A method for removing impurities from a waste positive electrode material leaching solution and regenerating the positive electrode material

Abstract

The present application belongs to the technical field of waste lithium ion battery recycling, and more particularly relates to a method for removing impurities from a waste positive electrode material leaching solution and regenerating a positive electrode material. First, the leaching solution is mixed with a metal complexing agent, heated and evaporated to obtain a sol-gel precursor, and then the precursor is pre-calcined to obtain a product to be removed impurities. During the pre-calcination process, cobalt, nickel and manganese elements form metal oxides, while inorganic anion or cation impurities still exist as water-soluble components, which can be removed by washing with water. After supplementing lithium to the solid phase obtained by solid-liquid separation, high-temperature calcination obtains regenerated lithium ion positive electrode material. Experiments show that the method can avoid the influence of impurities in the leaching solution on the regenerated positive electrode material, and the regenerated positive electrode material obtained can be assembled into a battery, and the battery has excellent electrochemical performance, with a capacity of 90% or more of the directly purchased commercial fresh positive electrode material.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery recycling technology. Specifically, it relates to a method for removing impurities and regenerating cathode materials from leachate of waste cathode materials. More specifically, it relates to a method for removing impurities and regenerating cathode materials from leachate of waste lithium-ion battery cathode materials. Background Technology

[0002] Lithium-ion batteries, as a new type of energy storage device, possess characteristics such as high capacity, flexible and wide operating conditions, high energy density, and good safety, and have been widely used in various fields, including renewable energy storage, new energy vehicles, and portable electronic devices. With technological advancements, an increasing number of commercially available electronic products are using lithium-ion batteries as energy storage units. Furthermore, considering the rapidly growing demand for lithium-ion batteries from the electric vehicle industry, the usage of lithium-ion batteries is facing a leapfrog increase. Given the current rapid growth in battery production and consumption, the number of retired lithium-ion batteries will continue to increase. If they are not properly disposed of, they will cause serious environmental problems. The cathode materials of waste lithium-ion batteries typically contain valuable metal elements such as lithium, cobalt, manganese, and nickel. Cobalt, in particular, is a strategic metal widely used in military and industrial fields and is the most valuable metal element in waste lithium-ion batteries. Recycling and regenerating lithium-ion batteries can avoid environmental pollution while generating considerable economic benefits.

[0003] Currently, the main method for processing spent lithium-ion battery cathode materials involves leaching with sulfuric acid, hydrochloric acid, nitric acid, acetic acid, malic acid, or citric acid under hydrothermal, ultrasonic, or microwave-assisted conditions. Subsequently, various metals are separated and recovered through pH adjustment, the addition of precipitants, and extraction for reuse. However, this traditional leaching-separation-purification method suffers from drawbacks such as cumbersome procedures, high reagent consumption, long processing times, and severe secondary pollution. Compared to traditional recycling methods, direct regeneration of battery materials holds significant potential in terms of environmental protection and manufacturing cost reduction. Therefore, direct regeneration of lithium-ion battery cathode materials through leaching solutions is widely considered an excellent pathway to improve the recycling efficiency of spent lithium-ion batteries.

[0004] The main methods for directly regenerating lithium-ion battery cathode materials from leachates include solid-state sintering, co-precipitation, and sol-gel methods. Compared with other methods, the lithium-ion battery cathode materials regenerated by the sol-gel method have advantages such as complete crystal structure, ordered metal arrangement, and small particle size, and exhibit excellent electrochemical performance. However, impurities in the leachate can hinder the regeneration of cathode materials and damage the crystal phase of the regenerated material. How to remove impurities from the leachate of lithium-ion battery cathode materials and regenerate them into cathode materials has become a difficult problem in this field. Some existing technologies, such as patent document CN111924900A, remove impurities from the cathode material leachate by adding additional removal agents. Introducing additional removal agents during the removal process increases costs and introduces new impurities, without considering the removal of cationic impurities. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for removing impurities and regenerating cathode materials from leachate of spent lithium-ion battery cathode materials. This method fully incorporates the compositional characteristics of leachate from spent lithium-ion battery cathode materials in existing technologies, specifically proposing the addition of a metal complexing agent to form a sol-gel precursor. The regenerated cathode material is then prepared through preliminary pre-calcination, water washing for impurity removal, lithium replenishment, and high-temperature calcination. This solves the technical problems of existing technologies, such as the introduction of new impurities during impurity removal from spent cathode material leachate, and the poor impurity removal effect affecting the electrochemical performance of the regenerated cathode material.

[0006] To achieve the above objectives, the present invention provides a method for removing impurities from the leachate of spent lithium-ion battery cathode materials. The leachate contains, in addition to lithium ions, one or more of nickel ions, cobalt ions, and manganese ions, as well as impurities. The method includes the following steps:

[0007] (1) The leachate of the waste lithium-ion battery cathode material is mixed with a metal complexing agent and then evaporated under heating conditions to obtain a sol-gel precursor.

[0008] (2) The sol-gel precursor is pre-calcined in an oxygen-containing atmosphere to form metal oxides of nickel, cobalt and manganese elements, thereby obtaining the product to be purified.

[0009] (3) The product to be purified is washed with water to remove impurities. The lithium ions and impurities are removed during the water washing process. The solid product obtained after water washing is rich in metal oxides containing nickel, cobalt and manganese.

[0010] Preferably, the cathode material of the waste lithium-ion battery is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide.

[0011] Preferably, the leachate of the waste lithium-ion battery cathode material is the filtrate obtained after leaching the cathode material in an acid and / or alkali and separating the solid and liquid components; wherein the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, tartaric acid, citric acid, and malic acid; and the alkali is sodium hydroxide or ammonia.

[0012] Preferably, the impurity is one or more of inorganic anions, organic anions, and inorganic cations; the inorganic anionic impurity is one or more of nitrate, chloride, fluoride, and sulfate; the inorganic cationic impurity is sodium and / or potassium ions; and the organic anion is one or more of acetate, citrate, malate, and tartrate.

[0013] Preferably, the metal complexing agent in step (1) is one or more of citric acid, ethylenediaminetetraacetic acid, malic acid, acetic acid, methanol, and ethanol, and the molar amount of the metal complexing agent added is 1-3 times the sum of the molar amounts of nickel, cobalt, and manganese in the leachate.

[0014] Preferably, the heating conditions in step (1) are heating to 60℃-120℃.

[0015] Preferably, the pre-calcination in step (2) has a calcination temperature of 300-500℃ and a calcination time of 180min-360min.

[0016] Preferably, in step (3), deionized water is used to rinse the product to be cleaned multiple times, and the ratio of the amount of deionized water used in a single rinse to the mass of the material to be cleaned is 10 ml / g to 50 ml / g.

[0017] According to another aspect of the present invention, a method for regenerating lithium-ion battery cathode materials using the solid-phase product obtained by the aforementioned impurity removal method is provided, comprising the steps of:

[0018] Lithium carbonate was added to the solid product obtained after water washing and impurity removal, and the mixture was stirred evenly. Then, a second calcination was carried out to obtain the regenerated cathode material.

[0019] Preferably, the molar amount of lithium carbonate added is 1 to 1.15 times the sum of the molar amounts of nickel, cobalt, and manganese in the leachate.

[0020] Preferably, the second calcination is carried out at a temperature of 800-950℃ and for a time of 600-900 minutes.

[0021] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0022] (1) This invention proposes a method for removing impurities and regenerating cathode materials from leachate of spent lithium-ion battery cathode materials. First, the leachate is mixed with a metal complexing agent and heated to evaporate, yielding a sol-gel precursor. Then, this precursor is pre-calcined to obtain the product to be removed. During the pre-calcination process, cobalt, nickel, and manganese elements form metal oxides, while inorganic anionic or cationic impurities remain as water-soluble components. Experiments show that water washing can remove the impurities. After solid-liquid separation and lithium replenishment of the solid phase, high-temperature calcination yields the regenerated cathode material. Experiments show that the regenerated cathode material obtained by the impurity removal and regeneration method of this invention, when assembled into a battery, exhibits excellent electrochemical performance, with a capacity reaching 90% or more of that of commercially available fresh cathode materials.

[0023] (2) This invention uses a metal complexing agent to prepare a sol-gel precursor, directly regenerating the cathode material from the leachate of spent lithium-ion battery cathode materials. Compared with traditional cathode material recycling methods, this avoids the disadvantages of cumbersome steps, significant impurity impact, high reagent consumption, and severe secondary pollution, achieving a short-process, high-efficiency recovery of valuable metal resources. Furthermore, because the complexing agent forms metal-organic coordination bonds with nickel, cobalt, and manganese metal ions through a complexation reaction, the metal ions exhibit a more uniform dispersion and binding capacity in the prepared sol-gel precursor. This results in lithium-ion battery cathode materials regenerated using this method possessing advantages such as a complete layered crystal structure, orderly metal arrangement, and small particle size, as well as excellent electrochemical performance.

[0024] (3) This invention converts soluble nickel, cobalt, and manganese metal ions in the sol-gel precursor into insoluble metal oxides through pre-calcination, and removes impurity elements from the leachate of waste lithium-ion battery cathode materials through a simple water washing separation process. Depending on the difference between the preparation process and the recycling process, different impurity elements may be introduced into the leachate of lithium-ion battery cathode materials, such as SO4 introduced through inorganic acid leaching. 2- NO3 - Cl - In addition to organic acid anion impurities, and the Na introduced by the added leaching enhancer. + K + Alkali metal salt ions are introduced as impurities. These ions can severely impact the regeneration process, hindering the formation of the crystal structure of the lithium-ion battery cathode material during regeneration by competing for lithium sources and impeding lattice growth. Na + K + During pre-calcination and calcination, metal ions occupy lithium vacancies in the positive electrode material of lithium-ion batteries, generating impurity phases such as NaCoO2 and KCoO2, and reacting with CO2 in the air to form carbonates such as Na2CO3 and K2CO3; SO4 2- NO3 - Cl -Impurity ions will significantly compete with Li during calcination. + The formation of impurity crystalline phases such as KLiSO4 and NaLiSO4 hinders lattice formation, preventing the orderly distribution of nickel, cobalt, and manganese metals, which are thus retained as single-metal oxide crystals such as NiO, Co3O4, and MnO2. During the pre-calcination process, the organic impurities in the precursor are converted into carbon dioxide and escape under heat treatment conditions. During the water washing process, the content and morphology of the key metal elements nickel, cobalt, and manganese remain unaffected, and their structures are fully preserved to ensure that the regenerated lithium-ion battery cathode material obtained in the subsequent regeneration process has good crystal form and performance. The impurity elements dissolve in deionized water in the form of soluble salts and are completely removed during solid-liquid separation, avoiding interference or obstruction to the formation of crystalline phases in the cathode material during the subsequent calcination process.

[0025] (4) This invention uses oxygen in the air to oxidize nickel, cobalt and manganese metals under high temperature conditions during calcination to obtain insoluble metal oxides for subsequent impurity removal and regeneration. This avoids the use of high-purity experimental gases, reduces the resource consumption of the recycling process and reduces additional processing steps, thus achieving clean and safe recycling of lithium-ion battery cathode materials.

[0026] (5) This invention realizes the development of a new method for recycling and reusing retired lithium-ion battery cathode materials. It directly regenerates lithium-ion battery cathode materials with excellent crystal structure and electrochemical performance from high-concentration valence metal ion leaching solution, which can be directly used for battery preparation and production, and has considerable potential in the field of electronic waste recycling.

[0027] (6) In view of the shortcomings of the prior art in the process of regenerating cathode materials from leachate of retired lithium-ion battery cathode materials, such as complicated recycling steps, large influence of impurities, large consumption of reagents and serious secondary pollution, this invention proposes a method for removing impurities from leachate of waste lithium-ion battery cathode materials and directly preparing regenerated cathode materials. After adding a metal complexing agent to the leachate and evaporating it to form a sol-gel precursor, nickel, cobalt and manganese metals are oxidized and retained in the solid phase by pre-calcination. Water-soluble impurity ions are removed by washing with water. After drying and replenishing lithium, the mixture is thoroughly ground and mixed, and finally calcined to obtain regenerated lithium-ion battery cathode materials. This invention utilizes a green and safe method to regenerate lithium-ion battery cathode materials using leachate from retired lithium-ion battery cathode materials as raw materials. The method employs a sol-gel process to regenerate the cathode materials, retaining nickel, cobalt, and manganese metals through calcination and removing impurity ions from the leachate through water washing. This eliminates the interference of impurity ions on the direct regeneration process, achieving a short-process, high-efficiency recovery of valuable metal resources. Furthermore, it is low-cost, pollution-free, safety-free, and simple in process. It is applicable to leachate from various types of waste lithium-ion battery cathode materials, easily scalable for production, and has promising prospects for widespread application. Attached Figure Description

[0028] Figure 1 The flowchart illustrates a method for removing impurities from leachate of waste lithium-ion battery cathode materials and directly preparing recycled cathode materials, as provided by this invention.

[0029] Figure 2 The X-ray diffraction (XRD) results are shown for intermediate products and regenerated cathode materials from the leaching solution of waste lithium-ion battery cathode materials in Example 2.

[0030] Figure 3 The results of scanning electron microscopy (SEM) are shown for the cathode material regenerated from the leachate of waste lithium-ion battery cathode material in Example 2 after impurity removal.

[0031] Figure 4 The results of single-rate charge-discharge cycle testing of the cathode material regenerated from the leachate of waste lithium-ion battery cathode material in Example 3 after impurity removal.

[0032] Figure 5 The results of multi-rate charge-discharge cycle testing of the cathode material regenerated from the leachate of waste lithium-ion battery cathode material in Example 3 after impurity removal.

[0033] Figure 6 The results of the volt-ampere cycle test are for the cathode material regenerated from the leachate of waste lithium-ion battery cathode material in Example 3 after impurity removal.

[0034] Figure 7 This is a comparison of the X-ray diffraction (XRD) results of the purified and regenerated cathode material in Comparative Example 1 with those of the unpurified and directly regenerated cathode material.

[0035] Figure 8 The results of multi-rate charge-discharge cycle tests are shown for the impurity-regenerated cathode material and the unregenerated direct-regenerated cathode material in Comparative Example 1. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] This invention provides a method for removing impurities and regenerating cathode materials from leachate of spent lithium-ion battery cathode materials. The leachate contains, in addition to lithium ions, one or more of nickel, cobalt, and manganese ions, and also one or more of organic anions, inorganic anions, and inorganic cations. The method uses the leachate of spent lithium-ion battery cathode materials as raw material, with a permetal complexing agent as an auxiliary additive, and obtains regenerated lithium-ion battery cathode materials through evaporation, pre-calcination, impurity removal, and calcination regeneration. Figure 1As shown, the specific steps include the following:

[0038] (1) The leachate of the waste lithium-ion battery cathode material is mixed with a metal complexing agent and then evaporated under heating conditions to obtain a sol-gel precursor.

[0039] (2) The sol-gel precursor is pre-calcined in an oxygen-containing atmosphere to form metal oxides of nickel, cobalt and manganese elements, thereby obtaining the product to be purified.

[0040] (3) The product to be purified is washed with water and then separated into solid and liquid phases. The lithium ions, inorganic anions and cationic impurities are removed during the water washing process and enter the liquid phase obtained after solid-liquid separation.

[0041] (4) Add lithium carbonate to the solid product obtained after solid-liquid separation, mix evenly, and then calcine for a second time to obtain the regenerated cathode material.

[0042] The cathode material of the waste lithium-ion battery described in this invention is one or a combination of two or more of the following ternary cathode materials: lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide.

[0043] The leachate for waste lithium-ion battery cathode materials described in this invention is obtained by leaching waste lithium-ion battery cathode materials using a leaching agent. The leaching agent includes, but is not limited to, acids, alkalis, oxidants, reducing agents, and various additives. Correspondingly, the introduction of various leaching agents introduces corresponding impurities along with lithium, cobalt, nickel, and manganese ions into the leachate. For example, leaching with inorganic acids such as sulfuric acid, nitric acid, or hydrochloric acid introduces a large amount of inorganic anionic impurities. Additives, reducing agents, or pH adjusters added during the leaching process, such as sodium thiosulfate and sodium hydroxide, introduce a large amount of potassium and sodium ions. Furthermore, the cathode material itself may contain impurity metal elements, or battery shell components may have been incorporated during the initial waste battery crushing and mixing process. Additionally, some cathode materials may have been doped with specific elements to improve performance, resulting in impurities such as calcium, magnesium, and lead in the leachate.

[0044] In some embodiments, the leachate of the waste lithium-ion battery cathode material is the filtrate obtained after leaching the cathode material in an acid and / or alkali and then separating the solid and liquid components. The acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, tartaric acid, citric acid, and malic acid; the alkali is sodium hydroxide or ammonia; the inorganic anionic impurities are one or more of nitrate, chloride, fluoride, and sulfate; the inorganic cationic impurities are sodium and / or potassium ions; the organic anionic impurities are one or more of acetate, citrate, malate, and tartrate; and the total concentration of the inorganic anionic impurities, organic anionic impurities, and inorganic cationic impurities is less than or equal to 100 g / L.

[0045] In some embodiments, the mass concentrations of nickel, cobalt, and manganese in the leachate are all less than or equal to 80 g / L.

[0046] In some embodiments, the metal complexing agent in step (1) is one or a combination of two or more of citric acid, ethylenediaminetetraacetic acid, malic acid, acetic acid, methanol, and ethanol, and the molar amount of the metal complexing agent added is 1-3 times the sum of the molar amounts of nickel, cobalt, and manganese in the leachate.

[0047] In some embodiments, the heating conditions in step (1) are heating to 60°C-120°C. Preferably, the water in the leachate is evaporated away under stirring and heating conditions, and the sol-gel precursor is obtained by evaporation.

[0048] In some embodiments, the pre-calcination in step (2) is carried out at a calcination temperature of 300-500℃ and a calcination time of 180min-360min. In a preferred embodiment, the pre-calcination is carried out in a muffle furnace at a heating rate of 2℃ / min-10℃ / min; the calcination atmosphere is an air atmosphere.

[0049] In some embodiments, the product to be purified is rinsed multiple times with deionized water during step (3). In a preferred embodiment, the product is rinsed 3-5 times, and the ratio of the amount of deionized water used in a single rinse to the mass of the material to be purified is 10 ml / g-50 ml / g. After rinsing, solid-liquid separation is performed, such as by vacuum filtration. After vacuum filtration, the filter cake is washed with water, and then the solid phase product obtained after washing is collected by combining solid-liquid separation methods such as centrifugation. The product is then dried, and lithium is added for the next step of regenerating the cathode material.

[0050] In some embodiments, the molar amount of lithium carbonate added in step (4) is 1 to 1.15 times the sum of the molar amounts of nickel, cobalt, and manganese in the leachate. After adding lithium carbonate, uniform mixing can be achieved by grinding.

[0051] In some embodiments, the second calcination in step (4) is carried out at a calcination temperature of 800-950℃ and a calcination time of 600min-900min; in a preferred embodiment, the second calcination is carried out in a tube furnace with a heating rate of 2℃ / min-10℃ / min; and the calcination atmosphere is an air atmosphere.

[0052] The regenerated cathode material obtained by the impurity removal and regeneration method according to the present invention is of the same type as the initial waste lithium-ion battery cathode material, namely, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, or lithium nickel cobalt manganese oxide cathode material. When the regenerated product is a ternary lithium nickel cobalt manganese oxide cathode material, the molar ratio of nickel, cobalt, and manganese metal elements in the leaching solution is any one of 1:1:1, 5:2:3, 6:2:2, or 8:1:1.

[0053] This invention proposes a method for removing impurities and regenerating cathode materials from leachate of spent lithium-ion battery cathode materials. First, a metal complexing agent is added and heated to dryness to form a sol-gel precursor. Then, pre-calcination is performed. By controlling a suitable pre-calcination temperature, it was accidentally discovered that after pre-calcination, cobalt, nickel, and manganese form water-insoluble metal oxides, while inorganic impurities remain in a water-soluble state. These inorganic impurities can be removed by water washing, while organic impurities are ablated and removed by carbon dioxide during pre-calcination. After impurity removal, lithium is added (lithium is also washed off during water washing), followed by high-temperature calcination to obtain a high-performance regenerated cathode material. This invention's steps—adding a metal complexing agent to form a sol-gel precursor, pre-calcination, water washing for impurity removal, and high-temperature calcination after lithium addition—are synergistic and inseparable. The water washing step is introduced between two calcination steps, and the order of these steps cannot be changed; they function as a whole. Ultimately, this impurity removal and regeneration method results in a regenerated cathode material with excellent crystal structure and electrochemical performance. The impurity removal and regeneration method of this invention can avoid the influence of impurities in the leachate on the regeneration process and realize the short-range utilization of leachate from waste lithium-ion battery cathode materials. At the same time, this invention has the advantages of low recycling cost, simple operation, high recovery rate, and no pollution.

[0054] The following is an example:

[0055] Example 1

[0056] This invention provides a method for removing impurities from the leachate of spent lithium-ion battery cathode materials and directly preparing recycled cathode materials, such as... Figure 1 As shown, it includes the following steps:

[0057] (1) 1g of waste lithium-ion battery cathode material was mixed with 50ml of 1.0mol / L dilute sulfuric acid and leached at 80℃ for 2h with stirring. The mixture was then filtered and diluted to obtain a leachate of the waste lithium-ion battery cathode material. 25ml of this leachate was taken, and the concentrations of lithium, nickel, cobalt, and manganese were found to be 0.006g / L, 5.869g / L, 5.893g / L, and 5.494g / L, respectively. The impurity components and their concentrations were as follows: Na... + 0.1 g / L with SO4 2- 2.3 g / L; after adding 4.6 g of ethylenediaminetetraacetic acid and 6.6 g of citric acid, the mixture was stirred and evaporated to dryness at 80 °C to obtain the sol-gel precursor;

[0058] (2) Transfer the sol-gel precursor to a 30ml ceramic crucible, then place it in a muffle furnace and heat it to 300℃ at a heating rate of 10℃ / min in an air atmosphere. Then keep it at 300℃ for calcination for 3h. After calcination and cooling, grind the product to obtain 5g of the product to be purified.

[0059] (3) Rinse 5g of the product to be purified with 100ml of deionized water and filter. Rinse the filter cake and centrifuge. Repeat three times. Dry the separated solid product at 40℃. After drying, add 0.61g of lithium carbonate, grind and mix evenly to obtain the purified product.

[0060] (4) The purified product was transferred to a 30ml ceramic crucible and then placed in a tube furnace and heated to 850℃ at a heating rate of 5℃ / min in an air atmosphere. The product was then calcined at 850℃ for 10h. After calcination and cooling, the product was ground to obtain 0.762g of regenerated lithium-ion battery cathode material.

[0061] Example 2

[0062] (1) The leachate preparation steps are the same as in Example 1. Take 10 ml of leachate from waste lithium-ion battery cathode material with lithium, nickel, cobalt, and manganese concentrations of 0.006 g / L, 5.869 g / L, 5.893 g / L, and 5.494 g / L, respectively. The impurity components and concentrations contained therein are as follows: Na + 0.1 g / L with SO4 2- 2.3 g / L; after adding 1.84 g of ethylenediaminetetraacetic acid and 2.64 g of citric acid, the mixture was stirred and evaporated to dryness at 80 °C to obtain the sol-gel precursor;

[0063] (2) Transfer the sol-gel precursor to a 30ml ceramic crucible, then place it in a muffle furnace and heat it to 300℃ at a heating rate of 10℃ / min in an air atmosphere. Then keep it at 300℃ for calcination for 3h. After calcination and cooling, grind the product to obtain 2g of the product to be removed.

[0064] (3) Wash 2g of the product to be purified with 40ml of deionized water and filter it. Wash the filter cake and centrifuge it. Repeat this process three times. Dry the separated solid product at 40℃. After drying, add 0.244g of lithium carbonate, grind and mix evenly to obtain the purified product.

[0065] (4) The purified product was transferred to a 30ml ceramic crucible and then placed in a tube furnace and heated to 850℃ at a heating rate of 5℃ / min in an air atmosphere. The product was then calcined at 850℃ for 10h. After calcination and cooling, the product was ground to obtain 0.762g of regenerated lithium-ion battery cathode material.

[0066] (5) The product to be purified, the purified product, and the regenerated lithium-ion battery cathode material obtained in the previous step were analyzed and characterized using X-ray diffraction and scanning electron microscopy. The characterization results are as follows: Figure 2 , Figure 3 As shown; Figure 2Content (i) shows the analytical results of the product to be purified obtained in this embodiment, which shows a distinct LiNaSO4 impurity phase, indicating that Na + SO4 2- Impurities can hinder the regeneration process of leachate from waste lithium-ion battery cathode materials; Figure 2 The analysis results of the product after impurity removal (ii) are shown in the middle. No characteristic diffraction peaks were observed in the product after impurity removal, indicating that the original impurities were completely removed after water washing. Figure 2 Content (iii) corresponds to the analysis results of the cathode material obtained from the leachate of waste lithium-ion battery cathode material regeneration, indicating that the lithium-ion battery cathode material obtained after impurity removal and regeneration by this process has a very good crystal structure. Figure 3 The scanning electron microscope (SEM) test results of the regenerated cathode material show that the regenerated cathode material consists of crystal particles with a complete layered structure and a particle size of about 10 μm. The particles are uniform in size, well dispersed, and there is no obvious agglomeration or structural collapse.

[0067] Example 3

[0068] (1) The leachate was obtained in the same way as in Example 1. 25 ml of leachate from waste lithium-ion battery cathode material with lithium, nickel, cobalt, and manganese concentrations of 0.006 g / L, 5.869 g / L, 5.893 g / L, and 5.494 g / L, respectively, was taken. The impurity components and their concentrations were as follows: Na + 0.1 g / L with SO4 2- 2.3 g / L; after adding 4.6 g of ethylenediaminetetraacetic acid and 6.6 g of citric acid, the mixture was stirred and evaporated to dryness at 80 °C to obtain the sol-gel precursor;

[0069] (2) Transfer the sol-gel precursor to a 30ml ceramic crucible, then place it in a muffle furnace and heat it to 300℃ at a heating rate of 10℃ / min in an air atmosphere. Then keep it at 300℃ for calcination for 3h. After calcination and cooling, grind the product to obtain 5g of the product to be purified.

[0070] (3) Rinse 5g of the product to be purified with 100ml of deionized water and filter. Rinse the filter cake and centrifuge. Repeat three times. Dry the separated solid product at 40℃. After drying, add 0.61g of lithium carbonate, grind and mix evenly to obtain the purified product.

[0071] (4) The purified product was transferred to a 30ml ceramic crucible and then placed in a tube furnace and heated to 850℃ at a heating rate of 5℃ / min in an air atmosphere. The product was then calcined at 850℃ for 10h. After calcination and cooling, the product was ground to obtain 0.762g of regenerated lithium-ion battery cathode material.

[0072] (5) The regenerated lithium-ion battery cathode material obtained in the previous step was mixed according to the mass ratio of cathode material: carbon black: polytetrafluoroethylene = 8:1:1. 0.2g of the mixture was weighed and ground. 400μl of 1-methyl-2-pyrrolidone was added and ground into a slurry. The slurry was coated on aluminum foil with a thickness of 100μm and dried in a vacuum drying oven at 120℃ for 12h to obtain a cathode sheet. The cathode sheet was cut into a circular sheet with a diameter of 12mm. A CR2032 coin cell was assembled with lithium sheet as the negative electrode and 20μl of 1.0M lithium hexafluorophosphate as the electrolyte for electrochemical performance testing.

[0073] (6) Electrochemical performance tests were conducted on coin cells assembled using recycled lithium-ion battery cathode materials, including single-rate charge-discharge cycle tests, multi-rate charge-discharge cycle tests, volt-ampere characteristic cycle tests, and electrochemical impedance spectroscopy tests. The test results are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0074] Figure 4 The results of single-rate charge-discharge cycle testing of the cathode material regenerated from the leachate of waste lithium-ion battery cathode material in this embodiment are shown. The test results show that at a rate current of 0.5C, the charge-discharge efficiency of the lithium-ion battery prepared from the regenerated cathode material remains at 98%, the initial capacity is 108.1 mAh / g, the capacity retention rate is 83.9% after 100 charge-discharge cycles, and the single-cycle capacity decay rate is 1.609‰, indicating that the regenerated cathode material has good electrochemical performance.

[0075] Figure 5 The results of multi-rate charge-discharge cycle tests on the cathode material regenerated from the leachate of spent lithium-ion battery cathode materials in this embodiment are shown. The test results indicate that, at current rates of 0.2C-3C, the discharge specific capacities of lithium-ion batteries prepared from the regenerated cathode material are 136.2 mAh / g, 116.9 mAh / g, 106.1 mAh / g, 91.7 mAh / g, and 83.7 mAh / g, respectively. The charge-discharge efficiency remains above 90% at all different rates, indicating that the regenerated cathode material can function normally under various usage conditions, exhibiting good material stability and cycle performance, and demonstrating excellent electrochemical performance. Under the same test conditions, the discharge specific capacities of lithium-ion batteries prepared from virgin commercial cathode materials are 150.7 mAh / g, 135.1 mAh / g, 119.3 mAh / g, 100.1 mAh / g, and 86.5 mAh / g, respectively, demonstrating that the capacity of the regenerated cathode material can reach over 90% of that of virgin commercial materials under different conditions.

[0076] Figure 6The current-voltage characteristic cycle test results of the cathode material regenerated from the leachate of spent lithium-ion battery cathode material in this embodiment are shown. The test results show that within the test range of 2.8V-4.3V, the regenerated cathode material exhibits uniform oxidation and reduction peaks; a reduction peak current with a peak value of 0.28mA was detected in the voltage range of 3.8V-3.9V, corresponding to Ni during the charging process. 2+ / Ni 4+ The occurrence of the redox reaction, and the decrease in peak voltage from 3.9V in the first cycle to 3.85V in the third cycle, indicate that the recycled material has good cycle stability and reversible electrochemical reaction, which is consistent with the characteristics of ternary cathode materials for lithium-ion batteries, indicating that the recycled cathode material has perfect electrochemical performance.

[0077] To facilitate comparison of the necessity of the method described in this invention, the advantages of this invention will be explained below with reference to comparative examples.

[0078] Comparative Example 1

[0079] (1) The leachate was obtained in the same way as in Example 1. 25 ml of leachate from waste lithium-ion battery cathode material with lithium, nickel, cobalt, and manganese concentrations of 0.006 g / L, 5.869 g / L, 5.893 g / L, and 5.494 g / L, respectively, was taken. The impurity components and their concentrations were as follows: Na... + 0.1g / L, K + 0.1g / L, SO4 2- 2.3g / L, NO3 - 1.2 g / L, sucrose 2.0 g / L; after adding 4.6 g EDTA and 6.6 g citric acid, the mixture was stirred and evaporated to dryness at 80 °C to obtain the sol-gel precursor;

[0080] (2) Transfer the sol-gel precursor to a 30ml ceramic crucible, then place it in a muffle furnace and heat it to 300℃ at a heating rate of 10℃ / min in an air atmosphere. Then keep it at 300℃ for calcination for 3h. After calcination and cooling, grind the product to obtain 5g of the product to be purified.

[0081] (3) The product to be purified was transferred to a 30ml ceramic crucible and then placed in a tube furnace and heated to 850℃ at a heating rate of 5℃ / min in an air atmosphere. Then it was kept at 850℃ for calcination for 10h. After calcination and cooling, the product was ground to obtain 0.762g of the unpurified direct regenerated product.

[0082] (4) The unpurified regenerated lithium-ion battery cathode material obtained in the previous step was analyzed and characterized using an X-ray diffractometer. The characterization results are as follows: Figure 7As shown, the curves in the figure, from bottom to top, correspond to: recycled material after impurity removal (LNCM), recycled material containing sucrose impurities (LNCM@Suc), and recycled material containing Na. + Impurity Regenerated Materials (LNCM@Na) + ), containing K + Impurity Recycled Materials (LNCM@K) + ), containing NO3 - Impurity Recycled Materials (LNCM@NO3) - )) Contains SO4 2- Impurity Recycled Materials (LNCM@SO4) 2- The unrefined, directly regenerated product, due to interference from impurity ions, exhibited characteristic impurity peaks in the characterization results that were not characteristic of lithium-ion battery cathode materials; in the K-containing... + Na + Impurity phases belonging to K2CO3, Na2CO3, and NaCoO2 were found in the regenerated products containing SO4; 2- The presence of characteristic peaks for Li₂SO₄ and Co₃O₄ (cobalt metal oxide) in the recycled product, which did not form the cathode material, indicates that impurities compete for the lithium source, hindering the formation of the ternary cathode material lattice. Furthermore, NO₃⁻... - Although no impurity phase is observed in the recycled product containing sucrose impurities, the hindering effect introduced by the impurities leads to poor crystal structure and lattice defects in the recycled cathode material.

[0083] The unpurified regenerated lithium-ion battery cathode material obtained in Comparative Example 1 was used to assemble a battery using the same method as in Example 3, and then subjected to multi-rate charge-discharge cycles. The test results are as follows: Figure 8 As shown in the figure, it can be seen that the performance of the cathode material obtained without impurity removal and regeneration is poor at charge / discharge rates of 0.2C-3C. The specific capacity of the regenerated cathode materials containing impurities, from highest to lowest, is K. + NO3 - Na + SO4 2- Under 1C conditions, their capacities are equivalent to 80%, 72%, 63%, and 52% of those of the purified and regenerated cathode material, respectively.

[0084] This comparative example illustrates that the water washing and impurity removal step is indispensable for the direct regeneration of leachate from spent lithium-ion battery cathode materials. Products regenerated without this impurity removal step exhibit significant defects in both structure and performance.

[0085] Comparative Example 2

[0086] (1) The leachate was obtained in the same way as in Example 1. 25 ml of leachate from waste lithium-ion battery cathode material with lithium, nickel, cobalt, and manganese concentrations of 0.006 g / L, 5.869 g / L, 5.893 g / L, and 5.494 g / L, respectively, was taken. The impurity components and their concentrations were as follows: Na... + 0.1g / L, K + 0.1g / L, SO4 2- 2.3g / L, NO3 - 1.2 g / L, sucrose 2.0 g / L; after adding 4.6 g EDTA and 6.6 g citric acid, the mixture was stirred and evaporated to dryness at 80 °C to obtain the sol-gel precursor;

[0087] (2) The sol-gel precursor was transferred to a 30ml ceramic crucible and then placed in a muffle furnace and heated to 850℃ at a heating rate of 10℃ / min in an air atmosphere. The temperature was then maintained at 850℃ for 10h. After calcination and cooling, the product was found to be a solidified colloidal state and tightly adhered to the ceramic crucible.

[0088] This comparative example illustrates that the pre-calcination step and its temperature control are indispensable for subsequent water washing for impurity removal and regeneration. Direct calcination regeneration without a pre-calcination step or at excessively high pre-calcination temperatures will cause impurities in the leachate to react with oxygen in the air to form molten alkali metal oxides, which will solidify upon cooling, making it impossible to separate the product from the container and hindering subsequent processes.

[0089] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing impurities and regenerating cathode materials from leachate of spent lithium-ion battery cathode materials, characterized in that, The leachate contains, in addition to lithium ions, one or more of nickel ions, cobalt ions, and manganese ions, and also contains impurities; the impurities are sodium ions and / or potassium ions; the method includes the following steps: (1) The leachate of the waste lithium-ion battery cathode material is mixed with a metal complexing agent and evaporated under heating conditions to obtain a sol-gel precursor; the metal complexing agent is one or more of citric acid, ethylenediaminetetraacetic acid, malic acid, acetic acid, methanol, and ethanol, and the molar amount of the metal complexing agent added is 1-3 times the sum of the molar amounts of nickel, cobalt, and manganese in the leachate; the heating conditions are heating to 60℃-120℃; (2) The sol-gel precursor is pre-calcined in an oxygen-containing atmosphere to obtain the product to be purified; The pre-calcination is carried out at a calcination temperature of 300°C for a calcination time of 180 min-360 min, so that the nickel, cobalt and manganese elements form metal oxides, while keeping the sodium and / or potassium ion impurities in the form of water-soluble salts. (3) The product to be purified is washed with water to remove impurities. The lithium ions and impurities are removed during the water washing process. The solid product obtained after water washing is rich in metal oxides containing nickel, cobalt and manganese. (4) Lithium carbonate is added to the solid product obtained after water washing and impurity removal, and the mixture is mixed evenly and then calcined for a second time to obtain a regenerated cathode material; the second calcination is carried out at a calcination temperature of 800-950℃ and a calcination time of 600 min-900 min.

2. The method as described in claim 1, characterized in that, The cathode material of the waste lithium-ion batteries is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide.

3. The method as described in claim 1, characterized in that, The leachate is the filtrate obtained after leaching the waste lithium-ion battery cathode material in acid and / or alkali and separating the solid and liquid components; the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, tartaric acid, citric acid, and malic acid; the alkali is sodium hydroxide or ammonia.

4. The method as described in claim 1, characterized in that, In step (3), the product to be cleaned is rinsed multiple times with deionized water. The ratio of the amount of deionized water used in a single rinse to the mass of the material to be cleaned is 10 ml / g to 50 ml / g.

5. The method as described in claim 1, characterized in that, The amount of lithium carbonate added in step (4) is 1 to 1.15 times the sum of the molar amounts of nickel, cobalt and manganese in the leachate.

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