A method for recycling waste polycrystalline positive electrode material, a positive electrode material and a positive electrode sheet

Abstract

The application relates to a recycling method of waste polycrystalline positive electrode materials, which comprises the following steps: grading waste polycrystalline positive electrode material particles according to particle size, and selecting a corresponding recycling method according to the particle grade, so that the particles of different size grades are recycled separately, the problem of performance degradation of regenerated positive electrode materials caused by mixed recycling of particles of different sizes is avoided, and the performance of the regenerated positive electrode materials is improved. The application also relates to a positive electrode material obtained by the recycling method, a positive electrode sheet comprising the positive electrode material and a lithium ion battery comprising the positive electrode sheet. The lithium ion battery has high specific capacity and capacity retention rate.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery cathode material recycling technology, specifically to a method for recycling waste polycrystalline cathode materials. Background Technology

[0002] Lithium-ion batteries have attracted much attention due to their high energy density, high capacity, good cycle stability, and excellent performance. The rapid growth in demand for lithium-ion batteries is a direct cause of soaring prices for cathode raw materials such as nickel, cobalt, and manganese ore, making the recycling of spent cathode materials an urgent matter. However, the performance of recycled cathode materials obtained through existing cathode material recycling processes deteriorates.

[0003] Therefore, there is an urgent need to develop a method for recycling waste polycrystalline cathode materials that can improve the performance of recycled cathode materials. Summary of the Invention

[0004] In view of the problems existing in the background technology, this application provides a method for recycling waste polycrystalline cathode materials, which can improve the performance of recycled cathode materials.

[0005] The method for recycling waste polycrystalline cathode materials provided in the first aspect of this application includes:

[0006] Provides waste polycrystalline cathode material particles;

[0007] A first classification threshold is set, and the polycrystalline cathode material particles are classified according to the first classification threshold to obtain first-level particles with a particle size smaller than the first classification threshold and second-level particles with a particle size greater than or equal to the first classification threshold; and

[0008] First-stage and second-stage particles were recovered using different methods;

[0009] The first grading threshold is 0.8-1.5μm.

[0010] In the technical solution of this application embodiment, by classifying the waste polycrystalline cathode material particles according to particle size and selecting the corresponding recycling method according to the particle size, the separate recycling of particles of different sizes is realized, avoiding the problem of performance degradation (including capacity and cycle performance) of recycled cathode materials caused by mixed recycling of particles of different sizes, thereby improving the performance of recycled cathode materials.

[0011] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the recycling method further includes: setting a second classification threshold, and classifying the second-level particles according to the second classification threshold to obtain third-level particles with a particle size smaller than the second classification threshold and fourth-level particles with a particle size greater than or equal to the second classification threshold; and recycling the third-level particles and fourth-level particles by different methods; wherein the second classification threshold is 5-8 μm. In this design, by classifying the second-level particles, the separation of medium-sized particles and large-sized particles (i.e., the separation of third-level particles and fourth-level particles) is achieved, making it possible to separately calcine particles of different sizes, avoiding over-burning of medium-sized particles, and thus avoiding the problem of performance degradation of the recycled cathode material.

[0012] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein at least a portion of the polycrystalline cathode material particles have cracks, and the recycling method further includes: ball milling the polycrystalline cathode material particles to break down the cracked polycrystalline cathode material particles before grading according to a first grading threshold. In this design, by breaking down large cracked polycrystalline cathode material particles into smaller particles, performance degradation of the regenerated cathode material due to the inclusion of large cracked particles is avoided.

[0013] In some embodiments, according to the first aspect, a third example of the first aspect is proposed, wherein the ball milling time is 10-120 min. In this design, by controlling the ball milling time, light ball milling is achieved, thereby ensuring that large particles with cracks are broken up without destroying intact large particles without cracks.

[0014] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, wherein recycling the first-stage particles includes: mixing the first-stage particles with a first lithium replenishment source, performing spray granulation, and calcining to obtain a regenerated polycrystalline cathode material; or, recycling the first-stage particles includes: performing wet recycling of the first-stage particles to obtain a regenerated cathode material. In this design, by spray granulation or wet recycling, powdered, failed microparticles can be regenerated into polycrystalline cathode materials with good performance, realizing the reuse of waste materials.

[0015] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, wherein the first lithium replenishment source is one or more of lithium hydroxide and lithium carbonate; the molar ratio of the first-stage particles to the first lithium replenishment source in terms of molar amount of lithium is 1:0.05-1:0.2. In this design, by selecting a specific lithium replenishment source and molar ratio, the regenerated cathode material can have high capacity and cycle performance.

[0016] In some embodiments, according to the first aspect, a sixth example of the first aspect is proposed, wherein calcination is performed at 500-650°C. In this design, calcination at 500-650°C can achieve effective lithium replenishment of the first-stage particles while avoiding over-burning.

[0017] In some embodiments, according to the first aspect, a seventh example of the first aspect is proposed, wherein recycling the second-stage particles includes: mixing the second-stage particles with a second lithium replenishment source and then calcining them to obtain a recycled cathode material. In this design, the use of a direct lithium replenishment recycling process to recycle the second-stage particles can significantly shorten the recycling cycle and improve the utilization rate of valuable metals.

[0018] In some embodiments, according to the first aspect, an eighth example of the first aspect is proposed, wherein the second lithium replenishment source is one or more of lithium hydroxide and lithium carbonate; the molar ratio of the second-stage particles to the second lithium replenishment source in terms of molar amount of lithium is 1:0.05-1:0.2. In this design, by selecting a specific lithium replenishment source and molar ratio, the regenerated cathode material can have high capacity and cycle performance.

[0019] In some embodiments, according to the first aspect, a ninth example of the first aspect is proposed, wherein the recycling of the third-stage particles includes: mixing the third-stage particles with a third lithium replenishment source and then calcining them at 700-900°C to obtain regenerated single-crystal cathode material. In this design, calcination at 700-900°C enables effective lithium replenishment of the third-stage particles. Furthermore, using a direct lithium replenishment recycling process to recycle the third-stage particles can significantly shorten the recycling cycle and improve the utilization rate of valuable metals.

[0020] In some embodiments, according to the first aspect, a tenth example of the first aspect is proposed, wherein the third lithium source is one or more of lithium hydroxide and lithium carbonate; the molar ratio of the third-stage particles to the third lithium source in terms of molar amount of lithium is 1:0.05-1:0.2. In this design, by selecting a specific lithium source and molar ratio, the regenerated single-crystal cathode material can have high capacity and cycle performance.

[0021] In some embodiments, according to the first aspect, an eleventh example of the first aspect is provided, wherein recycling the fourth-stage particles includes: mixing the fourth-stage particles with a fourth lithium replenishment source, and then calcining them at 500-650°C to obtain regenerated polycrystalline cathode material. In this design, calcination at 500-650°C enables effective lithium replenishment of the fourth-stage particles. Furthermore, using a direct lithium replenishment recycling process to recover the fourth-stage particles can significantly shorten the recycling cycle and improve the utilization rate of valuable metals.

[0022] In some embodiments, according to the first aspect, a twelfth example of the first aspect is proposed. The fourth lithium supplement source is one or more of lithium hydroxide and lithium carbonate; the molar ratio of the fourth-stage particles in terms of the molar amount of lithium element to the fourth lithium supplement source in terms of the molar amount of lithium element is 1:0.05 - 1:0.2. In this design, by selecting specific lithium supplement sources and molar ratios, the regenerated polycrystalline cathode material can have high capacity and cycling performance.

[0023] In some embodiments, according to the first aspect, a thirteenth example of the first aspect is proposed. The polycrystalline cathode material is a polycrystalline ternary cathode material Li[Ni x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1. The layered Li[Ni x Co y Mn 1-x-y O2 has low cost and high capacity, and is one of the most promising cathode materials to meet the requirements of electric vehicles and hybrid electric vehicles. Therefore, the recycling of this cathode material is of great significance.

[0024] The second aspect of the present application provides a cathode material obtained according to the recycling method described in the first aspect of the present application.

[0025] The third aspect of the present application provides a positive electrode sheet including the cathode material described in the second aspect of the present application.

[0026] The fourth aspect of the present application provides a lithium-ion battery including the positive electrode sheet described in the third aspect of the present application.

[0027] Compared with the prior art, the present application has at least the following beneficial effects:

[0028] 1. The present application provides a recycling method for waste polycrystalline cathode materials. By classifying the waste polycrystalline cathode material particles according to particle size and selecting corresponding recycling methods according to the particle level, separate recycling of particles of different size levels is achieved, avoiding the problem of deterioration of the performance (including capacity and cycling performance, etc.) of the regenerated cathode material caused by mixed recycling of large and small particles, thereby improving the performance of the regenerated cathode material. In the prior art, particles of different sizes are usually mixed and roasted. In order to ensure the performance of large particles, the roasting temperature is usually higher than the optimal temperature of small particles, resulting in over-roasting of small particles, and then the structure cannot reach the optimum, affecting its performance. In addition, the regenerated cathode material recovered by the prior art includes both large particles and small particles. Since the specific surface area of small particles is large and there are many side reactions, the overall performance of the regenerated cathode material will decrease when mixed with large particles. The present application successfully solves these problems existing in the prior art and improves the performance of the regenerated cathode material.

[0029] Furthermore, since some large, cracked particles exist in the waste polycrystalline cathode material, this application lightly ball-mills the polycrystalline cathode material particles before grading to prevent the performance of the recycled cathode material from deteriorating due to the presence of large, cracked particles. This process breaks down the large, cracked polycrystalline cathode material particles into smaller particles. The intact large particles, being crack-free and possessing high particle strength, retain their original size and shape.

[0030] 2. This application also provides a lithium-ion battery comprising a recycled cathode material obtained according to the above-described recycling method, which has a high specific capacity and capacity retention. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0032] Figure 1 This is a flowchart of the recycling method for waste polycrystalline cathode materials according to this application.

[0033] Figure 2 This is a scanning electron microscope image of the regenerated polycrystalline cathode powder obtained from the fourth-stage particle recovery in Example 1 of this application.

[0034] Figure 3 This is a scanning electron microscope image of the regenerated single-crystal cathode powder obtained from the third-stage particle recovery in Example 1 of this application.

[0035] Figure 4 This is a scanning electron microscope image of the regenerated polycrystalline cathode powder obtained from the first-stage particle recovery in Example 1 of this application.

[0036] Figure 5 This is a scanning electron microscope image of the regenerated cathode powder of Comparative Example 1.

[0037] Figure 6 The image shows a scanning electron microscope image of the regenerated polycrystalline cathode material obtained from the fourth-stage particles in Comparative Example 2.

[0038] Figure 7 This is a scanning electron microscope image of the regenerated cathode powder of Comparative Example 3. Detailed Implementation

[0039] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.

[0040] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0041] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more (including two).

[0042] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0043] Lithium-ion batteries have attracted much attention due to their high energy density, high capacity, good cycle stability, and excellent performance. The rapid growth in demand for lithium-ion batteries is a direct cause of soaring prices for cathode raw materials such as nickel, cobalt, and manganese ore, making the recycling of waste cathode materials an urgent priority. However, the performance of recycled cathode materials obtained through existing recycling processes deteriorates. Therefore, there is an urgent need to develop a recycling method for waste polycrystalline cathode materials that can improve the performance of recycled cathode materials.

[0044] The inventors discovered that polycrystalline cathode materials undergo lattice expansion and contraction during cycling. Due to the anisotropy of the grains, stress accumulation in the later stages of cycling causes the particles to crack. The freshly cracked interfaces further react with the electrolyte, ultimately leading to particle pulverization and failure. Therefore, waste battery cells contain a large number of small particles of polycrystalline cathode material due to pulverization. If these small particles are mixed with larger particles for recycling, the regenerated cathode material will inevitably contain small particles, which will degrade its performance. Therefore, waste polycrystalline cathode material particles are unsuitable for direct recycling due to the large number of small particles they contain.

[0045] Through in-depth research, the inventor has designed a method for recycling waste polycrystalline cathode materials. By classifying the waste polycrystalline cathode material particles according to particle size and selecting corresponding recycling methods according to the particle level, separate recycling of particles of different sizes is achieved, effectively avoiding the problem of deterioration of the performance of the recycled cathode material caused by mixed recycling of particles of different sizes, thereby improving the performance of the recycled cathode material.

[0046] Specifically, the first aspect of the present application provides a method for recycling waste polycrystalline cathode materials, which includes the following steps.

[0047] First, provide waste polycrystalline cathode material particles.

[0048] In some embodiments of the present application, the waste polycrystalline cathode material can be a polycrystalline ternary cathode material Li[Ni x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1. The layered Li[Ni x Co y Mn 1-x-y O2 has low cost and high capacity, and is one of the most promising cathode materials to meet the requirements of electric vehicles and hybrid electric vehicles. Therefore, the recycling of this cathode material is of great significance. Of course, the polycrystalline cathode material of the present application is not limited to this ternary cathode material, and other types of waste polycrystalline cathode materials are also suitable for recycling by the method of the present application. For example, in addition to lithium nickel cobalt manganese oxide, the polycrystalline cathode material can also be lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt oxide or lithium-rich manganese-based cathode material.

[0049] In some embodiments of this application, the method for preparing waste polycrystalline cathode material particles includes: discharging the waste battery cell, disassembling it, and separating the positive and negative electrode sheets, separator, and electrolyte; cleaning the positive electrode sheet, drying it, and then calcining the positive electrode sheet in an oxygen-containing atmosphere; after calcination, crushing the positive electrode sheet, separating the positive current collector, and obtaining polycrystalline cathode material particles. In some specific embodiments, cleaning includes: immersing the positive electrode sheet in a cleaning agent, followed by filtration. This application does not have any particular limitation on the specific type of cleaning agent, as long as it can remove the electrolyte and additives on the positive electrode sheet. For example, the cleaning agent can be dimethyl carbonate, etc. The immersion time can be 0.5-3 days. The drying temperature can be 70-90℃, preferably 75-85℃. The oxygen-containing atmosphere can be air or oxygen, etc. The calcination temperature can be 400-600℃, preferably 450-550℃. The calcination time can be 3-7 hours. Calcination can remove impurities such as conductive carbon and binders from the surface of the positive electrode sheet. In some specific embodiments, the positive electrode sheet can be mechanically crushed and then sieved for later use. Sieving can eliminate agglomeration and facilitate subsequent classification.

[0050] Then, a first classification threshold is set, and the waste polycrystalline cathode material particles are classified according to the first classification threshold to obtain first-level particles with a particle size smaller than the first classification threshold and second-level particles with a particle size greater than or equal to the first classification threshold.

[0051] In some embodiments of this application, the first grading threshold may be 0.8-1.5 μm, for example, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm. Preferably, the first grading threshold is 0.8-1.2 μm.

[0052] By classifying polycrystalline cathode material particles, the separation of small and large particles that have pulverized and failed (i.e., the separation of first-level and second-level particles) is achieved, making it possible to calcine large and small particles separately and avoiding the performance degradation problem of regenerated cathode materials.

[0053] In some embodiments of this application, wind force classification can be performed in a classifier.

[0054] Furthermore, some large, cracked particles exist in the waste polycrystalline cathode material. These large, cracked particles can undergo further side reactions with the electrolyte during lithium-filling roasting or when used as cathode material after regeneration, leading to particle pulverization and failure, thus degrading the performance of the regenerated cathode material. Therefore, to avoid performance degradation in regenerated cathode material due to the presence of large, cracked particles, the polycrystalline cathode material particles can be lightly ball-milled before grading to break the large, cracked particles into smaller ones. Since intact large particles are crack-free and have high strength, they retain their original size and morphology.

[0055] In some embodiments of this application, the ball milling time can be 10-120 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. Preferably, the ball milling time is 10-60 min, more preferably 20-40 min.

[0056] In some embodiments of this application, the diameter of the milling zirconium ball can be 1-12 mm, for example, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm or 12 mm. Preferably, the diameter of the milling zirconium ball is 3-7 mm.

[0057] In some embodiments of this application, the linear velocity of the ball mill can be 2-10 m / s, for example, 2 m / s, 3 m / s, 4 m / s, 5 m / s, 6 m / s, 7 m / s, 8 m / s, 9 m / s or 10 m / s. Preferably, the linear velocity can be 3-7 m / s.

[0058] The ball milling time, zircon ball diameter, and ball milling linear speed of this application can be selected according to actual needs, as long as they can break up large particles with cracks without destroying intact large particles without cracks.

[0059] The first-stage and second-stage particles can then be recovered using different methods.

[0060] The method for recycling the first-stage particles may include: mixing the first-stage particles with a first lithium replenishment source, followed by spray granulation and calcination, or wet recycling, to obtain regenerated polycrystalline cathode material. This application, through spray granulation or wet recycling, can regenerate powdered, failed microparticles into high-performance polycrystalline cathode material, achieving the reuse of waste materials.

[0061] In some embodiments of this application, spray granulation includes: mixing first-stage particles with a first lithium source and a solvent to obtain a slurry; transferring the slurry to a spray dryer for granulation. The granulation temperature can be 100-200°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C. At this temperature, the solvent evaporates, and the slurry forms spherical particles of uniform size. The solvent can be water. Mixing can be carried out in a ball mill.

[0062] In some embodiments of this application, the first lithium source may be one or more of lithium hydroxide and lithium carbonate.

[0063] In some embodiments of this application, the molar ratio of the first-stage particles (based on the molar amount of lithium) to the first lithium replenishment source (based on the molar amount of lithium) is 1:0.05-1:0.2, for example, it can be 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2. Preferably, the molar ratio is 1:0.08-1:0.17. More preferably, the molar ratio is 1:0.1-1:0.15.

[0064] This application enables the regenerated cathode material to possess high capacity and cycle performance by selecting specific lithium replenishment sources and molar ratios.

[0065] In some embodiments of this application, after spray granulation, the particles can be calcined at 500-650°C. Preferably, the calcination temperature is 500-600°C. Calcination within this temperature range can effectively replenish lithium to the first-stage particles while avoiding over-calcination.

[0066] In some embodiments of this application, wet recovery includes: dissolving the first-stage particles in an acid solution, co-precipitating, filtering to obtain a filtrate and a filter cake (i.e., a precursor); recrystallizing and drying the filtrate to obtain lithium hydroxide powder; and mixing the filter cake with the lithium hydroxide powder and then calcining. The acid solution can be a sulfuric acid solution or a hydrochloric acid solution, etc. The calcination temperature can be 700-900℃.

[0067] Compared to wet recycling, the method of recycling polycrystalline cathode materials by spray granulation and calcination is simpler and does not require a precursor preparation step, but the performance of the resulting recycled cathode material is slightly worse.

[0068] The method for recovering the second-stage particles may include: mixing the second-stage particles with a second lithium replenishment source, followed by calcination to obtain recycled cathode material. This application employs a direct lithium replenishment recovery process to recover the second-stage particles, which can significantly shorten the recovery cycle and improve the utilization rate of valuable metals.

[0069] In some embodiments of this application, the second lithium source may be one or more of lithium hydroxide and lithium carbonate.

[0070] In some embodiments of this application, the molar ratio of the second-stage particles (based on the molar amount of lithium) to the second lithium replenishment source (based on the molar amount of lithium) can be 1:0.05-1:0.2, for example, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2. Preferably, the molar ratio is 1:0.08-1:0.17. More preferably, the molar ratio is 1:0.1-1:0.15.

[0071] This application enables the regenerated cathode material to possess high capacity and cycle performance by selecting specific lithium replenishment sources and molar ratios.

[0072] In some embodiments of this application, the second-stage particles are mixed with a second lithium source and then calcined at 700-900°C. Preferably, the calcination temperature is 800-900°C.

[0073] Since the second-stage particles include medium-sized and large-sized particles, the calcination temperature is usually higher than the optimal temperature for medium-sized particles in order to ensure the performance of large-sized particles. This can lead to over-burning of medium-sized particles, which in turn causes their structure to fall short of the optimal level and affects their performance. Therefore, in order to avoid over-burning of medium-sized particles, this application further classifies the second-stage particles.

[0074] Methods for classifying second-level particles may include: setting a second classification threshold and classifying the second-level particles according to the second classification threshold to obtain third-level particles with a particle size smaller than the second classification threshold and fourth-level particles with a particle size greater than or equal to the second classification threshold; and recovering the third-level particles and fourth-level particles by different methods.

[0075] In some embodiments of this application, the second grading threshold may be 5-8 μm, for example, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm. Preferably, the second grading threshold may be 5.5-6.5 μm.

[0076] By classifying the second-stage particles, the separation of medium-sized and large-sized particles (i.e., the separation of third-stage and fourth-stage particles) is achieved, making it possible to calcine particles of different sizes separately and avoiding the performance degradation problem of recycled cathode materials.

[0077] In some embodiments of this application, wind force classification can be performed in a classifier.

[0078] In some embodiments of this application, the method for recovering the third-stage particles may include: mixing the third-stage particles with a third lithium replenishment source, and then calcining them at 700-900°C to obtain regenerated single-crystal cathode material. Preferably, the calcination temperature is 800-900°C. In some specific embodiments, the calcination time is 8-15 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours, preferably 10-15 hours. By calcining at 700-900°C, this application can achieve effective lithium replenishment of the third-stage particles. In addition, the direct lithium replenishment recovery process for recovering the third-stage particles can significantly shorten the recovery cycle and improve the utilization rate of valuable metals.

[0079] In this application, the third-stage particles are close to the size of commonly used single-crystal particles. After lithium supplementation and calcination at high temperature, the grain boundaries between polycrystalline primary particles can be melted to form large single-crystal particles, thereby realizing the regeneration of single-crystal cathode materials.

[0080] In some specific embodiments, the third lithium source may be one or more of lithium hydroxide and lithium carbonate.

[0081] In some specific embodiments, the molar ratio of the third-stage particles (based on the molar amount of lithium) to the third lithium replenishment source (based on the molar amount of lithium) can be 1:0.05-1:0.2, for example, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2. Preferably, the molar ratio is 1:0.08-1:0.17. More preferably, the molar ratio is 1:0.1-1:0.15.

[0082] This application enables the regenerated single-crystal cathode material to have high capacity and cycle performance by selecting specific lithium replenishment sources and molar ratios.

[0083] In some embodiments of this application, the method for recycling the fourth-stage particles may include: mixing the fourth-stage particles with a fourth lithium replenishment source, and then calcining the mixture at 500-650°C to obtain regenerated polycrystalline cathode material. Preferably, the calcination temperature may be 600-650°C.

[0084] In this application, the fourth-stage particles (i.e., complete polycrystalline large particles) can be regenerated by lithium supplementation roasting.

[0085] In some specific embodiments, the fourth lithium source may be one or more of lithium hydroxide and lithium carbonate.

[0086] In some specific embodiments, the molar ratio of the fourth-stage particles (based on the molar amount of lithium) to the fourth lithium replenishment source (based on the molar amount of lithium) can be 1:0.05-1:0.2, for example, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2. Preferably, the molar ratio is 1:0.08-1:0.17. More preferably, the molar ratio is 1:0.1-1:0.15.

[0087] This application enables the regenerated polycrystalline cathode material to possess high capacity and cycle performance by selecting specific lithium replenishment sources and molar ratios.

[0088] This application classifies waste polycrystalline cathode material particles into first-level particles and second-level particles based on a first classification threshold, and further classifies the second-level particles into third-level particles and fourth-level particles based on a second classification threshold. Then, the mixture of first-level particles and a first lithium source is regenerated into polycrystalline cathode material through spray granulation or wet recycling processes. The mixture of third-level particles and a third lithium source is calcined into single-crystal cathode material at 700-900℃, and the mixture of fourth-level particles and a fourth lithium source is calcined into polycrystalline cathode material at 500-650℃. This achieves separate recycling of the three types of particles, avoiding the performance degradation of the recycled cathode material caused by mixing large, medium, and small particles during recycling, thereby improving the performance of the recycled cathode material.

[0089] The second aspect of this application provides a cathode material obtained according to the recycling method described in the first aspect of this application.

[0090] Because the cathode material is obtained using the recycling method described in this application, it has improved performance.

[0091] A third aspect of this application provides a positive electrode sheet, comprising the positive electrode material described in the second aspect of this application.

[0092] Because the cathode material obtained by the recycling method of this application is used, the cathode sheet of this application has improved performance.

[0093] A fourth aspect of this application provides a lithium-ion battery, including the positive electrode sheet described in the third aspect of this application.

[0094] Because the cathode material obtained by the recycling method of this application is used, the lithium-ion battery of this application has high specific capacity and capacity retention.

[0095] Figure 1A flowchart of the recycling method of this application is provided. The invention will be further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0096] Recycling of waste polycrystalline cathode materials

[0097] Example 1

[0098] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0099] 2. Soak the positive electrode sheet obtained in the first step in dimethyl carbonate (DMC) for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode sheet at 80°C.

[0100] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0101] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil and sieve it; then, it is ball-milled for 0.5 hours to crush the large particles with cracks, and a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1) is obtained, wherein the zirconium ball diameter is 5 mm and the linear velocity is 5 m / s.

[0102] 5. Adjust the airflow in the classifier and divide the positive electrode particles obtained in step 4 into 3 particle size ranges according to the first classification threshold of 1μm and the second classification threshold of 6μm: 6-15μm (fourth-level particles), 1-6μm (third-level particles), and <1μm (first-level particles).

[0103] 6. The lithium loss of the cathode particles obtained in step 4 was found to be approximately 10% using inductively coupled plasma atomic emission spectrometry (ICP).

[0104] 7. The fourth-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the fourth-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 600°C for 6 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0105] 8. The third-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the third-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 850°C for 10 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated single-crystal cathode powder.

[0106] 9. The first-stage granular powder is ball-milled and mixed with lithium hydroxide, wherein the molar ratio of the first-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). After spray granulation, the mixture is calcined at 600°C for 6 hours in an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0107] Example 2

[0108] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0109] 2. Soak the positive electrode sheet obtained in the first step in dimethyl carbonate (DMC) for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode sheet at 80°C.

[0110] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0111] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil and sieve it; then, it is ball-milled for 0.5 hours to crush the large particles with cracks, and a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1) is obtained, wherein the zirconium ball diameter is 5 mm and the linear velocity is 5 m / s.

[0112] 5. Adjust the airflow in the classifier and divide the positive electrode particles obtained in step 4 into 3 particle size ranges according to the first classification threshold of 1μm and the second classification threshold of 6μm: 6-15μm (fourth-level particles), 1-6μm (third-level particles), and <1μm (first-level particles).

[0113] 6. The lithium loss of the cathode particles obtained in step 4 was found to be approximately 10% using inductively coupled plasma atomic emission spectrometry (ICP).

[0114] 7. The fourth-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the fourth-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 600°C for 6 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0115] 8. The third-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the third-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 850°C for 10 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated single-crystal cathode powder.

[0116] 9. Place the first-stage granular powder into a stirring tank, and add sulfuric acid solution and sodium thiosulfate solid into the stirring tank. The concentration of sulfuric acid is 0.5 mol / L, the solid-liquid ratio of the positive electrode sheet to the sulfuric acid solution is 20 g / L, the mass ratio of the positive electrode sheet to sodium thiosulfate is 2:1, the reaction temperature is 45℃, the reaction time is 1 h, and after the reaction is completed, filter to obtain a mixed solution containing nickel, cobalt, manganese and lithium elements.

[0117] 10. Nickel sulfate, cobalt sulfate, and manganese sulfate are added to a mixed solution to obtain a mixed salt solution, wherein the molar ratio of nickel, cobalt, and manganese in the obtained mixed salt solution is Ni:Co:Mn = 60:20:20. The mixed salt solution, sodium hydroxide, and ammonia are added to a continuous reactor to undergo a co-precipitation reaction. After filtration, the NCM precursor (Ni... 0.6 Co 0.2 Mn 0.2 The reaction mixture (OH)2, wherein the concentration of the mixed salt is 1.5 mol / L, the concentration of sodium hydroxide is 8 mol / L, the mass fraction of ammonia is 25%, the reaction temperature is 55℃, and the reaction time is 48 h.

[0118] 11. After filtration, the solvent in the filtrate is evaporated at 70°C, and wet lithium hydroxide is obtained by recrystallization. After drying, lithium hydroxide powder is obtained.

[0119] 12. The NCM precursor and lithium hydroxide powder were mixed evenly at a molar ratio of 1:1.05, calcined at 750℃ for 10 hours under an oxygen atmosphere, crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder (Li(Ni)). 0.6 Co 0.2 Mn 0.2 O2).

[0120] Example 3

[0121] Example 3 was carried out according to the method described in Example 1, except that the molar ratio in steps 7-9 was 1:0.1.

[0122] Example 4

[0123] Example 4 was carried out according to the method described in Example 1, except that the calcination temperature in step 8 was 600°C.

[0124] Example 5

[0125] Example 5 was carried out according to the method described in Example 1, except that the roasting time in step 8 was 6 hours.

[0126] Comparative Example 1: Particles were not graded

[0127] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0128] 2. Soak the positive electrode obtained in the first step in DMC for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode at 80°C.

[0129] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0130] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil and sieve it; then, it is ball-milled for 0.5 hours to crush the large particles with cracks, and a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1) is obtained, wherein the zirconium ball diameter is 5 mm and the linear velocity is 5 m / s.

[0131] 5. The lithium loss of the cathode particles obtained from the fourth step of ICP detection is approximately 10%.

[0132] 6. Mix the positive electrode powder with lithium hydroxide, wherein the molar ratio of the positive electrode powder to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). Calcinate at 600℃ for 6 hours in an oxygen atmosphere. After natural cooling, crush, sieve, and demagnetize to obtain regenerated positive electrode powder.

[0133] Comparative Example 2: Particles were not subjected to ball milling.

[0134] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0135] 2. Soak the positive electrode obtained in the first step in DMC for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode at 80°C.

[0136] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0137] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil, which is then sieved to obtain a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1).

[0138] 5. Adjust the airflow in the classifier and divide the positive electrode particles obtained in step 4 into 3 particle size ranges according to the first classification threshold of 1μm and the second classification threshold of 6μm: 6-15μm (fourth-level particles), 1-6μm (third-level particles), and <1μm (first-level particles).

[0139] 6. The lithium loss of the cathode particles obtained from the fourth step of ICP detection is approximately 10%.

[0140] 7. The fourth-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the fourth-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 600°C for 6 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0141] 8. The third-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the third-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 850°C for 10 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated single-crystal cathode powder.

[0142] 9. The first-stage granular powder is ball-milled and mixed with lithium hydroxide, wherein the molar ratio of the first-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). After spray granulation, the mixture is calcined at 600°C for 6 hours in an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0143] Comparative Example 3: Particles were not ball-milled, not classified, and recovered using wet processing.

[0144] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0145] 2. Soak the positive electrode obtained in the first step in DMC for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode at 80°C.

[0146] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0147] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil, which is then sieved to obtain a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1).

[0148] 5. Place the positive electrode obtained in step 4 into an immersion tank, and add sulfuric acid solution and sodium thiosulfate solid to the immersion tank. The concentration of sulfuric acid solution is 0.5 mol / L, the solid-liquid ratio of positive electrode to sulfuric acid solution is 20 g / L, the mass ratio of positive electrode to sodium thiosulfate is 2:1, the reaction temperature is 45℃, the reaction time is 6 h, and after the reaction is completed, filter to obtain a mixed solution containing nickel, cobalt, manganese and lithium elements.

[0149] 6. Nickel sulfate, cobalt sulfate, and manganese sulfate are added to a mixed solution to obtain a mixed salt solution, wherein the molar ratio of nickel, cobalt, and manganese in the obtained mixed salt solution is Ni:Co:Mn = 60:20:20. The mixed salt solution, sodium hydroxide, and ammonia are added to a continuous reactor to undergo a co-precipitation reaction. After filtration, the NCM precursor (Ni... 0.6 Co 0.2 Mn 0.2 The reaction mixture (OH)2, wherein the concentration of the mixed salt is 1.5 mol / L, the concentration of sodium hydroxide is 8 mol / L, the mass fraction of ammonia is 25%, the reaction temperature is 55℃, and the reaction time is 48 h.

[0150] 7. After filtration, the solvent in the filtrate is evaporated at 70°C, and wet lithium hydroxide is obtained by recrystallization. After drying, lithium hydroxide powder is obtained.

[0151] 8. The NCM precursor and lithium hydroxide powder were mixed evenly at a molar ratio of 1:1.05, calcined at 750℃ for 10 hours under an oxygen atmosphere, crushed, sieved, and demagnetized to obtain regenerated cathode powder (Li(Ni)). 0.6 Co 0.2 Mn 0.2 O2).

[0152] Comparative Example 4: The first and second grading thresholds are not within the range defined in this application.

[0153] 1. Discharge the used NCM622 battery cells in NaCl solution for 1 day, then disassemble them and separate the positive and negative electrode plates, separator and electrolyte.

[0154] 2. Soak the positive electrode obtained in the first step in DMC for 1 day to remove electrolyte and additives. After filtration, dry the positive electrode at 80°C.

[0155] 3. The positive electrode obtained in the second step is calcined at 500°C for 5 hours in an air atmosphere to remove impurities such as conductive carbon and binder on the surface.

[0156] 4. The positive electrode sheet obtained in step 3 is mechanically crushed to separate the aluminum foil and sieve it; then, it is ball-milled for 0.5 hours to crush the large particles with cracks, and a mixture of large, medium and small positive electrode particles (referred to as mixed particles in Table 1) is obtained, wherein the zirconium ball diameter is 5 mm and the linear velocity is 5 m / s.

[0157] 5. Adjust the airflow in the classifier and divide the positive electrode particles obtained in step 4 into 3 particle size ranges according to the first classification threshold of 3μm and the second classification threshold of 4μm: 4-18μm (fourth-level particles), 3-4μm (third-level particles), and <3μm (first-level particles).

[0158] 6. The lithium loss of the cathode particles obtained from the fourth step of ICP detection is approximately 10%.

[0159] 7. The fourth-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the fourth-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 600°C for 6 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0160] 8. The third-stage granular powder is mixed with lithium hydroxide, wherein the molar ratio of the third-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). The mixture is calcined at 850°C for 10 hours under an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated single-crystal cathode powder.

[0161] 9. The first-stage granular powder is ball-milled and mixed with lithium hydroxide, wherein the molar ratio of the first-stage granules to the lithium hydroxide is 1:0.15 (referred to as the lithium supplementation ratio in Table 1). After spray granulation, the mixture is calcined at 600°C for 6 hours in an oxygen atmosphere. After natural cooling, it is crushed, sieved, and demagnetized to obtain regenerated polycrystalline cathode powder.

[0162] Lithium-ion batteries were prepared using the recycled cathode powders prepared in Examples 1-4 and Comparative Examples 1-3, according to the general preparation method described below. The recycled cathode powders in Examples 1-4 and Comparative Example 2 each comprised three types: two types of recycled polycrystalline cathode powder and one type of recycled monocrystalline cathode powder. Each type of recycled cathode powder corresponds to one lithium-ion battery.

[0163] Preparation of lithium-ion batteries

[0164] The prepared regenerated positive electrode powder, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1.5:1.5, and N-methylpyrrolidone (NMP) solvent was added. After mixing evenly, a positive electrode slurry was obtained. The positive electrode slurry was then uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0165] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. They are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 100°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product.

[0166] Test of relevant parameters of cathode material

[0167] 1. Volume average particle size test

[0168] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20ml of deionized water, and simultaneously incubate for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0169] The test subjects included: the D50 values ​​of the graded particles (i.e., first-grade, second-grade, and fourth-grade particles) in Examples 1-4 and Comparative Example 2; the D50 values ​​of the mixed particles in Comparative Examples 1 and 3; and the D50, D10, and D90 values ​​of all regenerated particles (i.e., regenerated cathode powder) in Examples 1-4 and Comparative Examples 1-3. The Span value was calculated based on the D50, D10, and D90 values. The results are shown in Table 1 below.

[0170] 2. Morphological testing

[0171] All regenerated cathode powders prepared in the examples and comparative examples were tested using a ZEISS Sigma 300 scanning electron microscope, and then the morphology of the samples was observed according to standard JY / T010-1996. The test results are as follows. Figure 2-7 As shown.

[0172] It should be noted that the shape of the recycled cathode material in this application is not necessarily spherical; it may also be irregular, and can be either primary or secondary particles.

[0173] Table 1

[0174]

[0175]

[0176]

[0177]

[0178] Note: Span = (D90 - D10) / D50, which represents the particle size distribution.

[0179] Battery performance test

[0180] 1. Battery capacity retention test

[0181] Taking Example 1 as an example, the battery capacity retention rate test process is as follows: At 45°C, the lithium-ion battery corresponding to Example 1 is charged to 4.3V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.3V, left to rest for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded simultaneously. Then, the battery capacity retention rate Pn after each cycle is Pn = Cn / C0 * 100%.

[0182] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 200th cycle to n=200. The battery capacity retention rate data corresponding to Example 1 in Table 2 is the data measured after 200 cycles under the above test conditions, i.e., the value of P200.

[0183] The testing procedures for other embodiments and comparative examples are the same as above.

[0184] 2. Specific capacity test

[0185] At 25℃, the lithium-ion battery was charged to 4.3V at a constant current of 1 / 3C, then charged to 0.05C at a constant voltage of 4.3V, left to rest for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. The specific capacity was calculated as C0 / (m*97%), where m is the coating weight of the positive electrode active material (i.e., the recycled positive electrode powder) of the battery cell. The test results are shown in Table 2 below.

[0186] Table 2

[0187]

[0188]

[0189] A comparison of Example 1 and Comparative Example 1 shows that Comparative Example 1 did not grade the mixed large, medium, and small cathode particles. The specific capacity and capacity retention of the lithium-ion battery corresponding to Comparative Example 1 are significantly lower than those of the lithium-ion battery corresponding to Example 1. This indicates that grading the mixed large, medium, and small cathode particles can significantly improve their performance.

[0190] By comparing Example 1 and Comparative Example 2, it can be seen that Comparative Example 2 did not ball mill the mixed large, medium and small cathode particles. The regenerated cathode powder obtained from the fourth-level particles in Comparative Example 2 contains large cracked particles, which leads to its performance being inferior to that of the regenerated cathode powder obtained from the fourth-level particles in Example 1. Consequently, the specific capacity and capacity retention of the corresponding battery are lower.

[0191] By comparing Example 1 and Comparative Example 3, it can be seen that Comparative Example 3 did not undergo light ball milling or particle classification. The recycled cathode material obtained by wet recycling in Comparative Example 3 has higher capacity and cycle performance, but the entire recycling process is complicated, time-consuming and costly.

[0192] By comparing Example 1 and Comparative Example 4, it can be seen that the first and second grading thresholds of Comparative Example 4 are not within the ranges defined in this application (the first grading threshold is 0.8-1.5 μm, and the second grading threshold is 5-8 μm). The capacity and cycle performance of the regenerated cathode material obtained in Comparative Example 4 are significantly lower. This indicates that the selection of the first and second grading thresholds has a significant impact on the capacity and cycle performance of the regenerated cathode material.

[0193] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for recycling waste polycrystalline cathode materials, characterized in that, include: Provides waste polycrystalline cathode material particles; A first classification threshold is set, and the polycrystalline cathode material particles are classified according to the first classification threshold to obtain first-level particles with a particle size smaller than the first classification threshold and second-level particles with a particle size greater than or equal to the first classification threshold; and The recovery of the first-stage particles includes spray granulation or wet recovery. Wherein, the first grading threshold is 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm or 1.5μm; A second classification threshold is set, and the second-level particles are classified according to the second classification threshold to obtain third-level particles with a particle size smaller than the second classification threshold and fourth-level particles with a particle size greater than or equal to the second classification threshold. The second classification threshold is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, or 8 μm. The recovery of the third-stage particles includes mixing them with a third lithium source and then calcining them at a temperature greater than 800°C and less than 900°C. The recovery of the fourth-stage particles involves mixing them with a fourth lithium source and then calcining them at 500-650°C. The polycrystalline cathode material is a polycrystalline ternary cathode material Li[Ni]. x Co y Mn 1-x-y O2, where 0 <x < 1,0 < y < 1,0 < 1-x-y < 1。 2. The recycling method according to claim 1, characterized in that, At least some of the polycrystalline cathode material particles have cracks, and before grading according to the first grading threshold, the method further includes: ball milling the polycrystalline cathode material particles to break the polycrystalline cathode material particles with cracks.

3. The recycling method according to claim 2, characterized in that, The ball milling time is 10-120 min.

4. The recycling method according to claim 1, characterized in that, Recycling the first-stage particles includes: After mixing the first-stage particles with the first lithium source, spray granulation is performed, followed by calcination to obtain the regenerated polycrystalline cathode material. Alternatively, recycling the first-stage particles may involve: performing wet recycling of the first-stage particles to obtain recycled cathode material.

5. The recycling method according to claim 4, characterized in that, The first lithium source is one or more of lithium hydroxide and lithium carbonate; The molar ratio of the first-stage particles (based on the molar amount of lithium) to the first lithium replenishment source (based on the molar amount of lithium) is 1:0.05-1:0.

2.

6. The recycling method according to claim 4 or 5, characterized in that, After spray granulation, the product is calcined at 500-650℃.

7. The recycling method according to claim 1, characterized in that, The third lithium source is one or more of lithium hydroxide and lithium carbonate; The molar ratio of the third-stage particles to the third lithium source, measured in molar amounts of lithium, is 1:0.05-1:0.

2.

8. The recycling method according to claim 1, characterized in that, The fourth lithium source is one or more of lithium hydroxide and lithium carbonate; The molar ratio of the fourth-stage particles to the fourth lithium source, measured in molar amounts of lithium, is 1:0.05-1:0.

2.

9. A positive electrode material, characterized in that, Obtained by the recycling method according to any one of claims 1-8.

10. A positive electrode plate, characterized in that, Includes the cathode material as described in claim 9.

11. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 10.

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