used to transport the mixture in the intermediate tank to the solid-liquid separator, which is used to separate the solid material and liquid in the mixture.

[0016] Optionally, the washing system further includes a drying device, which includes a buffer chamber and a dryer. The buffer chamber is used to receive the solid material separated by the solid-liquid separator and to convey the solid material to the dryer, which is used to dry the solid material.

[0017] The present invention also provides a water washing method, comprising the following steps:

[0018] Two spiral shafts with interlaced spiral edges are placed inside the washing drum, and the two spiral shafts are made to rotate in the same direction. The rotation speed of the two spiral shafts and the washing time of the material in the washing drum are set.

[0019] The material to be washed and the washing solution are simultaneously added into the washing drum according to the preset dosage through the material inlet. After washing for the set washing time, the resulting mixture flows out through the material outlet.

[0020] Optionally, the ratio of the material to be washed to the washing solution is (1.653-2.125):1;

[0021] And / or, the mixing time of the material to be washed and the washing solution is 25-35 min;

[0022] And / or, the rotational speed range of the helical shaft is n, where 80 r / min ≤ n ≤ 200 r / min.

[0023] Optionally, the washing solution is a mixture of water and HF or boric acid, wherein the concentration of HF or boric acid in the washing solution is 0.01-1 mol / L.

[0024] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0025] Based on the washing system provided by this invention, the two spiral shafts in the washing device of the washing system have their spiral edges staggered, and the two spiral shafts rotate in the same direction. One spiral shaft pulls the material to be washed into the gap between the two spiral edges, while the other spiral shaft pushes the material out of the gap, causing the material to be washed to transfer from the spiral groove of one spiral shaft to the spiral groove of the other spiral shaft. The material to be washed is then forcibly conveyed along the spiral shafts in an "∞" shape towards the material outlet. Furthermore, the gap at the intersection of the two spiral shafts rotating in the same direction is very small, and the speed directions of the spiral edges and spiral grooves are opposite, resulting in a high relative speed. At this time, the intersection area of ​​the spiral edges has a high shearing speed and a large shearing force, which helps to homogenize and mix the material to be washed. This achieves high conveying efficiency and strong dispersion and mixing capabilities, ensuring uniform distribution of the material to be washed within the washing device and achieving excellent washing results. Furthermore, the material to be washed and the washing solution are continuously conveyed into the washing drum through the material inlet, ensuring the continuous washing process and enabling simultaneous feeding, mixing, dispersion, and washing. This reduces interruptions and allows for uninterrupted, instantaneous processing of large volumes of material to be washed with minimal water consumption. It also maintains the dispersion and mixing of solid components for an extended period, further improving the washing effect while reducing washing time and preventing any impact on the performance of the material to be washed. In addition, the simultaneous addition of the material to be washed and the washing solution prevents over-washing or under-washing, ensuring product consistency. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the water washing device according to an embodiment of the present invention;

[0029] Figure 2 This is a side view of the washing device according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the water washing process of the water washing system according to an embodiment of the present invention;

[0031] Figure 4 The images shown are scanning electron microscope (SEM) images of the washing and drying materials obtained using the method of Example 1.

[0032] Figure 5 Here are scanning electron microscope images of the washing and drying materials obtained using the method of Example 2;

[0033] Figure 6 Here are scanning electron microscope images of the washing and drying materials obtained using the method of Example 3;

[0034] Figure 7 Here are scanning electron microscope images of the washing and drying materials obtained using the method in Example 4;

[0035] Figure 8 Here are scanning electron microscope images of the washing and drying materials obtained using the method in Example 5;

[0036] Figure 9 The image shows a scanning electron microscope (SEM) image of the washed dry material obtained using the method in Comparative Example 1.

[0037] Explanation of reference numerals in the attached figures

[0038] 1. Washing device; 11. Washing drum; 111. Mixing chamber; 112. Material inlet; 1121. Feed inlet; 1122. Liquid inlet; 113. Material outlet; 12. Mixing assembly; 121. Spiral shaft; 13. Powder feeder; 14. Liquid feeder; 15. Powder raw material silo; 16. Liquid storage tank;

[0039] 2. Separation device; 21. Intermediate tank; 22. Transfer pump; 23. Solid-liquid separation unit;

[0040] 3. Drying device; 31. Buffer bin; 32. Dryer; 33. Storage bin. Detailed Implementation

[0041] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments and features of the present invention can be combined with each other.

[0042] The following description sets forth many specific details in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments described in the specification are only some, not all, of the embodiments of the invention.

[0043] Combination Figure 1 and Figure 2 As shown, the water washing system provided in the embodiment of the present invention includes a water washing device 1, which includes a water washing drum 11 and a stirring device.

[0044] The washing drum 11 has an internal stirring chamber 111. The shape of both the washing drum 11 and the stirring chamber 111 is not limited and can be designed according to actual needs. Preferably, the washing drum 11 adopts a horizontal cylindrical structure, and correspondingly, the stirring chamber 111 is a horizontally positioned cylindrical cavity structure. The washing drum 11 is provided with a material inlet 112 and a material outlet 113 communicating with the stirring chamber 111, respectively located at both ends of the washing drum 11. The material inlet 112 is used to continuously introduce the material to be washed and the washing solution, and the material outlet 113 allows for the continuous discharge of the mixture of washed material and washing solution. The washing drum 11 should have a certain length so that after the material to be washed and the washing solution are introduced into the stirring chamber 111, they have sufficient movement distance along the material inlet 112 towards the material outlet 113, ensuring sufficient washing time for the material to be washed within the stirring chamber 111 and guaranteeing the washing effect.

[0045] like Figure 2As shown, the stirring assembly 12 includes two spiral shafts 121 rotatably disposed within the washing drum 11. The spiral edges of the two spiral shafts 121 are staggered, and the two spiral shafts 121 rotate in the same direction. Specifically, each spiral shaft 121 includes a screw and spiral blades disposed on the outer periphery of the screw. The spiral blades of the spiral shaft 121 are spiral edges, and spiral grooves are formed between the spirally arranged spiral edges. The spiral shaft 121 is disposed along the axial direction (horizontal direction) of the washing drum 11. During rotation, the spiral shaft 121 can convey the material to be washed and the washing solution toward the material outlet 113. The difference between the outer diameter of the spiral shaft 121 and the inner wall of the washing drum 11 is no greater than 2 mm, that is, the distance between the spiral edges of the spiral shaft 121 and the inner wall of the washing drum 11 is no greater than 2 mm, to meet the design requirements of the spiral shaft 121, thereby enabling the material to be washed to undergo intense stirring, mixing, and shearing between the spiral shaft 121 and the washing drum 11.

[0046] The staggered arrangement of the helical ridges of the two helical shafts 121 means that the helical ridge of one helical shaft 121 is inserted into the helical groove of the other helical shaft 121, so that the helical ridges of the two helical shafts 121 are interlaced and spaced apart to avoid collision between the helical shafts 121 during rotation. Furthermore, the two helical shafts 121 rotate in the same direction, so that the flow direction of the fluid in the helical groove is consistent with the rotation direction of the helical ridge within the groove, resulting in a higher relative velocity and greater shear force at this location.

[0047] Based on the washing system provided by this invention, the two spiral shafts 121 in the washing device 1 of the washing system have their spiral edges interlaced, and the two spiral shafts 121 rotate in the same direction. One spiral shaft 121 pulls the material to be washed into the gap between the two spiral edges, while the other spiral shaft 121 pushes the material out of the gap, causing the material to be washed to transfer from the spiral groove of one spiral shaft 121 to the spiral groove of the other spiral shaft 121. The material to be washed is then forcibly conveyed along the spiral shafts 121 in an "∞" shape towards the material outlet 113. Furthermore, the gap at the intersection of the two spiral shafts 121 rotating in the same direction is very small, and the speed directions of the spiral edges and spiral grooves are opposite, resulting in a high relative speed. At this time, the intersection area of ​​the spiral edges has a high shearing speed and a large shearing force, which helps to... The homogenization and mixing of the washing materials achieve high conveying efficiency and strong dispersion and mixing capabilities, ensuring uniform distribution of the materials during their residence in the washing device 1, resulting in a good washing effect. Furthermore, the materials to be washed and the washing solution are continuously conveyed into the washing drum 11 through the material inlet 112, ensuring the continuous washing process of the materials to be washed. This achieves the effect of simultaneous feeding, mixing, dispersion, and washing, reducing interruptions and enabling uninterrupted instantaneous processing of large volumes of materials to be washed with relatively low water consumption. It can also maintain the dispersion and mixing of solid components for a long time, thereby further improving the washing effect while reducing washing time and avoiding affecting the performance of the materials to be washed. In addition, the simultaneous addition of the materials to be washed and the washing solution avoids over-washing or under-washing of the materials, ensuring product consistency.

[0048] The material to be washed can be a high-nickel ternary material. Based on this washing device 1, the washing process of the high-nickel ternary material can be continuously carried out, reducing interruptions and improving production efficiency. At the same time, it can ensure the uniformity of the washing of the high-nickel ternary material, avoid over-washing or under-washing, and ensure the consistency of the product.

[0049] The driving method of the spiral shaft 121 in this application is not limited. For example, the ends of both spiral shafts 121 extend out of the washing drum 11, and the ends of the washing drum 11 are provided with driving components for rotating the spiral shafts 121. The driving component can be a drive motor, and the output shaft of the drive motor is connected to the spiral shaft 121 to drive the spiral shaft 121 to rotate. Alternatively, the driving component can be a combination of a drive motor and a gearbox. In this case, the output shaft of the gearbox drives the spiral shaft 121 to rotate. The gearbox can be a reduction gearbox.

[0050] In some embodiments, there are two drive units, and the output shaft of each drive unit is connected to a helical shaft 121 so that the two drive units drive the two helical shafts 121 to rotate synchronously.

[0051] In other embodiments, there is one drive unit, and the output shaft of the drive unit drives two spiral shafts 121 to rotate synchronously via transmission gears. In this design, the ends of the two spiral shafts 121 extending out of the washing drum 11 are provided with driven gears, and the output shaft of the drive unit meshes with two driving gears through multiple transmission gears, thereby enabling the drive unit to drive the two spiral shafts 121 to rotate synchronously.

[0052] As can be seen, the configuration of the driving components is unrestricted and can be designed according to actual needs.

[0053] Combination Figure 1 and Figure 2 As shown, the material inlet 112 includes a feed inlet 1121 and a liquid inlet 1122 located above the washing drum 11 and connected to the mixing chamber 111 via a pipe. The feed inlet 1121 is used to introduce the material to be washed, and the liquid inlet 1122 is used to introduce the washing solution. The distances between the liquid inlet 1122 and the feed inlet 1121 and the end of the washing drum 11 are the same, and both the feed inlet 1121 and the liquid inlet 1122 are located above the feed end of the screw shaft 121. According to the function of different positions, the washing drum 11 may include a feeding section located at the feed end of the washing drum 11 and a discharge section located at the discharge end of the washing drum 11. The liquid inlet 1122 and the feed inlet 1121 are both located in the feeding section of the washing drum 11, and the material outlet 113 is located at the bottom of the discharge section of the washing drum 11.

[0054] In this design, the material to be washed and the washing solution can be introduced simultaneously through the feed inlet 1121 and the liquid inlet 1122, respectively. The distance between the liquid inlet 1122 and the feed inlet 1121 and the end of the washing cylinder 11 is the same, so that the material to be washed and the washing solution can enter the feed end of the screw shaft 121 at the same time. This allows the material to be washed and the washing solution to be instantly dispersed and mixed, avoiding the problem of overwashing or underwashing caused by a time difference when a large amount of material to be washed enters the washing device 1 and comes into contact with the washing solution.

[0055] In some embodiments, the spiral shaft 121 includes multiple spiral units. Specifically, the spiral unit is divided into two sections: a feeding spiral unit near the material inlet 112 and a discharging spiral unit near the material outlet 113. To reduce space occupation, the feeding spiral unit and the discharging spiral unit are connected by a mandrel and a kneading disc to transmit torque. The mandrel adopts an involute spline structure. One end of the feeding spiral unit is connected to the kneading disc via the mandrel, and the two kneading discs are also connected via the mandrel. The discharging spiral unit is also connected to the kneading disc via the mandrel, thus reducing space occupation while ensuring effective torque transmission.

[0056] The spiral shaft 121 designed in this way can avoid the phenomenon of individual processes affecting processing and transportation, and the connection method of the spiral shaft 121 can ensure the washing effect while effectively improving the conveying capacity and slurry pushing efficiency.

[0057] like Figure 3 As shown, the feed inlet 1121 is connected to the powder feeder 13, which provides the material to be washed to the washing drum 11 at a preset conveying speed. Specifically, the powder feeder 13 includes a metering hopper and a metering screw. The metering hopper has a feed chamber for receiving and containing the material to be washed conveyed by the powder raw material hopper 15. The metering screw conveys the material towards the discharge port, allowing it to enter the washing drum 11 through the feed inlet 1121. A weighing sensor is installed on the metering hopper, connected to a PLC control system. The rotation speed of the metering screw is adjusted based on the weight information fed back from the weighing sensor, thereby achieving automatic control of the discharge volume from the metering hopper. The weighing sensor can be a shear beam type or a bellows type. With this design, the feeding speed and uniformity of the material to be washed can be precisely controlled by controlling the conveying speed of the metering screw.

[0058] The inlet 1122 is connected to the liquid feeder 14, which supplies washing solution to the washing drum 11 at a preset conveying speed. Specifically, the liquid feeder 14 includes a metering tank and a metering pump. The metering tank has an inlet chamber that is connected to a liquid storage tank 16 to receive and contain the washing solution conveyed by the liquid storage tank 16. The metering pump conveys the washing solution towards the outlet so that the washing solution can enter the washing drum 11 through the inlet 1122. The metering pump controls the conveying capacity of the washing solution.

[0059] In this design, the conveying volume of the material to be washed and the washing solution can be controlled by the powder feeder 13 and the liquid feeder 14 respectively, so that the material to be washed and the washing solution can be conveyed into the washing drum 11 at the same time and evenly in a certain proportion, thereby improving the uniformity of washing of the material to be washed.

[0060] The washing device 1 also includes a seasoning component for adjusting the discharge amount of the material outlet 113. The seasoning component includes a pressure detection element installed at the material outlet 113 for detecting the discharge pressure of the mixed material and a regulating valve for adjusting the opening of the material outlet 113. The regulating valve is signal-connected to the pressure detection element and is configured to adjust the opening of the material outlet 113 according to the material pressure information fed back by the pressure detection element.

[0061] The pressure detection element can be installed at the material outlet 113, or between the material outlet 113 and the separation device 2 of the washing system. It only needs to ensure that the pressure detection element can detect the pressure of the flowing mixture. The pressure detection element can be a pressure measuring instrument, and the pressure measuring instrument is connected to the PLC control system to realize the reception and feedback of pressure detection signals, thereby controlling the regulating valve to change the opening degree of the material outlet 113. This method of information reception and feedback is conventional technology in the field; therefore, its working principle is not described in detail here.

[0062] This design method can precisely control the discharge amount of the mixed materials, so as to adjust the washing time of the materials to be washed and the washing solution in the washing drum 11 in accordance with the feeding of the materials to be washed and the washing solution, and ensure the washing effect of the materials to be washed.

[0063] The screw shaft 121 has an asymmetric spline groove, a screw pitch of S, a screw outer diameter of Ds, and a screw length of L, where S = (0.8-1)Ds and L = (22-28)Ds, preferably L = 25Ds. This design of the screw shaft 121 eliminates the radial force of the washing device 1, achieving a meshing ratio of 1.66 and a torque coefficient of 15 Nm / cm. 3 This results in higher energy efficiency and gives the water washing device 1 extremely high load-bearing capacity.

[0064] like Figure 3 As shown, the washing system also includes a separation device 2, which comprises an intermediate tank 21, a transfer pump 22, and a solid-liquid separator 23. The intermediate tank 21 receives the mixture discharged through the material outlet 113, meaning the inlet of the intermediate tank 21 is connected to the material outlet 113 of the washing drum 11. The transfer pump 22 transports the mixture in the intermediate tank 21 to the solid-liquid separator 23, which separates the solid and liquid components in the mixture. One transfer pump 22 or multiple pumps connected in parallel can be used, depending on the processing capacity of the solid-liquid separator 23. The solid-liquid separator 23 separates the solid and liquid components and transports them to designated locations. The solid-liquid separator 23 can be a centrifuge or a filter press, etc., and consists of at least two units connected in parallel to achieve the desired solid-liquid separation effect. Centrifuges and filter presses are conventional technologies in this field; therefore, their structures and specific working principles are not described in detail.

[0065] Continue to refer to Figure 3The washing system also includes a drying device 3, which comprises a buffer chamber 31 and a dryer 32. The buffer chamber 31 receives the solid material separated by the solid-liquid separator 23 and conveys the solid material to the dryer 32, which is used to dry the solid material. The dryer 32 can be a single unit or multiple units arranged in parallel, and can be designed according to actual processing requirements. The dryer 32 can be a vacuum plow dryer 32, a vibrating vacuum dryer 32, a flash dryer 32, or a vacuum dryer 32, etc. Since this type of dryer 32 uses conventional technology for drying materials, its structure and working principle are not described in detail here.

[0066] In addition, the drying device 3 may also include a storage silo 33, into which the solid material dried by the dryer 32 is stored.

[0067] The present invention also provides a water washing method, comprising the following steps:

[0068] Step S1: Place two spiral shafts 121 with interlaced spiral edges inside the washing drum 11, and make the two spiral shafts 121 rotate in the same direction. Set the rotation speed of the two spiral shafts 121 and the washing time of the material in the washing drum 11.

[0069] In step S2, the material to be washed and the washing solution are simultaneously added to the washing drum 11 through the material inlet 112 according to the preset dosage. After washing for the set washing time, the resulting mixture flows out through the material outlet 113.

[0070] The washing time of the material to be washed in the washing drum 11 can be adjusted by coordinating the feeding speed of the material and the washing solution, the discharge speed of the mixture, and the rotation speed of the screw shaft 121. For example, if the feeding speed of the material and the washing solution is slow, the opening of the material outlet 113 is small, the discharge speed of the mixture is slow, and the rotation speed of the screw shaft 121 is reduced, thereby increasing the washing time of the material in the washing drum 11. Conversely, the washing time of the material in the washing drum 11 can be reduced.

[0071] In some embodiments, the water washing method of the present invention is implemented by the water washing system described above, which includes all the technical features of the water washing system described above, and is not described in detail here.

[0072] The water washing method provided by this invention further includes the following steps:

[0073] Step S3 involves solid-liquid separation of the mixture to obtain solid material. Specifically, the material separation of the mixture can be achieved by the separation device 2 described above, and the separated solid material forms a filter cake under the action of the separation device 2.

[0074] Step S4 involves drying the solid material to obtain the finished product. Specifically, this drying process is achieved using the aforementioned drying device 3.

[0075] After being washed with water, the material is separated and dried to obtain the finished product.

[0076] In some embodiments, the ratio of the material to be washed to the washing solution is (1.653-2.125):1. This ratio of material to washing solution can meet the washing requirements of the material to be washed while reducing the amount of washing solution used.

[0077] In some embodiments, the mixing time between the material to be washed and the washing solution is 25-35 minutes. This washing time ensures the washing effect of the material to be washed while avoiding the phenomenon that the performance of the material to be washed may be affected due to over-washing.

[0078] In some embodiments, the rotational speed of the screw shaft 121 is in the range of n, where 80 r / min ≤ n ≤ 200 r / min. This rotational speed of the screw shaft 121 can ensure the washing effect of the material to be washed.

[0079] In some embodiments, the washing solution is a mixture of water and HF or boric acid, wherein the concentration of HF or boric acid in the washing solution is 0.01-1 mol / L. This type of washing solution is suitable for high-nickel ternary materials to be washed.

[0080] This design method uses HF or boric acid instead of pure water as the washing agent in the washing solution. HF, or hydrogen fluoride, reacts slowly with lithium hydroxide on the surface of the high-nickel ternary material, effectively reducing residual alkali. Furthermore, the boric acid or HF adhering to the surface of the high-nickel ternary material reacts chemically with any remaining lithium hydroxide that hasn't been removed by the water during the subsequent sintering process of the cathode material, forming a coating layer. This coating layer can penetrate deep into the surface of the high-nickel ternary material, making the structure of the washed high-nickel ternary material more stable.

[0081] The following description uses specific embodiments and comparative examples.

[0082] Example 1

[0083] Take 600 kg of high-nickel ternary material powder, chemical formula LiNi 1-x-y Co x Mn yO2 is added simultaneously to the washing cylinder 11 along with the powder and HF-added chilled water in the washing device 1 at a solid-liquid ratio of 2.125:1. Two spiral shafts 121 with an outer diameter Ds = 40 mm, a rod length L = 1000 mm, and a pitch of 40 mm are selected. The two spiral shafts 121 rotate in the same direction with a compression ratio of 1.3. The inner diameter of the washing cylinder 11 is 42 mm, the rotation speed of the two spiral shafts 121 is 180 r / min, and the washing time is 25 min. After washing, the slurry is discharged into the intermediate tank 21 and then conveyed by the transfer pump 22 to the solid-liquid separator 23 for solid-liquid separation to form a filter cake. The water content of the filter cake is ≤8%. The filter cake is dried using a plow dryer 32. After drying, the water content of the filter cake is <0.4%, resulting in a high-nickel ternary material. The residual alkali content of the high-nickel ternary material is shown in the table below.

[0084] The dried high-nickel ternary material is called the washed-dry material. SEM was used to analyze the washed-dry material, and the resulting microscopic images are shown below. Figure 4 As shown. SEM is a commonly used instrument for material analysis; its structure and working principle are not described in detail here.

[0085] Example 2

[0086] Unlike Example 1, in Example 2, the pitch S = 0.7 times the outer diameter Ds of the helix. The washed and dried material obtained by this method was analyzed using SEM, and microscopic images were obtained as follows: Figure 5 As shown.

[0087] Example 3

[0088] Unlike Example 1, in Example 3, the rotational speed of the screw shaft 121 is 60 r / min. The washed and dried material obtained by this method was analyzed using SEM, and microscopic images were obtained as follows: Figure 6 As shown.

[0089] Example 4

[0090] Unlike Example 1, in Example 4, no FH was added to the washing solution; that is, the washing solution was water. The washed and dried material obtained by this method was analyzed using SEM, and the resulting microscopic images are shown below. Figure 7 As shown.

[0091] Example 5

[0092] Unlike Example 1, in Example 5, the ratio of the length to the outer diameter of the spiral shaft 121 is outside the specified range, or the solid-liquid ratio of the high-nickel ternary material to the washing solution is outside the specified range. The washed and dried material obtained by this method was analyzed using SEM, and microscopic images were obtained as follows: Figure 8 As shown.

[0093] Comparative Example 1

[0094] High-nickel ternary materials were washed using a traditional water washing reactor. 600 kg of powder was conveyed under negative pressure into the washing hopper. Chilled water was pumped into the reactor at a solid-liquid ratio of 2.125:1, and the mixture was stirred at 10 Hz for 3 minutes. After mixing, the material was discharged into an intermediate tank 21 and then conveyed by a pump 22 to a separation device for solid-liquid separation to form a filter cake. The filter cake was dried using a plow dryer 32 to obtain the modified high-nickel ternary material. SEM was used to analyze the washed and dried material obtained by this method, and microscopic images were obtained as follows: Figure 9 As shown.

[0095] The water washing effect of the high-nickel ternary materials obtained using the above embodiments and comparative examples is as follows:

[0096]

[0097] Here, BET is the total area per unit mass of material.

[0098] It is evident that the total alkali content and quick water content of the filter cake of the high-nickel ternary material obtained by the water washing method of this application are much lower than those of the high-nickel ternary material obtained by the water washing method of the traditional water washing kettle. Furthermore, the total alkali content of the high-nickel ternary material obtained by the water washing method when each parameter is within the above-mentioned numerical range is lower than that of the high-nickel ternary material obtained by the water washing method when each parameter is outside the above-mentioned numerical range.

[0099] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0100] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A water washing system for washing positive electrode materials, characterized in that, Includes a water washing device (1), said water washing device (1) comprising: A washing drum (11) has a stirring chamber (111) inside. The washing drum (11) is provided with a material inlet (112) and a material outlet (113) communicating with the stirring chamber (111). The material inlet (112) is used to continuously introduce the material to be washed and the washing solution, and the material outlet (113) is used to continuously discharge the mixture of the washed material and the washing solution. The stirring assembly (12) includes two spiral shafts (121) rotatably disposed inside the washing drum (11), the spiral edges of the two spiral shafts (121) are staggered, and the two spiral shafts (121) rotate in the same direction; The spiral shaft (121) includes a feeding section spiral unit near the material inlet (112) and a discharging section spiral unit near the material outlet (113). The feeding section spiral unit and the discharging section spiral unit are connected by a mandrel and a kneading disc. The mandrel has an involute spline structure. The spiral groove of the spiral shaft (121) is an asymmetric spline, the pitch of the spiral shaft (121) is S, the outer diameter of the spiral shaft (121) is Ds, and the length of the screw is L, where S = (0.8-1)Ds and L = (22-28)Ds; The distance between the helical ridge of the spiral shaft (121) and the inner wall of the washing drum (11) is no greater than 2 mm; the ratio of the material to be washed to the washing solution is (1.653-2.125):1; the mixing time of the material to be washed and the washing solution is 25-35 min. The material inlet (112) includes a feed inlet (1121) and a liquid inlet (1122), and the liquid inlet (1122) and the feed inlet (1121) are at the same distance from the end of the washing drum (11); the washing system also includes a separation device (2), which includes an intermediate tank (21), a transfer pump (22) and a solid-liquid separator (23).

2. The water washing system according to claim 1, characterized in that, The material inlet (112) includes a feed inlet (1121) and a liquid inlet (1122) located above the washing drum (11) and in a pipe communicating with the stirring chamber (111). The feed inlet (1121) is used to introduce the material to be washed, and the liquid inlet (1122) is used to introduce the washing solution.

3. The water washing system according to claim 2, characterized in that, The feed inlet (1121) is used to connect to the powder feeder (13), which can provide the material to be washed to the washing drum (11) at a preset conveying speed; The inlet (1122) is used to connect to the liquid feeder (14), which is capable of supplying the washing solution to the washing drum (11) at a preset conveying speed.

4. The water washing system according to claim 1, characterized in that, The washing device (1) further includes a seasoning component for adjusting the discharge amount of the material outlet (113). The seasoning component includes a pressure detection element disposed at the material outlet (113) for detecting the discharge pressure of the mixture and a regulating valve for adjusting the opening of the material outlet (113). The regulating valve is signal-connected to the pressure detection element and is configured to adjust the opening of the material outlet (113) according to the material pressure information fed back by the pressure detection element.

5. The water washing system according to any one of claims 1 to 4, characterized in that, The intermediate tank (21) is used to receive the mixture discharged through the material outlet (113), and the transfer pump (22) is used to transport the mixture in the intermediate tank (21) to the solid-liquid separator (23), which is used to separate the solid material and liquid in the mixture.

6. The water washing system according to claim 5, characterized in that, The washing system also includes a drying device (3), which includes a buffer chamber (31) and a dryer (32). The buffer chamber (31) is used to receive the solid material separated by the solid-liquid separator (23) and can transport the solid material to the dryer (32). The dryer (32) is used to dry the solid material.

7. A water washing method, characterized in that, The washing system according to any one of claims 1-6 includes the following steps: Two spiral shafts (121) with interlaced spiral edges are placed inside the washing drum (11) so that the two spiral shafts (121) can rotate in the same direction. The rotation speed of the two spiral shafts (121) and the washing time of the material in the washing drum (11) are set. The material to be washed and the washing solution are simultaneously added to the washing drum (11) through the material inlet (112) according to the preset dosage. After washing for the set washing time, the resulting mixture flows out through the material outlet (113).

8. The water washing method according to claim 7, characterized in that, The rotational speed range of the helical shaft (121) is n, where 80r / min≤n≤200r / min.

9. The water washing method according to claim 7, characterized in that, The washing solution is a mixture of water and HF or boric acid, wherein the concentration of HF or boric acid in the washing solution is 0.01-1 mol / L.

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