Cobalt and nickel separation method

Abstract

The invention relates to a cobalt and nickel separation method. This method comprises: a heat treatment step (S1) in which a lithium ion secondary battery is heated and heat-treated; a pulverization and sorting step (S2) for obtaining an electrode material containing at least cobalt, nickel, copper and lithium by pulverizing and classifying the heat-treated lithium ion secondary battery; a leaching step (S3) for obtaining a leachate by immersing the electrode material in a treatment liquid containing sulfuric acid and hydrogen peroxide; a copper separation step (S4) in which a hydrogen sulfide compound is added to the leachate and stirred, and then solid-liquid separation is performed to obtain an eluent containing cobalt and nickel and a residue containing copper sulfide; and a cobalt-nickel separation step (S5) in which an alkali metal hydroxide is added to the eluent to adjust the pH, then a hydrogen sulfide compound is added, and stirring and solid-liquid separation are performed to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual liquid containing lithium.

Description

[0001] This application is a divisional application of the invention patent application with the application date of August 31, 2021, application number 202180053662.3, and invention name “Method for separating cobalt and nickel”. Technical Field

[0002] The present invention relates to a method for separating cobalt and nickel, which can accurately separate and recover cobalt and nickel contained in lithium-ion secondary batteries from other metals.

[0003] This application claims priority based on Japanese Patent Application No. 2020-148388 filed in Japan on September 3, 2020, and Japanese Patent Application No. 2021-138132 filed in Japan on August 26, 2021, the contents of which are incorporated herein by reference. Background Art

[0004] Lithium-ion secondary batteries are used as power sources for a wide range of applications, from small devices like various electronic devices to large devices like electric vehicles. When these lithium-ion secondary batteries are discarded, the useful metals contained in them need to be recovered and reused.

[0005] Lithium-ion secondary batteries are formed by dividing the negative electrode material and the positive electrode material with a porous polypropylene separator and stacking them into layers, and then sealing them in a casing made of aluminum or stainless steel together with an electrolyte such as lithium hexafluorophosphate (LiPF6) and an electrolyte solution.

[0006] The negative electrode material of a lithium-ion secondary battery is formed by coating a negative electrode active material such as graphite mixed with a binder onto a negative electrode current collector made of, for example, copper foil. Conversely, the positive electrode material is formed by coating a positive electrode active material such as lithium manganate, lithium cobaltate, or lithium nickelate mixed with a binder onto a positive electrode current collector made of, for example, aluminum foil.

[0007] The positive electrode active material of lithium-ion secondary batteries contains large amounts of cobalt and nickel. However, the positive electrode active material that is crushed and separated in advance during the recycling process contains, in addition to cobalt and nickel, manganese, copper, aluminum, lithium, etc. Therefore, in order to separate and recover cobalt and nickel from lithium-ion secondary batteries with high yield, it is necessary to accurately remove metals other than these.

[0008] Conventionally, as a method for separating and recovering cobalt and nickel contained in lithium-ion secondary batteries, for example, Patent Documents 1 and 2 disclose methods for recovering valuable metals from used lithium-ion secondary batteries, wherein a positive electrode material active substance is removed from the lithium-ion secondary battery, a leachate containing metals is obtained from the positive electrode active substance by acid leaching, and cobalt and nickel are separated from the leachate by solvent extraction.

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-113672 (A)

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-186118 (A)

[0011] The recovery methods disclosed in Patent Documents 1 and 2 remove impurity elements by adding an oxidizing agent or adjusting the pH to form a precipitate containing hydroxides, followed by solid-liquid separation. However, since cobalt, nickel, and other metals (copper, aluminum, manganese, iron, etc.) are removed simultaneously in this process, the cobalt, nickel, and other metals must be separated in multiple subsequent steps. This results in a complex, labor-intensive, and time-consuming separation process, leading to increased cobalt and nickel recovery costs. Summary of the Invention

[0012] The present invention has been completed in view of the above situation, and its purpose is to provide a method for separating cobalt and nickel, which can separate the cobalt, nickel and other metals contained in lithium-ion secondary batteries with high precision in fewer steps, and can recover cobalt and nickel from lithium-ion secondary batteries at low cost.

[0013] To solve the above-mentioned problems, a method for separating cobalt and nickel according to one embodiment of the present invention (hereinafter referred to as the "method for separating cobalt and nickel according to the present invention") separates cobalt and nickel from a lithium-ion secondary battery. The method for separating cobalt and nickel is characterized in that it includes: a crushing and sorting step of crushing and classifying the lithium-ion secondary battery to obtain an electrode material containing at least cobalt, nickel, copper and lithium; a leaching step of immersing the electrode material in a treatment solution containing sulfuric acid and hydrogen peroxide to obtain a leachate; a copper separation step of adding a hydrogen sulfide compound to the leachate, stirring the mixture, and then performing solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide; and a cobalt-nickel separation step of adding an alkali metal hydroxide to the eluate to adjust the pH, then adding a hydrogen sulfide compound, stirring the mixture, and performing solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual solution containing lithium.

[0014] According to the present invention, the method for separating cobalt and nickel utilizes a treatment solution containing sulfuric acid and hydrogen peroxide to elute metal components from an electrode material. A water-soluble hydrogen sulfide compound is then added to the resulting leachate and stirred, thereby selectively precipitating and separating only copper, among the metal components contained in the leachate, as an insoluble sulfide. Furthermore, after pH adjustment, the water-soluble hydrogen sulfide compound is added and stirred, thereby selectively precipitating only cobalt and nickel, among the metal components contained in the eluate, as insoluble sulfides. This method enables the separation of cobalt and nickel from lithium-ion secondary batteries with high precision and a reduced number of steps.

[0015] Furthermore, the method for separating cobalt and nickel of the present invention may further include: a redissolution step, in which a redissolution solution containing sulfuric acid is added to the precipitate separated in the cobalt-nickel separation step and stirred, and then solid-liquid separation is performed to obtain a cobalt-nickel solution containing cobalt and nickel; and a solvent extraction step, in which an extractant solution is added to the cobalt-nickel solution to obtain a cobalt extract and a nickel extract.

[0016] Furthermore, in the method for separating cobalt and nickel of the present invention, in the re-dissolution step, the precipitate may be immersed in the re-dissolution solution for 1 hour or longer.

[0017] Furthermore, in the method for separating cobalt and nickel of the present invention, in the leaching step, the temperature of the treatment liquid may be 60° C. or higher, and the concentration of sulfuric acid may be 2 mol / L or higher.

[0018] Furthermore, in the method for separating cobalt and nickel of the present invention, in the copper separation step, the pH of the leachate may be maintained at or below 1.0 from the start to the end of the addition of the hydrogen sulfide compound, and an aqueous sodium hydrogen sulfide solution may be added as the hydrogen sulfide compound until the oxidation-reduction potential (vsAg / AgCl) reaches or below 0 mV.

[0019] Furthermore, in the method for separating cobalt and nickel of the present invention, in the cobalt-nickel separation step, a sodium hydrogen sulfide aqueous solution can be used as the hydrogen sulfide compound, the pH of the eluent from the start to the end of the addition of the hydrogen sulfide compound can be maintained in the range of 2.0 to 5.0, and the hydrogen sulfide compound can be added to the eluent until the oxidation-reduction potential (vsAg / AgCl) reaches below -400 mV.

[0020] Furthermore, the present invention can maintain the pH of the eluent within a range of 2.0 to 3.5 during the period from the start to the end of the addition of the hydrogen sulfide compound.

[0021] Furthermore, in the method for separating cobalt and nickel of the present invention, in the pH adjustment in the cobalt-nickel separation step, the pH of the eluent may be adjusted to be within the range of 3.0 to 4.0.

[0022] Furthermore, in the method for separating cobalt and nickel of the present invention, in the re-dissolution step, the precipitate can be dissolved using the re-dissolution solution containing sulfuric acid and hydrogen peroxide solution, or the precipitate can be dissolved by adding the precipitate to the re-dissolution solution containing sulfuric acid and then performing air bubbling.

[0023] Furthermore, in the method for separating cobalt and nickel of the present invention, in the redissolution step, the liquid temperature of the redissolution liquid may be 60° C. or higher, and the sulfuric acid concentration may be 0.5 mol / L or higher.

[0024] Furthermore, in the method for separating cobalt and nickel of the present invention, a heat treatment step may be included as a pre-step before the pulverization and separation step, in which the lithium ion secondary battery is heated for heat treatment.

[0025] The present invention provides a method for separating cobalt and nickel, which can separate cobalt, nickel, and other metals contained in lithium-ion secondary batteries with high precision using fewer steps, and can recover cobalt and nickel from lithium-ion secondary batteries at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flowchart showing in stages a method for regenerating an electrode material of a lithium-ion secondary battery including the method for separating cobalt and nickel according to the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, a method for separating cobalt and nickel according to an embodiment of the present invention will be described with reference to the accompanying drawings. The embodiments shown below are specifically described for better understanding of the gist of the present invention, and the present invention is not limited thereto unless otherwise specified.

[0028] Figure 1 This is a flowchart showing in stages a method for regenerating an electrode material of a lithium-ion secondary battery including the method for separating cobalt and nickel according to the present invention.

[0029] (Heat treatment step S1)

[0030] As a pretreatment step for separating electrode materials constituting discarded lithium-ion secondary batteries (hereinafter referred to as waste LIBs), the waste LIBs are heat-treated by heating them to approximately 500° C. using, for example, superheated water vapor in a heating furnace.

[0031] Heat treatment can be performed under vacuum or atmospheric pressure, but is preferably performed by heating in an oxygen-free, inert atmosphere. In spent LIBs, the presence of a binder and electrolyte creates strong adhesion between the positive or negative electrode active material and the aluminum or copper foil serving as the current collector. Therefore, heat treatment at temperatures above 400°C facilitates separation of these active materials from the current collector. Setting the heating temperature for spent LIBs below 650°C prevents aluminum from melting and entraining the active material, which then solidifies upon cooling, making it difficult to extract the active material alone.

[0032] (Crushing and Sorting Process S2)

[0033] Next, the heat-treated waste LIBs are pulverized and then sieved to separate the electrode materials. The waste LIBs are pulverized using, for example, a biaxial shearing crusher or a hammer mill.

[0034] The crushed waste LIBs are then classified using a sieve with appropriate mesh size. The battery container, aluminum foil, copper foil, and nickel terminals are considered the oversize fraction, while the electrode material containing the positive electrode active material (such as LiCoO2) and the negative electrode active material (graphite) is recovered as the undersize fraction. For example, any electrode material that can pass through a sieve with a mesh size of approximately 0.5 mm will suffice.

[0035] The separated electrode materials mainly include cobalt, nickel, manganese, copper, iron, aluminum, lithium, calcium, etc., which are the constituent materials of the positive electrode active material and impurities, and carbon, etc., which are the constituent materials of the negative electrode active material.

[0036] (Leaching Step S3)

[0037] Next, the electrode material separated in the crushing and sorting step S2 is immersed in a treatment liquid to obtain a leachate. As the treatment liquid, a solution obtained by mixing sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) is used.

[0038] Co and Ni contained in waste LIBs also include trivalent and tetravalent forms that are difficult to dissolve in sulfuric acid. Therefore, by using hydrogen peroxide as a reducing agent, they can be reduced to divalent Co and Ni that are more easily soluble in sulfuric acid.

[0039] An example of a treatment solution is a solution prepared by mixing 5 mL or more of 30 wt% hydrogen peroxide with 100 mL of dilute sulfuric acid having a concentration of 2 mol / L or higher. By setting the concentration of the dilute sulfuric acid to 2 mol / L or higher and the amount of hydrogen peroxide added to 5 mL or higher, the leaching rate of cobalt and nickel can be increased. While there are no specific limitations, further increases in the leaching rate cannot be expected even with concentrations above these limits. Therefore, the upper limits of the sulfuric acid concentration are 18 mol / L and the upper limit of the amount of hydrogen peroxide added is 30 mL.

[0040] As a specific example of the leaching step S3, for example, the powdered electrode material separated in the pulverization and sorting step S2 is added to a treatment liquid heated to 60°C or higher and immersed for 4 hours or longer.

[0041] The leaching rate of cobalt and nickel can be increased by setting the treatment liquid temperature to 60°C or higher and the leaching (immersion) time to 4 hours or longer. Although there are no particular restrictions, further improvement in the leaching rate cannot be expected even if the temperature is set above these limits. Therefore, the upper limit of the treatment liquid temperature is 90°C, and the upper limit of the leaching time is 15 hours.

[0042] Through the leaching step S3 , metal components (cobalt, nickel, manganese, copper, iron, aluminum, lithium, calcium, etc.) derived from the positive electrode active material in the electrode material are dissolved in the treatment solution, while carbon derived from the negative electrode active material remains insoluble as carbon residue.

[0043] (Copper Separation Step S4)

[0044] Next, a hydrogen sulfide compound is added to the leachate obtained in the leaching step S3 and stirred, followed by solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide (CuS).

[0045] In the method for separating cobalt and nickel of the present invention, hydrogen sulfide compounds refer to compounds containing sulfur components and the sulfur components are H2S, HS - or S 2- The compound of the form.

[0046] As the hydrogen sulfide compound used in the copper separation step S4, a water-soluble alkali metal hydrogen sulfide is used, and in this embodiment, an aqueous solution of sodium hydrogen sulfide (NaSH) is used. As a specific example of the copper separation step S4, after diluting the leachate with ion-exchanged water, the aqueous solution of sodium hydrogen sulfide is added to the diluted leachate and stirred.

[0047] The addition of the aqueous sodium hydrogen sulfide solution is performed, for example, until the oxidation-reduction potential (vs Ag / AgCl) reaches 0 mV or less. By adding sodium hydrogen sulfide until the oxidation-reduction potential reaches 0 mV or less, substantially all of the copper contained in the leachate can be precipitated.

[0048] The pH of the leachate is preferably maintained at 1.0 or less from the start to the end of the addition of the hydrogen sulfide compound. If the pH of the leachate exceeds 1.0, cobalt and nickel sulfides may be generated, and their recovery rate in the eluate may decrease.

[0049] As the hydrogen sulfide compound, in addition to sodium hydrogen sulfide, for example, sodium sulfide, sodium thiosulfate, or sodium dithionite may be mentioned.

[0050] By adding a hydrogen sulfide compound to the leachate, the copper, among the metal components dissolved in the leachate, reacts with sulfur to form copper sulfide (CuS), which precipitates. Meanwhile, metal components other than copper (cobalt, nickel, manganese, iron, aluminum, lithium, calcium, etc.) remain in the liquid phase, yielding an eluate containing cobalt and nickel.

[0051] Thereafter, solid-liquid separation is performed using a filter material or the like, thereby separating the solid phase composed of the carbon residue produced in the leaching step S3 and the residue produced in the copper separation step S4 from the eluate (liquid phase).

[0052] In this embodiment, the carbon residue generated in the leaching step S3 is also filtered by the solid-liquid separation in the copper separation step S4. However, by also performing solid-liquid separation in the leaching step S3, the carbon residue can be separated in advance before the copper separation step S4.

[0053] Furthermore, in the copper separation step S4, before solid-liquid separation, the pH of the leachate can be adjusted to about 3.0 to 4.0 using sodium hydroxide (NaOH), so that the aluminum contained in the leachate is precipitated in the form of aluminum hydroxide (Al(OH)3), and separated from the leachate together with the carbon residue and the residue by solid-liquid separation.

[0054] The separated solid phase may be treated as waste after being repulped (water is added to the solid phase to resuspend it, and then purified by dehydration).

[0055] (Cobalt-Nickel Separation Step S5)

[0056] Next, an alkali metal hydroxide is added to the eluate to adjust the pH, and then a hydrogen sulfide compound is added, followed by stirring and solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual liquid containing lithium.

[0057] Examples of the alkali metal hydroxide used for adjusting the pH of the eluent in the initial stage of the cobalt-nickel separation step S5 include sodium hydroxide (NaOH) and potassium hydroxide (KOH). In this embodiment, a 25 wt% sodium hydroxide aqueous solution is used.

[0058] By adjusting the pH in this manner, the pH of the eluent is adjusted to be within the range of 3.0 to 4.0, for example, 3.5.

[0059] At this time, if the pH is low, the hydrogen sulfide compound may be less likely to react with cobalt and nickel. However, the pH of the eluent decreases with the addition of the hydrogen sulfide compound. After pH adjustment, if the pH is less than 3.0 at the start of hydrogen sulfide compound addition, the pH will drop excessively before the addition of the hydrogen sulfide compound is completed, necessitating further pH adjustment. Therefore, it is more effective to adjust the pH to 3.0 or above as a pretreatment for sulfidation.

[0060] Furthermore, when adjusting the pH to a value exceeding 4.0, the pH adjustment takes time, whereas adding a hydrogen sulfide compound immediately reduces the pH to 4.0 or below, which is inefficient. Therefore, the pH adjustment range is preferably 3.0 to 4.0.

[0061] Then, by adding a water-soluble hydrogen sulfide compound to the pH-adjusted eluate, cobalt and nickel contained in the eluate are precipitated as water-insoluble cobalt sulfide (CoS) and nickel sulfide (NiS), respectively.

[0062] Examples of the hydrogen sulfide compound used to sulfidize cobalt and nickel include water-soluble alkali metal hydrogen sulfides. The hydrogen sulfide compound may be the same as or different from the compound used in the copper separation step S4. In this embodiment, a 250 g / L aqueous solution of sodium hydrogen sulfide is used.

[0063] The addition of the aqueous sodium hydrogen sulfide solution is continued until the oxidation-reduction potential (vs Ag / AgCl) reaches -400 mV or less. By adding sodium hydrogen sulfide until the oxidation-reduction potential reaches -400 mV or less, almost all of the cobalt and nickel contained in the eluent can be precipitated.

[0064] The pH of the leachate is preferably maintained between 2.0 and 5.0, more preferably between 2.0 and 3.5, from the start to the end of the addition of the hydrogen sulfide compound. When the pH of the leachate is less than 2.0, a reaction between sodium hydrogen sulfide and sulfuric acid (NaSH + H2SO4 → H2S + Na2SO4) occurs, consuming the sodium hydrogen sulfide and making the sulfidation of cobalt and nickel difficult. On the other hand, if the pH of the leachate exceeds 5.0, hydroxides of other metals may form, reducing the purity of the precipitate. Furthermore, controlling the pH in this high range is difficult.

[0065] In addition, the cobalt sulfide mentioned herein may include cobalt sulfide compounds of various compositions, such as cobalt (II) sulfide, cobalt disulfide (CoS2), and nonacobalt octasulfide (Co9S8). Similarly, nickel sulfide (NiS) may include nickel sulfide compounds of various compositions, such as nickel (II) sulfide, nickel disulfide (NiS2), nickel tetrasulfide (Ni3S4), and nickel disulfide (Ni3S2).

[0066] On the other hand, metal components (manganese, iron, aluminum, lithium, calcium, etc.) other than cobalt and nickel remain in the liquid phase (raffinate) after the addition of the hydrogen sulfide compound. The manganese, iron, aluminum, lithium, calcium, etc. contained in the liquid phase obtained here can be separated and recovered separately by solvent extraction with pH adjustment, etc.

[0067] (Redissolution Step S6)

[0068] Next, a re-dissolving liquid containing sulfuric acid is added to the precipitate obtained in the cobalt-nickel separation step S5 and stirred, followed by solid-liquid separation to obtain a cobalt-nickel solution containing cobalt and nickel.

[0069] As the re-dissolving solution, for example, a solution obtained by mixing sulfuric acid and hydrogen peroxide as an oxidizing agent is used. An example of the re-dissolving solution is a solution obtained by mixing 20 mL of 30 wt% hydrogen peroxide solution with 100 mL of 1.5 mol / L dilute sulfuric acid.

[0070] As a specific example of the redissolution step S6, for example, the precipitate is added to a redissolution solution heated to 60°C or higher and immersed for 4 hours or longer. Further stirring is preferably performed during this process. Furthermore, air bubbling can also be performed when the precipitate is immersed without adding hydrogen peroxide solution to the redissolution solution.

[0071] In this case, the dissolution rate of cobalt and nickel can be increased by setting the treatment liquid temperature to 60°C or higher and the leaching time to 1 hour or longer. Although there are no particular restrictions, even if the temperature is set above these, no further improvement in the dissolution rate can be expected. Therefore, the upper limit of the treatment liquid temperature is 90°C, and the upper limit of the leaching time is 15 hours.

[0072] By treating the precipitate with this re-dissolving solution, cobalt and nickel are dissolved in the re-dissolving solution. Impurities that are insoluble in the re-dissolving solution and elemental sulfur generated in the cobalt-nickel separation step S5 remain as a solid phase. Subsequently, solid-liquid separation using a filter material or the like is performed to obtain a (purified) cobalt-nickel solution with increased cobalt and nickel purity.

[0073] The cobalt-nickel solution thus obtained contains almost no other components of the electrode material (copper, iron, aluminum, lithium, calcium, etc.) other than cobalt and nickel, and is suitable as a high-purity recovery raw material for cobalt and nickel.

[0074] Furthermore, as a pre-step of the redissolution step S6 , it is also preferable to remove impurities other than cobalt sulfide and nickel sulfide in advance by reslurrying the precipitate.

[0075] In the copper separation step S4, the step of removing aluminum before solid-liquid separation is as described above, but if this step is not performed, the precipitate may contain aluminum compounds. In this case, the aluminum compounds can be removed by reslurrying the precipitate.

[0076] (Solvent Extraction Step S7)

[0077] Next, the extractant solution is added to the cobalt-nickel solution obtained in the redissolution step S6 to obtain a cobalt extract and a nickel extract.

[0078] As the extractant solution, a mixed solution of a metal extractant and a diluent can be used. For example, a mixed solution of 20 vol% 2-ethylhexyl 2-ethylhexylphosphonate (PC88A: manufactured by Daihachi Chemical Industry Co., Ltd.) and 80 vol% kerosene (diluent) can be used.

[0079] The extractant solution is used to separate and recover cobalt sulfate (CoSO4) solution and nickel sulfate (NiSO4) solution from the cobalt-nickel solution through a mixer-settler.

[0080] The above process allows for the recovery of cobalt and nickel from waste LIBs at high yields. For example, assuming the amounts of cobalt and nickel in the electrode material extracted from the waste LIB are each 100%, the cobalt and nickel separation method of this embodiment can recover cobalt and nickel at yields exceeding 95%.

[0081] While the embodiments of the present invention have been described above, these embodiments are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments or modifications thereof are intended to be included within the scope and gist of the invention and are encompassed by the invention described in the claims and their equivalents.

[0082] Example

[0083] The effect of the method for separating cobalt and nickel of the present invention was verified.

[0084] (Steps of the Example of the Present Invention)

[0085] 14.5 g of electrode material extracted from a waste LIB was added to a treatment solution consisting of 100 mL of 2 mol / L sulfuric acid and 5 mL of 30% hydrogen peroxide solution. The solution was heated and stirred at 60°C for 4 hours (leaching step). After cooling to room temperature, an aqueous sodium hydrogen sulfide solution (dissolved in ion-exchanged water with stirring to a concentration of 250 g / L) was added to the leachate and stirred until the oxidation-reduction potential (ORP) of the leachate reached 0 mV (vs Ag / AgCl) or less (copper separation step).

[0086] At this stage, the carbon from the spent LIB's negative electrode material, which was insoluble during sulfuric acid leaching, and the resulting residue (copper sulfide) were filtered to separate the solid from the liquid. A 25 wt% sodium hydroxide solution was added to the resulting eluate to adjust the pH to 3.5. A 250 g / L sodium bisulfide aqueous solution was then added while stirring until the ORP reached below -400 mV (vs. Ag / AgCl).

[0087] After confirming that the black precipitate (cobalt sulfide and nickel sulfide) has been fully generated, solid-liquid separation is performed to recover the precipitate (cobalt-nickel separation step). On the other hand, impurities such as manganese, aluminum, iron, lithium, and calcium remain in the residual liquid and are treated as metal-containing waste liquid.

[0088] The precipitate was added to a redissolution solution consisting of 100 mL of 1.5 mol / L sulfuric acid and 20 mL of 30 wt% hydrogen peroxide solution, and heated and stirred at 60°C for 1 hour (redissolution step). After cooling to room temperature, undissolved components and elemental sulfur generated in the previous reaction were removed by filtration.

[0089] From the cobalt-nickel solution thus obtained, a cobalt sulfate solution and a nickel sulfate solution were separated and recovered using an extractant solution obtained by mixing 20 vol% of PC88A (manufactured by Daihachi Chemical Industry Co., Ltd.) as a metal extractant and 80 vol% of kerosene in a mixer-settler (solvent extraction step).

[0090] In the above-described steps of the present invention example, assuming the cobalt and nickel content of the electrode material extracted from the waste LIB is 100%, the cobalt content obtained in the extract by solvent extraction is 96.4% and the nickel content is 95.3%. Therefore, it was confirmed that the cobalt and nickel separation method of this embodiment can recover cobalt and nickel from waste LIBs at high yields.

[0091] The metal concentration was measured by ICP-AES, the pH was measured by a pH meter, and the ORP was measured by an ORP meter. The values ​​in % are based on mass.

[0092] (Leaching process)

[0093] Regarding the leaching process of the above-mentioned examples of the present invention, the leaching rates of cobalt and nickel in the liquid phase were measured for Experimental Examples 1 to 9, in which the concentration of the treatment solution, the amount of hydrogen peroxide solution, the temperature, and the leaching time were varied. The results are shown in Table 1.

[0094]

[0095] The results shown in Table 1 indicate that the sulfuric acid concentration of the treatment solution is preferably 2 mol / L or higher in Experiments 1 to 3. Furthermore, Experiments 3 to 5 indicate that the volume of the hydrogen peroxide solution in the treatment solution is preferably 5 mL (at a concentration of 30 wt%) or higher. Furthermore, Experiments 3, 6, and 7 indicate that the temperature of the treatment solution (liquid temperature) is preferably 60°C or higher. Furthermore, Experiments 5, 8, and 9 indicate that the leaching time is preferably 4 hours or longer.

[0096] (Copper separation process)

[0097] Next, regarding the copper separation process of the above-mentioned examples of the present invention, sodium hydrogen sulfide aqueous solution was added to the leachate obtained in Experiment 5, and the accompanying changes in pH, ORP, and metal concentration in the leachate were examined. In Experiment 10, measurements were performed on the leachate before addition. The addition and measurement of sodium hydrogen sulfide aqueous solution were repeated, and the process was terminated when the ORP reached 0 mV or less (Experiments 11 to 13). In addition, pH measurement was continued from the beginning of the addition of sodium hydrogen sulfide aqueous solution. After each addition, when the pH stabilized, the pH at that time and the time elapsed from the initial addition were recorded, and other measurements were also performed.

[0098] The results are shown in Table 2.

[0099]

[0100] The results shown in Table 2 indicate that by maintaining the pH of the leachate at 1.0 or less and adding a hydrogen sulfide compound until the ORP reaches 0 mV or less, almost all of the copper contained in the leachate can be precipitated, thereby enabling solid-liquid separation from other components such as nickel and cobalt.

[0101] (Cobalt-Nickel Separation Process)

[0102] Next, regarding the cobalt-nickel separation step of the above-mentioned example of the present invention, the effect of the pH of the eluent to which the hydrogen sulfide compound was added on the reaction was examined.

[0103] [pH 2.0~3.0]

[0104] In Experimental Example 14, the eluent obtained in Experimental Example 13 was used as the eluent, and the eluent before addition was measured. Next, sodium hydroxide aqueous solution was added, and the pH-adjusted solution was measured (Experimental Example 15). Thereafter, the addition and measurement of sodium hydrogen sulfide aqueous solution were repeated (Experiments 16 to 23). In order to maintain the pH within the range of 2.0 to 3.0 during the addition, sodium hydroxide aqueous solution and sulfuric acid were also added as appropriate along with the sodium hydrogen sulfide aqueous solution.

[0105] Table 3 shows the cumulative amount of each aqueous solution added after the start of addition of the sodium hydrogen sulfide aqueous solution, the liquid volume, pH, ORP, and metal concentration of the dissolved liquid at that time.

[0106] The pH measurement was performed continuously from the addition of the sodium hydrogen sulfide aqueous solution. After each addition, when the pH stabilized, the pH at that time and the elapsed time from the first addition were recorded. Other parameters were also measured.

[0107]

[0108] [pH 2.5~3.5]

[0109] The addition and measurement of aqueous solutions were performed in the same manner as in Experiments 14 to 23, except that the pH was changed. Experiment 24 shows the eluate before addition, Experiment 25 shows the solution after pH adjustment, and Experiments 26 to 33 show the eluates at various stages of addition. The measurement results are shown in Table 4.

[0110]

[0111] The results shown in Tables 3 and 4 show that the addition of the sodium bisulfide aqueous solution reduced the nickel and cobalt concentrations while maintaining the manganese concentration in the eluent. Adding the sodium bisulfide aqueous solution until the ORP reaches -400 mV or lower prevents manganese from precipitating, while nickel and cobalt precipitate as sulfides, enabling solid-liquid separation of nickel and cobalt.

[0112] [pH 3.5~5.0]

[0113] The addition and measurement of aqueous solutions were carried out in the same manner as in Experiments 14 to 23, except that the pH was changed. Experiment 34 shows the pH-adjusted solution, and Experiments 35 to 38 show the eluents added at each stage. The measurement results are shown in Table 5.

[0114]

[0115] The results shown in Table 5 show that the addition of the sodium bisulfide aqueous solution reduced the nickel and cobalt concentrations while maintaining the manganese concentration in the eluent. Adding the sodium bisulfide aqueous solution until the ORP reaches -400 mV prevents precipitation of manganese and other substances, while nickel and cobalt precipitate as sulfides, enabling solid-liquid separation of nickel and cobalt.

[0116] Furthermore, pH control was difficult in the pH range of 3.5 to 5.0, and the time it took for the pH to stabilize after each addition of sodium bisulfide aqueous solution was longer than in other experimental examples. Furthermore, if the pH reached 3.5 or higher, low-solubility hydroxides other than nickel and cobalt might begin to form.

[0117] [pH 1.6~2.3]

[0118] The addition and measurement of aqueous solutions were performed in the same manner as in Experiments 14 to 23, except that the pH was changed. Experiment 39 shows the solution after pH adjustment, and Experiments 40 to 43 show the eluents at each stage of addition. The measurement results are shown in Table 6.

[0119]

[0120] The results shown in Table 6 show that the eluent pH was not maintained above 2.0. Even when it temporarily dropped below 2.0, a larger amount of sodium bisulfide was required to convert cobalt and nickel into sulfides, compared to when the pH was maintained above 2.0 (Tables 3-5). In Experiments 42 and 43, which occurred in the latter half of the experiment, the pH reached above 2.0. However, in Experiments 40 and 41, which occurred in the first half of the experiment, the pH was below 2.0. Therefore, sodium bisulfide reacted with sulfuric acid and could not be effectively utilized for the sulfidation of cobalt and nickel and the formation of precipitation. Compared to Tables 3, 4, and 5, Table 6 shows that despite the use of the largest amount of sodium bisulfide aqueous solution, cobalt and nickel still remained in the solution. Furthermore, the ORP reached above -400 mV.

[0121] As can be seen from the above, in the cobalt-nickel separation step, it is sufficient to maintain the pH of the eluent in the range of 2.0 to 5.0 (more preferably, maintain the pH in the range of 2.0 to 3.5) and add sodium bisulfide aqueous solution until the ORP reaches -400 mV or less.

[0122] (Procedure of conventional example)

[0123] The leaching step and the copper separation step were carried out in the same manner as in the present invention example to obtain an eluate. Subsequently, the manganese separation step and the aluminum separation step, which are conventionally carried out, were carried out instead of the cobalt-nickel separation step.

[0124] A 12 wt% sodium hypochlorite aqueous solution was added to the eluate to oxidize manganese, thereby precipitating manganese dioxide (MnO 2 ). The manganese was then removed by solid-liquid separation using a filter (manganese separation step).

[0125] In this manganese separation step, part of cobalt and nickel is also oxidized to trivalent form and precipitated as hydroxides, and is separated into solid and liquid forms together with manganese dioxide, thereby reducing the yields of cobalt and nickel.

[0126] Next, a 25% sodium hydroxide aqueous solution was added to the filtrate obtained in the manganese separation step to adjust the pH of the filtrate to 5.5, thereby separating aluminum as a hydroxide precipitate (aluminum separation step).

[0127] In the aluminum separation step, part of cobalt and nickel is similarly precipitated as hydroxides and separated into solid and liquid forms together with aluminum hydroxide, further reducing the yields of cobalt and nickel.

[0128] In the above conventional example, assuming that the cobalt and nickel content of the electrode material extracted from the scrap LIB is 100%, 38.2% of the cobalt and 41.3% of the nickel are discharged from the system during the process, respectively, leaving the direct yields at 61.8% cobalt and 58.7% nickel.

[0129] [Manganese separation process]

[0130] In the manganese separation step of the aforementioned prior art example, a 5% aqueous sodium hypochlorite solution and a 25% aqueous sodium hydroxide solution were added to the eluate, and the accompanying changes in metal concentration in the eluate were measured. After measuring the eluate before addition in Prior Art Experiment 1, the addition and measurement of each aqueous solution were repeated in Prior Art Experiments 2 to 6. The results are shown in Table 7.

[0131] [Table 7]

[0132]

[0133] The results shown in Table 7 show that as the amount of each aqueous solution added increases, the precipitation of manganese progresses and part of cobalt and nickel also precipitate. The maximum loss of cobalt and nickel in the manganese separation step is about 15%.

[0134] [Aluminum separation process]

[0135] Next, regarding the aluminum separation step of the aforementioned prior art example, the concentrations of metals (cobalt, nickel, manganese, and aluminum) remaining in the filtrate and the pH were measured for prior art Experiments 7 to 10, in which the amount of sodium hydroxide aqueous solution added to the filtrate was varied. Prior art Experiment 7 was performed before the addition of the sodium hydroxide aqueous solution. Prior art Experiment 10 also added sulfuric acid. The results are shown in Table 8.

[0136] [Table 8]

[0137]

[0138] The filtrate is 200mL

[0139] The results shown in Table 8 show that at pH 5.46 (Conventional Experiment 9), where aluminum precipitated almost entirely as hydroxide, portions of cobalt and nickel also precipitated as hydroxides, resulting in a 23% nickel loss and a 17% cobalt loss. Furthermore, since aluminum hydroxide formed a gel, solid-liquid separation using a filter was difficult.

[0140] Industrial applicability

[0141] The cobalt and nickel separation method of the present invention can accurately separate valuable metals (particularly cobalt and nickel) from other metals contained in used lithium-ion secondary batteries and recover the other metals, thereby efficiently obtaining high-purity recycled resources from lithium-ion secondary batteries. Therefore, the method has industrial applicability.

Claims

1. A method for separating cobalt and nickel from a lithium-ion secondary battery, wherein the method comprises: a crushing and sorting step of crushing and classifying the lithium-ion secondary battery to obtain an electrode material containing at least cobalt, nickel, copper and lithium; a leaching step of immersing the electrode material in a treatment solution containing sulfuric acid and hydrogen peroxide to obtain a leachate; a copper separation step, wherein a hydrogen sulfide compound is added to the leachate and stirred, followed by solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide; and In the cobalt-nickel separation step, an alkali metal hydroxide is added to the eluate to adjust the pH, and then a hydrogen sulfide compound is added to the eluate for stirring and solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual liquid containing lithium.

2. The method for separating cobalt and nickel according to claim 1, wherein: include: a redissolution step of adding a redissolution solution containing sulfuric acid to the precipitate separated in the cobalt-nickel separation step, stirring the mixture, and then performing solid-liquid separation to obtain a cobalt-nickel solution containing cobalt and nickel; and In the solvent extraction step, an extractant solution is added to the cobalt-nickel solution to obtain a cobalt extract and a nickel extract.

3. The method for separating cobalt and nickel according to claim 2, characterized in that: In the re-dissolution step, the precipitate is immersed in the re-dissolution solution for 1 hour or longer.

4. The method for separating cobalt and nickel according to any one of claims 1 to 3, characterized in that: In the leaching step, the temperature of the treatment liquid is 60° C. or higher, and the concentration of sulfuric acid is 2 mol / L or higher.

5. The method for separating cobalt and nickel according to any one of claims 1 to 3, characterized in that: In the copper separation process, The pH of the leachate is maintained at 1.0 or less from the start to the end of the addition of the hydrogen sulfide compound. An aqueous sodium hydrogen sulfide solution was added as the hydrogen sulfide compound until the oxidation-reduction potential vs. Ag / AgCl reached 0 mV or less.

6. The method for separating cobalt and nickel according to any one of claims 1 to 3, characterized in that: In the cobalt-nickel separation process, Using sodium hydrogen sulfide aqueous solution as the hydrogen sulfide compound, The pH of the eluent is maintained within a range of 2.0 to 5.0 from the start to the end of the addition of the hydrogen sulfide compound, The hydrogen sulfide compound is added to the eluent until the oxidation-reduction potential vs Ag / AgCl reaches below -400 mV.

7. The method for separating cobalt and nickel according to claim 6, characterized in that: The pH of the eluate is maintained within a range of 2.0 to 3.5 from the start to the end of the addition of the hydrogen sulfide compound.

8. The method for separating cobalt and nickel according to any one of claims 1 to 3, characterized in that: In the pH adjustment in the cobalt-nickel separation step, the pH of the eluent is adjusted to be within the range of 3.0 to 4.

0.

9. The method for separating cobalt and nickel according to claim 2 or 3, characterized in that: In the re-dissolution step, the precipitate is dissolved in the re-dissolution solution containing sulfuric acid and hydrogen peroxide solution, or the precipitate is added to the re-dissolution solution containing sulfuric acid and then dissolved by air bubbling.

10. The method for separating cobalt and nickel according to claim 2 or 3, characterized in that: In the redissolution step, the liquid temperature of the redissolution liquid is 60° C. or higher, and the sulfuric acid concentration is 0.5 mol / L or higher.

11. The method for separating cobalt and nickel according to any one of claims 1 to 3, characterized in that: A heat treatment step is included as a pre-step of the pulverization and separation step. In the heat treatment step, the lithium ion secondary battery is heated to perform a heat treatment.

12. A method for separating cobalt and nickel from an electrode material containing at least cobalt, nickel, copper, and lithium, the method comprising: a leaching step of immersing the electrode material in a treatment solution containing sulfuric acid and hydrogen peroxide to obtain a leachate; a copper separation step, wherein a hydrogen sulfide compound is added to the leachate and stirred, followed by solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide; and In the cobalt-nickel separation step, an alkali metal hydroxide is added to the eluate to adjust the pH, and then a hydrogen sulfide compound is added to the eluate for stirring and solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual liquid containing lithium.

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