A method for recycling waste sodium batteries to prepare single-crystal ternary lithium cathodes based on a deep eutectic solvent-solvothermal regeneration system

Abstract

A method for recycling waste sodium batteries to prepare single-crystal ternary lithium anodes based on a deep eutectic solvent-solvothermal regeneration system belongs to the field of lithium ion battery and sodium ion battery recycling and reuse. The method is as follows: the waste battery is discharged and crushed, sodium in the waste sodium anode material is removed by liquid phase cleaning technology, and the waste sodium anode and the filtrate after filtration are obtained by removing part of the sodium; a deep eutectic solvent system composed of polyethylene glycol 200 and a hydrogen bond donor is used to selectively leach the waste sodium anode and the deep eutectic solvent system in a low temperature environment, and the active material after sodium removal treatment is obtained after centrifugal separation; the active material and the lithium alkali mixed solution are mixed under temperature control to complete component reconstruction, and the material after solvothermal lithium supplement is washed to remove the surface residual solution, and the regenerated lithium anode material is obtained. The present application adopts an integrated recycling mode of sodium ion battery anode material, compared with the traditional recycling mode, only manpower and material resources are needed for material classification, greatly reducing the recycling input cost.

Description

Technical Field

[0001] This invention relates to a method for preparing single-crystal ternary lithium cathode by recycling waste sodium batteries based on a deep eutectic solvent-solvent thermal regeneration system, and relates to the field of lithium-ion battery and sodium-ion battery recycling and reuse. Background Technology

[0002] In recent years, lithium battery technology has seen breakthrough developments, with lithium-ion batteries achieving significant improvements in energy density and undergoing fundamental changes in cost structure. Driven by both technological iteration and cost optimization, lithium-ion batteries have rapidly gained market dominance, becoming a core energy storage solution in the new energy field. Because sodium and lithium have similar chemical properties, researchers have considered sodium-ion batteries as a potential alternative to lithium batteries. However, due to the larger radius of sodium ions compared to lithium ions, the reactions that occur when sodium or lithium is embedded in the same structure differ greatly. Sodium-ion batteries exhibit less polarization, significantly impacting their structure and diffusion performance. Therefore, the replacement of lithium-ion batteries by sodium-ion batteries remains a long and arduous process. Currently, lithium-ion batteries remain the mainstream technology.

[0003] The production of lithium-ion batteries (LIBs) is growing exponentially and has become an essential raw material for many industries. However, the abundance of key elements required for LIBs—nickel, cobalt, and manganese—in the Earth's crust is limited. Sodium-ion batteries, on the other hand, have been widely used in some industries in recent years, and the amount of discarded sodium-ion batteries is increasing annually. While sodium itself has a relatively low recycling value, other valuable metals in sodium-ion batteries, such as nickel, cobalt, and manganese, still have significant recycling value. Therefore, developing regeneration technologies based on sodium-ion battery cathode materials and converting them into ternary single-crystal cathode materials for lithium-ion batteries represents a resource recycling strategy with significant research value and economic feasibility.

[0004] The morphology of ternary lithium cathode materials significantly impacts their performance. Although cathode materials with different morphologies exhibit excellent electrochemical performance, only a few morphologies are considered superior when considering factors such as mass production, industrial cost, material uniformity, and tap density. Single-crystal materials, in particular, are more practical. Single-crystal ternary cathode materials offer advantages in physical and chemical properties, including mechanical strength, structural stability, long-cycle performance, and thermal stability. Furthermore, the high stability and low specific surface area of ​​single-crystal cathodes effectively suppress side reactions in the battery. Therefore, preparing cathode materials as single crystals offers significant advantages.

[0005] Due to the wide variety and large quantity of batteries, their recycling generally involves two main processes: physical and chemical. Physical processes involve mechanical grinding or manual disassembly to separate the different components of the battery. However, this method results in significant loss of valuable metals and the retention of many impurities. Chemical processes generally refer to pyrometallurgy, hydrometallurgy, and direct regeneration. Pyrometallurgy uses high-temperature furnaces to heat waste batteries, causing the non-metallic components to decompose into gases and liquids, while the metallic components are fixed in metal compounds or solid residues at high temperatures. However, the incineration of waste batteries produces large amounts of harmful gases such as dioxins, halogenated hydrocarbons, and polycyclic aromatic hydrocarbons. If these waste gases and residues containing harmful gases and heavy metals are not strictly controlled, they will cause serious environmental damage. Hydrometallurgy selectively recovers valuable metals from waste batteries using acidic or reducing solutions, achieving high recovery rates and efficiency. However, the wastewater generated by hydrometallurgy and the large consumption of highly corrosive acids make it insufficient for modern waste battery recycling. Therefore, to reduce environmental pollution, the use of deep eutectic solvents for selective metal leaching has been proposed. Deep eutectic solvents (DESS) consist of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) and have a low melting point. Furthermore, DESSs are simple to synthesize, highly biodegradable, biocompatible, atom-economical, and stable, exhibiting high selectivity in metal extraction. Pyrometallurgical and hydrometallurgical processes are already industrialized for battery recycling, but they suffer from problems such as high-temperature smelting or the use of large amounts of acidic and alkaline chemicals. Therefore, a green and environmentally friendly recycling method, such as solvothermal regeneration, is needed. Solvothermal regeneration can restore the battery structure and performance to an unused state, and by controlling the reaction conditions, battery performance can be further improved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for recycling waste sodium batteries to prepare single-crystal ternary lithium cathodes based on a deep eutectic solvent-solvent thermal regeneration system. The preparation method includes steps such as waste sodium material pretreatment, water washing, deep eutectic solvent, solvent thermal regeneration, and sodium salt extraction. By precisely controlling key parameters of the leaching system, such as the type of leaching agent, molar concentration, solid-liquid ratio, and reaction time, and controlling the type of ligand / chelating agent during the leaching process, a new multi-component synergistic recycling method for retired sodium batteries is constructed.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing monocrystalline ternary lithium cathodes from waste sodium batteries based on a deep eutectic solvent-solvent thermal regeneration system, the method comprising:

[0009] S1. Pretreatment of waste sodium batteries: Waste batteries (O3 type NaNi) 0.4 Fe 0.2 Mn0.4 The O2 cathode material is discharged and pulverized in a suitable manner. Through a multi-stage deconstruction process, the retired battery after discharge treatment is precisely pulverized to achieve a particle size distribution of 1-100μm for both the positive and negative electrode materials. At the same time, components such as the separator and shell are disassembled into fragments of 2-20mm, achieving precise separation of each component. The positive and negative electrode materials can be separated by magnetic separation or suspension.

[0010] S2. Water washing: Sodium in waste sodium-ion battery cathode materials is removed by liquid phase cleaning technology. Pure water or organic solvents are used to uniformly mix with the cathode material and filter to obtain waste sodium cathode and filtrate with some sodium removed.

[0011] S3. Deep eutectic solvent: A deep eutectic solvent system is composed of polyethylene glycol 200 and hydrogen bond donor HBD in a molar ratio of 14:1. Waste sodium is selectively leached into the deep eutectic solvent system DESS at a mass ratio of 0.1:5 in a low-temperature environment. After separation by high-speed centrifugation (5000 rpm for 5 min), the sodium-removed active material is obtained. Hydrogen bond donors refer to substances that can provide hydrogen bonds to other solvents, such as water, phenols, ethanol, and acrylic acid.

[0012] S4, Solvent Thermal Regeneration: Lithium replenishment regeneration involves reconstructing the composition of the active material from S3 with a lithium-alkali mixture under controlled temperature conditions. After solvent thermal lithium replenishment, the material is thoroughly washed twice with deionized water to remove residual solution from the surface, and regenerated positive lithium material is obtained without much further processing; the lithium-alkali mixture is in excess relative to the active material.

[0013] S5. Sodium salt extraction: The filtrate is filtered through a nanofiltration membrane, and the filtrate is evaporated and crystallized to obtain sodium sulfate crystals.

[0014] Furthermore, in S1, the multi-stage deconstruction process achieves efficient separation and recycling of the shell, current collector, and cathode particles by dismantling, discharging, evaporating, crushing, and sorting retired sodium batteries.

[0015] Furthermore, in S1, during the discharge process, the conductive medium needs to completely cover the battery pack, and the voltage needs to be continuously adjusted until the terminal voltage reaches the safe threshold of 2-3V.

[0016] Furthermore, the conductive medium is any one of aluminum powder, copper powder, graphite, or layered carbon material.

[0017] Furthermore, in S2, the uniform mixing requires magnetic stirring at a speed of 1000-2000 r / min.

[0018] Furthermore, in S2, the organic solvent is ethanol or propanol.

[0019] Furthermore, in S3, the leaching temperature is 25-50°C, and the leaching time is 17 min-48 h.

[0020] Furthermore, in S4, the solute in the lithium-alkali mixed solution is LiOH with a concentration of 4 mol / L.

[0021] Furthermore, in S4, the solvothermal temperature is 160-220°C, and the treatment is continued for 1-6 hours.

[0022] Furthermore, in S5, the evaporation and crystallization temperature is 100°C.

[0023] The advantages of this invention over the prior art are as follows:

[0024] (1) The present invention adopts an integrated recycling method for sodium-ion battery cathode materials. Compared with the traditional recycling method, which only requires manpower and material resources to classify materials, the recycling cost is greatly reduced.

[0025] (2) The present invention adopts a multi-method combination process to regenerate retired sodium battery cathode material into reusable lithium battery active material. Compared with the traditional metal extraction process, it significantly simplifies the processing steps and reduces the overall processing cost by 40-60%.

[0026] (3) The waste liquid generated during the process of this invention can be reused after further treatment, realizing the recovery and internal circulation of process products and reducing the process production cost.

[0027] (4) The recycled cathode material synthesized by this invention has low cost, high value of recycled products, and obvious performance advantages over recycled cathode materials on the market.

[0028] (5) The sodium cathode regeneration process provided by the present invention has the characteristics of simple operation and environmental friendliness, which can realize the efficient value-added recycling of waste cathode materials and significantly improve resource utilization and economic benefits. Attached Figure Description

[0029] Figure 1 This is a flowchart of a method for preparing monocrystalline ternary lithium cathode by recycling waste sodium batteries based on a deep eutectic solvent-solvent thermal regeneration system.

[0030] Figure 2 This is a SEM image of a regenerated lithium positive single crystal material.

[0031] Figure 3 This is a TEM image of a recycled lithium positive single crystal material.

[0032] Figure 4 HRTEM images, FFT images, and interlayer distance images of regenerated lithium positive single crystal materials.

[0033] Figure 5 This is a rate performance curve for recycled lithium positive single crystal materials.

[0034] Figure 6 This is a graph showing the cycling performance of recycled lithium positive single crystal materials. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0036] This invention leverages the similarity in crystal structure between sodium and lithium ions, drawing inspiration from deep eutectic solvent recovery technology. Through innovative processes such as leaching and regeneration, it achieves the efficient recycling and upgrading of waste sodium-ion battery materials, transforming them into monocrystalline ternary lithium cathode materials. Simultaneously, during the lithium cathode material regeneration process, utilizing the advantage of waste sodium-ion cathodes as the recycling target, it innovatively retains sodium as a lattice stabilizer. By constructing composite phase materials through the ordered occupancy of sodium ions, the monocrystalline ternary cathode material is modified simultaneously, thereby improving its electrochemical performance. Furthermore, through a combined nanofiltration membrane separation-gradient evaporation crystallization process, sodium is directionally converted into industrial-grade sodium sulfate, achieving efficient recovery of high-purity sodium salts, improving the recycling rate of sodium resources, and realizing a closed-loop regeneration system.

[0037] This invention achieves efficient recycling and resource utilization of waste sodium battery cathode materials through steps including sodium waste pretreatment, water washing, deep eutectic solvent extraction, solvothermal regeneration, and sodium salt extraction. (O3-type NaNi) 0.4 Fe 0.2 Mn 0.4 O2 cathode materials possess high specific capacity, excellent temperature adaptability, and low cost (containing Fe / Mn elements), but they suffer from low conductivity and structural stability issues, requiring further improvement. This invention provides a method for preparing a single-crystal lithium cathode from recycled sodium cathode material, comprising the following steps: [The method involves processing waste batteries (O3 type NaNi...]] 0.4 Fe 0.2 Mn 0.4The O2 cathode material is discharged and pulverized in a suitable manner. A multi-stage deconstruction process is used to precisely pulverize the discharged retired battery, achieving a particle size distribution of 1-100 μm for both the positive and negative electrode materials. Simultaneously, components such as the separator and casing are disassembled into 2-20 mm fragments, achieving precise separation of each component. Subsequently, sodium in the waste sodium-ion cathode material is removed using liquid-phase cleaning technology, primarily by uniformly mixing the cathode material with pure water or organic solvents. After filtration, a partially sodium-containing waste sodium cathode and filtrate is obtained. Then, sodium ions are selectively extracted using a deep eutectic solvent. The deep eutectic solvent (DESS) is a mixture of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), possessing a low melting point due to its unique intermolecular interactions. The performance of the deep eutectic solvent (DESS) can be effectively optimized by adjusting the molar ratio of hydrogen bond donors (HBDs) to hydrogen bond acceptors (HBAs), selecting different component types, and controlling variations in component amounts. Therefore, a deep eutectic solvent system was synthesized using polyethylene glycol 200 and HBD. Waste sodium cathode material and DESS were selectively leached in a low-temperature environment, and the desodium-treated active material was obtained after high-speed centrifugation. After solvent extraction, most of the sodium was removed, and the remaining material could be directly regenerated into single-crystal cathode material for lithium-ion batteries. However, since sodium could not be completely removed and remained in the waste sodium cathode material, lithium replenishment was used to regenerate it into Li. 0.9-x Na 0.1+x Ni 0.6 Fe 0.2 Mn 0.2 O2 cathode material. Lithium replenishment regeneration involves recombining the leached active material with a lithium salt solution under controlled temperature conditions. After solvothermal lithium replenishment, the material undergoes two deionized water washes to thoroughly remove residual solution from the surface, yielding regenerated lithium cathode single crystal material without extensive processing. Finally, the filtrate is filtered through a nanofiltration membrane, and the filtrate is evaporated and crystallized to obtain sodium sulfate crystals. This method has advantages such as a clear process, simple operation, and excellent performance, making it suitable for large-scale recycling of waste sodium batteries.

[0038] Example 1:

[0039] S1: Waste sodium battery cathode material (O3 type NaNi) 0.4 Fe 0.2 Mn 0.4 O2 is discharged and pulverized in a suitable manner, and its components are precisely separated through a multi-stage deconstruction process. During the separation process, the positive and negative electrode active materials are dissociated into 1-100μm particles, while the separator, shell, and current collector are broken into coarse particles of 2-20mm. This multi-stage deconstruction process, through disassembly, discharge, evaporation, crushing, and sorting of decommissioned sodium batteries, achieves efficient separation and recycling of the shell, current collector, and cathode particles. During discharge, the battery pack needs to be completely coated with a conductive medium, and the voltage is continuously controlled until the terminal voltage reaches a safe threshold of 2-3V. The conductive medium is copper powder.

[0040] S2: Sodium in waste sodium-ion battery cathode materials is removed by liquid phase cleaning technology. Pure water is used to uniformly mix with cathode materials, and after filtration, waste sodium cathode and filtrate with some sodium removed are obtained.

[0041] S3: A deep eutectic solvent system was formed by combining polyethylene glycol 200 and hydrogen bond donor HBD in a molar ratio of 14:1. Waste sodium was selectively leached into the deep eutectic solvent system DESS at a mass ratio of 0.1:5 at 25°C for 17 minutes. After high-speed centrifugation, the sodium-desodium treated active material was obtained.

[0042] S4: Lithium replenishment and regeneration involves treating the active material obtained from leaching with a 4 mol / L LiOH solution at 160°C for 1 hour to complete component reconstruction. After solvothermal lithium replenishment, the material is thoroughly washed twice with deionized water to remove residual solution from the surface, and regenerated lithium positive material is obtained without much further processing.

[0043] S5: The filtrate from step S2 is filtered through a nanofiltration membrane, and the filtrate is evaporated and crystallized at 100°C to obtain sodium sulfate crystals.

[0044] This invention discloses a method for preparing single-crystal ternary lithium cathodes from waste sodium batteries using a deep eutectic solvent-solvent thermal regeneration system. The resulting recycled lithium cathodes exhibit a uniform particle size distribution of 2-4 μm. Figure 2 Furthermore, TEM analysis indicates that the recycled material has a single-crystal structure. Figure 3 ), while exhibiting a good layered structure ( Figure 4 a), with an interlayer spacing of 0.47 nm ( Figure 4 b). Furthermore, the cathode material prepared by this method exhibits excellent electrochemical performance, maintaining a current density of 200 mAh g⁻¹ at low current densities. -1 capacity ( Figure 5 Moreover, it still retains 90% of its capacity after 100 cycles. Figure 6 ).

[0045] Example 2: The only difference between this example and Example 1 is that in S1, the charge transfer carrier is aluminum.

[0046] Example 3: The only difference between this example and Example 1 is that in S1, the charge transfer carrier is graphite.

[0047] Example 4: The only difference between this example and Example 1 is that in S2, the water washing solution is ethanol.

[0048] Example 5: The only difference between this example and Example 1 is that in S2, the washing solution is propanol.

[0049] Example 6: The only difference between this example and Example 1 is that in S2, the water washing solution is ethanol.

[0050] Example 7: The only difference between this example and Example 1 is that in S2, the washing solution is propanol.

[0051] Example 8: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C.

[0052] Example 9: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C.

[0053] Example 10: The only difference between this example and Example 1 is that in S3, the leaching time is 6 hours.

[0054] Example 11: The only difference between this example and Example 1 is that in S3, the leaching time is 12h.

[0055] Example 12: The only difference between this example and Example 1 is that in S3, the leaching time is 24 hours.

[0056] Example 13: The only difference between this example and Example 1 is that in S3, the leaching time is 36 hours.

[0057] Example 14: The only difference between this example and Example 1 is that in S3, the leaching time is 48 hours.

[0058] Example 15: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C and the time is 6 hours.

[0059] Example 16: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C and the time is 12 hours.

[0060] Example 17: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C and the time is 24 hours.

[0061] Example 18: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C and the time is 36 hours.

[0062] Example 19: The only difference between this example and Example 1 is that in S3, the leaching temperature is 35°C and the time is 48h.

[0063] Example 20: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C and the time is 6 hours.

[0064] Example 21: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C and the time is 12 hours.

[0065] Example 22: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C and the time is 24 hours.

[0066] Example 23: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C and the time is 36 hours.

[0067] Example 24: The only difference between this example and Example 1 is that in S3, the leaching temperature is 50°C and the time is 48 hours.

[0068] Example 25: The only difference between this example and Example 1 is that in S4, the solvothermal reaction temperature is 180°C.

[0069] Example 26: The only difference between this example and Example 1 is that in S4, the solvothermal reaction temperature is 200°C.

[0070] Example 27: The only difference between this example and Example 1 is that in S4, the solvothermal reaction temperature is 220°C.

[0071] Example 28: The only difference between this example and Example 1 is that in S4, the solvothermal reaction time is 2 hours.

[0072] Example 29: The only difference between this example and Example 1 is that in S4, the solvothermal reaction time is 4 hours.

[0073] Example 30: The only difference between this example and Example 1 is that in S4, the solvothermal reaction time is 6 hours.

[0074] Example 31: The only difference between this example and Example 25 is that in S4, the solvothermal reaction time is 2 hours.

[0075] Example 32: The only difference between this example and Example 25 is that in S4, the solvothermal reaction time is 4 hours.

[0076] Example 33: The only difference between this example and Example 25 is that in S4, the solvothermal reaction time is 6 hours.

[0077] Example 34: The only difference between this example and Example 26 is that in S4, the solvothermal reaction time is 2 hours.

[0078] Example 35: The only difference between this example and Example 26 is that in S4, the solvothermal reaction time is 4 hours.

[0079] Example 36: The only difference between this example and Example 26 is that in S4, the solvothermal reaction time is 6 hours.

[0080] Example 37: The only difference between this example and Example 27 is that in S4, the solvothermal reaction time is 2 hours.

[0081] Example 38: The only difference between this example and Example 27 is that in S4, the solvothermal reaction time is 4 hours.

[0082] Example 39: The only difference between this example and Example 27 is that in S4, the solvothermal reaction time is 6 hours.

Claims

1. A method for preparing monocrystalline ternary lithium cathode by recycling waste sodium batteries based on a deep eutectic solvent-solvent thermal regeneration system, characterized in that: The method is as follows: S1. Waste Sodium Battery Pretreatment: Waste batteries are discharged and crushed in a suitable manner. Through a multi-stage deconstruction process, the discharged retired batteries are precisely crushed to achieve a particle size distribution of 1-100μm for the positive and negative electrode materials. At the same time, the separator and shell components are disassembled into 2-20mm fragments to achieve precise separation of each component. S2. Water washing: Sodium in waste sodium-ion battery cathode materials is removed by liquid phase cleaning technology. Pure water or organic solvent is used to uniformly mix with the cathode material, and after filtration, waste sodium cathode and filtrate with some sodium removed are obtained. S3, Deep eutectic solvent: Polyethylene glycol 200 and hydrogen bond donor are combined in a molar ratio of 14:1 to form a deep eutectic solvent system. Waste sodium is selectively leached into the deep eutectic solvent system in a mass ratio of 0.1:5 in a low-temperature environment. After high-speed centrifugation, sodium-desodium treated active material is obtained. S4, Solvent thermal regeneration: Lithium replenishment regeneration involves reconstructing the composition of the active material from S3 with a lithium-alkali mixture under controlled temperature conditions. After solvent thermal lithium replenishment, the material is thoroughly washed twice with deionized water to remove residual solution from the surface, and regenerated lithium positive material is obtained without much processing. S5. Sodium salt extraction: The filtrate is filtered through a nanofiltration membrane, and the filtrate is evaporated and crystallized to obtain sodium sulfate crystals.

2. The method according to claim 1, characterized in that: In S1, the multi-stage deconstruction process achieves efficient separation and recycling of the shell, current collector, and cathode particles by dismantling, discharging, evaporating, crushing, and sorting retired sodium batteries.

3. The method according to claim 1 or 2, characterized in that: In S1, the battery pack needs to be completely covered by a conductive medium during the discharge process, and the voltage needs to be continuously adjusted until the terminal voltage reaches the safe threshold of 2-3V.

4. The method according to claim 3, characterized in that: The conductive medium is any one of aluminum powder, copper powder, graphite, or layered carbon material.

5. The method according to claim 1, characterized in that: In S2, the uniform mixing requires magnetic stirring at a speed of 1000-2000 r / min.

6. The method according to claim 1, characterized in that: In S2, the organic solvent is ethanol or propanol.

7. The method according to claim 1, characterized in that: In S3, the leaching temperature is 25-50℃ and the leaching time is 17min-48h.

8. The method according to claim 1, characterized in that: In S4, the solute in the lithium-alkali mixed solution is LiOH with a concentration of 4 mol / L.

9. The method according to claim 1, characterized in that: In S4, the solvothermal temperature is 160-220℃, and the treatment lasts for 1-6 hours.

10. The method according to claim 1, characterized in that: In S5, the evaporation and crystallization temperature is 100℃.

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