A method for recovering valuable metals from waste ternary lithium batteries based on a deep eutectic solvent

Abstract

The application belongs to the technical field of resource utilization of waste lithium ion batteries, and discloses a method for recovering valuable metals from waste ternary lithium batteries based on a eutectic solvent. The method uses a eutectic solvent system of betaine hydrochloride-malic acid-water to simultaneously achieve the preliminary separation of lithium and manganese into the liquid phase and the precipitation of nickel and cobalt in the leaching stage. For the products after the preliminary separation, an extraction-back extraction process is used for purification: after the dissolution of the solid phase containing nickel and cobalt, the nickel and cobalt are co-extracted into the organic phase by using a thio-phosphinic acid extractant, and then by controlling the acidity gradient of the back extraction agent, cobalt salt products and nickel salt products are obtained by back extraction in steps; the lithium-rich manganese liquid phase is selectively extracted by using an acidic phosphorus extractant to separate lithium from manganese. The application combines leaching and precipitation integration with selective extraction technology, shortens the process flow, realizes the full-component high-purity recovery of valuable metals, and realizes the closed-loop utilization of leaching agents.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology for waste lithium-ion batteries, and more specifically, to a method for recycling valuable metals from waste ternary lithium batteries based on a eutectic solvent. Background Technology

[0002] With the rapid growth of the new energy vehicle industry, the amount of retired lithium-ion batteries (LIBs) has increased dramatically, especially the amount of retired ternary lithium batteries, which has seen explosive growth. Currently, hydrometallurgy has become the mainstream technology due to its high metal recovery rate, but in actual industrial applications, the traditional "leaching-step separation" route is still constrained by several technical bottlenecks.

[0003] First, traditional inorganic acid leaching processes are lengthy and have extremely high loads on subsequent separation. Existing industrial processes generally utilize strong acids to fully dissolve all metals in the cathode material, forming a complex leachate. For example, existing technology CN117083400A discloses a method for short-range recovery of valuable metals from spent ternary lithium batteries. This method uses sulfuric acid reduction leaching followed by a two-stage chemical precipitation process to separate nickel, cobalt, and manganese, combined with trisodium phosphate precipitation of lithium. However, this method has significant drawbacks: first, the leachate contains nickel, cobalt, manganese, and lithium, requiring large amounts of alkaline solution for multi-step pH adjustment and impurity removal, and introducing large amounts of trisodium phosphate precipitant, generating large amounts of saline wastewater; second, the leaching agent cannot be directly recycled, resulting in high acid and alkali consumption, increasing equipment investment and chemical reagent costs.

[0004] Secondly, nickel-cobalt separation is a major technical challenge, as traditional full-volume solvent extraction methods are costly. Due to the high similarity in chemical properties between nickel and cobalt, industrial processes primarily rely on organophosphorus extractants such as di(2-ethylhexyl)phosphoric acid (P204), P507, and Cyanex 272 for separation. For example, existing technology CN106319228A discloses a method for recovering valuable metals from nickel-cobalt-manganese waste residue. This method uses P204 extractant and achieves nickel removal and manganese and cobalt separation sequentially through multi-stage countercurrent extraction and stepwise back-extraction processes. Although solvent extraction can yield high-purity products, it faces challenges when processing full-volume leachates (i.e., complex solutions containing high concentrations of Ni, Co, Mn, and Li), including numerous extraction stages (often dozens), easy poisoning of the organic phase, and significant solvent loss. The industry needs a pretreatment process that can significantly simplify the composition of the feed solution at the extraction stage, i.e., achieving preliminary metal separation at the source to reduce the difficulty and cost of subsequent separation.

[0005] Finally, while the emerging deep eutectic solvent (DES) technology is environmentally friendly, it faces industrialization challenges due to its cycling stability. Although DES, as a green solvent, exhibits good selective leaching potential, existing research is largely limited to the initial leaching effect, neglecting the problem of impurity accumulation during the cycling process. For example, the prior art CN116732322A discloses a method for recovering cathode materials using a natural deep eutectic solvent combined with biomass powder. Although the leaching rate is improved by utilizing the reducibility of biomass, the introduction of exogenous organic solids leads to the presence of persistent organic impurities in the solvent, making purification extremely difficult. Furthermore, the prior art CN117821774A discloses a method for ball milling leaching of ternary lithium batteries using a novel deep eutectic solvent. While this DES achieves a high metal leaching rate, the process lacks an effective solvent regeneration mechanism. During multiple cycles, residual impurity ions and metal ions in the solution continuously accumulate, leading to a sharp increase in solvent viscosity, slower leaching kinetics, and decreased selectivity. Existing technologies often require energy-intensive regeneration processes for DES after use (such as back-extraction for impurity removal or distillation), which weakens its low-carbon advantage as a green solvent and makes it difficult to achieve a truly efficient closed-loop cycle.

[0006] In summary, existing technologies still face multiple bottlenecks in the field of waste ternary lithium battery recycling: (1) Traditional inorganic acid leaching processes are lengthy, consume a lot of acid and alkali reagents, and generate a large amount of high-salt wastewater in subsequent multi-step precipitation and impurity removal processes, resulting in a high environmental load; (2) Solvent extraction technology faces problems such as high separation difficulty, multiple extraction stages, high reagent costs, and easy poisoning of organic phases when dealing with complex leaching solutions containing nickel, cobalt, manganese, and lithium; (3) Although existing eutectic solvent technology is green, it generally lacks an effective impurity removal mechanism, leading to the accumulation of metal ions, a sharp increase in solvent viscosity, and activity decay during the recycling process, making it difficult to achieve long-term closed-loop operation with low energy consumption. Summary of the Invention

[0007] This invention addresses the problems of existing hydrometallurgical processes, such as the separation of leaching and separation steps, lengthy processes, and high reagent consumption. It proposes a method for recovering valuable metals from spent ternary lithium batteries based on a eutectic solvent. This invention constructs a specific betaine hydrochloride-malonic acid-water eutectic solvent system, simultaneously achieving lithium / manganese liquid-phase leaching and spontaneous precipitation of nickel / cobalt under mild conditions. By constructing an integrated "leaching-spontaneous separation-extraction" mechanism, and utilizing homologous solvent washing and selective extraction techniques, it achieves high-purity recovery of all components. Furthermore, impurities are removed through the spontaneous precipitation effect during the reaction process, achieving a self-purification closed-loop cycle of the leaching agent, resulting in significant economic and environmental benefits.

[0008] The technical solution of the present invention to solve the above problems is as follows:

[0009] This invention provides a method for recycling valuable metals from spent ternary lithium batteries based on a eutectic solvent. The method includes the following steps:

[0010] S1: Mix betaine hydrochloride, malonic acid and water, and heat and stir until the solid is completely dissolved to form a homogeneous and transparent liquid phase, thus obtaining a eutectic solvent.

[0011] S2. The waste ternary lithium battery cathode material powder is mixed with a eutectic solvent and leached under heating conditions. After the reaction, solid-liquid separation is performed to obtain a lithium-rich manganese liquid phase and a nickel-cobalt-containing solid precipitate. The lithium-rich manganese liquid phase is directly or recycled for the leaching of the next batch of cathode material powder after replenishment to enrich the lithium-manganese component in the liquid phase. After the lithium-manganese reaches the preset enrichment concentration, the liquid phase is no longer recycled to obtain a lithium-manganese enriched solution. The obtained nickel-cobalt-containing solid precipitate is collected to obtain a nickel-cobalt solid product.

[0012] S3. Dissolve the nickel-cobalt solid product in water, adjust the pH value, and then extract and back-extract stepwise to obtain cobalt salt and nickel salt respectively.

[0013] S4. Adjust the pH value of the lithium-manganese enrichment solution in step S2, and extract to obtain a manganese-rich organic phase and a lithium-rich aqueous phase. After back-extraction of the manganese-rich organic phase, manganese salt is obtained, and lithium salt is obtained by treatment of the lithium-rich aqueous phase.

[0014] Compared with the prior art, the beneficial effects of the present invention include:

[0015] (1) The method of this invention employs a novel and efficient "leaching-spontaneous separation-circulation" system. Compared with the traditional "leaching-removal-extraction" process, its core advantage lies in utilizing the component characteristics of the eutectic solvent to achieve the separation of nickel-cobalt and lithium-manganese during the leaching stage, significantly reducing the processing load of subsequent separation stages. This innovative design not only simplifies the process flow and effectively reduces operational complexity and system energy consumption, but also brings significant economic and environmental benefits: the cumbersome chemical precipitation removal and the large number of saponification steps before extraction in the traditional process are simplified or reduced, and the consumption of organic solvents and acids and alkalis is greatly reduced. At the same time, the amount of wastewater is also greatly reduced, thereby reducing the total operating cost and recycling cost. Experiments show that the single leaching rate of lithium ions is as high as 99.59%, and the nickel precipitation rate is as high as 95.47%. The lithium-rich manganese leaching solution utilizes the reaction-driven self-purification characteristics to achieve direct closed-loop operation, enabling continuous leaching for 8 times. The lithium leaching rate remains at 95.77% in the eighth leaching, and the nickel precipitation rate remains stable at 95.36%.

[0016] (2) This invention optimizes the extraction environment of the subsequent solid-phase product by combining spontaneous phase separation with homologous solvent washing during the leaching process. Spontaneous separation retains most manganese ions in the liquid phase, while homologous washing removes physically entrained residual lithium and manganese impurities from the solid phase, resulting in extremely low manganese content in the dissolved nickel-cobalt solution. This effectively avoids the co-extraction phenomenon caused by excessively high manganese ion concentration when using Cyanex 301 to extract nickel-cobalt, thereby reducing manganese loss and increasing the total manganese yield. Furthermore, it reduces the competitive interference of manganese ions on nickel-cobalt extraction, ensuring high purity of the nickel-cobalt product. After this coupled process, the nickel / cobalt separation factor reaches as high as 235.0, and the nickel co-extraction rate is only 1.65%.

[0017] (3) In the key separation stage, this invention not only efficiently removes impurities from the system, but also ensures that each component is ultimately converted into a valuable target product. Since most of the nickel and cobalt have been removed through solid-liquid separation at the front end, the selective interference of nickel and cobalt ions on the separation of manganese and lithium is reduced when the lithium-rich manganese liquid phase enters the P204 extraction stage, thus achieving efficient manganese extraction at a lower extraction stage. The nickel-cobalt-containing solid phase solution is treated with Cyanex 301 extractant to obtain high-purity cobalt and nickel salts; the lithium-rich manganese liquid phase is selectively extracted with P204 extractant to obtain pure manganese sulfate and lithium chloride solutions; the empty organic phase can be recycled. Compared with direct chemical precipitation or extraction methods, this invention alleviates the problem of excessive alkali consumption in traditional processes, significantly reduces wastewater treatment load, thereby greatly reducing production costs and improving the green and environmentally friendly level of the process.

[0018] (4) The eutectic solvent system selected in this invention exhibits excellent physicochemical properties and multiple reactivity. By constructing a hydration system, the excessively strong hydrogen bond network between components is broken, the solvent viscosity is reduced, and the mass transfer efficiency at the liquid-solid interface is improved, enabling the leaching reaction to be completed within 30 minutes under mild conditions. The malonic acid component in the solvent integrates the triple functions of "acid agent-reducing agent-precipitant": it provides an acidic dissolution environment, utilizes its reducing properties to achieve transition metal leaching without the addition of a reducing agent, and induces nickel and cobalt to form precipitates through specific coordination. This integrated design avoids the release of toxic gases in traditional inorganic strong acid processes, ensuring the green safety of the process from the source.

[0019] (5) This invention develops a full-component recycling and regeneration technology for waste ternary lithium battery cathode materials, which has high economic added value and is environmentally friendly. This technology successfully utilizes the characteristics of a eutectic solvent system to achieve efficient separation and recovery of Li, Ni, Co, and Mn, with a lithium recovery rate of 96.2%, and obtains high-purity nickel, cobalt, and manganese salt products, which greatly optimizes resource utilization efficiency and reduces operating costs, fully demonstrating the great industrial application prospects of this invention. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for recycling valuable metals from waste ternary lithium batteries based on a eutectic solvent, according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention. In the embodiments of this invention, unless otherwise stated, the analysis and calculation methods for each performance index are as follows:

[0022] 1. Analysis method for metal content: The mass fraction or concentration of metal elements such as lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) in waste cathode material powder, unleached residue after reaction, and various process liquid phases (leaching solution, washing solution, raffinate, back-extraction solution) were determined by flame atomic absorption spectrometry (FAAS).

[0023] 2. Calculation formula for core indicators

[0024] Leaching rate (η) of metal M:

[0025]

[0026] Where Ms is the mass of the leaching residue (g), Ws is the mass fraction of the metal in the leaching residue (wt%), Mo is the mass of the original cathode material (g), and Wo is the mass fraction of the metal in the original cathode material (wt%).

[0027] Precipitation rate (S) of metals:

[0028]

[0029] Where C m denoted as , where is the concentration of the metal in the filtrate from step 4 (g / L), V is the volume after final volume adjustment (L), Mo is the mass of the original cathode material (g), and Wo is the mass fraction of the metal in the original cathode material (wt%).

[0030] Separation factor (SF): Used to measure the difference in partitioning between two different metals in a liquid-solid phase.

[0031]

[0032] Among them, S Ni and S Li These represent the precipitation rates of nickel and lithium, respectively. This value reflects the tendency of nickel to enter the solid phase relative to lithium.

[0033] This invention proposes a method for recovering valuable metals from spent ternary lithium batteries based on eutectic solvents, which mainly includes four core processes: leaching-induced spontaneous phase separation and solvent recycling, solid-phase product separation, and liquid-phase product separation. Figure 1 Here is its flowchart.

[0034] like Figure 1 As shown, the method of the present invention specifically includes:

[0035] S1. Preparation of eutectic solvent: Using betaine hydrochloride and malonic acid as hydrogen bond donors and acceptors, an appropriate amount of deionized water was added to construct a hydrated eutectic solvent (DES) system.

[0036] Specific procedure: Mix betaine hydrochloride and malonic acid in a molar ratio of 1:2 to 1:7, controlling the total mass ratio of the two to water to be 10:1 to 2:1. Under heating and stirring conditions (preferably 60℃~90℃) until the solid is completely dissolved, forming a homogeneous and transparent liquid phase, which is the desired specific eutectic solvent.

[0037] S2, Leaching-induced spontaneous phase separation and solvent circulation: This section aims to utilize the specificity of the eutectic solvent components to simultaneously achieve liquid-phase leaching of lithium / manganese and solid-phase precipitation of nickel / cobalt within a single reaction system.

[0038] S2 can be operated as follows: Mix waste ternary lithium battery cathode material powder with a eutectic solvent and carry out a leaching reaction under heating conditions. After the reaction is completed, perform solid-liquid separation to obtain a lithium-rich manganese liquid phase and a nickel-cobalt-containing solid precipitate. The lithium-rich manganese liquid phase can be directly or recycled for the leaching of the next batch of cathode material powder after supplementing the components to enrich the lithium-manganese component in the liquid phase. After the lithium-manganese reaches the preset enrichment concentration, the liquid phase is no longer leached, and a lithium-manganese enriched solution is obtained. The obtained nickel-cobalt-containing solid precipitate is collected to obtain a nickel-cobalt solid product.

[0039] The above process of S2 can be specifically divided into three sub-steps: leaching reaction, preliminary solid-liquid separation, and solvent closed-loop circulation. The following is a detailed explanation of each sub-step.

[0040] S21, Leaching Reaction: The waste ternary lithium battery cathode material powder is mixed with the DES prepared in step S1. The liquid-to-solid mass ratio is controlled at 20:1 to 70:1, the reaction temperature at 60℃ to 120℃, and the reaction time at 20 minutes to 120 minutes. Under these conditions, lithium and manganese enter the liquid phase as soluble salts, while nickel and cobalt are converted into insoluble malonate compounds that precipitate.

[0041] S22. Preliminary solid-liquid separation: After the reaction in S21 is completed, the system is cooled to room temperature or lower to promote complete precipitation of the solid phase. After centrifugation or filtration, lithium-rich manganese liquid phase and nickel-cobalt solid phase precipitate are obtained, respectively.

[0042] S23, Solvent closed-loop circulation: The lithium-rich manganese liquid phase is directly returned to S21 for leaching of the next batch of raw materials (waste ternary lithium battery cathode material powder) without distillation or additional impurity removal. Alternatively, before returning, fresh DES components are added according to the mass loss during the leaching reaction in S21 and the separation process in S22, and then returned to S21 for leaching of the next batch of raw materials. This cycle is repeated multiple times until the lithium and manganese in the liquid phase reach the preset enrichment concentration, thereby obtaining a high-concentration lithium-rich manganese liquid phase (which is referred to as lithium-manganese enriched liquid in this invention).

[0043] S3. Solid-phase product extraction and separation: For the nickel-cobalt-containing solid precipitate separated in S2, a "washing-dissolving-extraction-stepwise back-extraction" process is constructed:

[0044] Washing pretreatment (optional, not mandatory): To improve product purity, before dissolution, the solid precipitate is washed for 10-60 minutes under heating conditions (e.g., 50°C~90°C) with a fresh eutectic solvent of the same composition as described in step S1. This step aims to effectively remove lithium and manganese impurities physically trapped on the surface and in the gaps of the solid phase using the properties of the solvent, thereby obtaining a high-purity nickel-cobalt intermediate.

[0045] Dissolution and Extraction: The high-purity nickel-cobalt intermediates or the unwashed solid precipitate obtained from S2, after washing and pretreatment, are dissolved in water. The pH is adjusted to 1.5-4.5, and a mixture of thiophosphonic acid extractant (preferably Cyanex 301) and sulfonated kerosene is added to the organic phase. The ratio (O / A, volume ratio) is controlled at 1:1-3:1 to co-extract nickel and cobalt ions into the organic phase, achieving complete separation from residual impurities.

[0046] Step-by-step reverse extraction:

[0047] Cobalt back-extraction: Taking advantage of the fact that cobalt complexes are less stable than nickel complexes, a multi-stage back-extraction is performed on the organic phase using a low-concentration acid (preferably 0.05 mol / L to 1.5 mol / L hydrochloric acid) to selectively strip cobalt ions to the aqueous phase, thereby obtaining a cobalt chloride solution.

[0048] Nickel back-extraction: The remaining organic phase is back-extracted in multiple stages using a high-concentration acid (preferably 2.0 mol / L to 8.0 mol / L hydrochloric acid) to break the strong bonds between nickel and the extractant, thereby obtaining a nickel chloride solution.

[0049] S4. Liquid-phase product extraction and separation: For the lithium-manganese enriched solution after S2 cycle enrichment, a "manganese removal extraction-direct lithium recovery" process is constructed:

[0050] Extraction and separation: Adjust the pH of the lithium-manganese enrichment solution to 2.0~5.0, and add an acidic phosphorus extractant (preferably P204) for extraction. Preferably, P204 can be partially saponified before extraction (saponification rate 20%~50%) to selectively extract manganese ions into the organic phase, and the remaining aqueous phase is the lithium-rich solution.

[0051] Product recycling:

[0052] Manganese products: The manganese-supported organic phase is back-extracted by acid (preferably 1.0 mol / L to 3.0 mol / L sulfuric acid) to obtain manganese sulfate solution.

[0053] Lithium products: Lithium carbonate or lithium phosphate products are prepared by concentrating, carbonizing or adding precipitants (such as phosphates) to lithium-rich solutions.

[0054] The following specific embodiments illustrate the technical effects of the present invention.

[0055] Example 1

[0056] (1) Leaching-induced spontaneous phase separation:

[0057] S1. First leaching: Prepare a eutectic solvent of betaine hydrochloride-malonic acid-water (BeCl-MA-H2O) as the leaching agent. Weigh 5.37g of betaine hydrochloride and 14.57g of malonic acid (molar ratio 1:4) into a reaction vessel, add 6mL of deionized water, and stir at 80℃ until the solid is completely dissolved to form a homogeneous and transparent solvent.

[0058] Weigh 20.0 g of the eutectic solvent prepared above and mix it with 0.5 g of waste NCM523 ternary lithium battery cathode material powder, stirring thoroughly. React for 30 min at a liquid-to-solid ratio of 40 g / g, a reaction temperature of 100℃, and a stirring speed of 300 rpm. After the reaction, allow the system to cool naturally to room temperature and separate by high-speed centrifugation (8000 rpm, 3 min) to obtain a lithium-rich manganese leachate and a nickel-cobalt-containing solid precipitate.

[0059] The liquid and solid phase compositions were determined using flame atomic absorption spectrometry. The results showed that the single-pass leaching rate of Li was 99.59%, Ni was 99.19%, Co was 99.16%, and Mn was 99.17%; while the precipitation rate of Ni was as high as 95.47%, and that of Co was 74.96%. Calculations indicated that the separation factor of lithium for nickel (SF) was... Ni / Li The value is 180.2.

[0060] S2. Solvent Cycle: The lithium-rich manganese leachate obtained in S1 was used as the starting solvent. Based on the mass loss during the reaction and centrifugation processes, freshly prepared BeCl-MA-H2O solvent was added to restore its mass to 20.0 g. A new batch of 0.5 g of NCM523 ternary lithium battery cathode material powder was added, and a second round of leaching was performed under the same conditions as in S1. The above replenishment-feeding-reaction-separation operation was repeated for a total of 8 leaching cycles. At the end of the 8th cycle, the Li leaching rate remained at 95.77%, and the Ni precipitation rate remained at 95.36%.

[0061] (2) Solid-phase product separation and purification

[0062] The nickel-cobalt-containing solid precipitates collected from the above eight cycles were combined and washed with freshly prepared BeCl-MA-H2O eutectic solvent to remove the mother liquor adhering to the surface. Deionized water was added, and the mixture was mechanically stirred at room temperature until the solid was fully dissolved. The pH of the solution was adjusted to 2.5 with dilute hydrochloric acid to obtain a nickel-cobalt mixed solution. An extractant was prepared using di(2,4,4-trimethylpentyl)dithiophosphonic acid (Cyanex 301) diluted with sulfonated kerosene, with a Cyanex 301 volume fraction of 20%. At room temperature, the extractant was mixed with the nickel-cobalt mixed solution at a volume ratio of O / A = 2:1, and extracted by shaking in a separatory funnel for 30 min. After standing and separation, the nickel-cobalt-loaded organic phase and the raffinate aqueous phase were separated. The single-stage extraction rates for nickel and cobalt were 99.9% and 99.5%, respectively, the manganese extraction rate was 3.8%, and lithium was almost unextracted.

[0063] The above-mentioned nickel-cobalt-loaded organic phase was mixed with 0.5 mol / L hydrochloric acid solution at a ratio of O / A = 2:1, and back-extracted for 30 min in a water bath with constant temperature shaker at room temperature. This process was repeated for a total of three back-extraction stages, and the aqueous phases from each stage were combined to obtain a cobalt chloride solution.

[0064] The remaining organic phase after cobalt back-extraction was mixed with 5.0 mol / L hydrochloric acid solution at a ratio of O / A = 0.5:1. The system was heated to 80℃ and shaken for 30 min. The above operation was repeated for two-stage back-extraction, and the aqueous phases of each stage were combined to obtain a nickel chloride solution.

[0065] Tests showed that the nickel-cobalt separation factor (β) Ni / Co The yield was 235.0, the cobalt recovery rate was 79.81%, and the nickel co-extraction rate was only 1.65%.

[0066] (3) Liquid phase product separation and purification

[0067] After the 8th cycle of S2 in step (1), 50 mL of the lithium-rich manganese leachate obtained was adjusted to pH 3.5 with sodium hydroxide solution. An extractant was prepared, consisting of di(2-ethylhexyl) phosphate (P204) diluted with sulfonated kerosene, with a P204 volume fraction of 10%. Sodium hydroxide solution was then added to the extractant for saponification, controlling the degree of saponification to 30%. At room temperature, the saponified P204 organic phase and the pH-adjusted lithium-rich manganese liquid phase were mixed at a volume ratio of O / A = 1:1 and extracted by shaking in a separatory funnel for 15 min. After standing and separating, a manganese-loaded organic phase and a lithium-rich raffinate aqueous phase were obtained, with a single-stage extraction rate of 97.6% for manganese.

[0068] The manganese-loaded organic phase was mixed with a 2.5 mol / L sulfuric acid solution and subjected to back-extraction in a water bath constant-temperature shaker to obtain a manganese sulfate solution with a manganese back-extraction rate of 99.6%. The lithium-rich raffinate phase was a lithium chloride-rich solution with a lithium recovery rate of 96.2%.

[0069] Example 2

[0070] (1) Leaching reaction: Prepare a eutectic solvent of betaine hydrochloride-malonic acid-water (BeCl-MA-H2O) as the leaching agent. Weigh 9.22g of betaine hydrochloride and 12.48g of malonic acid (molar ratio 1:2) into a reaction vessel, add 6.5mL of deionized water, and stir at 80℃ until the solid is completely dissolved to form a homogeneous and transparent solvent.

[0071] Weigh 20.0 g of the eutectic solvent prepared above and mix it with 0.66 g of waste NCM523 ternary lithium battery cathode material powder, stirring thoroughly. React for 30 min at a liquid-to-solid ratio of 30 g / g, a reaction temperature of 90℃, and a stirring speed of 300 rpm. After the reaction is complete, allow the system to cool naturally to room temperature and separate by high-speed centrifugation (8000 rpm, 3 min) to obtain a lithium-rich manganese leachate and a nickel-cobalt-containing solid precipitate.

[0072] The liquid and solid phase compositions were determined using flame atomic absorption spectrometry. The results showed that the leaching rate of Li was 97.60%, and that of Mn was 94.19%; the precipitation rate of Ni was 90.67%, and that of Co was 40.12%. Correspondingly, the residual Ni in the liquid phase was only 9.33%, and the residual Co was 59.88%. The separation factor of lithium for nickel (SF) was also determined. Ni / Li The value is 94.47.

[0073] (2) Solid-phase product separation and purification: The nickel-cobalt-containing solid precipitate obtained above was washed and dissolved in 50 mL of deionized water, and the pH was adjusted to 2. A 20% (v / v) Cyanex 301 (sulfonated kerosene diluted) organic phase was prepared. At room temperature, the organic phase was mixed with the nickel-cobalt mixed solution at a volume ratio of O / A = 2:1, and extracted by shaking in a separatory funnel for 30 min. The extraction rates of nickel and cobalt were 99.6% and 99.4%, respectively, the extraction rate of manganese was 3.2%, and lithium was almost not extracted.

[0074] Take the above-mentioned nickel-cobalt-loaded organic phase and mix it with 0.8 mol / L hydrochloric acid solution at a volume ratio of O / A = 1:1. Then, back-extract the mixture in a water bath at room temperature for 15 min. Repeat the above operation for a total of three stages of back-extraction, and combine the aqueous phases from each stage to obtain a cobalt chloride solution.

[0075] The remaining organic phase after cobalt back-extraction was mixed with 5.0 mol / L hydrochloric acid solution at a ratio of O / A = 0.5:1. The system was heated to 80℃ and shaken for 30 min. The above operation was repeated for two-stage back-extraction, and the aqueous phases of each stage were combined to obtain a nickel chloride solution.

[0076] Tests showed that the nickel-cobalt separation factor (β) Ni / Co The yield was 181.3, the cobalt recovery rate was 92.2%, and the nickel co-extraction rate was 6.12%.

[0077] (3) Liquid phase product separation and purification

[0078] Take 50 mL of the lithium-rich manganese leachate obtained in step (1) and adjust the pH to 3.5 with sodium hydroxide solution. Prepare an extractant, which is di(2-ethylhexyl) phosphate (P204) diluted with sulfonated kerosene, with a volume fraction of 10%. Then, add sodium hydroxide solution to the extractant for saponification treatment, controlling the degree of saponification to 30%. At room temperature, mix the saponified P204 organic phase with the pH-adjusted lithium-rich manganese liquid phase at a volume ratio of O / A = 1:1, and place in a separatory funnel for shaking extraction for 15 min. After standing and separating the layers, a manganese-loaded organic phase and a lithium-rich raffinate aqueous phase are obtained. The single-stage extraction rate of manganese is 98.9%.

[0079] The manganese-loaded organic phase was mixed with a 2.5 mol / L sulfuric acid solution and subjected to back-extraction in a water bath with constant temperature shaker to obtain a manganese sulfate solution. The manganese back-extraction rate reached 99.7%. The lithium-rich raffinate phase was a lithium chloride-rich solution, with a lithium recovery rate of 95.6%. Calculations showed that the Mn / Li separation factor (β) was [data missing]. Mn / Li (Up to 1035)

[0080] Example 3

[0081] This embodiment aims to verify the "homogeneous solvent washing" mechanism described in the claims, and to verify its technical effectiveness in removing lattice and surface impurities and enriching nickel and cobalt components.

[0082] (1) Raw material preparation: The nickel-cobalt solid precipitate accumulated and combined from 8 cycles in Example 1 was dried under vacuum at 60°C to constant weight. The initial metal composition was determined to be: Ni 58.39%, Co 24.44%, Mn 14.15%, Li 2.99%.

[0083] (2) Primary washing: Prepare a fresh BeCl-MA-H2O eutectic solvent according to the method described in Example 1. Weigh 1.6 g of the dried solid mixture and add 10 mL of fresh eutectic solvent (solid-liquid ratio 160 g / L). Heat the system to 80 °C and stir magnetically for 30 minutes to remove impurities using the solvent properties.

[0084] (3) Solid-liquid separation: After the reaction was completed, the system was cooled to room temperature and centrifuged at 8000 rpm for 2 minutes. The primary washing liquid and solid precipitate were separated.

[0085] (4) Secondary washing: Add 10 mL of fresh BeCl-MA-H2O eutectic solvent to the solid precipitate after primary washing, and repeat steps (2) and (3) to perform secondary washing and separation.

[0086] (5) Results and Analysis: The washed solid product was washed with water, dried, and its metal composition was analyzed. Experimental data showed that washing with a homologous solvent achieved a significant impurity removal effect: after two stages of washing, the relative content of the most difficult-to-remove entrained impurity, Li, decreased sharply from 2.99% to 0.03% (removal rate >99%); Mn decreased from 14.15% to 3.65%. Meanwhile, the relative content of nickel increased significantly from 58.39% to 77.91%. Furthermore, the cobalt-nickel separation factor (SF) of the first stage of washing... Ni / Co The value was 30.71, confirming that the DES system has preferential dissolution ability for impurity metal salts. This example demonstrates that a nickel-rich precursor with low impurity content can be prepared by simple washing with a homologous solvent before entering the subsequent extraction stage.

[0087] Example 4

[0088] (1) Leaching reaction: S1. First leaching: Prepare a eutectic solvent of betaine hydrochloride-malonic acid-water (BeCl-MA-H2O) (molar ratio 1:4). Weigh 50.0g of leaching agent and mix it with 1.25g of waste NCM523 ternary lithium battery cathode material powder (liquid-solid ratio 40g / g). React at 100℃ and 300rpm for 30min. Centrifuge to separate the initial lithium-rich manganese liquid phase and solid precipitate.

[0089] The liquid and solid phase compositions were determined using flame atomic absorption spectrometry. The results showed that the single-pass leaching rate of Li was 99.59%, and that of Mn was 98.87%; while the precipitation rate of Ni was as high as 95.21%, and that of Co was 71.84%. The residual Ni in the liquid phase was only 4.79%, and the residual Co was 28.16%. Calculations indicated that the separation factor of lithium for nickel (SF) was... Ni / Li The value is 178.89.

[0090] S2. Cyclic Leaching: The lithium-rich manganese liquid phase obtained in S1 is directly used as the leaching agent for the next round. Without adding any fresh solvent, a new batch of NCM523 ternary lithium battery cathode material powder is added according to the initially designed liquid-solid ratio, and the leaching reaction is carried out under the same conditions. The above operation is repeated for a total of 5 rounds of cyclic leaching.

[0091] Cycling performance: Experimental data shows that as the number of cycles increases, the solvent viscosity rises slightly but remains within an operable range. At the fifth cycle, the Li leaching rate remained at 90.83%, and the Ni precipitation rate remained at 88.93%.

[0092] (2) Solid-phase product separation and purification

[0093] The nickel-cobalt-containing solid precipitates collected from the above five cycles were combined, washed, and then added to deionized water. The mixture was mechanically stirred at room temperature until the solids were fully dissolved, and the pH of the solution was adjusted to 2.5 with dilute hydrochloric acid to obtain a nickel-cobalt mixed solution. An extractant was prepared using 20% ​​(v / v) di(2,4,4-trimethylpentyl)dithiophosphonic acid (Cyanex 301) diluted with sulfonated kerosene. At room temperature, the extractant was mixed with the nickel-cobalt mixed solution at a volume ratio of O / A = 2:1, and the mixture was shaken and extracted for 30 min in a separatory funnel. After standing and separation, the nickel-cobalt-loaded organic phase and the raffinate aqueous phase were separated. The single-stage extraction rates for nickel and cobalt were 99.9% and 99.5%, respectively, the manganese extraction rate was 3.8%, and lithium was almost unextracted.

[0094] Take the above-mentioned nickel-cobalt-loaded organic phase and mix it with 0.5 mol / L hydrochloric acid solution at a volume ratio of O / A = 1:1. Then, back-extract the mixture in a water bath at room temperature for 15 min. Repeat the above operation for a total of three stages of back-extraction, and combine the aqueous phases from each stage to obtain a cobalt chloride solution.

[0095] The remaining organic phase after cobalt back-extraction was mixed with 5.0 mol / L hydrochloric acid solution at a volume ratio of O / A = 0.5:1. The system was heated to 80℃ and shaken for 30 min. The above operation was repeated for two-stage back-extraction, and the aqueous phases of each stage were combined to obtain a nickel chloride solution.

[0096] Tests showed that the nickel-cobalt separation factor (β)Ni / Co The yield was 161.1, the cobalt recovery rate was 83.79%, and the nickel co-extraction rate was 3.15%.

[0097] (3) Liquid phase product separation and purification

[0098] Take 50 mL of the lithium-rich manganese leachate obtained in step (1) and adjust the pH to 3.5 with sodium hydroxide solution. Prepare an extractant, which is di(2-ethylhexyl) phosphate (P204) diluted with sulfonated kerosene, with a volume fraction of 10%. Then, add sodium hydroxide solution to the extractant for saponification treatment, controlling the degree of saponification to 30%. At room temperature, mix the saponified P204 organic phase with the pH-adjusted lithium-rich manganese liquid phase at a volume ratio of O / A = 1:1, and place in a separatory funnel for shaking extraction for 15 min. After standing and separating the layers, a manganese-loaded organic phase and a lithium-rich raffinate aqueous phase are obtained. The single-stage extraction rate of manganese is 97.2%.

[0099] The manganese-loaded organic phase was mixed with a 2.5 mol / L sulfuric acid solution and subjected to back-extraction in a water bath constant-temperature shaker to obtain a manganese sulfate solution with a manganese back-extraction rate of 99.6%. The lithium-rich raffinate phase was a lithium chloride-rich solution with a lithium recovery rate of 95.8%.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for recycling valuable metals from spent ternary lithium batteries based on a eutectic solvent, characterized in that, Includes the following steps: S1: Mix betaine hydrochloride, malonic acid and water, and heat and stir until the solid is completely dissolved to obtain a eutectic solvent; S2. Mix the waste ternary lithium battery cathode material powder with a eutectic solvent and carry out a leaching reaction under heating conditions. After the reaction is completed, perform solid-liquid separation to obtain a lithium-rich manganese liquid phase and a nickel-cobalt-containing solid precipitate. The lithium-rich manganese liquid phase can be directly or recycled for the leaching of the next batch of cathode material powder after supplementing the components until the lithium and manganese in the liquid phase reach the preset enrichment concentration to obtain a lithium-manganese enriched solution. The obtained nickel-cobalt-containing solid precipitate was collected to obtain the nickel-cobalt solid product; S3. Dissolve the nickel-cobalt solid product in water, adjust the pH value, and then extract and back-extract stepwise to obtain cobalt salt and nickel salt respectively. S4. Adjust the pH value of the lithium-manganese enrichment solution in step S2, and extract to obtain a manganese-rich organic phase and a lithium-rich aqueous phase. After back-extraction of the manganese-rich organic phase, manganese salt is obtained, and lithium salt is obtained by concentration or treatment with the addition of a precipitant to the lithium-rich aqueous phase.

2. The method according to claim 1, characterized in that, In step S1, the molar ratio of betaine hydrochloride to malonic acid is 1:2 to 1:7, and the ratio of the total mass of betaine hydrochloride and malonic acid to the mass of water is 10:1 to 2:

1.

3. The method according to claim 1, characterized in that, In step S2, the leaching reaction temperature is 60°C to 120°C, and the reaction time is 20 minutes to 120 minutes; the liquid-solid mass ratio of the eutectic solvent to the waste ternary lithium battery cathode material powder is 20:1 to 70:

1.

4. The method according to claim 1, characterized in that, In step S2, during the circulation process, the lithium-rich manganese liquid phase is replenished with fresh eutectic solvent components to restore its initial volume or mass based on the amount of solvent lost during the leaching reaction and separation process, and then used for the leaching of the next batch of cathode material powder.

5. The method according to claim 1, characterized in that, Before step S3, the process includes washing and removing impurities from the nickel-cobalt solid precipitate obtained in step S2: using a fresh eutectic solvent with the same composition as the eutectic solvent described in step S1, the nickel-cobalt solid precipitate is washed at 20°C to 80°C. After solid-liquid separation, a high-purity nickel-cobalt solid precipitate is obtained, which is then dissolved in step S3.

6. The method according to claim 1, characterized in that, In step S3, the pH of the aqueous phase is adjusted to 1.5 to 4.5 after the nickel-cobalt solid product is dissolved; the extractant used in step S3 is di(2,4,4-trimethylpentyl)dithiophosphonic acid; the volume ratio of the organic phase to the aqueous phase during the extraction process is 1:1 to 3:

1.

7. The method according to claim 1 or 6, characterized in that, In step S3, the stepwise back-extraction includes: firstly, using a hydrochloric acid solution with a concentration of 0.05 mol / L to 1.5 mol / L as a low-concentration acid to back-extract the organic phase obtained by extraction in S3, selectively stripping cobalt ions to the aqueous phase to obtain a cobalt salt solution; then, using a hydrochloric acid solution with a concentration of 2.0 mol / L to 8.0 mol / L as a high-concentration acid to back-extract the remaining organic phase to obtain a nickel salt solution.

8. The method according to claim 1, characterized in that, In step S4, the pH of the lithium manganese enrichment solution is adjusted to 2.0 to 5.0; the extractant used in the extraction process of step S4 is di(2-ethylhexyl)phosphoric acid; the extractant is selectively saponified before extraction, and the saponification rate is 20% to 50%.

9. The method according to claim 1, characterized in that, In step S4, obtaining manganese salt by back-extraction of the manganese-rich organic phase refers to back-extracting the manganese-rich organic phase with a sulfuric acid solution of 1.0 mol / L to 3.0 mol / L to obtain a manganese sulfate solution; obtaining lithium salt by processing the lithium-rich aqueous phase refers to concentrating the lithium-rich aqueous phase or adding a precipitant to prepare lithium carbonate or lithium phosphate products.

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