A selective extraction process for lithium nickel cobalt manganese salt of ternary lithium battery

Abstract

The present application relates to the technical field of waste lithium ion battery recycling, in particular to a selective extraction process of lithium nickel cobalt manganese salt of ternary lithium battery. The preparation method comprises the following steps: leaching treatment of positive electrode material metal; selective co-precipitation of leaching solution; separation of mixed solid precipitate. By adopting the solvent composed of L-carnitine and methanesulfonic acid as the leaching medium, efficient dissolution of lithium, nickel, cobalt and manganese is realized, and the risk of halogen-containing waste gas and equipment corrosion is eliminated. At the same time, oxalic acid is synchronously added in the system, and oxalate and dissolved cobalt and manganese ions form soluble complexes, reducing the secondary precipitation coating of insoluble high-valence state metals and ensuring the continuous progress of the leaching reaction; oxalic acid can also partially replace methanesulfonic acid to participate in the supply and reduction reaction, reducing the consumption of effective components in the eutectic solvent, prolonging the service life of the solvent, the whole leaching step process is simple, the metal leaching rate is high, and it has significant environmental protection and economic advantages.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery recycling technology, specifically to a selective extraction process for lithium nickel cobalt manganese salts from ternary lithium batteries. Background Technology

[0002] With the rapid development of the electric vehicle and energy storage industries, ternary lithium batteries, represented by nickel-cobalt-manganese (NCM) lithium oxide, are about to enter a large-scale retirement phase. Retired ternary cathode materials are rich in strategic metals such as lithium, nickel, cobalt, and manganese, with grades far exceeding those of natural ores, possessing extremely high resource recovery value. However, improper handling can lead to serious pollution of soil and groundwater by the heavy metal ions and organic electrolytes within them, threatening ecological security and human health.

[0003] Currently, the recycling of cathode materials for ternary lithium batteries mainly employs pyrometallurgical or hydrometallurgical methods. Pyrometallurgical methods are extremely energy-intensive, and lithium is difficult to recover effectively. While traditional hydrometallurgy can achieve simultaneous leaching of multiple metals, its leaching stage typically requires large amounts of strong inorganic acids (such as sulfuric acid and hydrochloric acid) and external reducing agents (such as hydrogen peroxide and sodium sulfite). This not only results in high reagent costs but also generates large amounts of high-salinity wastewater and toxic gases. In the subsequent metal separation stage, industry mainly relies on solvent extraction, using acidic extractants such as P204 and P507 to extract manganese, cobalt, and nickel stepwise. However, this process requires the use of large amounts of volatile organic solvents and strong alkalis for saponification, generating large amounts of difficult-to-treat organic wastewater and ammonia nitrogen pollution, increasing the environmental burden and operational risks. Furthermore, directly using stepwise chemical precipitation methods often leads to co-precipitation due to the similar solubility products of the various metal hydroxides or sulfides, making it difficult to achieve battery-grade purity. Summary of the Invention

[0004] The purpose of this invention is to provide a selective extraction process for lithium nickel cobalt manganese salts used in ternary lithium batteries. This process fundamentally solves the problems of high reagent consumption, severe environmental pollution, and poor separation selectivity in existing technologies.

[0005] A selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries includes the following steps: S1: Leaching treatment of cathode material metal L-carnitine and methanesulfonic acid were mixed and heated to obtain an L-carnitine / methanesulfonic acid solvent. The cathode powder obtained from the treatment of waste ternary lithium batteries was ball-milled and sieved. The obtained ternary cathode active material powder was added to the L-carnitine / methanesulfonic acid solvent, and then oxalic acid was added to leach the solution by heating and stirring. The solution was then filtered and the filter cake was washed with deionized water. The filtrates were combined to obtain a lithium, nickel, cobalt and manganese leachate. S2: Selective coprecipitation of leachate The lithium, nickel, cobalt, and manganese leaching solution was cooled and stirred, while ammonium sulfate and oxalic acid were added. After stirring, the solution was allowed to stand and age. The mixture was then filtered to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, as well as a filtrate containing cobalt and manganese. The pH of the filtrate containing cobalt and manganese was adjusted to 3.8–4.2, and an aqueous oxalic acid solution was added. After stirring and filtering, a mixed solid precipitate of cobalt oxalate and manganese oxalate dihydrate was obtained. The residual filtrate was subjected to vacuum distillation to recover methanesulfonic acid and L-carnitine. S3: Separation of mixed solid precipitates Furthermore, the leaching treatment of the cathode material metal in step S1 specifically includes the following steps: S1.1: Add L-carnitine and methanesulfonic acid to the reactor at a molar ratio of 1:(2~3), heat to 70~80℃ under nitrogen protection, and stir at a constant temperature of 250~350rpm for 60~90 minutes until the mixture becomes a homogeneous and stable viscous liquid, which is the L-carnitine / methanesulfonic acid solvent. S1.2: The positive electrode powder obtained after discharging, dismantling and separating aluminum foil from waste ternary lithium batteries is placed in a ball mill and ground at a speed of 200-300 rpm for 15-20 minutes. It is then passed through a 200-mesh sieve to obtain ternary positive electrode active material powder. S1.3: Add the ternary cathode active material powder to L-carnitine / methanesulfonic acid solvent, control the solid-liquid ratio to 15-25 g / L, then add oxalic acid, heat to 75-85℃, and leach at a stirring speed of 300-400 rpm for 2-3 hours. After leaching, filter, rinse the filter cake with deionized water, and combine the filtrates to obtain lithium, nickel, cobalt and manganese leachate.

[0006] Furthermore, the selective co-precipitation of the leachate in step S2 specifically includes the following steps: S2.1: Cool the lithium, nickel, cobalt and manganese leaching solution to 25-30℃, add ammonium sulfate while stirring at 300-400 rpm, stir and dissolve for 10 minutes, then add oxalic acid, the total amount of oxalic acid added is 10-16 g / L, continue stirring for 45-60 minutes after the addition is complete, then let stand and age for 1-1.5 hours, filter to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, and a filtrate containing cobalt and manganese; S2.2: Under stirring conditions of 25-35℃ and 200-300rpm, ammonia water is added dropwise to the cobalt and manganese-containing filtrate obtained in step S2.1 to adjust the pH to 3.8-4.2. The ammonia complex of cobalt and manganese partially disintegrates and returns to its free state. Then, an equal volume of oxalic acid aqueous solution with a concentration of 0.15-0.2mol / L is slowly added. After the addition is complete, stirring is continued for 25-35 minutes. The mixture is filtered to obtain a mixed solid precipitate of cobalt oxalate and manganese oxalate dihydrate. The residual filtrate is distilled under reduced pressure to recover methanesulfonic acid and L-carnitine.

[0007] Furthermore, the separation of the mixed solid precipitate in step S3 specifically includes the following steps: S3.1: The mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate obtained in step S2.1 is added to deionized water at a solid-liquid ratio of 1:(8-12) g / mL. The mixture is stirred to obtain a mixed slurry. Under the stirring conditions of 25-35℃ and 200-300rpm, an ammonia solution with a concentration of 2-3mol / L is slowly added dropwise to the mixed slurry to adjust the pH of the system to 9-9.5. The mixture is stirred for 30-45 minutes and then filtered to separate the lithium oxalate solid and the filtrate containing nickel ammonia complex. S3.2: The cobalt oxalate and manganese oxalate dihydrate mixed solid precipitate obtained in step S2.2 is added to deionized water at a solid-liquid ratio of 1:(10-15) g / mL. A uniform suspension slurry is prepared by stirring at 30-40℃ and 250-350 rpm. A hydrochloric acid solution with a concentration of 0.5-1 mol / L is slowly added to the slurry to adjust the pH of the system to 2-2.5. Stirring is continued for 20-30 minutes to completely dissolve the precipitate, resulting in a chloride solution containing cobalt and manganese. S3.3: Under the conditions of stirring at 40-50℃ and 150-200rpm, slowly add sodium hydroxide solution with a concentration of 2-3mol / L to the above chloride solution to adjust the pH to 4.5-5, and at the same time slowly add an appropriate amount of hydrogen peroxide with a concentration of 3%. After the reaction continues for 40-60 minutes, filter to obtain manganese dioxide hydrate precipitate and cobalt-containing filtrate.

[0008] Furthermore, in step S1.3, the amount of oxalic acid added is 6 to 10 g / L relative to the L-carnitine / methanesulfonic acid solvent.

[0009] Furthermore, in step S2.1, the amount of ammonium sulfate added is 0.8–1.2 mol / L relative to the volume of the leachate.

[0010] Furthermore, in step S3.3, the amount of 3% hydrogen peroxide added is 2-4 mL / L relative to the chloride solution.

[0011] The beneficial effects are as follows: 1. This invention uses a solvent composed of L-carnitine and methanesulfonic acid as the leaching medium. Compared with traditional inorganic strong acid or haloquaternary ammonium salt systems, this solvent has both strong acidity and excellent coordination ability, enabling efficient dissolution of lithium, nickel, cobalt, and manganese under mild conditions of 75-85℃. Furthermore, L-carnitine, as a natural metabolite, is biodegradable, and methanesulfonic acid is halogen-free, eliminating the risk of halogen-containing waste gas and equipment corrosion at the source. Simultaneously, the oxalic acid added to the system serves two purposes: firstly, the oxalate ions form soluble complexes with the dissolved cobalt and manganese ions, reducing secondary precipitation and coating of sparingly soluble high-valence metals, ensuring the continuous progress of the leaching reaction; secondly, the oxalic acid molecules themselves can partially replace methanesulfonic acid in proton donation and reduction reactions, reducing the consumption of effective components in the eutectic solvent and extending the solvent cycle life. The entire leaching process does not require the addition of reducing agents such as hydrogen peroxide, resulting in a simple process, high metal leaching rate, and significant environmental and economic advantages.

[0012] 2. This invention introduces ammonium sulfate as a salting-out-complexing synergistic regulator. The strong salting-out effect of ammonium sulfate reduces the solubility of lithium oxalate and nickel oxalate to extremely low levels, thereby increasing the co-precipitation rate of the two target metals. Simultaneously, ammonium ions selectively complex with cobalt and manganese ions, and combined with the coordination shielding effect of residual methanesulfonate and oxalate ions in the solution, cobalt and manganese are firmly locked in the liquid phase in the form of soluble complex anions, significantly reducing the co-precipitation loss rate. Then, a trace amount of ammonia is used to adjust the pH to 3.8-4.2, precisely destroying the coordination layer of the cobalt and manganese complex and restoring them to their free state, achieving efficient precipitation of cobalt and manganese. The reaction conditions are controllable, the endpoint is clear, and the two steps work synergistically. Not only can the separation of lithium-nickel groups and cobalt-manganese groups be completed under room temperature to low temperature conditions, but the obtained intermediate products also have high purity and few impurities, laying a solid foundation for subsequent refining and separation, and the recovery rate of the separated products is high. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0014] A selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries specifically includes the following steps: S1: Leaching treatment of cathode material metal S1.1: Add L-carnitine and methanesulfonic acid to the reactor at a molar ratio of 1:2, heat to 70°C under nitrogen protection, and stir at a constant temperature of 250 rpm for 60 minutes until the mixture becomes a homogeneous and stable viscous liquid, which is the L-carnitine / methanesulfonic acid solvent. S1.2: The positive electrode powder obtained after discharging, dismantling and separating aluminum foil from waste ternary lithium batteries is placed in a ball mill and ground at 200 rpm for 15 minutes. It is then passed through a 200-mesh sieve to obtain ternary positive electrode active material powder. S1.3: Add the ternary cathode active material powder to L-carnitine / methanesulfonic acid solvent, control the solid-liquid ratio to 15 g / L, then add oxalic acid, the amount of oxalic acid added is 6 g / L relative to L-carnitine / methanesulfonic acid solvent, heat to 75℃, and leach at a stirring speed of 300 rpm for 2 hours. After leaching, filter, rinse the filter cake with deionized water, and combine the filtrates to obtain lithium, nickel, cobalt and manganese leachate.

[0015] S2: Selective coprecipitation of leachate S2.1: Cool the lithium, nickel, cobalt and manganese leaching solution to 25°C, add ammonium sulfate while stirring at 300 rpm, the amount of ammonium sulfate added is 0.8 mol / L relative to the volume of the leaching solution, stir and dissolve for 10 minutes, then add oxalic acid, the total amount of oxalic acid added is 10 g / L, continue stirring for 45 minutes after the addition is complete, then let stand and age for 1 hour, filter to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, and a filtrate containing cobalt and manganese; S2.2: Under the conditions of stirring at 25℃ and 200rpm, ammonia water was first added dropwise to the cobalt and manganese-containing filtrate obtained in step S2.1 to adjust the pH to 3.8. The ammonia complex of cobalt and manganese partially disintegrated and returned to the free state. Then, an equal volume of 0.15mol / L oxalic acid aqueous solution was slowly added. After the addition was completed, stirring was continued for 25 minutes. The mixture of cobalt oxalate and manganese oxalate dihydrate was filtered to obtain a mixed solid precipitate. The residual filtrate was distilled under reduced pressure to recover methanesulfonic acid and L-carnitine.

[0016] S3: Separation of mixed solid precipitates S3.1: The mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate obtained in step S2.1 is added to deionized water at a solid-liquid ratio of 1:8 g / mL. The mixture is stirred to obtain a mixed slurry. Under the stirring conditions of 25℃ and 200 rpm, an ammonia solution with a concentration of 2 mol / L is slowly added dropwise to the mixed slurry to adjust the pH of the system to 9. The mixture is stirred for 30 minutes and then filtered to separate the lithium oxalate solid and the filtrate containing nickel ammonia complex. S3.2: The cobalt oxalate and manganese oxalate dihydrate mixed solid precipitate obtained in step S2.2 is added to deionized water at a solid-liquid ratio of 1:10 g / mL. A uniform suspension slurry is prepared by stirring at 30℃ and 250 rpm. A 0.5 mol / L hydrochloric acid solution is slowly added to the slurry to adjust the pH of the system to 2. Stirring is continued for 20 minutes to completely dissolve the precipitate, resulting in a chloride solution containing cobalt and manganese. S3.3: Under the conditions of 40℃ and 150rpm stirring, a sodium hydroxide solution with a concentration of 2mol / L was slowly added dropwise to the above chloride solution to adjust the pH to 4.5. At the same time, an appropriate amount of hydrogen peroxide with a concentration of 3% was slowly added dropwise, with the amount added being 2mL / L relative to the chloride solution. After the reaction continued for 40 minutes, the mixture was filtered to obtain manganese dioxide hydrate precipitate and cobalt-containing filtrate. Example

[0017] A selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries specifically includes the following steps: S1: Leaching treatment of cathode material metal S1.1: Add L-carnitine and methanesulfonic acid to the reactor at a molar ratio of 1:2.5, heat to 75°C under nitrogen protection, and stir at a constant temperature of 350 rpm for 60 minutes until the mixture becomes a homogeneous and stable viscous liquid, which is the L-carnitine / methanesulfonic acid solvent. S1.2: The positive electrode powder obtained after discharging, dismantling and separating aluminum foil from waste ternary lithium batteries is placed in a ball mill and ground at 200 rpm for 20 minutes. It is then passed through a 200-mesh sieve to obtain ternary positive electrode active material powder. S1.3: Add the ternary cathode active material powder to L-carnitine / methanesulfonic acid solvent, control the solid-liquid ratio to 20 g / L, then add oxalic acid, the amount of oxalic acid added is 8 g / L relative to L-carnitine / methanesulfonic acid solvent, heat to 80℃, and leach at a stirring speed of 400 rpm for 2 hours. After leaching, filter, rinse the filter cake with deionized water, combine the filtrates to obtain lithium, nickel, cobalt and manganese leachate.

[0018] S2: Selective coprecipitation of leachate S2.1: Cool the lithium, nickel, cobalt and manganese leaching solution to 30°C, add ammonium sulfate while stirring at 300 rpm, the amount of ammonium sulfate added is 1 mol / L relative to the volume of the leaching solution, stir to dissolve for 10 minutes and then add oxalic acid, the total amount of oxalic acid added is 13 g / L, continue stirring for 60 minutes after the addition is complete, then let stand and age for 1 hour, filter to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, and a filtrate containing cobalt and manganese; S2.2: Under the conditions of stirring at 25℃ and 300rpm, ammonia water was first added dropwise to the cobalt and manganese-containing filtrate obtained in step S2.1 to adjust the pH to 3.8. The ammonia complex of cobalt and manganese partially disintegrated and returned to the free state. Then, an equal volume of 0.18mol / L oxalic acid aqueous solution was slowly added. After the addition was completed, stirring was continued for 35 minutes. The mixture of cobalt oxalate and manganese oxalate dihydrate was filtered to obtain a mixed solid precipitate. The residual filtrate was distilled under reduced pressure to recover methanesulfonic acid and L-carnitine.

[0019] S3: Separation of mixed solid precipitates S3.1: The mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate obtained in step S2.1 is added to deionized water at a solid-liquid ratio of 1:10 g / mL. The mixture is stirred to obtain a mixed slurry. Under stirring conditions of 30℃ and 250 rpm, an ammonia solution with a concentration of 2.5 mol / L is slowly added dropwise to the mixed slurry to adjust the pH of the system to 9. The mixture is stirred for 45 minutes and then filtered to separate the lithium oxalate solid and the filtrate containing nickel ammonia complex. S3.2: The cobalt oxalate and manganese oxalate dihydrate mixed solid precipitate obtained in step S2.2 is added to deionized water at a solid-liquid ratio of 1:12 g / mL. A uniform suspension slurry is prepared by stirring at 35℃ and 300 rpm. A 0.8 mol / L hydrochloric acid solution is slowly added to the slurry to adjust the pH of the system to 2.5. Stirring is continued for 20 minutes to completely dissolve the precipitate, resulting in a chloride solution containing cobalt and manganese. S3.3: Under the conditions of 50℃ and 150rpm stirring, a sodium hydroxide solution with a concentration of 2.5mol / L was slowly added dropwise to the above chloride solution to adjust the pH to 5. At the same time, an appropriate amount of hydrogen peroxide with a concentration of 3% was slowly added dropwise, with the amount added being 3mL / L relative to the chloride solution. After the reaction continued for 50 minutes, the mixture was filtered to obtain manganese dioxide hydrate precipitate and cobalt-containing filtrate. Example

[0020] A selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries specifically includes the following steps: S1: Leaching treatment of cathode material metal S1.1: Add L-carnitine and methanesulfonic acid to the reactor in a molar ratio of 1:3, heat to 80°C under nitrogen protection, and stir at a constant temperature of 350 rpm for 90 minutes until the mixture becomes a homogeneous and stable viscous liquid, which is the L-carnitine / methanesulfonic acid solvent. S1.2: The positive electrode powder obtained after discharging, dismantling and separating aluminum foil from the waste ternary lithium battery is placed in a ball mill and ground at 300 rpm for 20 minutes. It is then passed through a 200-mesh sieve to obtain ternary positive electrode active material powder. S1.3: Add the ternary cathode active material powder to L-carnitine / methanesulfonic acid solvent, control the solid-liquid ratio to 25 g / L, then add oxalic acid, the amount of oxalic acid added is 10 g / L relative to L-carnitine / methanesulfonic acid solvent, heat to 85℃, and leach at a stirring speed of 400 rpm for 3 hours. After leaching, filter, rinse the filter cake with deionized water, combine the filtrates to obtain lithium, nickel, cobalt and manganese leachate.

[0021] S2: Selective coprecipitation of leachate S2.1: Cool the lithium, nickel, cobalt and manganese leaching solution to 30°C, add ammonium sulfate while stirring at 400 rpm, the amount of ammonium sulfate added is 1.2 mol / L relative to the volume of the leaching solution, stir to dissolve for 10 minutes, then add oxalic acid, the total amount of oxalic acid added is 16 g / L, continue stirring for 60 minutes after the addition is complete, then let stand and age for 1.5 hours, filter to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, and a filtrate containing cobalt and manganese; S2.2: Under stirring conditions of 35℃ and 300rpm, ammonia water was first added dropwise to the cobalt and manganese-containing filtrate obtained in step S2.1 to adjust the pH to 4.2. The ammonia complex of cobalt and manganese partially disintegrated and returned to the free state. Then, an equal volume of 0.2mol / L oxalic acid aqueous solution was slowly added. After the addition was completed, stirring was continued for 35 minutes. The mixture of cobalt oxalate and manganese oxalate dihydrate was filtered to obtain a solid precipitate. The residual filtrate was distilled under reduced pressure to recover methanesulfonic acid and L-carnitine.

[0022] S3: Separation of mixed solid precipitates S3.1: The mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate obtained in step S2.1 is added to deionized water at a solid-liquid ratio of 1:12 g / mL. The mixture is stirred to obtain a mixed slurry. Under stirring conditions of 35℃ and 300 rpm, an ammonia solution with a concentration of 3 mol / L is slowly added dropwise to the mixed slurry to adjust the pH of the system to 9.5. The mixture is stirred for 45 minutes and then filtered to separate the lithium oxalate solid and the filtrate containing nickel ammonia complex. S3.2: The cobalt oxalate and manganese oxalate dihydrate mixed solid precipitate obtained in step S2.2 is added to deionized water at a solid-liquid ratio of 1:15 g / mL. The mixture is stirred at 40℃ and 350 rpm to form a uniform suspension slurry. A 1 mol / L hydrochloric acid solution is slowly added to the slurry to adjust the pH of the system to 2.5. The mixture is stirred for 30 minutes to completely dissolve the precipitate, resulting in a chloride solution containing cobalt and manganese. S3.3: Under stirring conditions of 50℃ and 200rpm, a sodium hydroxide solution with a concentration of 3mol / L was slowly added dropwise to the above chloride solution to adjust the pH to 5. At the same time, an appropriate amount of hydrogen peroxide with a concentration of 3% was slowly added dropwise, with the amount added being 4mL / L relative to the chloride solution. After the reaction continued for 60 minutes, the mixture was filtered to obtain manganese dioxide hydrate precipitate and cobalt-containing filtrate.

[0023] Comparative Example 1: The difference from Example 1 is that step S1.1 is removed in this comparative example, and the L-carnitine / methanesulfonic acid solvent in step S1.3 is replaced with betaine hydrochloride / pyruvate solvent in a molar ratio of 1:8. The remaining steps are the same as in Example 1.

[0024] Comparative Example 2: The difference from Example 1 is that ammonium sulfate was not added in step S2.1 in this comparative example, and the remaining steps are the same as in Example 1.

[0025] Take 20g of the ternary cathode active material powder prepared in step S1.2 from the same batch, digest it with aqua regia with HNO3:HCl = 1:3 (volume ratio), and then determine its lithium, cobalt, nickel and manganese metal content using inductively coupled plasma atomic emission spectrometry (ICPOES), and record it as M lithium, M cobalt, M nickel and M manganese.

[0026] 20g of the above-mentioned ternary cathode active material powder was taken and metal extraction was performed using the extraction processes of Examples 1-3 and Comparative Examples 1-2. The content of each metal element in the final product lithium oxalate solid, the filtrate containing nickel-ammonia complex, the manganese dioxide hydrate precipitate, and the cobalt-containing filtrate was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and denoted as mlithium, mcobalt, mnickel, and mmanganese. Three extraction tests were conducted for each metal element. The average recovery rate of each metal element was calculated, and the data are shown in Table 1.

[0027] Table 1: Average Recovery Rate of Each Metal Element Example 1 97.4 96.2 97.6 96.8 Example 2 97.1 96.8 97.1 96.5 Example 3 97.8 96.5 96.9 97.4 Comparative Example 1 91.1 90.6 88.1 89.8 Comparative Example 2 86.4 82.4 88.7 83.1 As shown in Table 1, the recovery rates of the four metals in Examples 1-3 were all stable above 96%. However, in Comparative Example 1, because the leaching solvent was replaced with betaine hydrochloride / pyruvic acid, the coordination breaking ability of this system for high-valence nickel, cobalt, and manganese oxides was significantly insufficient, resulting in a sharp decline in the leaching rate of each metal. The final recovery rate was only maintained at 88% to 91%, which was far lower than that of the Example Group of this invention. This proves that the L-carnitine and methanesulfonic acid solvent prepared in this application, combined with oxalic acid, can achieve efficient dissolution of lithium, nickel, cobalt, and manganese, laying a solid foundation for the overall recovery rate. While Comparative Example 2 maintained the highly efficient leaching solvent of the previous example, the absence of ammonium sulfate in the precipitation stage resulted in the simultaneous disappearance of the salting-out effect and the complexation shielding effect. As a result, the precipitation of lithium oxalate and nickel oxalate was incomplete, and a large amount of cobalt and manganese co-precipitated in the first step. This not only reduced the recovery rate of the product but also lowered the purity of the precipitated product. This demonstrates that the introduction of ammonium sulfate as a salting-out-complexation synergistic regulator can complete the separation of the lithium-nickel group and the cobalt-manganese group under room temperature to low temperature conditions, laying a solid foundation for subsequent refining and separation and significantly improving the recovery rate of the separated product.

[0028] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries, characterized in that, Includes the following steps: S1: Leaching treatment of cathode material metal L-carnitine and methanesulfonic acid were mixed and heated to obtain an L-carnitine / methanesulfonic acid solvent. The cathode powder obtained from the treatment of waste ternary lithium batteries was ball-milled and sieved. The obtained ternary cathode active material powder was added to the L-carnitine / methanesulfonic acid solvent, and then oxalic acid was added to leach the solution by heating and stirring. The solution was then filtered and the filter cake was washed with deionized water. The filtrates were combined to obtain a lithium, nickel, cobalt and manganese leachate. S2: Selective coprecipitation of leachate The lithium, nickel, cobalt, and manganese leaching solution was cooled and stirred, while ammonium sulfate and oxalic acid were added. After stirring, the solution was allowed to stand and age. The mixture was then filtered to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, as well as a filtrate containing cobalt and manganese. The pH of the filtrate containing cobalt and manganese was adjusted to 3.8–4.2, and an aqueous oxalic acid solution was added. After stirring and filtering, a mixed solid precipitate of cobalt oxalate and manganese oxalate dihydrate was obtained. The residual filtrate was subjected to vacuum distillation to recover methanesulfonic acid and L-carnitine. S3: Separation of mixed solid precipitates.

2. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 1, characterized in that, Step S1, the leaching treatment of the positive electrode material metal, specifically includes the following steps: S1.1: Add L-carnitine and methanesulfonic acid to the reactor at a molar ratio of 1:(2~3), heat to 70~80℃ under nitrogen protection, and stir at a constant temperature of 250~350rpm for 60~90 minutes until the mixture becomes a homogeneous and stable viscous liquid, which is the L-carnitine / methanesulfonic acid solvent. S1.2: The positive electrode powder obtained after discharging, dismantling and separating aluminum foil from waste ternary lithium batteries is placed in a ball mill and ground at a speed of 200-300 rpm for 15-20 minutes. It is then passed through a 200-mesh sieve to obtain ternary positive electrode active material powder. S1.3: Add the ternary cathode active material powder to L-carnitine / methanesulfonic acid solvent, control the solid-liquid ratio to 15-25 g / L, then add oxalic acid, heat to 75-85℃, and leach at a stirring speed of 300-400 rpm for 2-3 hours. After leaching, filter, rinse the filter cake with deionized water, and combine the filtrates to obtain lithium, nickel, cobalt and manganese leachate.

3. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 1, characterized in that, The selective coprecipitation of the leachate in step S2 specifically includes the following steps: S2.1: Cool the lithium, nickel, cobalt and manganese leaching solution to 25-30℃, add ammonium sulfate while stirring at 300-400 rpm, stir and dissolve for 10 minutes, then add oxalic acid, the total amount of oxalic acid added is 10-16 g / L, continue stirring for 45-60 minutes after the addition is complete, then let stand and age for 1-1.5 hours, filter to obtain a mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate, and a filtrate containing cobalt and manganese; S2.2: Under stirring conditions of 25-35℃ and 200-300rpm, ammonia water is added dropwise to the cobalt and manganese-containing filtrate obtained in step S2.1 to adjust the pH to 3.8-4.

2. The ammonia complex of cobalt and manganese partially disintegrates and returns to its free state. Then, an equal volume of oxalic acid aqueous solution with a concentration of 0.15-0.2mol / L is slowly added. After the addition is complete, stirring is continued for 25-35 minutes. The mixture is filtered to obtain a mixed solid precipitate of cobalt oxalate and manganese oxalate dihydrate. The residual filtrate is distilled under reduced pressure to recover methanesulfonic acid and L-carnitine.

4. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 1, characterized in that, Step S3, the separation of the mixed solid precipitate, specifically includes the following steps: S3.1: The mixed solid precipitate of lithium oxalate and nickel oxalate dihydrate obtained in step S2.1 is added to deionized water at a solid-liquid ratio of 1:(8-12) g / mL. The mixture is stirred to obtain a mixed slurry. Under the stirring conditions of 25-35℃ and 200-300 rpm, an ammonia solution with a concentration of 2-3 mol / L is slowly added dropwise to the mixed slurry to adjust the pH of the system to 9-9.

5. The mixture is stirred for 30-45 minutes and then filtered to separate the lithium oxalate solid and the filtrate containing nickel ammonia complex. S3.2: The cobalt oxalate and manganese oxalate dihydrate mixed solid precipitate obtained in step S2.2 is added to deionized water at a solid-liquid ratio of 1:(10-15) g / mL. A uniform suspension slurry is prepared by stirring at 30-40℃ and 250-350 rpm. A hydrochloric acid solution with a concentration of 0.5-1 mol / L is slowly added to the slurry to adjust the pH of the system to 2-2.

5. Stirring is continued for 20-30 minutes to completely dissolve the precipitate, resulting in a chloride solution containing cobalt and manganese. S3.3: Under the conditions of stirring at 40-50℃ and 150-200rpm, slowly add sodium hydroxide solution with a concentration of 2-3mol / L to the above chloride solution to adjust the pH to 4.5-5, and at the same time slowly add an appropriate amount of hydrogen peroxide with a concentration of 3%. After the reaction continues for 40-60 minutes, filter to obtain manganese dioxide hydrate precipitate and cobalt-containing filtrate.

5. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 2, characterized in that, In step S1.3, the amount of oxalic acid added is 6 to 10 g / L relative to the L-carnitine / methanesulfonic acid solvent.

6. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 3, characterized in that, In step S2.1, the amount of ammonium sulfate added is 0.8–1.2 mol / L relative to the volume of the leachate.

7. The selective extraction process for lithium nickel cobalt manganese salts in ternary lithium batteries according to claim 4, characterized in that, In step S3.3, the amount of 3% hydrogen peroxide added is 2-4 mL / L relative to the chloride solution.