Method for extracting valuable metal of waste lithium ion battery by using eutectic solvent and regeneration method of positive electrode material

Abstract

The invention provides a method for extracting valuable metals in waste lithium ion batteries by using a deep-eutectic solvent and a method for regenerating a positive electrode material, which are used for extracting the valuable metals in the waste lithium ion batteries and regenerating the positive electrode material by using the deep-eutectic solvent with specific composition as a leaching agent. Comprising the following steps: preparation of a eutectic solvent, acquisition of a waste positive electrode material, leaching of valuable metals from the eutectic solvent, regeneration and recycling of the eutectic solvent, recovery of transition metal elements, recovery of a lithium element, re-preparation of the positive electrode material and the like. According to the method for extracting the valuable metal of the waste lithium ion battery through the eutectic solvent and the regeneration method of the positive electrode material, the high-temperature and long-time requirements of an existing eutectic solvent leaching process can be effectively met, and the subsequent metal recovery step is remarkably simplified and even reconstructed; and short-process, low-energy-consumption and low-cost closed-loop regeneration of the positive electrode material of the waste lithium ion battery is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic waste resource treatment, and specifically relates to a method for extracting valuable metals from waste lithium-ion batteries using a low eutectic solvent and a method for regenerating positive electrode materials. Background Art

[0002] Lithium-ion batteries, with their significant advantages such as high energy density, low memory effect, and low self-discharge, 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 service life. 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. 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 metals such as lithium (Li), cobalt (Co), nickel (Ni), and manganese (Mn). Improper handling and disposal of these waste batteries not only results in a massive waste of valuable metal resources but can also lead to serious ecological and environmental risks due to heavy metal leakage. Therefore, the development of efficient, 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 is the mainstream technology for recycling waste lithium-ion batteries. It mainly uses inorganic acid (such as hydrochloric acid, sulfuric acid, nitric acid) leaching, solvent extraction, chemical precipitation, electrodeposition and other unit operations to efficiently extract target valuable metal elements from waste cathode materials. This technology route is relatively mature and has shown technical advantages such as relatively controllable energy consumption, high overall recovery rate of metal elements and high purity of recycled products. However, its disadvantages cannot be ignored: the use of strong inorganic acids inevitably causes significant corrosion to equipment, increasing equipment maintenance and replacement costs; more seriously, the leaching process produces a large amount of acidic wastewater and chlorine (Cl2), sulfur oxides (SO x ), nitrogen oxides (NO x ) and other harmful gas emissions, which bring prominent secondary environmental pollution and safety risks, and are contrary to 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 (HBAs) and hydrogen bond donors (HBDs) in a specific molar ratio, with a melting point significantly lower than that of any individual component. Deep eutectic solvents generally have outstanding properties such as low preparation cost, a wide liquid temperature window, low vapor pressure, biodegradability, and environmental friendliness. Studies have shown that deep eutectic solvents composed of some specific components exhibit excellent solubility properties for metal oxides, making them highly promising green leaching agents to replace corrosive inorganic strong acids, and are suitable for the resource recovery of waste lithium-ion battery positive electrode materials.

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

[0006] CN115692908A describes a method for selectively recovering cathode materials from spent lithium iron phosphate (LiFePO4) batteries in an ozone atmosphere. Choline chloride-ethylene glycol-type DES is used as a leaching agent, and ozone is used to selectively extract lithium. This method focuses on the selective extraction of valuable metals and relies on a specific ozone atmosphere. The recovery process is 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 is composed of a ternary system of choline chloride, oxalic acid, and p-toluenesulfonic acid. By adjusting the molar ratio of the three and adding a specific polar aprotic solvent (dimethyl sulfoxide, dimethylacetamide, etc.) to the leachate, the nickel element in the waste cathode material can be selectively separated and recovered. This method also emphasizes the selective leaching and separation and recovery of valuable metals, but the operation process is cumbersome, with problems such as a long process flow and high recovery costs.

[0008] In summary, existing deep eutectic solvent recovery technologies suffer from high leaching temperatures, long leaching times, and high energy consumption for valuable metal recovery through electrodeposition. Furthermore, the leaching recovery process focuses on the selective leaching and separation of valuable metals, resulting in a lengthy and costly process. Therefore, developing a green and efficient deep eutectic solvent-based recovery technology to achieve a short-process, closed-loop regeneration of spent lithium-ion battery cathode materials has become a key technical challenge urgently needed to be overcome in the current resource recycling field. Summary of the Invention

[0009] In response to the above technical problems, the purpose of the present invention is to provide a method for regenerating valuable metals and cathode materials from waste lithium-ion batteries by extracting them using a deep eutectic solvent, effectively overcoming the high temperature and long time requirements of the existing DES leaching process, and significantly simplifying or even reconstructing the subsequent metal recovery steps, thereby achieving a short-process, low-energy, low-cost, closed-loop regeneration of cathode materials from waste lithium-ion batteries.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

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

[0012] S1. A hydrogen bond acceptor and a hydrogen bond donor are mixed at a molar ratio of hydrogen bond acceptor to hydrogen bond donor of 1:6 to 1:9 to form a first mixture; deionized water accounting for 0 to 20% of the total mass of the first mixture 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 deep eutectic solvent; the hydrogen bond acceptor is selected from choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvic acid;

[0013] S2. Pre-treating the waste lithium-ion batteries to obtain waste positive electrode materials;

[0014] S3. The low eutectic solvent obtained in step S1 is mixed with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, and the valuable metals are leached by heating and stirring. After the leaching is completed, a leachate is obtained.

[0015] Furthermore, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvic acid, 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 batteries is: completely discharging the waste lithium-ion batteries, disassembling them to obtain positive electrode sheets, cutting and calcining the positive electrode sheets to obtain waste positive electrode materials.

[0017] Furthermore, in step S3, the leaching temperature is 80-90° C., and the leaching time is 40-90 min.

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

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

[0020] A second aspect of the present invention is to provide a method for regenerating a positive electrode material, which is based on the above-mentioned method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent, and in addition to steps S1 to S3, further comprises the following steps:

[0021] S4. After the leachate obtained in step S3 is cooled to room temperature, deionized water is added to the leachate to dilute it and filter it to obtain a filtrate;

[0022] S5. Oxalic acid was added to the filtrate as a precipitant, and the reaction was fully reacted and centrifuged to obtain a solid precipitate and a supernatant;

[0023] S6. The supernatant obtained in step S5 is subjected to reduced pressure distillation to remove water to obtain a recovered deep eutectic solvent;

[0024] S7. The recovered deep eutectic solvent is used for a new round of valuable metal extraction from waste lithium-ion batteries, and steps S2 to S6 are repeated 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, which is calcined to obtain a transition metal oxide;

[0026] S9. To the lithium-rich solution obtained in step S7, sodium hydroxide solution was added to adjust the pH and filter to remove impurities, followed by addition of a saturated sodium carbonate solution to react fully. After completion of the reaction, the solid obtained by filtration was washed and dried to obtain lithium carbonate;

[0027] S10. The total amount of transition metal elements: lithium elements = 1: (1.01-1.09) in a molar ratio. The transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9 are mixed and fully ground to obtain a second mixture; the second mixture is then calcined to obtain a regenerated lithium-ion battery positive electrode 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 the transition metal elements in the leachate, the reaction temperature is 60 to 70° C., the reaction time is 180 to 360 min, and the centrifugal operation speed is 8000 to 10000 rpm, and the time is 10 to 30 min.

[0030] Furthermore, in step S6, the temperature of the reduced pressure distillation is 60-80° C., and the time is 6-12 hours.

[0031] Furthermore, in step S8, the drying temperature is 70~90°C, and the drying time is 12~16h; the calcination process of the positive electrode material precursor is: placing the positive electrode material precursor in a muffle furnace, heating it from room temperature to 200~210°C at a heating rate of 4~6°C / min, removing the crystalline water in the precursor, and then heating it to 395~405°C at a heating rate of 2~3°C / min, and keeping the temperature constant for 1~2h to ensure complete reaction.

[0032] Furthermore, step S9 is specifically as follows: adjusting the pH to 10-12 with sodium hydroxide solution, stirring at 50-60° C. for 20-40 minutes, and filtering to remove impurities; continuing to add sodium hydroxide solution to the filtrate obtained after filtration to adjust the pH to greater than 12, adding saturated sodium carbonate solution at 90-95° C., washing the filtered solid three times with 80-90° C. hot water, and then drying 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: placing the second mixture in a muffle furnace, heating the temperature from room temperature to 500°C at a heating rate of 3°C / min, and maintaining the temperature at 500°C for 5 hours; then heating the temperature to 850-950°C at a heating rate of 3°C / min and maintaining the temperature 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, and the calcination process of the second mixture is: placing the second mixture in a muffle furnace, heating the temperature from room temperature to 500°C at a heating rate of 3°C / min, and maintaining the temperature at 500°C for 5 hours; then heating the temperature to 900°C at a heating rate of 3°C / min and maintaining the temperature for 12 hours.

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

[0036] The method for regenerating valuable metals and cathode materials from waste lithium-ion batteries using a deep eutectic solvent provided by the present invention has achieved breakthrough progress compared to the prior art. Its beneficial effects can be systematically summarized into the following five core aspects:

[0037] 1. Innovative solvent system achieves gentle and efficient leaching: The present invention breaks through the bottleneck of existing technologies by using a deep eutectic solvent with a specific composition (hydrogen bond acceptors are selected from tetraethylammonium chloride, betaine hydrochloride, etc., and pyruvic acid is the hydrogen bond donor, 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 minutes) under relatively mild conditions (80°C). Compared with traditional deep eutectic solvent processes (such as the choline chloride-ethylene glycol system that requires 220°C / 24 hours), the energy consumption is significantly reduced, solving the problem of high temperature and long-term dependence of existing DES leaching processes.

[0038] 2. Integrated short-process design eliminates high-energy post-processing: This invention creatively integrates precipitation-distillation-calcination steps, eliminating complex units such as electrodeposition. Oxalic acid precipitation directly recovers transition metals to form oxalate precursors (such as CoC2O4·2H2O), which are converted into high-purity transition metal oxides (such as Co3O4) through medium-temperature calcination (400-420°C). Reduced-pressure distillation (60-80°C) achieves efficient solvent regeneration, and even after five cycles, the leaching performance remains above 80%, significantly 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 raw material compatibility: The method of the present invention shows excellent adaptability to mainstream positive electrode materials, including multi-element systems such as LiCoO2, NCM111, NCM523, NCM622 and NCM811, and lithium, nickel, cobalt and manganese can all be almost completely leached; the key lies in the efficient coordination ability of the low eutectic solvent for various transition metal elements, which is not limited by the proportion of positive electrode material components, perfectly adapts to the needs of lithium-ion battery technology iteration, and provides a universal solution for large-scale industrial recycling.

[0040] 4. Double improvement of environmental protection and economy: the whole process avoids the use of strong acid (such as sulfuric acid, hydrochloric acid) and the emission of harmful gases (such as NO x / Cl2), significantly reducing the risk of equipment corrosion; the solvent's biodegradability reduces environmental pollution at the source. Furthermore, mild operating conditions reduce equipment maintenance costs, and the solvent recycling mechanism reduces raw material consumption. Overall recovery costs are significantly lower than those of traditional hydrometallurgy, ensuring both economic and environmental benefits.

[0041] 5. The performance of recycled materials is close to that of commercial cathode materials: The regenerated cathode materials (such as lithium cobalt oxide) have been verified by electrochemical tests: the initial discharge capacity reaches 147.5mAh / g (0.1C), and the capacity retention rate after 100 cycles (0.5C) is >89%, 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 achieve high-value recycling of resources.

[0042] In summary, the present invention systematically solves the three major defects of the existing DES recovery process, namely high energy consumption, long process and high cost, through solvent innovation, process reconstruction and recycling mechanism. It achieves leapfrog progress in five dimensions: mild and efficient leaching, short process closed-loop regeneration, multi-material universality, green and low cost, and high-quality regeneration, providing key technical support for the sustainable development of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The process flow chart of the positive electrode material regeneration method of the present invention.

[0044] Figure 2 IR spectra of the deep eutectic solvents prepared in Examples 2 and 5 to 8 of the present invention.

[0045] Figure 3 The figures are data on the leaching performance of valuable metals by betaine hydrochloride-pyruvic acid deep eutectic solvents at different molar ratios in Examples 2 and 5 to 8 of the present invention.

[0046] Figure 4 (a) leaching performance data of betaine hydrochloride-pyruvic acid deep eutectic solvents with different water contents for valuable metals in Examples 6 and Examples 9 to 12 of the present invention, and (b) viscosity data at different temperatures.

[0047] Figure 5 1 is a graph showing the leaching performance data of valuable metals at different liquid-to-solid ratios in Example 10 and Examples 13 to 17 of the present invention.

[0048] Figure 6 1 is a graph showing the leaching performance data of valuable metals at different leaching temperatures in Example 10 and Examples 18 to 21 of the present invention.

[0049] Figure 7 1 is a graph showing the leaching performance data of valuable metals at different leaching times in Example 10 and Examples 22 to 29 of the present invention.

[0050] Figure 8 (a) IR spectra and (b) NMR spectra of the fresh and regenerated deep eutectic solvents obtained in Example 34 of the present invention.

[0051] Figure 9 Graphs showing (a) the concentration of valuable metals in the deep eutectic solvent and (b) the leaching performance of the valuable metals at different cycle times in Example 34 of the present invention.

[0052] Figure 10 1 and 2 are XRD spectra of (a) cobalt oxalate dihydrate and (b) cobalt trioxide obtained in Example 34 of the present invention.

[0053] Figure 11This is the XRD spectrum of the lithium carbonate obtained in Example 34 of the present invention.

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

[0055] Figure 13 (a) XRD spectrum, (b) scanning electron microscope image, and (c) transmission electron microscope image of the lithium cobalt oxide obtained in Example 38 of the present invention. DETAILED DESCRIPTION

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

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

[0058] S1. A hydrogen bond acceptor and a hydrogen bond donor are mixed at a molar ratio of hydrogen bond acceptor to hydrogen bond donor of 1:6 to 1:9 to form a first mixture; deionized water (0 to 20% by weight of the total weight of the first mixture) 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 deep eutectic solvent; the hydrogen bond acceptor is selected from choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvic acid;

[0059] S2. Pre-treating the waste lithium-ion batteries to obtain waste positive electrode materials;

[0060] S3. The low eutectic solvent obtained in step S1 is mixed with the waste positive electrode material obtained in step S2 at a liquid-to-solid ratio of 40:1 to 90:1 g / g, and the valuable metals are leached by heating and stirring. After the leaching is completed, a leachate (containing valuable metal ions) is obtained.

[0061] According to the present invention, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvic acid, 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.

[0062] According to the present invention, in step S2, the pretreatment process of the waste lithium-ion batteries is as follows: the waste lithium-ion batteries are completely discharged (discharged in salt water or discharged in a discharge cabinet), disassembled to obtain positive electrode sheets, and the positive electrode sheets are cut and calcined to obtain waste positive electrode materials. To facilitate the experimental process, the size of the cut positive electrode sheets in the following embodiments is all 10 cm × 10 cm, the calcination temperature is 550° C., and the calcination time is 2 h.

[0063] According to the present invention, the types of cathode materials for waste lithium-ion batteries include lithium cobalt oxide (LiCoO2), 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 O2) or more.

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

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

[0066] Based on the above method of extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent, the present invention further provides a method for regenerating positive electrode materials, such as Figure 1 Said method comprises the following steps:

[0067] S1. A hydrogen bond acceptor and a hydrogen bond donor are mixed at a molar ratio of hydrogen bond acceptor to hydrogen bond donor of 1:6 to 1:9 to form a first mixture; deionized water (0 to 20% by weight of the total weight of the first mixture) 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 deep eutectic solvent; the hydrogen bond acceptor is selected from choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvic acid;

[0068] S2. Pre-treating the waste lithium-ion batteries to obtain waste positive electrode materials;

[0069] S3. Mixing the deep eutectic solvent obtained in step S1 with the waste cathode material obtained in step S2 at a liquid-to-solid ratio of 40:1 to 90:1 g / g, heating and stirring to leach the valuable metals, and obtaining a leachate (containing valuable metal ions) after the leaching is completed;

[0070] S4. After the leachate obtained in step S3 is cooled to room temperature, deionized water is added to the leachate to dilute it and filter it to remove the undissolved waste cathode material powder in the leachate to obtain a filtrate;

[0071] S5. Oxalic acid was added to the filtrate as a precipitant, and the reaction was fully reacted and centrifuged to obtain a solid precipitate and a supernatant;

[0072] S6. The supernatant obtained in step S5 is subjected to reduced pressure distillation to remove water to obtain a recovered deep eutectic solvent;

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

[0074] S8. The solid precipitate obtained in step S5 is washed 2 to 4 times with anhydrous ethanol and dried in a vacuum drying oven to obtain a cathode material precursor, which is then calcined in a muffle furnace to obtain a transition metal oxide.

[0075] S9. To the lithium-rich solution obtained in step S7, sodium hydroxide solution was added to adjust the pH and filter to remove impurities, followed by addition of a saturated sodium carbonate solution to react fully. After the reaction was completed, the solid obtained by filtration was washed with hot water and dried to obtain lithium carbonate;

[0076] S10. The total amount of transition metal elements: lithium elements = 1: (1.01-1.09) in a molar ratio. The transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9 are mixed and fully ground to obtain a second mixture; the second mixture is then calcined to obtain a regenerated lithium-ion battery positive electrode material.

[0077] According to the present invention, in step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvic acid, 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 betaine hydrochloride and pyruvic acid.

[0078] According to the present invention, in step S2, the pretreatment process of the waste lithium-ion batteries is as follows: the waste lithium-ion batteries are completely discharged (discharged in salt water or discharged in a discharge cabinet), disassembled to obtain positive electrode sheets, and the positive electrode sheets are cut and calcined to obtain waste positive electrode materials. To facilitate the experimental process, the size of the cut positive electrode sheets in the following embodiments is all 10 cm × 10 cm, the calcination temperature is 550° C., and the calcination time is 2 h.

[0079] According to the present invention, the types of cathode materials for waste lithium-ion batteries include lithium cobalt oxide (LiCoO2), 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 O2) or more.

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

[0081] According to the present invention, in step S3, the liquid-to-solid ratio of the deep eutectic solvent to the waste positive electrode material is preferably 50:1 g / g; the leaching temperature is 80-90°C, and the leaching time is 40-90 min, preferably 80°C 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 the transition metal elements in the leachate, the reaction temperature is 60 to 70°C, the reaction time is 180 to 360 min, and the speed of the centrifugal operation 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 the reduced pressure distillation is 60-80° C., and the time is 6-12 hours.

[0085] According to the present invention, in step S8, the drying temperature is 70~90°C, and the drying time is 12~16h; the calcination process of the positive electrode material precursor is: placing the positive electrode material precursor in a muffle furnace, heating it from room temperature to 200~210°C at a heating rate of 4~6°C / min, removing the crystallization water in the precursor, and then heating it to 395~405°C at a heating rate of 2~3°C / min, and keeping the temperature constant for 1~2h to ensure complete reaction.

[0086] According to the present invention, step S9 is specifically: adjusting the pH to 10-12 with sodium hydroxide solution, stirring at 50-60° C. for 20-40 minutes, and filtering to remove impurities; continuing to add sodium hydroxide solution to the filtrate obtained after filtration to adjust the pH to greater than 12, adding saturated sodium carbonate solution at 90-95° C., washing the filtered solid three times with 80-90° C. hot water, and then drying 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 calcination stage: the second mixture is placed in a muffle furnace, the temperature is increased from room temperature to 500°C at a heating rate of 3°C / min, and the temperature is maintained at 500°C for 5 hours; the second calcination stage: the temperature is increased to 850-950°C at a heating rate of 3°C / min and the temperature is maintained for 12 hours.

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

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

[0090] Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples.

[0091] The battery cycle stability test of the present invention is to use the obtained recycled positive electrode material as the electrode material to prepare a button battery for charge and discharge testing, comprising the following steps:

[0092] 1. Preparation of button batteries;

[0093] 2. Standstill: Let the assembled battery stand for 12 hours to allow the electrolyte to fully infiltrate the electrode material;

[0094] 3. Charge and discharge cycle test;

[0095] a. Test system: The constant current charge-discharge cycle test was performed using the CT2001A battery test system from Blue Power Electronics Co., Ltd.

[0096] b. Test conditions

[0097] Temperature: Room temperature.

[0098] Voltage range: 3.0–4.2V.

[0099] c.Testing process:

[0100] First, cycle 4 times at 0.05C to activate the electrode material.

[0101] Then a long cycle test was carried out at 0.5C to evaluate the battery cycling stability.

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

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

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

[0105] Step 2: Electrode preparation

[0106] Use a four-sided preparation device (scraper) to evenly coat the electrode slurry onto a flat aluminum foil, place the coated electrode in a vacuum oven, and dry at 90°C for 16 hours;

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

[0108] Step 3: Battery Assembly

[0109] Complete assembly in a vacuum glove box, ensuring that the water and oxygen value in the glove box is less than 0.01ppm;

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

[0111] Diaphragm: Celgaed2400 polypropylene film;

[0112] Counter electrode: metallic lithium sheet.

[0113] Example 1

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

[0115] S1. Preparation of a deep eutectic solvent: Choline chloride and pyruvic acid were placed in a round-bottom flask at a molar ratio of 1:6. Without deionized water, the mixture was heated at 70°C with stirring for 40 minutes to obtain a homogeneous, transparent deep eutectic solvent.

[0116] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0117] S3. Leaching valuable metals with a low eutectic solvent: Place 0.2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 20 ml glass bottle, then add 10 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 80°C, and stir for 60 minutes to obtain a leachate containing valuable metal ions.

[0118] The concentrations of valuable metals in the leachate were analyzed using inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium and cobalt were 92.4% and 88.7%, respectively.

[0119] Example 2

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

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

[0122] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0123] S3. Leaching valuable metals with a low eutectic solvent: Place 0.2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 20 ml glass bottle, then add 10 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 80°C, and stir for 60 minutes to obtain a leachate containing valuable metal ions.

[0124] The concentration of valuable metals in the leachate was analyzed by inductively coupled plasma optical emission spectrometry, and 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 of this embodiment includes the following steps:

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

[0128] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0129] S3. Leaching valuable metals with a low eutectic solvent: Place 0.2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 20 ml glass bottle, then add 10 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 80°C, and stir for 60 minutes to obtain a leachate containing valuable metal ions.

[0130] The concentration of valuable metals in the leachate was analyzed by inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium and cobalt were 92.1% and 88.4%, respectively.

[0131] Example 4

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

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

[0134] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0135] S3. Leaching valuable metals with a low eutectic solvent: Place 0.2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 20 ml glass bottle, then add 10 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 80°C, and stir for 60 minutes to obtain a leachate containing valuable metal ions.

[0136] The concentration of valuable metals in the leachate was analyzed by inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium and cobalt were 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 comprises the following steps:

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

[0140] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0141] S3. Leaching valuable metals with a low eutectic solvent: Place 0.2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 20 ml glass bottle, then add 10 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 180°C, and stir for 24 hours to obtain a leachate containing valuable metal ions.

[0142] The concentration of valuable metals in the leachate was analyzed by inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium and cobalt were 86.7% and 81.9%, respectively.

[0143] The leaching rates of lithium and cobalt elements in Examples 1 to 4 and Comparative Example 1 are summarized in Table 1.

[0144] Table 1

[0145]

[0146] As can be seen from Table 1, the deep eutectic solvents of Examples 1 to 4 can achieve efficient leaching of valuable metals in waste LiCoO2 positive electrode materials at 80°C / 60min, which is significantly lower than the leaching temperature and leaching time required by traditional deep eutectic solvent processes (such as choline chloride-ethylene glycol), significantly reducing the energy consumption required for leaching; and under the action of the deep eutectic solvent composed of betaine hydrochloride and pyruvic acid, the leaching rate of lithium and cobalt elements in waste LiCoO2 positive electrode materials is the highest, and the leaching effect is the best.

[0147] Examples 5 to 8

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

[0149] Under the conditions of 0 wt% water content (no deionized water was added in step S1), liquid-to-solid ratio of 50:1 g / g, leaching temperature of 80°C, 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 positive electrode materials.

[0150] Among them, the molar ratio of Example 5 is betaine hydrochloride: pyruvic acid = 1:7; the molar ratio of Example 6 is betaine hydrochloride: pyruvic acid = 1:8; the molar ratio of Example 7 is betaine hydrochloride: pyruvic acid = 1:9; the molar ratio of Example 8 is betaine hydrochloride: pyruvic acid = 1:10;

[0151] The structures of the deep eutectic solvents prepared in Examples 2 and 5 to 8 were characterized by Fourier transform infrared spectroscopy. Figure 2 As shown, from Figure 2 As can be seen from the figure, the hydroxyl vibration peaks of betaine hydrochloride (BeCl) and pyruvic acid (PA) are located at 3438 cm -1 and 3215cm -1 The prepared deep eutectic solvent is only at 1344 cm -1 There is a hydroxyl vibration peak at 1726 cm -1 and 1138cm -1 There are vibration peaks of C=O and CO bonds at , respectively, confirming that the substance prepared in step S1 is indeed a low eutectic solvent.

[0152] The leaching rates of lithium and cobalt in Examples 5 to 8 were calculated, and the effects of the molar ratio (Example 2, Example 5 to 8) on the leaching rate of valuable metals were summarized as follows: Figure 3 ,from Figure 3 It can be seen that when the molar ratio of betaine hydrochloride to pyruvic acid is 1:6~1:9, the leaching rate of valuable metals is above 90%; and with the increase of pyruvic acid in the system, the leaching of valuable metals first increases and then decreases. 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 molar ratio of betaine hydrochloride to pyruvic acid in the optimal leaching solvent should be 1:8.

[0153] Examples 9-12

[0154] The basic steps are the same as those 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°C, 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 particular, the amount of deionized water added in step S1 of Example 9 is 5% of the total mass of betaine hydrochloride and pyruvic acid; the amount of deionized water added in step S1 of Example 10 is 10% of the total mass of betaine hydrochloride and pyruvic acid; the amount of deionized water added in step S1 of Example 11 is 15% of the total mass of betaine hydrochloride and pyruvic acid; the amount of deionized water added in step S1 of Example 12 is 20% of the total mass of betaine hydrochloride and pyruvic acid;

[0157] The leaching rates of lithium and cobalt in Examples 9 to 12 were calculated, and the effects of water content (Examples 6 and 9 to 12) on the leaching rates of valuable metals were summarized as follows: Figure 4 ,from Figure 4 It can be seen that when the water content of the low eutectic solvent is 0wt%~20wt%, the leaching rate of valuable metals is above 90%; and with the increase of the water content in the configured low eutectic solvent (BeCl-PA), the leaching of valuable metals first increases and then decreases; when the water content of the low eutectic solvent is 0wt%, the leaching rates of lithium and cobalt are 98.7% and 95.0%, respectively; when the water content of the low eutectic solvent increases to 10wt%, the leaching rates of lithium and cobalt reach the maximum value, increasing to 99.9% and 99.5%, respectively; when the water content of the low eutectic solvent further increases to 20wt%, the leaching rates of lithium and cobalt decrease to 96.2% and 91.9%, respectively; and the addition of water can significantly reduce the viscosity of the low eutectic solvent, facilitate the contact of the solid-liquid phase, and increase the transfer rate; therefore, the optimal water content in the leaching solvent should be 10wt%.

[0158] Examples 13-17

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

[0160] Under the conditions of a water content of 10 wt% (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°C, and a leaching time of 60 min, the liquid-to-solid ratio (the mass ratio of the low eutectic solvent placed in the glass bottle in step S3 to the waste LiCoO2 positive electrode material) was taken as a variable to study the effect of the liquid-to-solid ratio on the leaching rate of valuable metals in waste positive electrode materials.

[0161] Among them, the liquid-solid ratio in Example 13 is 20:1g / g (the amount of waste LiCoO2 positive electrode material added in step S3 is 0.5g, and the amount of low eutectic solvent added is 10g); the liquid-solid ratio in Example 14 is 30:1g / g (the amount of waste LiCoO2 positive electrode material added in step S3 is 0.333g, and the amount of low eutectic solvent added is 10g); the liquid-solid ratio in Example 15 is 40:1g / g (the amount of waste LiCoO2 positive electrode material added in step S3 is 0.333g, and the amount of low eutectic solvent added is 10g). The amount of the waste LiCoO2 cathode material added in the comparative example is 0.25 g, and the amount of the deep eutectic solvent added is 10 g); in Example 16, the liquid-to-solid ratio is 60:1 g / g (the amount of the waste LiCoO2 cathode material added in the comparative example in step S3 is 0.167 g, and the amount of the deep eutectic solvent added is 10 g); in Example 17, the liquid-to-solid ratio is 70:1 g / g (the amount of the waste LiCoO2 cathode material added in the comparative example in step S3 is 0.143 g, and the amount of the deep eutectic solvent added is 10 g);

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

[0163] Examples 18-21

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

[0165] Under the conditions of a water content of 10 wt% (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 positive electrode materials was studied.

[0166] The leaching temperature of Example 18 is 50°C; the leaching temperature of Example 19 is 60°C; the leaching temperature of Example 20 is 70°C; and the leaching temperature of Example 21 is 90°C.

[0167] The leaching rates of lithium and cobalt in Examples 18 to 21 were calculated, and the effects of leaching temperature (Example 10, Examples 18 to 21) on the leaching rates of valuable metals were summarized as follows: Figure 6 ,from Figure 6 It can be seen from the data that 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 has a significant 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 increases 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, and only the leaching rate of cobalt increases by 0.1%). Therefore, the optimal leaching temperature should be 80℃.

[0168] Examples 22 to 29

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

[0170] Under the conditions of a water content of 10 wt% (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°C, the effect of leaching time on the leaching rate of valuable metals in waste positive electrode materials was studied.

[0171] Among them, the leaching time of Example 22 is 10 minutes; the leaching time of Example 23 is 20 minutes; the leaching time of Example 24 is 30 minutes; the leaching time of Example 25 is 40 minutes; the leaching time of Example 26 is 50 minutes; the leaching time of Example 27 is 70 minutes; the leaching time of Example 28 is 80 minutes; and the leaching time of Example 29 is 90 minutes.

[0172] The leaching rates of lithium and cobalt in Examples 22 to 29 were calculated, and the effects of leaching time (Example 10, Examples 22 to 29) on the leaching rates of valuable metals were summarized as follows: 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 between 10 min and 60 min, the leaching rate of valuable metals has a significant 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 to 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, and only the leaching rate of cobalt increases by 0.1%). Therefore, the optimal leaching time should be 60 min.

[0173] Examples 30-33

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

[0175] Under the conditions of a water content of 10 wt% (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°C, and a leaching time of 60 min, different types of waste electrodes were taken to verify the versatility of the deep eutectic solvent of the present invention in leaching valuable metals from waste lithium-ion batteries.

[0176] In step S2 of Example 30, the waste NCM111 battery is pretreated to obtain waste LiNi 0.33 Co 0.33 Mn 0.33 O2 positive electrode material; In step S2 of Example 31, the waste NCM523 battery is pretreated to obtain waste LiNi 0.5 Co 0.2 Mn 0.3 O2 positive electrode 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 positive electrode material; In step S2 of Example 33, 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 to 33 were calculated, and the leaching rates of valuable metals of different waste positive electrode materials (Examples 30 to 33) are summarized in Table 2.

[0178] Table 2

[0179]

[0180] As can be seen from Table 2, the deep eutectic solvent of the present invention exhibits excellent leaching effects when leaching different types of valuable metals from waste lithium-ion batteries, and the leaching rate of each transition metal element exceeds 99%, indicating that the deep eutectic solvent of the present invention is versatile for leaching valuable metals from waste lithium-ion batteries.

[0181] Example 34

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

[0183] S2. Obtaining Waste Cathode Materials: Used LiCoO2 batteries were thoroughly discharged by soaking them in a 10 g / L sodium chloride solution for 24 hours. The batteries were then air-dried and manually disassembled to obtain cathode sheets, which were cut into 10 cm × 10 cm pieces. The sheets were then calcined in a muffle furnace at 550°C for 2 hours to remove impurities such as binders and electrolytes. After calcination, the powder was brushed off the aluminum foil surface and ground to obtain the waste LiCoO2 cathode materials.

[0184] S3. Leaching valuable metals with a low eutectic solvent: Place 2 g of the waste LiCoO2 positive electrode material obtained in step S2 in a 250 ml glass bottle, then add 100 g of the low eutectic solvent obtained in step S1 to the glass bottle. After adding a magnet, seal the bottle. Place the glass bottle in an oil bath, heat to 80°C, and stir for 60 minutes to obtain a leachate containing valuable metal ions.

[0185] The concentration of valuable metals in the leachate was analyzed by inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium and cobalt were 99.6% and 99.2%, respectively.

[0186] S4-S7. Regeneration and recycling of low eutectic solvent: After the leachate is cooled to room temperature, 60 ml of deionized water is added to the leachate to dilute it and filter it to obtain a filtrate; 2 g of oxalic acid is added to the filtrate, heated and stirred at 60°C for 240 minutes, and then centrifuged at 10,000 rpm for 30 minutes to obtain a solid precipitate and a supernatant, respectively; the supernatant is subjected to reduced pressure distillation at 80°C for 8 hours to remove water to obtain a recovered low eutectic solvent (regenerated low eutectic solvent). The structures of the fresh low eutectic solvent and the regenerated low eutectic solvent are characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The results are as follows: Figure 8 As shown, from Figure 8It can be seen that the structure of the recycled deep eutectic solvent has no significant change compared with the fresh deep eutectic solvent; the recycled deep eutectic solvent is used for a new round of valuable metal extraction from waste lithium-ion batteries, and a lithium-rich solution is obtained after 5 cycles; after each cycle, the concentration of valuable metals in the leachate is analyzed using inductively coupled plasma emission spectrometry, and the leaching rates of lithium and cobalt elements are calculated. The results are shown in Figure 9 ,from Figure 9 It can be seen that after 5 cycles, the leaching rate of lithium and cobalt by the deep eutectic solvent is still over 80%. The repeated use of the deep eutectic solvent can reduce wastewater discharge and reagent costs, indicating that the present invention has high economic and sustainable properties.

[0187] S8. Recovery of cobalt element: 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 a positive electrode material precursor. The positive electrode material precursor was placed in a muffle furnace for calcination. The calcination procedure was as follows: the temperature was increased from room temperature to 200°C at a heating rate of 5°C / min, and then increased to 400°C at a heating rate of 2°C / min, and maintained at 400°C for 2 hours to obtain a black powder. The XRD test results of the positive electrode material precursor and the black powder are shown 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 tetraoxide (Co3O4);

[0188] S9. Lithium recovery: sodium hydroxide solution was added to the lithium-rich solution obtained in steps S4-S7 to adjust the pH to 11, stirred at 55°C for 30 minutes, filtered to remove impurities, and then sodium hydroxide solution was added to the filtrate to adjust the pH to 13. Saturated sodium carbonate solution was added at 90°C to allow sufficient reaction. After the reaction was completed, the filtered solid was washed three times with 85°C hot water, and dried in a vacuum drying oven at 110°C for 5 hours to obtain a white solid powder. The dried white solid powder was subjected to XRD test. The results were as follows: Figure 11 As shown, its chemical structure was confirmed to be lithium carbonate (Li2CO3).

[0189] Example 35

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

[0191] S2. Obtaining waste positive electrode materials: The waste NCM622 batteries were immersed in 10g / L sodium chloride solution for 24 hours for thorough discharge, and then naturally air-dried. The positive electrode sheets were manually disassembled and cut into 10cm×10cm sizes. The positive electrode sheets were placed in a muffle furnace and calcined 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 valuable metals with a low eutectic solvent: 2 g of the waste LiNi obtained in step S2 0.6 Co 0.2 Mn 0.2 The O2 positive electrode material was placed in a 250 ml glass bottle, and 100 g of the low eutectic solvent prepared in step S1 was added to the glass bottle. After adding a magnet, the bottle was sealed. The glass bottle was placed in an oil bath, 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 by inductively coupled plasma optical emission spectrometry, and the calculated leaching rates of lithium, manganese, cobalt and nickel were 99.4%, 99.2%, 99.1% and 99.0% respectively.

[0194] S4-S7. Regeneration and recycling of the deep eutectic solvent: After the leachate is cooled to room temperature, 65 ml of deionized water is added to dilute the leachate and filtered to obtain a filtrate; 2 g of oxalic acid is added to the filtrate, and the mixture is heated and stirred at 65°C for 300 min, followed by centrifugation at 10,000 rpm for 30 min to obtain a solid precipitate and a supernatant, respectively; the supernatant is subjected to reduced pressure distillation at 80°C for 8 h to remove water to obtain a recovered deep eutectic solvent, which is used for a new round of valuable metal extraction from waste lithium-ion batteries. After five cycles, a lithium-rich solution is obtained;

[0195] S8. Recovery of transition metal elements: 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 a positive electrode material precursor. The positive electrode material precursor was placed in a muffle furnace for calcination. The calcination procedure was as follows: the temperature was increased from room temperature to 200°C at a heating rate of 5°C / min, and then increased to 400°C at a heating rate of 2°C / min, and maintained at 400°C for 2 hours to obtain a black powder. The XRD test results of the positive electrode material precursor and the black powder are shown as follows. Figure 12 As shown, it is confirmed that the cathode material precursor is (Ni 0.6 Co 0.2 Mn 0.2)C2O4·2H2O, black powder is (Ni 0.6 Co 0.2 Mn 0.2 )3O4;

[0196] S9. Lithium recovery: sodium hydroxide solution was added to the lithium-rich solution obtained in steps S4-S7 to adjust the pH to 11, stirred at 55°C for 30 minutes, filtered to remove impurities, and then the pH of the filtrate was adjusted to 13 by sodium hydroxide solution. Saturated sodium carbonate solution was added at 90°C to allow sufficient reaction. After the reaction was completed, the solution was filtered and washed three times with hot water at 85°C. The solid was dried in a vacuum drying oven at 110°C for 5 hours to obtain lithium carbonate.

[0197] Examples 36-40

[0198] S10. The lithium carbonate and cobalt oxide obtained in Example 34 were mixed and fully ground in a lithium:cobalt molar ratio 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) to obtain a second mixture consisting of lithium carbonate and cobalt oxide. The second mixture 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, maintained at 500°C for 5 hours, and then the temperature was increased to 900°C at a heating rate of 3°C / min and maintained at the temperature for 12 hours to obtain a regenerated lithium cobalt oxide positive electrode material. The XRD, scanning electron microscopy and transmission electron microscopy characterization results of the lithium cobalt oxide prepared with a lithium:cobalt molar ratio of 1.05:1 in Example 38 are shown as follows. Figure 13 As shown in the figure, it can be seen that the structure of the prepared material is determined to be lithium cobalt oxide.

[0199] The lithium cobalt oxide positive electrode material regenerated with different lithium:cobalt molar ratios 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 button battery was prepared according to the above button battery preparation steps, and a charge and discharge test (1C=150mAh / g) was performed. The regenerated lithium cobalt oxide positive electrode material 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 The first discharge capacities (0.1C) of the lithium cobalt oxide positive electrode materials were 138.8 mAh / g, 142.9 mAh / g, 147.5 mAh / g, 144.9 mAh / g and 136.0 mAh / g, respectively. The capacity retention rates after 100 cycles (0.5C) were 87.6%, 88.3%, 89.1%, 88.6% and 88.0%, respectively. Among them, the lithium cobalt oxide positive electrode material regenerated with a lithium:cobalt molar ratio of 1.05:1 in Example 38 performed 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 oxide obtained in Example 34 are mixed in a lithium:cobalt molar ratio of 1.05:1 and fully ground to obtain a second mixture consisting of lithium carbonate and cobalt oxide; the second mixture is placed in a muffle furnace and calcined, and the calcination procedure is as follows: the temperature is increased from room temperature to 500°C at a heating rate of 3°C / min, and the temperature is maintained at 500°C for 5 hours, and then the temperature is increased to 850°C (Example 41) and 950°C (Example 42) at a heating rate of 3°C / min, and the temperature is maintained for 12 hours to obtain a regenerated lithium cobalt oxide positive electrode material.

[0202] The lithium cobalt oxide positive electrode 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. Coin-type batteries were produced according to the aforementioned coin-type battery production steps and subjected to charge and discharge tests (1C = 150 mAh / g). The regenerated lithium cobalt oxide positive electrode materials prepared at calcination temperatures of 850°C (Example 41), 900°C (Example 38), and 950°C (Example 42) had initial discharge capacities (0.1C) of 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. The lithium cobalt oxide positive electrode material regenerated at a second calcination temperature of 900°C in Example 38 performed best, and therefore 900°C was selected as the optimal calcination temperature.

[0203] Example 43

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

[0205] Regenerate LiNi in step S10 0.6 Co 0.2 Mn 0.2 O2 positive electrode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent in a mass ratio of 8:1:1 to form a slurry. A button battery was produced according to the aforementioned button battery production steps, and charge and discharge tests were carried out (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 positive electrode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent in a mass ratio of 8:1:1 to form a slurry. A button battery was manufactured according to the aforementioned button battery production steps. Charge and discharge tests were performed (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] Commercializing LiNi 0.6 Co 0.2 Mn 0.2 O2 positive electrode material, acetylene black, and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solvent in a mass ratio of 8:1:1 to form a slurry. A button battery was produced according to the aforementioned button battery production steps, and charge and discharge tests were carried out (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 positive electrode materials based on a deep eutectic solvent of the present invention can achieve almost complete leaching of valuable metals in waste lithium-ion battery positive electrode materials at a lower leaching temperature and a shorter leaching time, thereby realizing a short-process closed-loop regeneration of waste lithium-ion battery positive electrode materials. The present invention is also well applicable to the recovery of various waste lithium-ion positive electrode materials.

[0211] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent, characterized in that: The following steps are involved: S1. A hydrogen bond acceptor and a hydrogen bond donor are mixed at a molar ratio of hydrogen bond acceptor to hydrogen bond donor of 1:6 to 1:9 to form a first mixture; deionized water accounting for 0 to 20% of the total mass of the first mixture 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 deep eutectic solvent; the hydrogen bond acceptor is selected from choline chloride, betaine hydrochloride, tetraethylammonium chloride, and tetrapropylammonium chloride, and the hydrogen bond donor is pyruvic acid; S2. Pre-treating the waste lithium-ion batteries to obtain waste positive electrode materials; S3. The low eutectic solvent obtained in step S1 is mixed with the waste cathode material obtained in step S2 at a liquid-solid ratio of 40:1 to 90:1 g / g, and the valuable metals are leached by heating and stirring. After the leaching is completed, a leachate is obtained.

2. The method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent according to claim 1, wherein: In step S1, the hydrogen bond acceptor is betaine hydrochloride, the hydrogen bond donor is pyruvic acid, 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 waste lithium-ion batteries using a deep eutectic solvent according to claim 1, wherein: In step S2, the pretreatment process of the waste lithium-ion batteries is: completely discharging the waste lithium-ion batteries, disassembling them to obtain positive electrode sheets, cutting and calcining the positive electrode sheets to obtain waste positive electrode materials.

4. The method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent according to claim 1, wherein: In step S3, the leaching temperature is 80-90° C., and the leaching time is 40-90 min.

5. The method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent according to claim 1, wherein: In step S3, the liquid-to-solid ratio of the deep eutectic solvent to the waste positive electrode material is 50:1 g / g, the leaching temperature is 80° C., and the leaching time is 60 min.

6. The method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent according to claim 1, wherein: The waste positive electrode material is at least one of lithium cobalt oxide, NCM111, NCM523, NCM622, and NCM811.

7. A method for regenerating a positive electrode material, characterized in that: The method is based on the method for extracting valuable metals from waste lithium-ion batteries using a deep eutectic solvent according to any one of claims 1 to 6, and in addition to steps S1 to S3, further comprises the following steps: S4. After the leachate obtained in step S3 is cooled to room temperature, deionized water is added to the leachate to dilute it and filter it to obtain a filtrate; S5. Oxalic acid was added to the filtrate as a precipitant, and the reaction was fully reacted and centrifuged to obtain a solid precipitate and a supernatant; S6. The supernatant obtained in step S5 is subjected to reduced pressure distillation to remove water to obtain a recovered deep eutectic solvent; S7. The recovered deep eutectic solvent is used for a new round of valuable metal extraction from waste lithium-ion batteries, and steps S2 to S6 are repeated 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, which is calcined to obtain a transition metal oxide; S9. To the lithium-rich solution obtained in step S7, sodium hydroxide solution was added to adjust the pH and filter to remove impurities, followed by addition of a saturated sodium carbonate solution to react fully. After completion of the reaction, the solid obtained by filtration was washed and dried to obtain lithium carbonate; S10. The total amount of transition metal elements: lithium elements = 1: (1.01-1.09) in a molar ratio. The transition metal oxide obtained in step S8 and the lithium carbonate obtained in step S9 are mixed and fully ground to obtain a second mixture; the second mixture is then calcined to obtain a regenerated lithium-ion battery positive electrode material.

8. The cathode material regeneration method according to claim 7, characterized in that: In step S4, the amount of deionized water added is 0.5 to 1 times the volume of the leachate.

9. The cathode material regeneration method according to claim 7, characterized in that: In step S5, the amount of oxalic acid added is 1.05 to 1.15 times the total molar amount of the transition metal elements in the leachate, the reaction temperature is 60 to 70° C., the reaction time is 180 to 360 min, and the centrifugal operation speed is 8000 to 10000 rpm, and the time is 10 to 30 min.

10. The cathode material regeneration method according to claim 7, characterized in that: In step S6, the temperature of the reduced pressure distillation is 60-80° C., and the time is 6-12 hours.

11. The cathode material regeneration method according to claim 7, characterized in that: In step S8, the drying temperature is 70-90°C, and the drying time is 12-16 hours. The calcination process of the positive electrode material precursor is as follows: the positive electrode material precursor is placed in a muffle furnace, and the temperature is raised from room temperature to 200-210°C at a heating rate of 4-6°C / min to remove the crystallized water in the precursor, and then the temperature is raised to 395-405°C at a heating rate of 2-3°C / min, and the temperature is kept constant for 1-2 hours to ensure complete reaction.

12. The cathode material regeneration method according to claim 7, characterized in that: The step S9 specifically comprises: adjusting the pH to 10-12 with a sodium hydroxide solution, stirring at 50-60° C. for 20-40 minutes, and filtering to remove impurities; further adding sodium hydroxide solution to the filtrate obtained after filtration to adjust the pH to greater than 12, adding a saturated sodium carbonate solution at 90-95° C., washing the filtered solid three times with hot water at 80-90° C., and then drying in a vacuum drying oven at 105-120° C. for 4-6 hours to obtain lithium carbonate.

13. The positive electrode material regeneration method according to claim 7, characterized in that: In step S10, the calcination process of the second mixture is as follows: placing the second mixture in a muffle furnace, heating the temperature from room temperature to 500°C at a heating rate of 3°C / min, and maintaining the temperature at 500°C for 5 hours; then heating the temperature to 850-950°C at a heating rate of 3°C / min and maintaining the temperature for 12 hours.

14. The cathode material regeneration method according to claim 7, characterized in that: In step S10, a transition metal oxide and lithium carbonate are mixed in a molar ratio of total amount of 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, the temperature is increased from room temperature to 500° C. at a heating rate of 3° C. / min, and the temperature is maintained at 500° C. for 5 hours; then the temperature is increased to 900° C. at a heating rate of 3° C. / min and the temperature is maintained for 12 hours.

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