Method for extracting valuable metals from waste lithium ion batteries by using deep eutectic solvent and method for regenerating positive electrode material

Abstract

This invention provides a method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent and a method for regenerating cathode materials. The method utilizes a eutectic solvent of a specific composition as a leaching agent to extract valuable metals from spent lithium-ion batteries and regenerate cathode materials. The steps include: preparation of the eutectic solvent, acquisition of spent cathode materials, leaching of valuable metals using the eutectic solvent, regeneration and recycling of the eutectic solvent, recovery of transition metal elements, recovery of lithium elements, and reprocessing of cathode materials. This invention's method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent and regenerating cathode materials effectively overcomes the high temperature and long processing time requirements of existing eutectic solvent leaching processes and significantly simplifies or even restructures subsequent metal recovery steps, achieving a short-process, low-energy-consumption, and low-cost closed-loop regeneration of spent lithium-ion battery cathode materials.

Description

Technical Field

[0001] This invention belongs to the field of electronic waste resource utilization technology, specifically relating to a method for extracting valuable metals from waste lithium-ion batteries using a eutectic solvent and a method for regenerating cathode materials. Background Technology

[0002] Lithium-ion batteries, with their significant advantages such as high energy density, low memory effect, and low self-discharge rate, have been widely used in various fields, including electric vehicles, smartphones, and large-scale energy storage systems. However, lithium-ion batteries have inherent limitations in their lifespan. After long-term charge-discharge cycles, factors such as the structural collapse of the cathode material, irreversible decomposition of the electrolyte, and aging of the separator lead to battery failure and disposal. It is estimated that by 2030, the total amount of waste lithium-ion batteries disposed of globally will exceed 11 million tons. The cathode materials of waste lithium-ion batteries are rich in high-value metal elements such as lithium (Li), cobalt (Co), nickel (Ni), and manganese (Mn). Improper handling and disposal of these waste batteries will not only result in a huge waste of important metal resources but may also trigger a severe ecological and environmental crisis due to heavy metal leakage. Therefore, developing efficient and closed-loop recycling technologies for waste lithium-ion batteries is of vital practical significance for achieving resource recycling and supporting global sustainable development.

[0003] Hydrometallurgical technology, as the mainstream technology for recycling waste lithium-ion batteries, mainly extracts target valuable metal elements from waste cathode materials through unit operations such as leaching with inorganic acids (such as hydrochloric acid, sulfuric acid, and nitric acid), solvent extraction, chemical precipitation, and electrodeposition. This technology is relatively mature and exhibits advantages such as relatively controllable energy consumption, high overall metal element recovery rate, and high purity of recycled products. However, its drawbacks cannot be ignored: the use of strong inorganic acids inevitably causes significant corrosion to the equipment, increasing equipment maintenance and replacement costs; more seriously, the leaching process generates a large amount of acidic wastewater, as well as chlorine gas (Cl2) and sulfur oxides (SO4). x ), nitrogen oxides (NO) x The emission of harmful gases such as , etc., brings significant secondary environmental pollution and safety risks, which contradicts the concept of green environmental protection.

[0004] Deep eutectic solvents (DES) are an emerging class of green solvents. They are low-melting-point eutectic mixtures composed of hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) in a specific molar ratio, with melting points significantly lower than any single component. Deep eutectic solvents typically possess outstanding properties such as low preparation cost, wide liquid temperature window, low vapor pressure, biodegradability, and environmental friendliness. Studies have shown that deep eutectic solvents composed of certain specific components exhibit excellent dissolution performance on metal oxides, making them highly promising green leaching agents to replace corrosive inorganic strong acids, and suitable for the resource recycling of waste lithium-ion battery cathode materials.

[0005] There are existing reports on the application of eutectic solvents in battery recycling: for example, Tran et al. first reported the use of a eutectic solvent composed of choline chloride (ChCl) and ethylene glycol (EG) (molar ratio 1:2) as a leaching agent to recycle waste lithium cobalt oxide (LiCoO2) cathode materials; however, in order to achieve a more ideal leaching effect, this method requires a reaction at a leaching temperature of 220℃ and a liquid-to-solid ratio of 50:1 (g / g) for 24 hours, at which time the cobalt leaching rate reaches 94.1%; and the subsequent cobalt recovery requires the deposition of cobalt ions in the form of Co(OH)2 on a stainless steel mesh working electrode by electrodeposition, which has problems such as harsh leaching conditions, high energy consumption, and complex recycling process.

[0006] CN115692908A describes a method for selectively recycling cathode materials from spent lithium iron phosphate (LiFePO4) batteries under an ozone atmosphere. The method uses choline chloride-ethylene glycol type DES as a leaching agent and leverages the effect of ozone to achieve selective leaching of lithium. This method focuses on the selective leaching of valuable metals and requires a specific ozone atmosphere, making the recycling process complex and costly.

[0007] CN119800070A discloses a DES leaching agent and method for selectively leaching metal elements from waste nickel-containing lithium-ion battery cathode materials (such as NCM / NCA). The leaching agent consists of a ternary system of choline chloride, oxalic acid, and p-toluenesulfonic acid. By adjusting the molar ratio of the three components and adding specific polar aprotic solvents (such as dimethyl sulfoxide and dimethylacetamide) to the leachate, selective separation and recovery of nickel from waste cathode materials can be achieved. This method also emphasizes the selective leaching and separation and recovery of valuable metals, but the operation process is cumbersome and has the problems of long process flow and high recovery cost.

[0008] In summary, existing eutectic solvent recovery technologies suffer from problems such as high leaching temperatures and long leaching times, and high energy consumption in electrodeposition for recovering valuable metals. Furthermore, leaching recovery processes focus on the selective leaching and separation of valuable metals, resulting in lengthy and costly processes. Therefore, developing a green and efficient recovery technology based on eutectic solvents to achieve short-process closed-loop regeneration of spent lithium-ion battery cathode materials has become a key technological challenge urgently needing breakthroughs in the field of resource recycling. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a method for extracting valuable metals and regenerating cathode materials from waste lithium-ion batteries using a eutectic solvent. This method effectively overcomes the high-temperature and long-time requirements of existing DES leaching processes and significantly simplifies or even restructures subsequent metal recycling steps, achieving short-process, low-energy-consumption, low-cost, and closed-loop regeneration of cathode materials from waste lithium-ion batteries.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The first aspect of this invention is to provide a method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent, comprising the following steps:

[0012] S1. Hydrogen bond acceptors and hydrogen bond donors are mixed according to a molar ratio of hydrogen bond acceptor:hydrogen bond donor = 1:6 to 1:9 to form a first mixture; 0 to 20% of deionized water is added to the first mixture, and the mixture is stirred at 60 to 80°C for 30 to 60 minutes to obtain a homogeneous and transparent eutectic solvent; the hydrogen bond acceptor is selected from one of choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvate;

[0013] S2. Pre-treat the waste lithium-ion batteries to obtain waste cathode materials;

[0014] S3. Mix the eutectic solvent obtained in step S1 with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, heat and stir to leach the valuable metals, and obtain the leachate after the leaching is completed.

[0015] Furthermore, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvate, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:8, and the amount of deionized water added is 10% of the total mass of the first mixture.

[0016] Furthermore, in step S2, the pretreatment process of the waste lithium-ion battery is as follows: the waste lithium-ion battery is completely discharged, disassembled to obtain the positive electrode sheet, and the positive electrode sheet is cut and calcined to obtain the waste positive electrode material.

[0017] Furthermore, in step S3, the leaching temperature is 80~90℃ and the leaching time is 40~90min.

[0018] Furthermore, in step S3, the liquid-to-solid ratio of the eutectic solvent to the waste cathode material is 50:1 g / g, the leaching temperature is 80℃, and the leaching time is 60 min.

[0019] Furthermore, the waste cathode material is at least one of lithium cobalt oxide, NCM111, NCM523, NCM622, and NCM811.

[0020] A second aspect of the present invention provides a method for regenerating cathode materials, the method being based on the above-mentioned method for extracting valuable metals from waste lithium-ion batteries using eutectic solvents, and including, in addition to steps S1-S3, the following steps:

[0021] S4. After the leachate obtained in step S3 has cooled to room temperature, deionized water is added to the leachate for dilution and the solution is filtered to obtain the filtrate.

[0022] S5. Add oxalic acid as a precipitant to the filtrate, and after the reaction is complete, centrifuge to obtain a solid precipitate and a supernatant.

[0023] S6. The supernatant obtained in step S5 is subjected to vacuum distillation to remove water, and the recovered eutectic solvent is obtained.

[0024] S7. Use the recovered eutectic solvent for a new round of extraction of valuable metals from waste lithium-ion batteries, repeat steps S2 to S6 4 ​​to 6 times to obtain a lithium-rich solution;

[0025] S8. The solid precipitate obtained in step S5 is washed 2 to 4 times with anhydrous ethanol and then dried to obtain a cathode material precursor. The cathode material precursor is then calcined to obtain a transition metal oxide.

[0026] S9. Add sodium hydroxide solution to the lithium-rich solution obtained in step S7 to adjust the pH and filter to remove impurities. Then add saturated sodium carbonate solution to allow for a full reaction. After the reaction is complete, filter and wash and dry the solid obtained from the filter to obtain lithium carbonate.

[0027] S10. Take the transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9, mix them and grind them thoroughly to obtain a second mixture; then calcine the second mixture to obtain a regenerated lithium-ion battery cathode material.

[0028] Furthermore, in step S4, the amount of deionized water added is 0.5 to 1 times the volume of the leachate.

[0029] Furthermore, in step S5, the amount of oxalic acid added is 1.05 to 1.15 times the total molar amount of transition metal elements in the leachate, the reaction temperature is 60 to 70°C, the reaction time is 180 to 360 min, the centrifugation speed is 8000 to 10000 rpm, and the time is 10 to 30 min.

[0030] Furthermore, in step S6, the temperature of vacuum distillation is 60~80℃, and the time is 6~12h.

[0031] Furthermore, in step S8, the drying temperature is 70~90℃ and the drying time is 12~16h; the calcination process of the cathode material precursor is as follows: the cathode material precursor is placed in a muffle furnace and heated from room temperature to 200~210℃ at a heating rate of 4~6℃ / min to remove the water of crystallization in the precursor, and then heated to 395~405℃ at a heating rate of 2~3℃ / min and held at a constant temperature for 1~2h to ensure complete reaction.

[0032] Further, step S9 specifically involves: adjusting the pH to 10-12 using sodium hydroxide solution, stirring at 50-60°C for 20-40 minutes, and filtering to remove impurities; adding more sodium hydroxide solution to the filtrate to adjust the pH to greater than 12, adding saturated sodium carbonate solution at 90-95°C, washing the filtered solid three times with hot water at 80-90°C, and then drying it in a vacuum drying oven at 105-120°C for 4-6 hours to obtain lithium carbonate.

[0033] Furthermore, in step S10, the calcination process of the second mixture is as follows: the second mixture is placed in a muffle furnace and heated from room temperature to 500°C at a heating rate of 3°C / min, and kept at 500°C for 5 hours; then the temperature is raised to 850~950°C at a heating rate of 3°C / min and kept at 500°C for 12 hours.

[0034] Furthermore, in step S10, the transition metal oxide and lithium carbonate are mixed in a molar ratio of total transition metal elements (Ni+Co+Mn): lithium element (Li) = 1:1.05. The calcination process of the second mixture is as follows: the second mixture is placed in a muffle furnace and heated from room temperature to 500°C at a heating rate of 3°C / min, and held at 500°C for 5 hours; then the temperature is raised to 900°C at a heating rate of 3°C / min and held at 900°C for 12 hours.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The method for extracting valuable metals and regenerating cathode materials from spent lithium-ion batteries using eutectic solvents provided by this invention represents a breakthrough compared to existing technologies. Its beneficial effects can be systematically summarized into the following five core aspects:

[0037] 1. Innovative solvent system achieves mild and efficient leaching: This invention breaks through the existing technical bottleneck by using a low eutectic solvent with a specific composition (hydrogen bond acceptors selected from tetraethylammonium chloride, betaine hydrochloride, etc., and hydrogen bond donors from pyruvate, with a molar ratio of 1:6 to 1:9). This solvent can achieve almost complete leaching of valuable metals in a short time (60 min) under relatively mild (80℃) conditions. Compared with traditional low eutectic solvent processes (such as the choline chloride-ethylene glycol system which requires 220℃ / 24h), the energy consumption is significantly reduced, solving the problem of high temperature and long time dependence in existing DES leaching processes.

[0038] 2. Integrated short-process design eliminates high-energy-consumption post-processing: This invention creatively integrates precipitation-distillation-calcination steps, eliminating complex units such as electrodeposition; oxalic acid precipitation directly recovers transition metals to generate oxalate precursors (such as CoC2O4·2H2O), which are then converted into high-purity transition metal oxides (such as Co3O4) through medium-temperature calcination (400~420℃); vacuum distillation (60~80℃) achieves efficient solvent regeneration, and the leaching performance still maintains more than 80% after 5 cycles of recycling, greatly reducing solvent costs; this closed-loop regeneration mechanism compresses the traditional multi-step process into a single continuous process, significantly improving production efficiency.

[0039] 3. Strong universality and wide material compatibility: The method of this invention shows excellent adaptability to mainstream cathode materials, including multi-component systems such as LiCoO2, NCM111, NCM523, NCM622 and NCM811. Lithium, nickel, cobalt and manganese can be almost completely leached. Its key lies in the efficient coordination ability of the eutectic solvent for a variety of transition metal elements. It is not limited by the composition ratio of cathode materials, perfectly adapts to the iterative needs of lithium-ion battery technology, and provides a universal solution for large-scale industrial recycling.

[0040] 4. Dual improvement in green environmental protection and economy: The entire process avoids the use of strong acids (such as sulfuric acid and hydrochloric acid) and the emission of harmful gases (such as NO). x The risk of equipment corrosion is significantly reduced due to the presence of Cl2; the biodegradable nature of the solvent reduces environmental pollution at the source. Furthermore, mild operating conditions reduce equipment maintenance costs, the solvent recycling mechanism reduces raw material consumption, and the overall recovery cost is significantly lower than that of traditional hydrometallurgy, thus ensuring both economic and environmental benefits.

[0041] 5. Regenerated materials have performance close to commercial cathode materials: Electrochemical tests have verified that the regenerated cathode materials (such as lithium cobalt oxide) have an initial discharge capacity of 147.5 mAh / g (0.1C) and a capacity retention rate of >89% after 100 cycles (0.5C), which is close to the performance of commercial cathode materials. This is due to the high crystallinity of the transition metal oxide precursor and the precise control of the lithium:transition metal ratio, proving that this technology can realize the high-value recycling of resources.

[0042] In summary, this invention systematically solves the three major defects of existing DES recycling processes—high energy consumption, long process, and high cost—through solvent innovation, process reconstruction, and recycling mechanisms. It achieves leapfrog progress in five dimensions: mild and efficient leaching, short-process closed-loop regeneration, universality of multiple materials, green and low-cost, and high-quality regeneration, providing key technical support for the sustainable development of lithium-ion batteries. Attached Figure Description

[0043] Figure 1 This is a process flow diagram of the cathode material regeneration method of the present invention.

[0044] Figure 2 The infrared spectra of the eutectic solvents prepared in Examples 2 and 5-8 of this invention are shown.

[0045] Figure 3 The figures show the leaching performance data of valuable metals by different molar ratios of betaine hydrochloride-pyruvic acid eutectic solvent in Examples 2 and 5-8 of this invention.

[0046] Figure 4 The figures show (a) leaching performance data of valuable metals by the betaine hydrochloride-pyruvic acid eutectic solvent with different water contents in Examples 6 and 9-12 of this invention, and (b) viscosity data at different temperatures.

[0047] Figure 5 The figures show the leaching performance data of valuable metals with different liquid-to-solid ratios in Examples 10 and 13-17 of this invention.

[0048] Figure 6 The figures show the leaching performance data of valuable metals at different leaching temperatures in Examples 10 and 18-21 of this invention.

[0049] Figure 7 The figures show the leaching performance data of valuable metals at different leaching times in Examples 10 and 22-29 of this invention.

[0050] Figure 8 The images show (a) infrared spectra and (b) nuclear magnetic resonance spectra of the fresh and regenerated eutectic solvents obtained in Example 34 of this invention.

[0051] Figure 9 The graph shows the concentration of valuable metals in the eutectic solvent (a) and the leaching performance of valuable metals (b) under different cycles in Example 34 of the present invention.

[0052] Figure 10 The XRD patterns of (a) cobalt oxalate dihydrate and (b) cobalt tetroxide obtained in Example 34 of this invention are shown.

[0053] Figure 11The image shows the XRD pattern of lithium carbonate obtained in Example 34 of this invention.

[0054] Figure 12 The XRD spectra of (a) transition metal oxalate dihydrate and (b) transition metal oxide obtained in Example 35 of this invention are shown.

[0055] Figure 13 The images shown are (a) XRD pattern, (b) scanning electron microscope image and (c) transmission electron microscope image of lithium cobalt oxide obtained in Example 38 of this invention. Detailed Implementation

[0056] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0057] This invention first provides a method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent, comprising the following steps:

[0058] S1. Mix hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:6 to 1:9 to form a first mixture; add 0-20% deionized water to the first mixture and stir at 60-80°C for 30-60 minutes to obtain a homogeneous and transparent eutectic solvent; the hydrogen bond acceptor is selected from one of choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvate;

[0059] S2. Pre-treat the waste lithium-ion batteries to obtain waste cathode materials;

[0060] S3. Mix the eutectic solvent obtained in step S1 with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, heat and stir to leach out the valuable metals, and obtain the leachate (containing valuable metal ions) after leaching.

[0061] According to the present invention, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvate, the molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:8, and the amount of deionized water added is 10% of the total mass of the first mixture.

[0062] According to the present invention, in step S2, the pretreatment process of the waste lithium-ion battery is as follows: the waste lithium-ion battery is completely discharged (salt water discharge or discharge cabinet discharge), disassembled to obtain the positive electrode sheet, the positive electrode sheet is cut and calcined to obtain the waste positive electrode material; for the convenience of the experimental process, the size of the cut positive electrode sheet in the following embodiments is 10cm×10cm, the calcination temperature is 550℃, and the calcination time is 2h.

[0063] According to the present invention, the types of cathode materials for spent lithium-ion batteries include lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (NCM111, LiNi). 0.33 Co 0.33 Mn 0.33 O2), NCM523 (LiNi) 0.5 Co 0.2 Mn 0.3 O2), NCM622 (LiNi) 0.6 Co 0.2 Mn 0.2 O2), NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 One or more of the following (O2).

[0064] According to the present invention, the water content of the eutectic solvent used in the leaching process of valuable metals in waste lithium-ion battery cathode materials is 0~20wt%, preferably 10wt%.

[0065] According to the present invention, in step S3, the liquid-to-solid ratio of the eutectic solvent to the waste cathode material is preferably 50:1 g / g; the leaching temperature is 80~90℃, and the leaching time is 40~90 min, preferably leaching at 80℃ for 60 min.

[0066] Based on the above-mentioned method for extracting valuable metals from spent lithium-ion batteries using eutectic solvents, this invention further provides a method for regenerating cathode materials, such as... Figure 1 The above includes the following steps:

[0067] S1. Mix hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:6 to 1:9 to form a first mixture; add 0-20% deionized water to the first mixture and stir at 60-80°C for 30-60 minutes to obtain a homogeneous and transparent eutectic solvent; the hydrogen bond acceptor is selected from one of choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvate;

[0068] S2. Pre-treat the waste lithium-ion batteries to obtain waste cathode materials;

[0069] S3. Mix the eutectic solvent obtained in step S1 with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, heat and stir to leach out the valuable metals, and obtain the leachate (containing valuable metal ions) after leaching.

[0070] S4. After the leachate obtained in step S3 has cooled to room temperature, deionized water is added to the leachate for dilution and filtration is performed to remove undissolved waste cathode material powder from the leachate, and filtrate is obtained.

[0071] S5. Add oxalic acid as a precipitant to the filtrate, and after the reaction is complete, centrifuge to obtain a solid precipitate and a supernatant.

[0072] S6. The supernatant obtained in step S5 is subjected to vacuum distillation to remove water, and the recovered eutectic solvent is obtained.

[0073] S7. Use the recovered eutectic solvent for a new round of extraction of valuable metals from waste lithium-ion batteries, repeat steps S2 to S6 4 ​​to 6 times to obtain a lithium-rich solution (lithium-rich eutectic solvent leachate).

[0074] S8. After washing the solid precipitate obtained in step S5 with anhydrous ethanol 2 to 4 times, dry it in a vacuum drying oven to obtain a cathode material precursor. Place the cathode material precursor in a muffle furnace for calcination to obtain a transition metal oxide.

[0075] S9. Add sodium hydroxide solution to the lithium-rich solution obtained in step S7 to adjust the pH and filter to remove impurities. Then add saturated sodium carbonate solution to allow for a full reaction. After the reaction is complete, filter and wash and dry the filtered solid with hot water to obtain lithium carbonate.

[0076] S10. Take the transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9, mix them and grind them thoroughly to obtain a second mixture; then calcine the second mixture to obtain a regenerated lithium-ion battery cathode material.

[0077] According to the present invention, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvate, the molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:8, and the amount of deionized water added is 10% of the total mass of betaine hydrochloride and pyruvate.

[0078] According to the present invention, in step S2, the pretreatment process of the waste lithium-ion battery is as follows: the waste lithium-ion battery is completely discharged (salt water discharge or discharge cabinet discharge), disassembled to obtain the positive electrode sheet, the positive electrode sheet is cut and calcined to obtain the waste positive electrode material; for the convenience of the experimental process, the size of the cut positive electrode sheet in the following embodiments is 10cm×10cm, the calcination temperature is 550℃, and the calcination time is 2h.

[0079] According to the present invention, the types of cathode materials for spent lithium-ion batteries include lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (NCM111, LiNi). 0.33 Co 0.33 Mn 0.33 O2), NCM523 (LiNi) 0.5 Co 0.2 Mn 0.3O2), NCM622 (LiNi) 0.6 Co 0.2 Mn 0.2 O2), NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 One or more of the following (O2).

[0080] According to the present invention, the water content of the eutectic solvent used in the leaching process of valuable metals in waste lithium-ion battery cathode materials is 0~20wt% (the amount of deionized water added in step S1 is 0~20% of the total mass of the first mixture), preferably 10wt%.

[0081] According to the present invention, in step S3, the liquid-solid ratio of the eutectic solvent to the waste cathode material is preferably 50:1 g / g; the leaching temperature is 80~90℃, and the leaching time is 40~90 min, preferably leaching at 80℃ for 60 min.

[0082] According to the present invention, in step S4, the amount of deionized water added is 0.5 to 1 times the volume of the leachate.

[0083] According to the present invention, in step S5, the amount of oxalic acid added is 1.05 to 1.15 times the total molar amount of transition metal elements in the leachate, the reaction temperature is 60 to 70°C, the reaction time is 180 to 360 min, the centrifugation speed is 8000 to 10000 rpm, and the time is 10 to 30 min.

[0084] According to the present invention, in step S6, the temperature of vacuum distillation is 60~80℃ and the time is 6~12h.

[0085] According to the present invention, in step S8, the drying temperature is 70~90℃ and the drying time is 12~16h; the calcination process of the cathode material precursor is as follows: the cathode material precursor is placed in a muffle furnace and heated from room temperature to 200~210℃ at a heating rate of 4~6℃ / min to remove the water of crystallization in the precursor, and then heated to 395~405℃ at a heating rate of 2~3℃ / min and held at a constant temperature for 1~2h to ensure complete reaction.

[0086] According to the present invention, step S9 specifically involves: adjusting the pH to 10-12 using sodium hydroxide solution, stirring at 50-60°C for 20-40 minutes, and filtering to remove impurities; adding sodium hydroxide solution to the filtrate to adjust the pH to greater than 12, adding saturated sodium carbonate solution at 90-95°C, washing the filtered solid three times with hot water at 80-90°C, and then drying it in a vacuum drying oven at 105-120°C for 4-6 hours to obtain lithium carbonate.

[0087] According to the present invention, in step S10, the calcination process of the second mixture includes two stages: the first stage of calcination: the second mixture is placed in a muffle furnace and heated from room temperature to 500°C at a heating rate of 3°C / min, and held at 500°C for 5 hours; the second stage of calcination: the temperature is raised to 850~950°C at a heating rate of 3°C / min and held at 500°C for 12 hours.

[0088] According to the present invention, step S10 is preferably to mix the transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9 with a molar ratio of total transition metal elements (Ni+Co+Mn): lithium element (Li) = 1:1.05 and grind them thoroughly to obtain a second mixture; the second stage calcination of the second mixture is preferably to raise the temperature to 900°C at a heating rate of 3°C / min and hold it at that temperature for 12 hours.

[0089] Unless otherwise specified, all materials and equipment used in this invention are commercially available products well known to those skilled in the art.

[0090] The following examples and comparative examples will be used to illustrate the implementation of this application in more detail.

[0091] The battery cycle stability test of this invention uses the obtained recycled positive electrode material as the electrode material to prepare a coin cell for charge-discharge testing, and includes the following steps:

[0092] 1. Preparation of button cells;

[0093] 2. Settling: Let the assembled battery stand for 12 hours to allow the electrolyte to fully wet the electrode materials;

[0094] 3. Charge-discharge cycle test;

[0095] a. Testing System: Constant current charge-discharge cycle testing was conducted using the CT2001A battery testing system from Landian Electronics Co., Ltd.

[0096] b. Test conditions

[0097] Temperature: Room temperature.

[0098] Voltage range: 3.0–4.2V.

[0099] c. Testing process:

[0100] First, circulate the electrode material for 4 cycles at 0.05C to activate it.

[0101] Then, a long-cycle test was conducted at 0.5C to evaluate the battery's cycle stability.

[0102] The preparation of button cells includes the following steps:

[0103] Step 1: Electrode material mixing and slurry preparation

[0104] The recycled cathode material obtained in step S10, acetylene black, and polyvinylidene fluoride are uniformly mixed in N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry.

[0105] Step 2: Electrode preparation

[0106] The electrode paste was uniformly coated onto a flat aluminum foil using a four-sided preparation tool (scraper). The coated electrode was then placed in a vacuum oven and dried at 90°C for 16 hours.

[0107] Use a slicer to cut the electrode into 12mm diameter round pieces and place them in a glove box for later use;

[0108] Step 3: Battery Assembly

[0109] Assembly was completed in a vacuum glove box, ensuring that the oxygen level in the glove box was below 0.01 ppm;

[0110] Electrolyte: 1 mol / L lithium hexafluorophosphate in ethylene carbonate and dimethyl carbonate (volume ratio 1:1).

[0111] Membrane: Celgaed 2400 polypropylene membrane;

[0112] Counter electrode: Lithium metal sheet.

[0113] Example 1

[0114] The extraction of valuable metals from waste lithium-ion batteries in this embodiment includes the following steps:

[0115] S1. Preparation of eutectic solvent: Choline chloride and pyruvic acid were placed in a round-bottom flask in a molar ratio of 1:6 without adding deionized water. The mixture was heated and stirred at 70°C for 40 min to obtain a homogeneous and transparent eutectic solvent.

[0116] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0117] S3. Leaching of valuable metals with eutectic solvent: Place 0.2g of the waste LiCoO2 cathode material obtained in step S2 into a 20ml glass bottle, add 10g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 80℃ and stir for 60min to obtain a leachate containing valuable metal ions.

[0118] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 92.4% and 88.7%, respectively.

[0119] Example 2

[0120] The extraction of valuable metals from waste lithium-ion batteries in this embodiment includes the following steps:

[0121] S1. Preparation of eutectic solvent: Betaine hydrochloride and pyruvic acid were placed in a round-bottom flask in a molar ratio of 1:6 without adding deionized water. The mixture was heated and stirred at 80°C for 60 min to obtain a homogeneous and transparent eutectic solvent.

[0122] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0123] S3. Leaching of valuable metals with eutectic solvent: Place 0.2g of the waste LiCoO2 cathode material obtained in step S2 into a 20ml glass bottle, add 10g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 80℃ and stir for 60min to obtain a leachate containing valuable metal ions.

[0124] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 94.5% and 90.1%, respectively.

[0125] Example 3

[0126] The extraction of valuable metals from waste lithium-ion batteries in this embodiment includes the following steps:

[0127] S1. Preparation of eutectic solvent: Tetraethylammonium chloride and pyruvic acid were placed in a round-bottom flask in a molar ratio of 1:6 without adding deionized water. The mixture was heated and stirred at 75°C for 50 min to obtain a homogeneous and transparent eutectic solvent.

[0128] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0129] S3. Leaching of valuable metals with eutectic solvent: Place 0.2g of the waste LiCoO2 cathode material obtained in step S2 into a 20ml glass bottle, add 10g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 80℃ and stir for 60min to obtain a leachate containing valuable metal ions.

[0130] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 92.1% and 88.4%, respectively.

[0131] Example 4

[0132] The extraction of valuable metals from waste lithium-ion batteries in this embodiment includes the following steps:

[0133] S1. Preparation of eutectic solvent: Tetrapropylammonium chloride and pyruvic acid were placed in a round-bottom flask in a molar ratio of 1:6 without adding deionized water. The mixture was heated and stirred at 75°C for 60 min to obtain a homogeneous and transparent eutectic solvent.

[0134] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0135] S3. Leaching of valuable metals with eutectic solvent: Place 0.2g of the waste LiCoO2 cathode material obtained in step S2 into a 20ml glass bottle, add 10g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 80℃ and stir for 60min to obtain a leachate containing valuable metal ions.

[0136] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 91.7% and 87.8%, respectively.

[0137] Comparative Example 1

[0138] The extraction of valuable metals from waste lithium-ion batteries in this comparative example includes the following steps:

[0139] S1. Preparation of eutectic solvent: Choline chloride and ethylene glycol were placed in a round-bottom flask in a molar ratio of 1:6 without adding deionized water. The mixture was heated and stirred at 80°C for 60 min to obtain a homogeneous and transparent eutectic solvent.

[0140] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0141] S3. Leaching of valuable metals with eutectic solvent: Place 0.2g of the waste LiCoO2 cathode material obtained in step S2 into a 20ml glass bottle, add 10g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 180℃ and stir for 24h to obtain a leachate containing valuable metal ions.

[0142] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 86.7% and 81.9%, respectively.

[0143] Table 1 summarizes the lithium and cobalt leaching rates of Examples 1-4 and Comparative Example 1.

[0144] Table 1

[0145]

[0146] As can be seen from Table 1, the eutectic solvents in Examples 1-4 can achieve efficient leaching of valuable metals from waste LiCoO2 cathode materials at 80℃ / 60min, which significantly reduces the leaching temperature and time required compared to traditional eutectic solvent processes (such as choline chloride-ethylene glycol), thus significantly reducing the energy consumption required for leaching. Furthermore, under the action of the eutectic solvent composed of betaine hydrochloride and pyruvic acid, the leaching rates of lithium and cobalt elements in waste LiCoO2 cathode materials are the highest, and the leaching effect is the best.

[0147] Examples 5-8

[0148] The basic steps are the same as in Example 2.

[0149] Under the conditions of 0 wt% water content (no deionized water added in step S1), liquid-to-solid ratio of 50:1 g / g, leaching temperature of 80℃, and leaching time of 60 min, the molar ratio of betaine hydrochloride to pyruvic acid was used as a variable to study the effect of the molar ratio on the leaching rate of valuable metals in waste cathode materials.

[0150] In Example 5, the molar ratio of betaine hydrochloride to pyruvic acid was 1:7; in Example 6, the molar ratio of betaine hydrochloride to pyruvic acid was 1:8; in Example 7, the molar ratio of betaine hydrochloride to pyruvic acid was 1:9; and in Example 8, the molar ratio of betaine hydrochloride to pyruvic acid was 1:10.

[0151] The structures of the eutectic solvents prepared in Examples 2 and 5-8 were characterized using Fourier transform infrared spectroscopy, and the results are as follows: Figure 2 As shown, from Figure 2 As can be seen from the data, the hydroxyl vibration peaks of betaine hydrochloride (BeCl) and pyruvic acid (PA) are located at 3438 cm⁻¹, respectively. -1 and 3215cm -1 The prepared eutectic solvent was only at 1344 cm⁻¹. -1 There is a hydroxyl vibration peak at 1726 cm⁻¹. -1 and 1138cm -1 The presence of vibrational peaks for C=O and CO bonds at the locations confirms that the substance prepared in step S1 is indeed a eutectic solvent.

[0152] The leaching rates of lithium and cobalt in Examples 5-8 were calculated, and the effect of the molar ratio (Examples 2, 5-8) on the leaching rate of valuable metals is summarized in [reference needed]. Figure 3 ,from Figure 3 It can be seen that when the molar ratio of betaine hydrochloride to pyruvic acid is 1:6 to 1:9, the leaching rate of valuable metals is above 90%. Furthermore, as the amount of pyruvic acid in the system increases, the leaching rate of valuable metals first rises and then falls. When the molar ratio of betaine hydrochloride to pyruvic acid is 1:6, the leaching rates of lithium and cobalt are 94.5% and 90.1%, respectively. When the molar ratio of betaine hydrochloride to pyruvic acid changes to 1:8, the leaching rates of lithium and cobalt increase to 98.7% and 95.0%, respectively. When the molar ratio of betaine hydrochloride to pyruvic acid changes to 1:10, the leaching rates of lithium and cobalt decrease to 93.2% and 88.8%, respectively. Therefore, the optimal molar ratio of betaine hydrochloride to pyruvic acid in the leaching solvent should be 1:8.

[0153] Examples 9-12

[0154] The basic steps are the same as in Example 6.

[0155] Under the conditions of a molar ratio of betaine hydrochloride to pyruvic acid of 1:8, a liquid-to-solid ratio of 50:1 g / g, a leaching temperature of 80℃, and a leaching time of 60 min, the effect of water content (the amount of deionized water added in step S1) on the leaching rate of valuable metals in waste cathode materials was studied.

[0156] In Example 9, step S1, the amount of deionized water added was 5% of the total mass of betaine hydrochloride and pyruvic acid; in Example 10, step S1, the amount of deionized water added was 10% of the total mass of betaine hydrochloride and pyruvic acid; in Example 11, step S1, the amount of deionized water added was 15% of the total mass of betaine hydrochloride and pyruvic acid; and in Example 12, step S1, the amount of deionized water added was 20% of the total mass of betaine hydrochloride and pyruvic acid.

[0157] The leaching rates of lithium and cobalt in Examples 9-12 were calculated, and the effect of water content (Examples 6, 9-12) on the leaching rate of valuable metals is summarized in [the table below]. Figure 4 ,from Figure 4 As can be seen, when the water content of the eutectic solvent is between 0 wt% and 20 wt%, the leaching rate of valuable metals is above 90%. Furthermore, with the increase of water content in the prepared eutectic solvent (BeCl-PA), the leaching rate of valuable metals first increases and then decreases. When the water content of the eutectic solvent is 0 wt%, the leaching rates of lithium and cobalt are 98.7% and 95.0%, respectively. When the water content of the eutectic solvent increases to 10 wt%, the leaching rates of lithium and cobalt reach their maximum values, increasing to 99.9% and 99.5%, respectively. When the water content of the eutectic solvent further increases to 20 wt%, the leaching rates of lithium and cobalt decrease to 96.2% and 91.9%, respectively. The addition of water significantly reduces the viscosity of the eutectic solvent, which facilitates solid-liquid phase contact and increases the transport rate. Therefore, the optimal water content in the leaching solvent should be 10 wt%.

[0158] Examples 13-17

[0159] The basic steps are the same as in Example 10.

[0160] Under the conditions of 10wt% water content (the amount of deionized water added in step S1 is 10% of the total mass of betaine hydrochloride and pyruvic acid), a molar ratio of betaine hydrochloride to pyruvic acid of 1:8, a leaching temperature of 80℃, and a leaching time of 60min, the liquid-solid ratio (the mass ratio of the eutectic solvent placed in the glass bottle in step S3 to the waste LiCoO2 cathode material) was used as a variable to study the effect of the liquid-solid ratio on the leaching rate of valuable metals in the waste cathode material.

[0161] In Example 13, the liquid-to-solid ratio was 20:1 g / g (in step S3, the amount of waste LiCoO2 cathode material added in the comparative example was 0.5 g, and the amount of eutectic solvent added was 10 g); in Example 14, the liquid-to-solid ratio was 30:1 g / g (in step S3, the amount of waste LiCoO2 cathode material added in the comparative example was 0.333 g, and the amount of eutectic solvent added was 10 g); in Example 15, the liquid-to-solid ratio was 40:1 g / g (in step S3, the amount of waste LiCoO2 cathode material added in the comparative example was 0.333 g, and the amount of eutectic solvent added was 10 g); In Example 16, the liquid-to-solid ratio was 60:1 g / g (in step S3, the amount of waste LiCoO2 cathode material added in the comparative example was 0.167 g, and the amount of eutectic solvent added was 10 g); in Example 17, the liquid-to-solid ratio was 70:1 g / g (in step S3, the amount of waste LiCoO2 cathode material added in the comparative example was 0.143 g, and the amount of eutectic solvent added was 10 g).

[0162] The leaching rates of lithium and cobalt in Examples 13-17 were calculated, and the effect of the liquid-to-solid ratio (Examples 10, 13-17) on the leaching rate of valuable metals is summarized in [reference needed]. Figure 5 ,from Figure 5 It can be seen that when the liquid-to-solid ratio is 40:1~70:1 g / g, the leaching rate of valuable metals is above 90%; and when the liquid-to-solid ratio is between 20:1 g / g and 50:1 g / g, the leaching rate of valuable metals shows a significant upward trend (when the liquid-to-solid ratio is 20:1 g / g, the leaching rates of lithium and cobalt are 86.1% and 71.7%, respectively; when the liquid-to-solid ratio is 50:1 g / g, the leaching rates of lithium and cobalt are...). The leaching rates were 99.9% and 99.5%, respectively. When the liquid-to-solid ratio was further increased (from 50:1 g / g to 70:1 g / g), the leaching rate of valuable metals increased, but not significantly (when the liquid-to-solid ratio was 70:1 g / g, the leaching rates of lithium and cobalt were 99.9% and 99.9%, respectively, with only the cobalt leaching rate increasing by 0.4%). Therefore, the optimal leaching liquid-to-solid ratio should be 50:1 g / g.

[0163] Examples 18-21

[0164] The basic steps are the same as in Example 10.

[0165] Under the conditions of 10wt% water content (the amount of deionized water added in step S1 is 10% of the total mass of betaine hydrochloride and pyruvic acid), a molar ratio of betaine hydrochloride to pyruvic acid of 1:8, a liquid-solid ratio of 50:1 g / g, and a leaching time of 60 min, the effect of leaching temperature on the leaching rate of valuable metals in waste cathode materials was studied, with leaching temperature as the variable.

[0166] In Example 18, the leaching temperature was 50°C; in Example 19, the leaching temperature was 60°C; in Example 20, the leaching temperature was 70°C; and in Example 21, the leaching temperature was 90°C.

[0167] The leaching rates of lithium and cobalt in Examples 18-21 were calculated, and the effect of leaching temperature (Examples 10, 18-21) on the leaching rate of valuable metals is summarized in [reference needed]. Figure 6 ,from Figure 6 As can be seen, when the leaching temperature is 80-90℃, the leaching rate of valuable metals is close to 100%. When the leaching temperature is between 50℃ and 80℃, the leaching rate of valuable metals shows a clear upward trend (when the leaching temperature is 50℃, the leaching rates of lithium and cobalt are 57.8% and 29.0%, respectively; when the leaching temperature is increased to 80℃, the leaching rates of lithium and cobalt increase to 99.9% and 99.5%, respectively). When the leaching temperature is further increased (80℃ to 90℃), the leaching rate of valuable metals increases, but not significantly (when the leaching temperature is 90℃, the leaching rates of lithium and cobalt are 99.9% and 99.6%, respectively, with only the cobalt leaching rate increasing by 0.1%). Therefore, the optimal leaching temperature should be 80℃.

[0168] Examples 22-29

[0169] The basic steps are the same as in Example 10.

[0170] Under the conditions of 10wt% water content (the amount of deionized water added in step S1 is 10% of the total mass of betaine hydrochloride and pyruvic acid), a molar ratio of betaine hydrochloride to pyruvic acid of 1:8, a liquid-solid ratio of 50:1 g / g, and a leaching temperature of 80℃, the effect of leaching time on the leaching rate of valuable metals in waste cathode materials was studied, with leaching time as the variable.

[0171] In Example 22, the leaching time was 10 min; in Example 23, the leaching time was 20 min; in Example 24, the leaching time was 30 min; in Example 25, the leaching time was 40 min; in Example 26, the leaching time was 50 min; in Example 27, the leaching time was 70 min; in Example 28, the leaching time was 80 min; and in Example 29, the leaching time was 90 min.

[0172] The leaching rates of lithium and cobalt in Examples 22-29 were calculated, and the effect of leaching time (Examples 10, 22-29) on the leaching rate of valuable metals is summarized in [reference needed]. Figure 7 ,from Figure 7It can be seen that when the leaching time is 40-90 min, the leaching rate of valuable metals is above 90%; and when the leaching time is 10 min-60 min, the leaching rate of valuable metals shows a clear upward trend (when the leaching time is 10 min, the leaching rates of lithium and cobalt are 77.5% and 55.2%, respectively; when the leaching time increases to 60 min, the leaching rates of lithium and cobalt increase to 99.9% and 99.5%, respectively); when the leaching time is further increased (60 min-90 min), the leaching rate of valuable metals increases, but not significantly (when the leaching time is 90 min, the leaching rates of lithium and cobalt are 99.9% and 99.6%, respectively, with only the cobalt leaching rate increasing by 0.1%). Therefore, the optimal leaching time should be 60 min.

[0173] Examples 30-33

[0174] The basic steps are the same as in Example 10.

[0175] Under the conditions of 10wt% water content (the amount of deionized water added in step S1 is 10% of the total mass of betaine hydrochloride and pyruvic acid), a molar ratio of betaine hydrochloride to pyruvic acid of 1:8, a liquid-solid ratio of 50:1 g / g, a leaching temperature of 80℃, and a leaching time of 60 min, different types of waste electrodes were taken to verify the versatility of the eutectic solvent leaching of valuable metals from waste lithium-ion batteries of the present invention.

[0176] In Example 30, step S2 involves pre-treating the waste NCM111 battery to obtain waste LiNi. 0.33 Co 0.33 Mn 0.33 O2 cathode material; In Example 31, step S2 involves pretreatment of waste NCM523 batteries to obtain waste LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode material; In step S2 of Example 32, the waste NCM622 battery is pretreated to obtain waste LiNi 0.6 Co 0.2 Mn 0.2 O2 cathode material; In Example 33, step S2, the waste NCM811 battery is pretreated to obtain waste LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode material;

[0177] The leaching rates of lithium, manganese, cobalt, and nickel in Examples 30-33 were calculated, and the leaching rates of valuable metals in different waste cathode materials (Examples 30-33) are summarized in Table 2.

[0178] Table 2

[0179]

[0180] As can be seen from Table 2, the eutectic solvent of the present invention exhibits excellent leaching effect when leaching valuable metals from different types of waste lithium-ion batteries. The leaching rate of each transition metal element exceeds 99%, indicating that the eutectic solvent of the present invention has universality in leaching valuable metals from waste lithium-ion batteries.

[0181] Example 34

[0182] S1. Preparation of eutectic solvent: Betaine hydrochloride and pyruvic acid were placed in a round-bottom flask at a molar ratio of 1:8, and 10wt% deionized water was added. The mixture was heated and stirred at 80℃ for 60 min to obtain a homogeneous and transparent eutectic solvent (fresh eutectic solvent).

[0183] S2. Obtaining waste positive electrode material: Soak waste LiCoO2 batteries in a 10g / L sodium chloride solution for 24 hours to completely discharge them, then air dry them naturally. Manually disassemble them to obtain positive electrode sheets and cut them into 10cm×10cm sizes. Place them in a muffle furnace and calcine at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, use a brush to peel the powder off the aluminum foil surface and grind it to obtain waste LiCoO2 positive electrode material.

[0184] S3. Leaching of valuable metals with eutectic solvent: Place 2g of the waste LiCoO2 cathode material obtained in step S2 into a 250ml glass bottle, add 100g of the eutectic solvent prepared in step S1 into the glass bottle, add a magnetic spool and seal the bottle, place the glass bottle in an oil bath and heat to 80℃ and stir for 60min to obtain a leachate containing valuable metal ions.

[0185] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates of lithium and cobalt were calculated to be 99.6% and 99.2%, respectively.

[0186] S4-S7. Regeneration and Recycling of Eutectic Solvent: After the leachate cooled to room temperature, 60 ml of deionized water was added to dilute the leachate and the mixture was filtered to obtain the filtrate. 2 g of oxalic acid was added to the filtrate, and the mixture was heated and stirred at 60 °C for 240 min, followed by centrifugation at 10000 rpm for 30 min to obtain a solid precipitate and a supernatant. The supernatant was subjected to vacuum distillation at 80 °C for 8 h to remove water, yielding the recovered eutectic solvent (regenerated eutectic solvent). The structures of the fresh and regenerated eutectic solvents were characterized using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, with results as follows: Figure 8 As shown, from Figure 8As can be seen, the structure of the recovered eutectic solvent did not change significantly compared to the fresh eutectic solvent. The recovered eutectic solvent was used for a new round of extraction of valuable metals from spent lithium-ion batteries, and a lithium-rich solution was obtained after 5 cycles. After each cycle, the concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the leaching rates of lithium and cobalt were calculated. The results are shown in [Figure number missing]. Figure 9 ,from Figure 9 As can be seen, after 5 cycles, the leaching rate of lithium and cobalt by the eutectic solvent is still over 80%. The repeated use of the eutectic solvent can reduce wastewater discharge and reagent costs, indicating that the present invention has high economic efficiency and sustainability.

[0187] S8. Cobalt element recovery: The solid precipitate obtained in steps S4-S7 was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 80℃ for 12 hours to obtain the cathode material precursor. The cathode material precursor was then calcined in a muffle furnace according to the following procedure: the temperature was increased from room temperature to 200℃ at a rate of 5℃ / min, then increased to 400℃ at a rate of 2℃ / min, and held at 400℃ for 2 hours to obtain a black powder. The XRD test results of the cathode material precursor and the black powder are as follows: Figure 10 As shown, it was confirmed that the cathode material precursor was cobalt oxalate dihydrate (CoC2O4·2H2O) and the black powder was cobalt tetroxide (Co3O4).

[0188] S9. Lithium Element Recovery: Add sodium hydroxide solution to the lithium-rich solution obtained in steps S4-S7 to adjust the pH to 11. Stir at 55℃ for 30 min, filter to remove impurities, then add sodium hydroxide solution to the filtrate to adjust the pH to 13. Add saturated sodium carbonate solution at 90℃ to allow for complete reaction. After the reaction is complete, filter. Wash the filtered solid three times with 85℃ hot water. Dry the solid in a vacuum drying oven at 110℃ for 5 h to obtain a white solid powder. Perform XRD analysis on the dried white solid powder. The results are as follows: Figure 11 As shown, its chemical structure is confirmed to be lithium carbonate (Li2CO3).

[0189] Example 35

[0190] S1. Preparation of eutectic solvent: Betaine hydrochloride and pyruvic acid were placed in a round-bottom flask at a molar ratio of 1:8, 10wt% deionized water was added, and the mixture was heated and stirred at 80℃ for 60 min to obtain a homogeneous and transparent eutectic solvent.

[0191] S2. Obtaining waste positive electrode material: Waste NCM622 batteries were soaked in a 10g / L sodium chloride solution for 24 hours to completely discharge them. After that, they were air-dried, manually disassembled to obtain positive electrode sheets, and cut into 10cm×10cm pieces. These sheets were then calcined in a muffle furnace at 550℃ for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was peeled off from the aluminum foil surface with a brush and ground to obtain waste LiNi. 0.6 Co 0.2 Mn 0.2 O2 cathode material;

[0192] S3. Leaching of valuable metals with a eutectic solvent: 2g of the waste LiNi obtained in step S2... 0.6 Co 0.2 Mn 0.2 The O2 cathode material was placed in a 250ml glass bottle, and 100g of the eutectic solvent prepared in step S1 was added to the glass bottle. After adding a magnetic spool, the bottle was sealed and placed in an oil bath to be heated to 80°C and stirred for 60 minutes to obtain a leachate containing valuable metal ions.

[0193] The concentration of valuable metals in the leachate was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leaching rates were calculated to be 99.4% for lithium, 99.2% for manganese, 99.1% for cobalt, and 99.0% for nickel.

[0194] S4-S7. Regeneration and recycling of eutectic solvent: After the leachate cools to room temperature, add 65 ml of deionized water to dilute and filter to obtain filtrate; add 2 g of oxalic acid to the filtrate, heat and stir at 65°C for 300 min, then centrifuge at 10000 rpm for 30 min to obtain solid precipitate and supernatant respectively; remove water from the supernatant by vacuum distillation at 80°C for 8 h to obtain the recovered eutectic solvent; use the recovered eutectic solvent for a new round of extraction of valuable metals from waste lithium-ion batteries, and obtain a lithium-rich solution after 5 cycles;

[0195] S8. Transition Metal Element Recovery: The solid precipitate obtained in steps S4-S7 was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 80°C for 12 hours to obtain the cathode material precursor. The cathode material precursor was then calcined in a muffle furnace according to the following procedure: the temperature was increased from room temperature to 200°C at a rate of 5°C / min, then increased to 400°C at a rate of 2°C / min, and held at 400°C for 2 hours to obtain a black powder. The XRD test results of the cathode material precursor and the black powder are as follows: Figure 12 As shown, this confirms that the cathode material precursor is (Ni 0.6 Co 0.2 Mn 0.2C2O4·2H2O, the black powder is (Ni 0.6 Co 0.2 Mn 0.2 )3O4;

[0196] S9. Lithium element recovery: Add sodium hydroxide solution to the lithium-rich solution obtained in steps S4-S7 to adjust the pH to 11, stir at 55℃ for 30 min, filter to remove impurities, then add sodium hydroxide solution to the filtrate to adjust the pH to 13, add saturated sodium carbonate solution at 90℃, and allow it to react fully. After the reaction is complete, filter, wash the filtered solid three times with hot water at 85℃, and dry the solid in a vacuum drying oven at 110℃ for 5 h to obtain lithium carbonate.

[0197] Examples 36-40

[0198] S10. The lithium carbonate and cobalt tetroxide obtained in Example 34 were mixed and thoroughly ground in lithium:cobalt molar ratios of 1.01:1 (Example 36), 1.03:1 (Example 37), 1.05:1 (Example 38), 1.07:1 (Example 39), and 1.09:1 (Example 40), respectively, to obtain a second mixture composed of lithium carbonate and cobalt tetroxide. This second mixture was then calcined in a muffle furnace using the following procedure: the temperature was increased from room temperature to 500°C at a rate of 3°C / min, held at 500°C for 5 hours, and then increased to 900°C at a rate of 3°C / min and held for 12 hours to obtain regenerated lithium cobalt oxide cathode material. The XRD, scanning electron microscopy, and transmission electron microscopy characterization results of the lithium cobalt oxide prepared in Example 38 with a lithium:cobalt molar ratio of 1.05:1 are as follows: Figure 13 As shown in the figure, the structure of the prepared material is determined to be lithium cobalt oxide.

[0199] The lithium cobalt oxide cathode material regenerated in step S10 with different lithium:cobalt molar ratios, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry. A coin cell was then fabricated according to the aforementioned coin cell fabrication steps, and charge-discharge tests (1C=150mAh / g) were conducted. Regenerated lithium cobalt oxide cathode materials prepared with lithium:cobalt molar ratios of 1.01:1 (Example 36), 1.03:1 (Example 37), 1.05:1 (Example 38), 1.07:1 (Example 39), and 1.09:1 (Example 40) were used. The initial discharge capacities (0.1C) of the lithium cobalt oxide cathode materials were 138.8 mAh / g, 142.9 mAh / g, 147.5 mAh / g, 144.9 mAh / g, and 136.0 mAh / g, respectively. After 100 cycles (0.5C), the capacity retention rates were 87.6%, 88.3%, 89.1%, 88.6%, and 88.0%, respectively. Among them, the lithium cobalt oxide cathode material regenerated in Example 38 with a lithium:cobalt molar ratio of 1.05:1 performed the best. Therefore, 1.05:1 was selected as the optimal lithium:cobalt molar ratio.

[0200] Examples 41-42

[0201] S10. The lithium carbonate and cobalt tetroxide obtained in Example 34 were mixed and ground thoroughly in a lithium:cobalt molar ratio of 1.05:1 to obtain a second mixture composed of lithium carbonate and cobalt tetroxide. The second mixture was placed in a muffle furnace for calcination. The calcination procedure was as follows: the temperature was increased from room temperature to 500°C at a heating rate of 3°C / min, and held at 500°C for 5 hours. Then, the temperature was increased to 850°C (Example 41) and 950°C (Example 42) at a heating rate of 3°C / min, and held at 850°C for 12 hours to obtain the regenerated lithium cobalt oxide cathode material.

[0202] The lithium cobalt oxide cathode material regenerated at different calcination temperatures in step S10, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry. A coin cell was fabricated according to the aforementioned coin cell fabrication steps, and charge-discharge tests were conducted (1C = 150 mAh / g). The initial discharge capacity (0.1C) of the regenerated lithium cobalt oxide cathode material prepared at calcination temperatures of 850℃ (Example 41), 900℃ (Example 38), and 950℃ (Example 42) were 134.6 mAh / g, 147.5 mAh / g, and 129.1 mAh / g, respectively. After 100 cycles (0.5C), the capacity retention rates were 85.2%, 89.1%, and 80.7%, respectively. Among these, the lithium cobalt oxide cathode material regenerated at the second calcination temperature of 900℃ in Example 38 performed best; therefore, 900℃ was selected as the optimal calcination temperature.

[0203] Example 43

[0204] S10. The lithium carbonate and (Ni) obtained in Example 35 are mixed. 0.6 Co 0.2 Mn 0.2 )3O4 was mixed with lithium and (nickel + cobalt + manganese) in a molar ratio of 1.05:1 and thoroughly ground to obtain a mixture of lithium carbonate and (Ni 0.6 Co 0.2 Mn 0.2 A second mixture consisting of 3O4 was placed in a muffle furnace and calcined. The calcination procedure was as follows: the temperature was increased from room temperature to 500°C at a heating rate of 3°C / min, held at 500°C for 5 hours, and then increased to 900°C at a heating rate of 3°C / min and held at 900°C for 12 hours to obtain regenerated LiNi. 0.6 Co 0.2 Mn 0.2 O2 cathode material.

[0205] Regenerating LiNi in step S10 0.6 Co 0.2 Mn 0.2 O2 cathode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry. A coin cell was fabricated according to the aforementioned coin cell manufacturing steps and a charge-discharge test was conducted (1C=180mAh / g). The initial discharge capacity (0.1C) and the capacity retention rate after 100 cycles (0.5C) were 165.8mAh / g and 89.8%, respectively.

[0206] Comparative Example 2

[0207] Commercial lithium cobalt oxide cathode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry. A coin cell was fabricated according to the aforementioned coin cell manufacturing steps. Charge-discharge tests were conducted (1C=150mAh / g). The initial discharge capacity (0.1C) and the capacity retention rate after 100 cycles (0.5C) were 149.3mAh / g and 90.4%, respectively.

[0208] Comparative Example 3

[0209] Commercial LiNi 0.6 Co 0.2 Mn 0.2 O2 cathode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1 to form a slurry. A coin cell was fabricated according to the aforementioned coin cell manufacturing steps and a charge-discharge test was conducted (1C=180mAh / g). The initial discharge capacity (0.1C) and the capacity retention rate after 100 cycles (0.5C) were 168.4mAh / g and 91.2%, respectively.

[0210] In summary, the method for extracting valuable metals from waste lithium-ion batteries and regenerating cathode materials based on eutectic solvents of the present invention can achieve almost complete leaching of valuable metals from waste lithium-ion battery cathode materials at a lower leaching temperature and with a shorter leaching time, thereby realizing short-process closed-loop regeneration of waste lithium-ion battery cathode materials. Moreover, the present invention has good applicability to the recycling of various waste lithium-ion cathode materials.

[0211] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent, characterized in that, Includes the following steps: S1. Hydrogen bond acceptors and hydrogen bond donors are mixed in a molar ratio of 1:6 to 1:9 to form a first mixture; 0-20% of deionized water is added to the first mixture, and the mixture is stirred at 60-80°C for 30-60 minutes to obtain a homogeneous and transparent eutectic solvent; the hydrogen bond acceptor is selected from one of choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvic acid; S2. Pre-treat the waste lithium-ion batteries to obtain waste cathode materials; S3. Mix the eutectic solvent obtained in step S1 with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, heat and stir to leach the valuable metals, the leaching temperature is 80 to 90°C, the leaching time is 40 to 90 min, and the leachate is obtained after the leaching is completed.

2. The method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent according to claim 1, characterized in that, In step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvate, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:8, and the amount of deionized water added is 10% of the total mass of the first mixture.

3. The method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent according to claim 1, characterized in that, In step S2, the pretreatment process of waste lithium-ion batteries is as follows: the waste lithium-ion batteries are completely discharged, disassembled to obtain positive electrode sheets, and the positive electrode sheets are cut and calcined to obtain waste positive electrode materials.

4. The method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent according to claim 1, characterized in that, In step S3, the liquid-to-solid ratio of the eutectic solvent to the waste cathode material is 50:1 g / g, the leaching temperature is 80℃, and the leaching time is 60 min.

5. The method for extracting valuable metals from spent lithium-ion batteries using a eutectic solvent according to claim 1, characterized in that, The waste cathode material is at least one of lithium cobalt oxide, NCM111, NCM523, NCM622, and NCM811.

6. A method for regenerating cathode materials, characterized in that, The method, based on the method for extracting valuable metals from waste lithium-ion batteries using a eutectic solvent according to any one of claims 1 to 5, further includes the following steps in addition to steps S1 to S3: S4. After the leachate obtained in step S3 has cooled to room temperature, deionized water is added to the leachate for dilution and the solution is filtered to obtain the filtrate. S5. Add oxalic acid as a precipitant to the filtrate, and after the reaction is complete, centrifuge to obtain a solid precipitate and a supernatant. S6. The supernatant obtained in step S5 is subjected to vacuum distillation to remove water, and the recovered eutectic solvent is obtained. S7. Use the recovered eutectic solvent for a new round of extraction of valuable metals from waste lithium-ion batteries, repeat steps S2 to S6 4 ​​to 6 times to obtain a lithium-rich solution. S8. The solid precipitate obtained in step S5 is washed 2 to 4 times with anhydrous ethanol and then dried to obtain a cathode material precursor. The cathode material precursor is then calcined to obtain a transition metal oxide. S9. Add sodium hydroxide solution to the lithium-rich solution obtained in step S7 to adjust the pH and filter to remove impurities. Then add saturated sodium carbonate solution to allow for a full reaction. After the reaction is complete, filter and wash and dry the solid obtained from the filter to obtain lithium carbonate. S10. Take the transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9, mix them and grind them thoroughly to obtain a second mixture; then calcine the second mixture to obtain a regenerated lithium-ion battery cathode material.

7. The method for regenerating cathode materials according to claim 6, characterized in that, In step S4, the amount of deionized water added is 0.5 to 1 times the volume of the leachate.

8. The method for regenerating cathode materials according to claim 6, characterized in that, In step S5, the amount of oxalic acid added is 1.05 to 1.15 times the total molar amount of transition metal elements in the leachate, the reaction temperature is 60 to 70°C, and the reaction time is 180 to 360 min; the centrifugation speed is 8000 to 10000 rpm, and the time is 10 to 30 min.

9. The method for regenerating cathode materials according to claim 6, characterized in that, In step S6, the temperature of vacuum distillation is 60-80℃, and the time is 6-12h.

10. The method for regenerating cathode materials according to claim 6, characterized in that, In step S8, the drying temperature is 70-90℃ and the drying time is 12-16h. The calcination process of the cathode material precursor is as follows: the cathode material precursor is placed in a muffle furnace and heated from room temperature to 200-210℃ at a heating rate of 4-6℃ / min to remove the water of crystallization in the precursor. Then, the temperature is raised to 395-405℃ at a heating rate of 2-3℃ / min and held at a constant temperature for 1-2h to ensure complete reaction.

11. The method for regenerating cathode materials according to claim 6, characterized in that, Step S9 specifically involves: adjusting the pH to 10-12 using sodium hydroxide solution, stirring at 50-60°C for 20-40 minutes, and filtering to remove impurities; adding more sodium hydroxide solution to the filtrate to adjust the pH to greater than 12, adding saturated sodium carbonate solution at 90-95°C, washing the filtered solid three times with hot water at 80-90°C, and then drying it in a vacuum drying oven at 105-120°C for 4-6 hours to obtain lithium carbonate.

12. The method for regenerating cathode materials according to claim 6, characterized in that, In step S10, the calcination process of the second mixture is as follows: the second mixture is placed in a muffle furnace and heated from room temperature to 500°C at a heating rate of 3°C / min, and kept at 500°C for 5 hours; then the temperature is raised to 850-950°C at a heating rate of 3°C / min and kept at 500°C for 12 hours.

13. The method for regenerating cathode materials according to claim 6, characterized in that, In step S10, a mixture of transition metal oxide and lithium carbonate is prepared with a molar ratio of total transition metal element: lithium element = 1:1.

05. The calcination process of the second mixture is as follows: the second mixture is placed in a muffle furnace and heated from room temperature to 500°C at a heating rate of 3°C / min, and kept at 500°C for 5 hours; then the temperature is raised to 900°C at a heating rate of 3°C / min and kept at 900°C for 12 hours.

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