Method for selectively extracting metals in waste ternary lithium battery by using eutectic solvent

Abstract

The application discloses a method for selectively extracting metals from waste ternary lithium batteries by using a eutectic solvent. The method uses a eutectic solvent DES synthesized by choline chloride and oxalic acid as an extraction agent, quotes dimethyl sulfoxide DMSO and water as diluents, introduces a circulation and extraction step on the basis of metal element series immersion, i.e. extracts lithium oxalate from the leaching solution with ethanol and recycles the DES by fractional distillation, and makes innovations in recycling of metal lithium and recycling of the DES. The application has the advantages of high efficiency extraction, high precision purification, innovative extraction of lithium element and innovative recovery of the reagent DES.

Description

Technical fields:

[0001] This invention relates to a method for selectively extracting metals from spent ternary lithium batteries. Background Technology

[0002] Given the massive usage of used lithium-ion batteries, their potential pollution hazards, resource scarcity, and the value of their contained metallic elements such as nickel and cobalt, the significance of recycling and reusing used lithium-ion batteries is even more pronounced in today's increasingly energy-constrained world.

[0003] In existing technologies, eutectic solvents have been widely used in the recycling of spent lithium-ion batteries, but their leaching efficiency for metal elements is generally low. Therefore, improving the leaching efficiency of eutectic solvents is the focus of this invention. For example, the patent "Eutectic Solvent for Recycling Positive Electrode Sheets of Spent Lithium-ion Batteries and Its Application," publication number CN115537567A, 2022-11-24, describes a eutectic solvent composed of hydrogen bond acceptors, hydrogen bond donors, and additives. The hydrogen bond acceptor is choline chloride, the hydrogen bond donors are at least two of urea, aminosulfonic acid, acetamide, polyethylene glycol, and methylurea, and the additives are at least one of ascorbic acid, acetaldehyde, and glucose. The solvent is stirred at 80°C for 30 minutes until the solid gradually dissolves completely, forming a colorless, transparent, viscous eutectic solvent. Different metals are then leached from the positive electrode powder using the eutectic solvent under different experimental conditions. While this method can achieve the recycling of metals from waste lithium-ion batteries, it has limitations due to the need to use a eutectic solvent as a carbon source to regenerate the cathode material during the high-temperature calcination process. These limitations include the unresolved issue of recycling the eutectic solvent and the difficulty in implementing subsequent separation steps because the obtained metals are mixed in the leaching solution. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of current technologies by providing a method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent. This method uses DES (hereinafter referred to as DES), a eutectic solvent synthesized from choline chloride and oxalic acid, as the extractant, and dimethyl sulfoxide (DMSO) and water as diluents. Based on the tandem leaching of metal elements, a recycling and extraction step is introduced: lithium oxalate is extracted from the leachate with ethanol, and DES is recycled using fractional distillation. This invention innovates in the recovery of lithium metal and the recycling of DES. This invention has the advantages of high extraction efficiency, high-precision purification, innovative extraction of elemental lithium, and innovative recovery of the reagent DES.

[0005] The technical solution of this invention is as follows:

[0006] A method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent, the method comprising the following steps:

[0007] (1) After mixing choline chloride and oxalic acid, stir at 50-70°C for 50-60 minutes to obtain a eutectic solvent; wherein the molar ratio of choline chloride to oxalic acid is 1-2:1;

[0008] (2) Add waste ternary lithium battery positive electrode powder to a eutectic solvent, heat in a mixed oil bath at 100-130°C for 8-12 hours, add dimethyl sulfoxide as a diluent, let stand for 3-5 hours, and centrifuge to obtain nickel oxalate dihydrate precipitate. After washing with DMSO, the first filter residue and the first filtrate are obtained respectively. Water is added to the first filtrate and heated in a water bath at 70-75°C for 2-3 hours to obtain cobalt oxalate dihydrate precipitate. The second filter residue and the second filtrate are separated. Ethanol is added to the second filtrate for extraction and filtration to obtain lithium oxalate precipitate as the third filter residue and the third filtrate. Sodium hydroxide is then added to adjust the pH of the third filtrate to 12 to form manganese hydroxide precipitate. The fourth filter residue and the fourth filtrate are separated. The fourth filtrate is heated and fractionated. The components distilled out in sequence are ethanol, water and DMSO. The fractionation residue is replenished with oxalic acid and then put into the subsequent recycling step (2) to achieve recycling.

[0009] The solid-liquid ratio of the battery positive electrode powder to the eutectic solvent is 1:20 to 40; the volume ratio of the additive dimethyl sulfoxide to the eutectic solvent is 1:1.5 to 2; the volume ratio of the first filtrate to water is 1:1 to 2; and the volume ratio of the second filtrate to ethanol is 1:3 to 5.

[0010] (3) The three precipitates were calcined to obtain the corresponding metal oxides.

[0011] The stirring speed in step (1) is 60-90 rpm.

[0012] In step (2), the positive electrode powder and the eutectic solvent are mixed and heated at a stirring rate of 340 to 360 rpm.

[0013] In step (2), the centrifugation rate is 8000-10000 rpm and the time is 3-5 minutes.

[0014] In step (2), the fractionation temperatures were successively controlled at 78.3–80℃, 100–110℃, and 189–195℃.

[0015] In step (3), nickel oxalate precipitate and cobalt oxalate precipitate are calcined at 500-520℃ for 2-3 hours; lithium oxalate precipitate is calcined at 600-620℃ for 2-3 hours; and manganese hydroxide precipitate is calcined at 800-820℃ for 2-3 hours.

[0016] The ternary lithium battery mentioned is specifically of type NCM811, NCM523, or NCM622.

[0017] The beneficial effects of this invention are as follows:

[0018] (I) Compared with traditional metallurgical processes

[0019] Pyrometallurgical recycling processes are energy-intensive, have low recovery rates, are not environmentally friendly, have low economic benefits, and can only recover a limited variety of metals. In contrast, this invention can effectively recover a variety of metals and is environmentally friendly by not producing harmful gases, having low energy consumption, and low economic costs.

[0020] Hydrometallurgy emits toxic gases, is environmentally unfriendly, and corrodes instruments and equipment. In contrast, this invention not only does not corrode instruments and equipment, but also avoids the dangers of using strong acids, does not produce harmful gases, and allows for solution recycling, saving a significant amount of water resources. Overall, it is more green and environmentally friendly.

[0021] (II) Compared with other methods for extracting metals using eutectic solvents

[0022] Compared with other existing technologies that use eutectic solvents to extract metals, existing technologies can only achieve general metal recovery with low recovery rates. In contrast, this invention achieves selective extraction and stepwise enrichment of these metals, allowing the four metals nickel, cobalt, manganese, and lithium to be enriched and precipitated in different steps, eliminating the need for metal separation in the later stages of other technologies.

[0023] This invention involves calcining the recovered metals to obtain oxides of various metals, which can be directly used in production.

[0024] Most technologies cannot recover lithium metal, but this invention enables the recovery of lithium metal from batteries, so our process is more comprehensive in terms of metal recovery.

[0025] Secondly, this invention has a high metal extraction rate, reaching over 90%; the extraction purity is high, and the final metal oxide can be directly used in the next round of production. It is easy to operate and has low cost.

[0026] This invention utilizes the different melting points of solvents to perform fractional distillation, which can separate water and diluent. The remaining solvent can be reused, and the extractant can also be reused. Therefore, the process is more environmentally friendly and green, and effectively reduces costs. Attached Figure Description

[0027] The following are accompanying drawings of embodiments of the present invention:

[0028] Figure 1 Line graphs showing the metal extraction rates of NCM811 at different solid-liquid ratios in Examples 1, 3, and 4;

[0029] Figure 2 Line graphs showing the metal extraction rates of NCM811 at different experimental temperatures in Examples 1, 5, and 6;

[0030] Figure 3 Line graphs showing the metal extraction rates of NCM523 with different solid-liquid ratios in Examples 2, 7, 8, and 9;

[0031] Figure 4 Line graphs showing the metal extraction rates of NCM523 at different experimental temperatures in Examples 2, 10, and 11;

[0032] Figure 5 Line graphs showing the metal extraction rates of NCM622 with different solid-liquid ratios in Examples 12, 13, 14, and 15;

[0033] Figure 6 Line graphs showing the metal extraction rates of NCM622 at different experimental temperatures in Examples 14, 16, 17, and 18;

[0034] Figure 7 The graph shows the optimal extraction rate data for different batteries in Examples 1, 2, and 14. Detailed Implementation

[0035] This invention provides a method for selectively extracting and recovering metals from spent ternary lithium-ion batteries. In an exemplary embodiment of this method, the steps may include:

[0036] Choline chloride and oxalic acid were mixed and heated at 50°C, and stirred evenly at 60 rpm to obtain a eutectic solvent.

[0037] Waste ternary lithium battery cathode powder was mixed with a eutectic solvent at a certain solid-liquid ratio and then heated in an oil bath for 10 hours.

[0038] Dimethyl sulfoxide (DMSO) at a volume ratio of 1:1.5 was added to the filtrate, and the mixture was stirred and allowed to stand for 5 hours. After centrifugation at 10,000 rpm, nickel oxalate dihydrate precipitate and a filtrate containing lithium, cobalt, and manganese were obtained. Water was added to the filtrate, and the mixture was heated at 70°C for 3 hours to separate cobalt oxalate precipitate and a filtrate containing lithium and manganese.

[0039] Lithium oxalate precipitate was obtained by extraction with ethanol at a volume ratio of 1:3, and the precipitate was then separated from the filtrate.

[0040] Adjust the pH of the filtrate to 12 to obtain manganese hydroxide precipitate.

[0041] Nickel oxalate precipitate and cobalt oxalate precipitate were calcined at 500℃ for 2 hours to obtain high-purity nickel oxide and cobalt oxide; lithium oxalate precipitate was calcined at 600℃ for 2 hours to obtain high-purity lithium oxide; and manganese hydroxide precipitate was calcined at 800℃ for 2 hours to obtain high-purity manganese oxide.

[0042] The leachate is then fractionated to extract water, ethanol, and diluent. The fractionation residue can be recycled by adding oxalic acid according to the specified ratio.

[0043] ① The eutectic solvent used in the experiment was choline chloride / oxalic acid eutectic solvent (C5H). 14 The synthesis mechanism of ClNO-H2C2O4 is as follows:

[0044]

[0045] ② After diluting DES with different solvents, metal ions such as Ni, Co, and Mn will be in different coordination environments. Once each metal element is in its specific coordination environment, the gradual separation of elements such as Ni, Co, Mn, and Li can be achieved by combining the subsequent leaching and separation processes.

[0046] ③ After dissolving the ternary lithium-ion battery cathode material in DES solvent, Ni, Co, Mn, and Li all react with oxalic acid in the solvent to form oxalic acid compounds. Among them, the hydrates of cobalt oxalate, lithium oxalate, and manganese oxalate have high solubility in DES solvent, while the nickel oxalate dihydrate is almost insoluble in DES solvent.

[0047] ④ Then, DMSO is added as a diluent to the filtrate. Its function is not only to reduce the viscosity of the system to facilitate subsequent filtration, but also to separate the Ni element through filtration and to change the complex form of the Co element, from tetrahedral [CoCl4]. 2- To the octahedral [Co(H2O)6] 2+ This causes its solubility in aqueous solution to decrease, while Mn element is unaffected. Adding an appropriate amount of water to the solution and filtering again will yield Co element as a precipitate.

[0048] ⑤ Add ethanol to separate lithium oxalate by taking advantage of the fact that lithium oxalate is insoluble in ethanol. When separating Mn element, the pH value of the remaining filtrate can be changed by using sodium hydroxide solution to obtain manganese hydroxide precipitate.

[0049] ⑥ The obtained metal precipitates are calcined to obtain various metal oxides.

[0050] ⑦ Fractionation is performed to remove diluent, water, and ethanol, and oxalic acid is added to achieve the recycling of DES solvent.

[0051] The mainstream nickel-cobalt-manganese ratio in ternary lithium batteries involved in this invention is 5:2:3. Current technology tends to gradually increase the proportion of nickel and reduce the amount of cobalt; therefore, this experiment primarily uses NCM811 batteries. This experiment uses NCM523, NCM622, and NCM811 batteries as examples for extraction. The nickel-cobalt-manganese ratio in the NCM523 battery is 5:2:3, with the chemical formula Li(Ni) 0.5 Co 0.2 Mn 0.3 O2 is a type of battery with high specific capacity and good thermal stability; the nickel-cobalt-manganese ratio in the NCM622 battery is 6:2:2, and its chemical formula is Li(Ni) 0.6 Co 0.2 Mn 0.2 O2 has good processing performance, high heat output, and is easy to sinter at relatively low temperatures; the nickel-cobalt-manganese ratio in NCM811 batteries is 8:1:1, making it a new type of high-nickel lithium-ion battery material with the chemical formula Li(Ni) 0.8 Co 0.1 Mn 0.1 )02 has advantages such as high capacity and low price.

[0052] Example 1

[0053] This embodiment describes a method for selectively extracting metals from spent ternary lithium batteries using the eutectic solvent DES, comprising the following steps:

[0054] (1) The recycled waste ternary lithium batteries (NCM811 type, with LiNi cathode material) were collected. 0.8 Co 0.1 Mn 0.1 02) After immersion and discharge, the steel shell is initially manually removed with clamps, and then the positive and negative electrodes are separated. The removed positive electrode material is added to a muffle furnace and calcined at 600 degrees Celsius for 5 hours to remove impurities such as polyvinylidene fluoride (PVDF) and carbon powder from the positive electrode sheet, and the final positive electrode powder sample is obtained as experimental raw material.

[0055] (2) Mix 6.3035 g of solid oxalic acid (OxA) and 6.981 g of solid choline chloride (ChCl) in a flask at a molar ratio of 1:1, heat in an oil bath to maintain the temperature at 50°C, and stir at a speed of 60 rpm for 30 minutes to obtain a transparent and colorless liquid, which is the eutectic solvent DES.

[0056] (3) Heat 10 ml of DES to 120 °C with stirring at 350 rpm, then add NCM811 cathode powder at a solid-liquid ratio of 1:20 and store for 10 h. After leaching, add 15 ml of dimethyl sulfoxide (DMSO) to the flask, shake well, and let stand for 5 h. Place the diluted solution in a high-speed centrifuge and centrifuge at 10,000 rpm for 5 minutes. The first filter residue (nickel oxalate dihydrate precipitate) is washed twice with DMSO (5 ml each time) to obtain a first filtrate with a volume of 35 ml.

[0057] (4) Then dilute the first filtrate with 50ml of water, heat to 70℃ and keep for 3h to form a large amount of pink precipitate, then separate by vacuum filtration to obtain the second filter residue (cobalt oxalate dihydrate precipitate) and the second filtrate.

[0058] (5) Add ethanol at a volume ratio of 1:3 to the remaining filtrate (filtrate: extractant) to extract the third filter residue (lithium oxalate precipitate) from the solution.

[0059] (6) The pH of the second filtrate was adjusted to 12 by adding an appropriate amount of 1 mol / L NaOH solution, and the precipitate was separated by filtration to obtain the fourth filter residue (which is manganese hydroxide precipitate).

[0060] (7) The first and second filter residues are calcined at 500°C for 2 hours to obtain nickel oxide and cobalt oxide with a purity greater than 80%, the third filter residue is calcined at 600°C for 2 hours to obtain lithium oxide with a purity greater than 90%, and the fourth filter residue is calcined at 800°C for 2 hours to obtain manganese oxide with a purity greater than 90%.

[0061] (8) Neutralize the filtrate with oxalic acid to pH 7 and perform fractional distillation. Control the temperature at 80℃, 110℃ and 190℃ respectively to obtain ethanol, water and DMSO. Finally, choline chloride is left. Add solid oxalic acid to it according to the ratio and perform step (2) to obtain DES solvent that can be used in the next round of experiments and recycled.

[0062] Metal selective extraction experiments were conducted on NCM811 batteries at a solid-solution ratio of 1:20 and a reaction temperature of 120℃. The mass fraction of metal elements in different samples was determined using an Agilent 5110 inductively coupled plasma optical emission spectrometer (ICP-OES). The gas flux flow rate was set to 0.7 L / min, and each element was tested using at least two wavelengths in axial mode: Ni (216.555 nm, 227.021 nm), Co (237.863 nm, 238.892 nm, 228.615 nm), and Mn (259.372 nm, 257.610 nm, 293.931 nm).

[0063] Table 1 ICP-OES Test Data

[0064]

[0065] The extraction rate and extraction purity of this method were calculated. The formula for calculating purity is as follows:

[0066] p = w x / (w Ni +w Co +w Mn )×100%

[0067] The extraction rate is calculated using the following formula:

[0068] η=(mw x / m x )×100%

[0069]

[0070] Where w x It is the final mass fraction (ppm) of x (nickel, cobalt, or manganese) in the solution, w Ni w Co and w Mn This represents the final mass fraction of nickel, cobalt, and manganese. m is the final mass of the leaching solution (in grams), where... It is the mass of lithium element in lithium oxide. This is the mass of lithium in the battery's positive electrode material. x w is the initial mass (in grams) of x in the active material. x w Ni w Co and w Mn The values ​​are obtained based on data measured via ICP-OES. m and m x The value was obtained from the analytical balance.

[0071] The above data were obtained through ICP-OES testing. Calculations showed that the extraction rates were 96.3% for nickel, 97.4% for cobalt, 94.4% for manganese, and 94.3% for lithium; the extraction purity was 91.1% for nickel, 90.4% for cobalt, 93.8% for manganese, and 95.6% for lithium.

[0072] Example 2

[0073] This embodiment describes a method for selectively extracting metals from spent ternary lithium batteries using the eutectic solvent DES, comprising the following steps:

[0074] (1) Using waste ternary lithium batteries (NCM523 type, with LiNi as the positive electrode material)0.5 Co 0.2 Mn 0.3 The positive electrode powder (O2) after calcination is used as raw material.

[0075] (2) Mix 6.3035 g of solid oxalic acid (OxA) and 6.981 g of solid choline chloride (ChCl) in a flask at a molar ratio of 1:1, heat in an oil bath to maintain the temperature at 50°C, and stir at a speed of 60 rpm for 30 minutes to obtain a transparent and colorless liquid, which is the eutectic solvent DES.

[0076] (3) Heat 10 ml of DES to 120 °C with stirring at 350 rpm, then add NCM523 cathode powder at a solid-liquid ratio of 1:20 and store for 10 h. After leaching, add 15 ml of dimethyl sulfoxide (DMSO) to the flask, shake well, and let stand for 5 h. Place the diluted solution in a high-speed centrifuge and centrifuge at 10,000 rpm for 5 minutes. The first filter residue (nickel oxalate dihydrate precipitate) is washed twice with DMSO (5 ml each time) to obtain a first filtrate with a volume of 35 ml.

[0077] (4) Then dilute the first filtrate with 50ml of water, heat to 70℃ and keep for 3h to form a large amount of pink precipitate, then separate by vacuum filtration to obtain the second filter residue (cobalt oxalate dihydrate precipitate) and the second filtrate.

[0078] (5) Add ethanol at a volume ratio of 1:3 to the remaining filtrate (filtrate: extractant) to extract the third filter residue (lithium oxalate precipitate) from the solution.

[0079] (6) The pH of the second filtrate was adjusted to 12 by adding an appropriate amount of 1 mol / L NaOH solution, and the precipitate was separated by filtration to obtain the fourth filter residue (which is manganese hydroxide precipitate).

[0080] (7) The first and second filter residues are calcined at 500°C for 2 hours to obtain nickel oxide and cobalt oxide with a purity greater than 80%, the third filter residue is calcined at 600°C for 2 hours to obtain lithium oxide with a purity greater than 90%, and the fourth filter residue is calcined at 800°C for 2 hours to obtain manganese oxide with a purity greater than 90%.

[0081] (8) Neutralize the filtrate with oxalic acid to pH 7 and perform fractional distillation. Control the temperature at 80℃, 110℃ and 190℃ respectively to obtain ethanol, water and DMSO. Finally, choline chloride is left. Add solid oxalic acid to it according to the ratio and perform step (2) to obtain DES solvent that can be used in the next round of experiments and recycled.

[0082] Metal selective extraction experiments were conducted on NCM523 batteries at a solid-solution ratio of 1:30 and a reaction temperature of 120℃. The mass fraction of metal elements in different samples was determined using an Agilent 5110 inductively coupled plasma optical emission spectrometer (ICP-OES). The gas flux flow rate was set to 0.7 L / min, and each element was tested using at least two wavelengths in axial mode: Ni (216.555 nm, 227.021 nm), Co (237.863 nm, 238.892 nm, 228.615 nm), and Mn (259.372 nm, 257.610 nm, 293.931 nm).

[0083] After obtaining data from ICP-OES testing, calculations showed that the extraction rates of nickel were 94.7%, cobalt 95.2%, manganese 92.1%, and lithium 93.6%; the extraction purity of nickel was 90.1%, cobalt 88.7%, manganese 87.1%, and lithium 90.5%.

[0084] Table 2 Summary of Examples 3-18

[0085]

[0086]

[0087] Solid-liquid ratio variable of NCM811 battery:

[0088] Using the extraction rates of nickel, cobalt, and manganese as a reference, and the solid-liquid ratio (the ratio of cathode material to DES eutectic solvent) as a parameter, the preferred range of the variable is 1:20 to 1:40, and the experimental temperature is set at 120℃.

[0089] ① Taking a solid-liquid ratio of 1:20 as an example, the extraction rate of nickel is 96.3%, the extraction rate of cobalt is 97.4%, and the extraction rate of manganese is 94.4%, corresponding to Example 1;

[0090] ② Taking a solid-liquid ratio of 1:30 as an example, the extraction rate of nickel is 96.3%, the extraction rate of cobalt is 97.35%, and the extraction rate of manganese is 94.2%, corresponding to Example 3. Overall, this is lower than the extraction efficiency when the solid-liquid ratio is 1:20;

[0091] ③ Taking a solid-liquid ratio of 1:40 as an example, the extraction rate of nickel is 96.4%, the extraction rate of cobalt is 97.2%, and the extraction rate of manganese is 94.3%, corresponding to Example 4. Overall, this is lower than the extraction efficiency when the solid-liquid ratio is 1:20.

[0092] Therefore, considering all factors, the optimal solid-liquid ratio is 1:20, at which point the lithium extraction rate is 94.3%.

[0093] Temperature variations of NCM811 batteries:

[0094] Using the extraction rates of nickel, cobalt, and manganese as a reference, and experimental temperature as a parameter, the optimal range of the variable is 100℃~130℃, and the solid-liquid ratio is set to 1:20.

[0095] ① Taking an experimental temperature of 120℃ as an example, the extraction rate of nickel was 96.4%, the extraction rate of cobalt was 95.35%, and the extraction rate of manganese was 94.2%, corresponding to Example 1;

[0096] ② Taking the experimental temperature of 100℃ as an example, the extraction rate of nickel was 90.3%, the extraction rate of cobalt was 97.4%, and the extraction rate of manganese was 93.4%. In comparison with Example 5, the extraction rates are lower than those at the experimental temperature of 120℃.

[0097] ③ Taking the experimental temperature of 130℃ as an example, the extraction rate of nickel was 95.8%, the extraction rate of cobalt was 94.2%, and the extraction rate of manganese was 95.3%. In comparison with Example 6, the extraction rates were lower than those at the experimental temperature of 120℃.

[0098] Therefore, taking all factors into consideration, the optimal reaction temperature was 120℃, at which point the lithium extraction rate was 94.3%.

[0099] Solid-liquid ratio variable of NCM523 battery:

[0100] Using the extraction rates of nickel, cobalt, and manganese as references, and the solid-liquid ratio as a parameter, the optimal range of the variable was 1:10 to 1:35, and the experimental temperature was set at 120℃.

[0101] ① Taking a solid-liquid ratio of 1:30 as an example, the extraction rate of nickel is 94.7%, the extraction rate of cobalt is 95.2%, and the extraction rate of manganese is 92.1%, corresponding to Example 2;

[0102] ② Taking a solid-liquid ratio of 1:10 as an example, the extraction rate of nickel is 93.5%, the extraction rate of cobalt is 92.0%, and the extraction rate of manganese is 91.1%. According to Example 7, the overall extraction rate is lower than that when the solid-liquid ratio is 1:30.

[0103] ③ Taking a solid-liquid ratio of 1:15 as an example, the extraction rate of nickel is 93.7%, the extraction rate of cobalt is 93.8%, and the extraction rate of manganese is 93.2%. According to Example 8, the overall extraction rate is lower than that when the solid-liquid ratio is 1:30.

[0104] ④ Taking a solid-liquid ratio of 1:35 as an example, the extraction rate of nickel is 94.2%, the extraction rate of cobalt is 95.0%, and the extraction rate of manganese is 92.5%. In comparison with Example 9, the extraction rates are lower than those when the solid-liquid ratio is 1:30.

[0105] Therefore, considering all factors, the optimal solid-liquid ratio is 1:30, at which point the lithium extraction rate is 91.8%.

[0106] Temperature variations of NCM523 batteries:

[0107] Using the extraction rates of nickel, cobalt, and manganese as a reference, and experimental temperature as a parameter, the optimal range of the variable is 105℃~125℃, and the solid-liquid ratio is set to 1:30.

[0108] ① Taking an experimental temperature of 120℃ as an example, the extraction rate of nickel was 94.6%, the extraction rate of cobalt was 95.2%, and the extraction rate of manganese was 93.0%, corresponding to Example 2;

[0109] ② Taking the experimental temperature of 105℃ as an example, the extraction rate of nickel was 92.8%, the extraction rate of cobalt was 94.0%, and the extraction rate of manganese was 92.6%. In comparison with Example 10, the extraction rate is lower than that at the experimental temperature of 120℃.

[0110] ③ Taking the experimental temperature of 125℃ as an example, the extraction rate of nickel was 93.1%, the extraction rate of cobalt was 93.5%, and the extraction rate of manganese was 93.7%. According to Example 11, the overall extraction rate is lower than that at the experimental temperature of 120℃.

[0111] Therefore, taking all factors into consideration, the optimal reaction temperature was 120℃, at which the lithium extraction rate was 91.8%.

[0112] Solid-liquid ratio variable of NCM622 battery:

[0113] Using the extraction rates of nickel, cobalt, and manganese as references, and the solid-liquid ratio as a parameter, the optimal range of the variable was 1:20 to 1:50, and the experimental temperature was set at 125℃.

[0114] ① Taking a solid-liquid ratio of 1:40 as an example, the extraction rate of nickel is 93.8%, the extraction rate of cobalt is 89.7%, and the extraction rate of manganese is 90.3%, corresponding to Example 14;

[0115] ② Taking a solid-liquid ratio of 1:20 as an example, the extraction rate of nickel is 85.5%, the extraction rate of cobalt is 92.0%, and the extraction rate of manganese is 89.2%. In comparison with Example 12, the extraction rate is lower than that when the solid-liquid ratio is 1:40.

[0116] ③ Taking a solid-liquid ratio of 1:30 as an example, the extraction rate of nickel is 86.7%, the extraction rate of cobalt is 92.3%, and the extraction rate of manganese is 92.7%. According to Example 13, the overall extraction rate is lower than that when the solid-liquid ratio is 1:40.

[0117] ④ Taking a solid-liquid ratio of 1:50 as an example, the extraction rate of nickel is 91.7%, the extraction rate of cobalt is 91.0%, and the extraction rate of manganese is 88.0%. In comparison with Example 15, the extraction rate is lower than that when the solid-liquid ratio is 1:40.

[0118] Therefore, considering all factors, the optimal solid-liquid ratio is 1:40, at which point the lithium extraction rate is 93.3%.

[0119] Temperature variations in NCM622 batteries:

[0120] Using the extraction rates of nickel, cobalt, and manganese as a reference, and experimental temperature as a parameter, the preferred range of the variable is 110℃~130℃, and the solid-liquid ratio is set to 1:40.

[0121] ① Taking an experimental temperature of 125℃ as an example, the extraction rate of nickel was 93.8%, the extraction rate of cobalt was 91.0%, and the extraction rate of manganese was 92.2%, corresponding to Example 14;

[0122] ② Taking the experimental temperature of 110℃ as an example, the extraction rate of nickel was 85.8%, the extraction rate of cobalt was 86.0%, and the extraction rate of manganese was 88.5%. According to Example 16, the overall extraction rate is lower than that at the experimental temperature of 125℃.

[0123] ③ Taking the experimental temperature of 115℃ as an example, the extraction rate of nickel was 86.1%, the extraction rate of cobalt was 87.7%, and the extraction rate of manganese was 89.0%. According to Example 17, the overall extraction rate is lower than that at the experimental temperature of 125℃.

[0124] ④ Taking the experimental temperature of 130℃ as an example, the extraction rate of nickel was 92.0%, the extraction rate of cobalt was 89.6%, and the extraction rate of manganese was 88.0%. In comparison with Example 18, the extraction rates were lower than those at the experimental temperature of 125℃.

[0125] Therefore, taking all factors into consideration, the optimal reaction temperature was 125℃, at which point the lithium extraction rate was 93.3%.

[0126] Table 3. Optimal experimental conditions for NCM811, NCM523, and NCM622 batteries: metal extraction rate and purity.

[0127]

[0128] As can be seen from the above embodiments, through research and experiments on solid-liquid ratio, temperature, reaction time, etc., the present invention can achieve a very good purification rate and purity of nickel, cobalt, and manganese in waste batteries, which is of great significance for resource recycling and environmental protection.

[0129] Matters not covered in this invention are common knowledge.

Claims

1. A method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent, characterized in that the method comprises the following steps: (1) Choline chloride and oxalic acid are mixed and stirred at 50–70°C for 50–60 minutes to obtain a eutectic solvent; wherein, The molar ratio of choline chloride to oxalic acid is 1–2:1; (2) Add waste ternary lithium battery positive electrode powder to a eutectic solvent, heat in a mixed oil bath at 100-130°C for 8-12 hours, add dimethyl sulfoxide as a diluent, let stand for 3-5 hours, and centrifuge to obtain nickel oxalate dihydrate precipitate. After washing with DMSO, the first filter residue and the first filtrate are obtained respectively. Water is added to the first filtrate and heated in a water bath at 70-75°C for 2-3 hours to obtain cobalt oxalate dihydrate precipitate. The second filter residue and the second filtrate are separated. Ethanol is added to the second filtrate for extraction and filtration to obtain lithium oxalate precipitate as the third filter residue and the third filtrate. Sodium hydroxide is then added to adjust the pH of the third filtrate to 12 to form manganese hydroxide precipitate. The fourth filter residue and the fourth filtrate are separated. The fourth filtrate is heated and fractionated. The components distilled out in sequence are ethanol, water and DMSO. The fractionation residue is replenished with oxalic acid and then put into the subsequent recycling step (2) to achieve recycling. The solid-liquid ratio of the battery positive electrode powder to the eutectic solvent is 1:20 to 40; the volume ratio of the additive dimethyl sulfoxide to the eutectic solvent is 1:1.5 to 2; the volume ratio of the first filtrate to water is 1:1 to 2; and the volume ratio of the second filtrate to ethanol is 1:3 to 5. (3) The three precipitates were calcined to obtain the corresponding metal oxides.

2. The method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent as described in claim 1, characterized in that: The stirring speed in step (1) is 60-90 rpm; In step (2), the positive electrode powder is mixed with the eutectic solvent and heated at a stirring rate of 340–360 rpm. In step (2), the centrifugation rate is 8000-10000 rpm and the time is 3-5 minutes.

3. The method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent as described in claim 1, characterized in that: In step (3), nickel oxalate precipitate and cobalt oxalate precipitate are calcined at 500-520℃ for 2-3 hours; lithium oxalate precipitate is calcined at 600-620℃ for 2-3 hours; and manganese hydroxide precipitate is calcined at 800-820℃ for 2-3 hours.

4. The method for selectively extracting metals from waste ternary lithium batteries using a eutectic solvent as described in claim 1, wherein the ternary lithium battery is specifically of type NCM811, NCM523, or NCM622.

5. The method for selectively extracting metals from spent ternary lithium batteries using a eutectic solvent as described in claim 1, characterized in that: In step (2), the fractionation temperature is controlled successively at 78.3~80℃, 100℃~110℃, and 189~195℃.

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