Method for treating waste lithium battery by using ultrasonic-enhanced deep eutectic solvent

Abstract

The invention discloses a method for treating a waste lithium battery by using an ultrasonic-enhanced deep eutectic solvent. The method comprises the following steps: pretreating the waste lithium battery to obtain positive electrode material powder; mixing the hydrogen bond donor and the hydrogen bond acceptor to form a deep eutectic solvent; adding the positive electrode material powder into a deep eutectic solvent, and performing leaching reaction under the action of an ultrasonic external field to obtain filtrate and filter residues; adding a precipitator into the filtrate, and reacting under the ultrasonic-assisted action to obtain lithium carbonate, carbonate or oxalate precipitate and post-precipitation liquid; treating the precipitated liquid to obtain a purified deep eutectic solvent for recycling; and washing and drying the lithium carbonate, carbonate or oxalate precipitate to obtain a nickel-cobalt-manganese precursor and battery-grade lithium carbonate. According to the method, the mass transfer problem caused by high viscosity of the deep eutectic solvent is solved by means of the cavitation effect and the micro-jet effect through the ultrasonic external field strengthening technology, the high leaching rate of key metal is achieved, meanwhile, the reaction time is shortened, and the process economy and industrial feasibility are improved.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery recycling technology, and in particular to a method for treating waste lithium batteries using ultrasonically enhanced deep eutectic solvent. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, the use of lithium-ion batteries (LIBs) continues to grow, leading to a surge in the accumulation of waste batteries. Waste lithium batteries contain key metals such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), which have significant resource value and strategic importance. Therefore, achieving efficient and green recycling has become a key focus of current research and industrial application. Currently, hydrometallurgical processes are widely used in the waste lithium battery recycling field, typically relying on inorganic acids as leaching agents. While these processes offer high leaching efficiency, they generally suffer from significant drawbacks: high acid consumption, high impurity content in the leachate, resulting in complex and cumbersome subsequent separation and purification processes; furthermore, the process generates harmful gas emissions and wastewater, making it difficult to meet the current dual requirements of green environmental protection and economic feasibility.

[0003] In recent years, deep eutectic solvents, with their low volatility, designability, and strong metal dissolving capacity, have been regarded as green solvents to replace traditional strong acid systems and have received widespread attention in the field of metal recycling. As a novel leaching agent, deep eutectic solvents can improve metal selectivity and reduce environmental pollution risks to a certain extent. However, deep eutectic solvents themselves have high viscosity, which hinders mass transfer during the leaching process, affecting not only the metal dissolving efficiency but also the solid-liquid separation effect, thus limiting their widespread application in large-scale industrial recycling.

[0004] In summary, existing waste lithium battery recycling technologies suffer from insufficient environmental friendliness or limited industrial application. Developing a waste lithium battery recycling method that balances high efficiency, environmental friendliness, and industrial feasibility is of significant practical importance and application value. Summary of the Invention

[0005] This invention provides a method for treating waste lithium batteries using ultrasonic-enhanced deep eutectic solvents. By introducing ultrasonic external field enhancement technology, and utilizing its cavitation effect and micro-jet effect, the method overcomes the mass transfer problem caused by the high viscosity of deep eutectic solvents, accelerates metal dissolution and diffusion, and improves solid-liquid separation. This achieves a high leaching rate of key metals while shortening the reaction time, thereby improving the economic efficiency and industrial feasibility of the process.

[0006] This invention provides a method for treating spent lithium batteries using ultrasonically enhanced deep eutectic solvents, comprising: S1. The waste lithium batteries after discharge treatment are disassembled, crushed, and screened in sequence, and the aluminum foil current collector is removed to obtain positive electrode material powder. S2. Mix the hydrogen bond donor and hydrogen bond acceptor according to the set molar ratio, heat to 60~100℃ and stir evenly to form a transparent colorless or light yellow deep eutectic solvent. S3. The positive electrode material powder obtained in step S1 is added to the deep eutectic solvent obtained in step S2, and the solid-liquid ratio is adjusted to a set value. The leaching reaction is carried out under the action of an ultrasonic external field, and the solid and liquid are separated by suction filtration after the reaction is completed to obtain a filtrate and filter residue containing valence metal ions. S4. Add precipitant to the filtrate from step S3 in sequence, carry out precipitation reaction under ultrasonic assistance, and filter to separate lithium carbonate, carbonate or oxalate precipitate, and precipitate solution. S5. The precipitated liquid is concentrated by low-pressure evaporation, and residual impurities and metal ions are removed by membrane separation to obtain purified deep eutectic solvent for recycling. S6. The lithium carbonate, carbonate or oxalate precipitate is washed and dried to obtain nickel cobalt manganese precursor and battery-grade lithium carbonate.

[0007] Further, in step S1, the positive electrode material powder comprises lithium nickel cobalt manganese oxide, conductive carbon black, and PVDF binder, wherein the lithium nickel cobalt manganese oxide is... , where x+y+z≈1.

[0008] Furthermore, in S2, the hydrogen bond acceptor includes at least one of choline bromide, tetramethylammonium chloride, benzalkonium chloride, and betaine; The hydrogen bond donors include one or more of oxalic acid, citric acid, formic acid, acetic acid, urea, glycerol, and thiourea. The molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:1 to 1:2; Furthermore, in step S2, the stirring temperature is 60~100℃ and the stirring time is 10~60 min.

[0009] Furthermore, in step S3, the solid-liquid ratio is set to 10~50 g / L, the ultrasonic frequency is 20~80 kHz, the ultrasonic power is 200~600 W, the leaching temperature is 30~110℃, and the leaching time is 0.5~6 h.

[0010] Further, in step S4, the precipitant is sodium carbonate, sodium bicarbonate, ammonium oxalate, or a mixture thereof; Under ultrasonic assistance, a precipitation reaction is carried out, preferentially precipitating Ni, Co, and Mn to form carbonate or oxalate precipitates. Subsequently, the conditions are further adjusted to precipitate Li as lithium carbonate.

[0011] Furthermore, in step S5, the membrane separation uses a microfiltration membrane with a pore size of 0.1–10 μm.

[0012] Furthermore, in step S6, the nickel-cobalt-manganese precursor is a uniform NiCoMn oxalate or carbonate, and the battery-grade lithium carbonate has a purity greater than 99.5%.

[0013] The beneficial effects of this invention are as follows: This invention utilizes a deep eutectic solvent combined with ultrasonic external field enhancement technology to solve the problems of limited mass transfer and low leaching efficiency caused by the high viscosity of traditional deep eutectic solvent systems. By accelerating solvent molecule diffusion and disrupting the passivation layer on the particle surface through ultrasonic action, the metal leaching rate is significantly improved, enabling near-complete leaching of Ni, Co, Mn, and Li in a shorter time. Compared with traditional inorganic acid leaching processes, the deep eutectic solvent system used in this invention has advantages such as low corrosivity and recyclability, reducing chemical reagent consumption and wastewater discharge, lowering overall energy consumption, and improving environmental friendliness and economy. Simultaneously, through reasonable control of the precipitation system, the graded recovery of valuable metals is achieved, ultimately obtaining high-purity battery-grade lithium carbonate and homogeneous nickel-cobalt-manganese oxalate precursors, which can be directly used for the remanufacturing of battery materials. The overall process of this invention is simple and efficient, combining green environmental protection with feasibility for industrial application. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0015] Figure 2 These are phase analysis and microstructure observation diagrams of battery-grade lithium carbonate in this invention.

[0016] Figure 3 This is a phase analysis and microstructure observation diagram of the nickel-cobalt-manganese oxalate precursor in this invention.

[0017] Figure 4 This is a schematic diagram showing the leaching rates of Li, Ni, Co, and Mn in Examples 1-5 and Comparative Examples 1-2 of this invention.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and experimental examples. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0020] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0021] While deep eutectic solvents are environmentally friendly and have good metal dissolving capabilities, their high viscosity severely hinders solute diffusion and mass transfer, resulting in low metal leaching rates and excessively long reaction times, thus limiting the improvement of recovery efficiency. Furthermore, due to the high viscosity of the system, the solid-liquid separation efficiency after leaching is poor, easily leading to impurity residues and secondary losses of valuable metals, affecting product purity and overall recovery rate.

[0022] This invention proposes a metal recovery method combining deep eutectic solvents and ultrasonic field enhancement. The cavitation effect and microjets generated by ultrasound not only disrupt the passivation layer on the surface of cathode particles but also effectively reduce the limitations of high-viscosity solvent systems on diffusion and mass transfer, enhancing the migration rate of metal ions in the solvent and thus significantly improving leaching efficiency. Simultaneously, by rationally optimizing the ultrasonic parameters and solvent system, efficient leaching can be achieved at lower temperatures and in shorter times, while ensuring solvent recycling, reducing energy and reagent consumption, and minimizing environmental pollution. This provides a feasible new approach for the green recycling of waste lithium batteries.

[0023] like Figure 1 As shown, this invention provides a method for treating spent lithium batteries using ultrasonic-enhanced deep eutectic solvents. This method utilizes deep eutectic solvents combined with ultrasonic field enhancement to efficiently leach and separate valuable metals from the cathode materials of spent lithium batteries. Specifically, it includes the following steps: S1. The spent lithium batteries after discharge treatment are disassembled, crushed, and sieved sequentially, and the aluminum foil current collector is removed to obtain positive electrode material powder; the positive electrode material powder includes lithium nickel cobalt manganese oxide (… , where x+y+z≈1), conductive carbon black and PVDF binder.

[0024] S2. Mix hydrogen bond donors (one or more of oxalic acid, citric acid, formic acid, acetic acid, urea, glycerol, and thiourea) with hydrogen bond acceptors (at least one of choline bromide, tetramethylammonium chloride, benzalkonium chloride, and betaine) according to a set molar ratio of 1:1 to 1:2. Then heat to 60-100°C and stir until homogeneous. The stirring water bath temperature is 60-100°C, preferably 60-80°C. The stirring time is 10-60 min, preferably about 20-30 min, to finally form a transparent, colorless or light yellow deep eutectic solvent.

[0025] S3. The positive electrode material powder obtained in step S1 is added to the deep eutectic solvent obtained in step S2, and the solid-liquid ratio is adjusted to a set value. The leaching reaction is carried out under the action of an ultrasonic external field, and the solid and liquid are separated by suction filtration after the reaction is completed to obtain a filtrate containing valence metal ions and a filter residue containing insoluble matter. The solid-liquid ratio is set to 10~50 g / L; the ultrasonic frequency is 20~80 kHz, preferably 40 kHz; the ultrasonic power is 200~600 W, preferably 200~400 W; the leaching temperature is 30~110℃, preferably 50~90℃; and the leaching time is 0.5~6 h, preferably 1~2 h.

[0026] S4. Add a precipitant (sodium carbonate, sodium bicarbonate, ammonium oxalate or a mixture thereof) sequentially to the filtrate from step S3, and carry out a precipitation reaction under ultrasonic assistance. Filter to separate lithium carbonate and carbonates. ) or oxalate ( The precipitation and the post-precipitate solution are subjected to a precipitation reaction under the assistance of ultrasound. Ni, Co, and Mn are preferentially precipitated to form carbonate or oxalate precipitates. Subsequently, the conditions are further adjusted to precipitate Li as lithium carbonate.

[0027] S5. The precipitated liquid is concentrated by low-pressure evaporation and then separated by membrane separation (microfiltration membrane, pore size 0.1-10 μm) to remove residual impurities and metal ions, and the purified deep eutectic solvent is recycled.

[0028] S6. The lithium carbonate, carbonate, or oxalate precipitate is washed and dried to obtain a nickel-cobalt-manganese precursor and battery-grade lithium carbonate; wherein the nickel-cobalt-manganese precursor is a uniform NiCoMn oxalate or carbonate, and the battery-grade lithium carbonate has a purity greater than 99.5%. Figure 2 , Figure 3 The phase analysis and microstructure observation diagram are shown.

[0029] To avoid repetition, the raw materials or parameters involved in the following embodiments and comparative examples of the present invention are uniformly described as follows: The main chemical composition of the waste ternary lithium battery cathode material powder is Li 3%~5%, Ni 10%~15%, Co 5%~10%, Mn 12~15%, Cu 0.1%~0.2%, Al 0.1%~1%, C 0.5%~2%, with the balance being other element oxides and loss on ignition. Example 1

[0030] (1) Mix betaine and formic acid in a molar ratio of 1:2 and stir in a constant temperature water bath at 60°C for 20 min to obtain a clear and transparent deep eutectic solvent.

[0031] (2) Take 5.0 g of positive electrode material powder and place it in a flask. Slowly add the deep eutectic solvent obtained in step (1) into the flask and mix it with the positive electrode material. The solid-liquid ratio is 20 g / L. Under the action of ultrasonic water bath (frequency 40 kHz, power 200W), the water bath temperature is 60℃ and the reaction time is 2 h.

[0032] (3) Filter and separate the filtrate, collect the filtrate, determine the contents of Li, Ni, Co and Mn by ICP-OES, and calculate the leaching rate (LMe) of these four metals respectively using the following formula:

[0033] in, The concentration of metal ions in the leachate (mg / L). The volume of the leachate (L); m 0 represents the mass (g) of the positive electrode material powder; The content (wt.%) of each metal in the cathode material powder.

[0034] (4) Add precipitants (sodium bicarbonate, ammonium oxalate and sodium carbonate) to the filtrate in sequence, and use ultrasound to precipitate Ni, Co and Mn oxalates, and then precipitate Li to obtain lithium carbonate; finally, wash and dry to obtain nickel cobalt manganese oxalate precursor and battery-grade lithium carbonate.

[0035] (5) The supernatant after precipitation is concentrated by low-pressure evaporation and the residual metal ions are removed by microfiltration membrane (pore size 0.1–10 μm) to achieve deep eutectic solvent recovery. Example 2

[0036] The preparation of the deep eutectic solvent was the same as in Example 1; in the leaching reaction, the ultrasonic conditions were the same as in Example 1, but the reaction time was 1 h, and the other conditions remained unchanged; the separation, determination and precipitation recovery were the same as in Example 1. Example 3

[0037] The preparation of the deep eutectic solvent was the same as in Example 1; in the leaching reaction, the ultrasonic conditions were the same as in Example 1, but the solid-liquid ratio in the leaching process was 40 g / L, and the other conditions remained unchanged; the separation, determination and precipitation recovery were the same as in Example 1. Example 4

[0038] The preparation of the deep eutectic solvent was the same as in Example 1; in the leaching reaction, the ultrasonic conditions were the same as in Example 1, but the leaching temperature was 80°C, and the other conditions remained unchanged; the separation, determination and precipitation recovery were the same as in Example 1. Example 5

[0039] In the preparation of the deep eutectic solvent, the hydrogen bond acceptor and hydrogen bond donor were modified to choline bromide and acetic acid, respectively, while the other conditions remained unchanged from Example 1; the leaching reaction was the same as in Example 1; and the separation, determination and precipitation recovery were the same as in Example 1.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the ultrasonic power in step (2) is different. Specifically, the flask is placed in a constant temperature water bath and magnetically stirred at 60°C for 2 hours with a stirring speed of 300 rpm; the rest is the same as in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the reaction method in step (2) is different. Specifically, the reaction is carried out under the action of an ultrasonic water bath (frequency 40 kHz, power 400 W), the water bath temperature is 60℃, and the reaction time is 2 h; the rest is the same as in Example 1.

[0042] The leaching rates of Li, Ni, Co, and Mn in Examples 1-5 and Comparative Examples 1-2 are shown in the table below. Figure 4 As shown.

[0043]

[0044] The results of Examples 1-5 confirm that the present invention, by preparing a deep eutectic solvent with a specific molar ratio of green solvent and treating waste lithium battery cathode materials under suitable solid-liquid ratio and temperature conditions, can achieve efficient leaching of valuable metals such as lithium, nickel, cobalt, and manganese at relatively low temperatures (below 100°C) and in a short reaction time. In Examples 4 and 5, the leaching rates of all four metals exceeded 98%, with lithium and manganese leaching rates approaching 100%, indicating that the method of the present invention has a high metal leaching capacity.

[0045] Comparing Example 1 and Comparative Example 1, it can be seen that under the same temperature (60℃), the leaching effect of the ultrasonic-assisted reaction is significantly better than that of the simple magnetic stirring condition. In Example 1, the leaching rates of lithium, nickel, cobalt, and manganese reached 94.26%, 89.25%, 83.96%, and 96.86%, respectively, while those of Comparative Example 1 were only 64.06%, 59.33%, 55.23%, and 57.41%, respectively. This indicates that the ultrasonic field has a significant enhancing effect on metal leaching.

[0046] Comparing Example 1 and Comparative Example 2, under the same temperature (60℃) and reaction time (2 h), Comparative Example 2, while achieving nearly 100% leaching rates for all metals when the ultrasonic power was increased to 400 W, experienced a significant increase in energy consumption. In contrast, Example 1, with a moderate ultrasonic power (200 W), achieved high leaching efficiency (lithium, nickel, cobalt, and manganese leaching rates all above 90%), demonstrating that effective leaching can be achieved without excessively high ultrasonic power. Therefore, moderate ultrasonic power ensures leaching efficiency while balancing energy consumption control and system stability, better meeting the needs of green and industrial applications.

[0047] In summary, by uniformly mixing betaine and formic acid at a specific solid-liquid ratio to form a deep eutectic solvent, and then leaching valuable metals from spent lithium batteries under the enhanced effect of an ultrasonic field, the processing of spent lithium batteries can be achieved, effectively simplifying the metal leaching operation in traditional hydrometallurgical processes. This invention can significantly reduce the temperature and time of traditional pyrometallurgical-hydrometallurgical processes, achieving short-time, low-energy, and high-efficiency recovery of valuable metals from spent lithium batteries.

[0048] This invention introduces ultrasonic external field enhancement technology, utilizing cavitation and microjets to effectively weaken the restriction of high viscosity on material migration, significantly accelerating the dissolution and diffusion process of metals and achieving efficient leaching. Simultaneously, the ultrasonic effect improves the fluidity and dispersibility of the leachate, increasing the solid-liquid separation rate and thus reducing impurity entrainment and metal loss. Through this synergistic effect, this invention not only ensures high leaching rates for key metals such as lithium, nickel, cobalt, and manganese, but also significantly shortens the reaction time, improving the overall economic efficiency and industrial feasibility of the process.

[0049] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0050] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for treating waste lithium batteries using ultrasonically enhanced deep eutectic solvent, characterized in that, include: S1. The waste lithium batteries after discharge treatment are disassembled, crushed, and screened in sequence, and the aluminum foil current collector is removed to obtain positive electrode material powder. S2. Mix the hydrogen bond donor and hydrogen bond acceptor according to the set molar ratio, heat to 60~100℃ and stir evenly to form a transparent colorless or light yellow deep eutectic solvent. S3. The positive electrode material powder obtained in step S1 is added to the deep eutectic solvent obtained in step S2, and the solid-liquid ratio is adjusted to a set value. The leaching reaction is carried out under the action of an ultrasonic external field, and the solid and liquid are separated by suction filtration after the reaction is completed to obtain a filtrate and filter residue containing valence metal ions. S4. Add precipitant to the filtrate from step S3 in sequence, carry out precipitation reaction under ultrasonic assistance, and filter to separate lithium carbonate, carbonate or oxalate precipitate, and precipitate solution. S5. The precipitated liquid is concentrated by low-pressure evaporation, and residual impurities and metal ions are removed by membrane separation to obtain purified deep eutectic solvent for recycling. S6. The lithium carbonate, carbonate or oxalate precipitate is washed and dried to obtain nickel cobalt manganese precursor and battery-grade lithium carbonate.

2. The method for treating waste lithium batteries with ultrasonic-enhanced deep eutectic solvent according to claim 1, characterized in that, In step S1, the positive electrode material powder comprises lithium nickel cobalt manganese oxide, conductive carbon black, and PVDF binder, wherein the lithium nickel cobalt manganese oxide is... , where x+y+z≈1.

3. The method for treating waste lithium batteries with ultrasonic-enhanced deep eutectic solvent according to claim 1, characterized in that, In S2, the hydrogen bond acceptor includes at least one of choline bromide, tetramethylammonium chloride, benzalkonium chloride, and betaine; The hydrogen bond donors include one or more of oxalic acid, citric acid, formic acid, acetic acid, urea, glycerol, and thiourea. The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:

2.

4. The method for treating waste lithium batteries with ultrasonic-enhanced deep eutectic solvent according to claim 3, characterized in that, In step S2, the stirring temperature is 60~100℃ and the stirring time is 10~60 min.

5. The method for treating waste lithium batteries using ultrasonically enhanced deep eutectic solvent according to claim 1, characterized in that, In step S3, the solid-liquid ratio is set to 10~50 g / L, the ultrasonic frequency is 20~80 kHz, the ultrasonic power is 200~600 W, the leaching temperature is 30~110℃, and the leaching time is 0.5~6 h.

6. The method for treating waste lithium batteries using ultrasonically enhanced deep eutectic solvent according to claim 1, characterized in that, In step S4, the precipitant is sodium carbonate, sodium bicarbonate, ammonium oxalate, or a mixture thereof. Under ultrasonic assistance, a precipitation reaction is carried out, preferentially precipitating Ni, Co, and Mn to form carbonate or oxalate precipitates. Subsequently, the conditions are further adjusted to precipitate Li as lithium carbonate.

7. The method for treating waste lithium batteries using ultrasonically enhanced deep eutectic solvent according to claim 1, characterized in that, In step S5, the membrane separation uses a microfiltration membrane with a pore size of 0.1–10 μm.

8. The method for treating waste lithium batteries with ultrasonic-enhanced deep eutectic solvent according to claim 1, characterized in that, In step S6, the nickel-cobalt-manganese precursor is a uniform NiCoMn oxalate or carbonate, and the battery-grade lithium carbonate has a purity greater than 99.5%.

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