Metal element recovery method for recovering metal element from lithium ion battery

Abstract

Disclosed is a metal element recovery method which comprises: a step (1) for obtaining an acidic first solution by dissolving a metal in a crushed product of a lithium ion battery in an acidic aqueous solution; a step (2) for changing divalent iron ions in the first solution to trivalent iron ions; a step (3) for obtaining a second solution and a first precipitate that contains an iron compound or the like by adjusting the pH of the first solution to fall within the range of 3.0 to 5.0; a step (4) for obtaining a third solution and a second precipitate that contains copper sulfide by adding a sulfurizing agent to the second solution and adjusting the pH of the second solution to fall within the range of 4.0 to 5.0; a step (5) for obtaining a fourth solution and a third precipitate that contains nickel hydroxide or the like by adjusting the pH of the third solution to fall within the range of 7.0 to 8.5; and a step (6) for obtaining a fifth solution and a fourth precipitate that contains a lithium compound by concentrating the fourth solution while injecting a carbon dioxide gas thereinto.

Description

METHOD FOR RECOVERING METAL ELEMENTS FROM LITHIUM ION BATTERIES CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-054153, filed on March 28, 2024 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a method for recovering metal elements from lithium ion batteries.

[0003] A large number of lithium-ion batteries are currently in use. These batteries contain rare metals, such as lithium, nickel, and cobalt. Therefore, it is desirable to recover these metal elements from used batteries. However, because metals in lithium-ion batteries exist in a variety of forms, it is not easy to separate and recover them. Various methods for recovering metal elements from batteries have been proposed.

[0004] Claim 1 of Patent Document 1 (JP 2023-103929 A) discloses "a method for recovering lithium from waste lithium-ion batteries, comprising: a dissolving step of dissolving active material powder obtained by pretreating waste lithium-ion batteries in a mineral acid; a first alkali hydroxide addition step of adding at least one of sodium hydroxide and potassium hydroxide to the solution obtained in the dissolving step; a second alkali hydroxide addition step of again adding at least one of sodium hydroxide and potassium hydroxide to the solution obtained in the first alkali hydroxide addition step; a separation step of separating a lithium salt and at least one salt of sodium and potassium from the aqueous alkali mixed salt solution obtained in the second alkali hydroxide addition step; and a lithium recovery step of recovering lithium from the first aqueous lithium salt solution obtained in the separation step."

[0005] Claim 1 of Patent Document 2 (JP 2023-103795 A) describes a method for recovering lithium from waste lithium-ion batteries, comprising: a dissolving step of dissolving active material powder obtained by pretreating waste lithium-ion batteries with a mineral acid; an alkali hydroxide adding step of adding at least one of sodium hydroxide and potassium hydroxide to the solution obtained in the dissolving step; an extraction step of extracting at least one of iron, aluminum, manganese, cobalt, and nickel contained in the active material powder from the solution obtained in the alkali hydroxide adding step with an organic solvent by solvent extraction; a separation step of separating a lithium salt and at least one salt of sodium and potassium from the aqueous alkali mixed salt solution obtained in the extraction step; a carbonation step of carbonate the lithium salt aqueous solution obtained in the separation step to obtain lithium carbonate; and an electrolysis step of electrolyzing the aqueous solution of at least one salt of sodium and potassium obtained from the separation step using an ion exchange membrane to obtain an aqueous alkali hydroxide solution, The document discloses a method for recovering lithium from waste lithium-ion batteries, comprising: reusing the aqueous alkali hydroxide solution obtained in the electrolysis step in at least one of the alkali hydroxide addition step, the extraction step, and the separation step; and reusing at least one of the mineral acid obtained by recovering the gas generated in the electrolysis step and the mineral acid obtained in the anode chamber of the electrolysis step in the dissolution step.

[0006] JP 2023-103929 A JP 2023-103795 A

[0007] It is desirable to recover not only lithium but also other metals (such as nickel and cobalt) from lithium-ion batteries. Patent Document 2 discloses a method for extracting various metals using an organic solvent. However, extraction using an organic solvent may require relatively large-scale equipment and may be expensive. In this situation, one of the objectives of the present disclosure is to provide a method capable of recovering various metal elements from crushed lithium-ion batteries at low cost.

[0008] One aspect of the present disclosure is a method for recovering metal elements from crushed lithium-ion batteries, the method comprising the steps of: (1) dissolving the metals in the crushed lithium-ion batteries in an acidic aqueous solution to obtain an acidic first solution in which the metals are dissolved; (2) oxidizing divalent iron ions in the first solution to trivalent iron ions; (3) adjusting the pH of the first solution to a range of 3.0 to 5.0 to obtain a first precipitate containing an iron compound and an aluminum compound and a second solution; (4) adding a sulfiding agent to the second solution and adjusting the pH of the second solution to a range of 4.0 to 5.0 to precipitate copper ions in the second solution as copper sulfide, thereby obtaining a second precipitate containing copper sulfide and a third solution; and (5) adjusting the pH of the third solution to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution. and (6) concentrating the fourth solution while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution.

[0009] According to the present disclosure, it is possible to recover various metals from crushed lithium-ion batteries at low cost. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0010] Fig. 1 is a flowchart of an example of a recovery method according to embodiment 1. Fig. 2 is a flowchart of another example of a recovery method according to embodiment 1.

[0011] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention of the present disclosure can be implemented. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0012] (Metal Element Recovery Method) The metal element recovery method according to this embodiment may be referred to as "metal element recovery method (M)" or "recovery method (M)" hereinafter. The recovery method (M) is a method for recovering metal elements from lithium ion batteries (discarded lithium ion batteries). The recovery method (M) includes steps (1) to (6) in this order. The metals can be recovered in the form of compounds. The solutions obtained in the following steps may be diluted with water as needed.

[0013] The recovery method (M) is a method for recovering metal elements from crushed lithium-ion batteries, and includes the steps of: (1) dissolving the metals in the crushed lithium-ion batteries in an acidic aqueous solution to obtain an acidic first solution containing the dissolved metals; (2) oxidizing divalent iron ions in the first solution to trivalent iron ions; (3) adjusting the pH of the first solution to a range of 3.0 to 5.0 to obtain a first precipitate containing iron compounds and aluminum compounds and a second solution; (4) adding a sulfiding agent to the second solution and adjusting the pH of the second solution to a range of 4.0 to 5.0 to precipitate copper ions in the second solution as copper sulfide, thereby obtaining a second precipitate containing copper sulfide and a third solution; and (5) adjusting the pH of the third solution to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution. and step (6) of concentrating the fourth solution while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution.

[0014] Conventional metal element recovery methods have been insufficient in recovering each metal species. Furthermore, conventional recovery methods that use organic solvents to extract metals have the problem of high organic solvent costs and the need for large-scale equipment. On the other hand, recovery method (M) can be implemented at low cost. Furthermore, recovery method (M) allows for the recovery of roughly each metal species. Furthermore, recovery method (M) can be implemented using relatively simple equipment. Therefore, it has the advantage of being easily implemented in small-scale plants.

[0015] (Step (1)) In step (1), metals (metal elements) in crushed lithium-ion battery material are dissolved in an acidic aqueous solution to obtain a first acidic solution in which the metals are dissolved. A lithium-ion battery is a battery containing lithium. The battery may be a primary battery or a secondary battery. Examples of lithium-ion batteries include lithium-ion secondary batteries. The metals in the crushed material are present in at least one form selected from the group consisting of elemental metals, alloys, and metal compounds. Examples of metal compounds include oxides.

[0016] Crushed lithium-ion batteries can be obtained by crushing lithium-ion batteries (e.g., used lithium-ion batteries). The lithium-ion batteries may be crushed together with the outer can. In this case, the crushed material includes the outer can, a positive electrode current collector, a negative electrode current collector, and active materials (positive electrode active material, negative electrode active material). Typically, the crushed outer can, positive electrode current collector, and negative electrode current collector contain iron, aluminum, and copper as metal elements. In one example, the outer can contains iron, the positive electrode current collector contains aluminum, and the negative electrode current collector contains copper. The active materials typically contain lithium, nickel, and cobalt as metal elements, for example, lithium, nickel, cobalt, and manganese. Crushed lithium-ion batteries typically contain iron, copper, aluminum, lithium, nickel, and cobalt as metal elements, and may further contain manganese.

[0017] The crushed material may be crushed material obtained by crushing lithium-ion batteries, then subjecting the crushed battery material to fluoride treatment and classification (sieving), etc. Crushed battery material is sometimes called "black mass." In one example of fluoride treatment, the crushed battery material is heated to 100°C to 200°C to vaporize the electrolyte, and then the fluoride is recovered as calcium fluoride powder by treatment such as hydrolysis. Alternatively, the fluoride may be decomposed by heating.

[0018] The acidic aqueous solution used in step (1) may be an aqueous solution of an inorganic acid. Examples of aqueous solutions of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, etc. Hydrochloric acid is preferred because it can be easily reused.

[0019] The pH of the acidic aqueous solution is adjusted to a range in which the metals to be recovered (lithium, cobalt, nickel, manganese, iron, copper, etc.) dissolve. The pH of the acidic aqueous solution may be 2.0 or less. The pH of the acidic aqueous solution may be 2.0 or less (for example, in the range of -1.1 to 2.0) or 1.0 or less (for example, in the range of -1.1 to 1.0). In order to promote the dissolution of the metals, it is preferable to heat the acidic aqueous solution. The temperature of the acidic aqueous solution may be in the range of 25 to 97°C (for example, in the range of 50 to 97°C).

[0020] In step (1), the metal in the black mass may be dissolved in the acidic aqueous solution by immersing the black mass in a hydrochloric acid solution (concentration: 20 to 30% by mass) maintained at a temperature in the range of 25 to 97°C (e.g., 50 to 97°C). The amount of dissolved metal can be increased by extending the immersion time. The immersion time may be 4 hours or more. On the other hand, in consideration of efficiency, the immersion time may be 3 hours or less. In step (1), the acidic aqueous solution containing the black mass may be stirred. The first solution is obtained by separating the acidic aqueous solution containing the dissolved metal from the solid matter (e.g., carbon and Si-based Li compounds contained in the negative electrode) that did not dissolve in the acidic aqueous solution. The pH of the first solution is usually 2.0 or less.

[0021] (Step (2)) In step (2), the divalent iron ions in the first solution are oxidized to trivalent iron ions. In step (2), the method for oxidizing the divalent iron ions in the first solution is not particularly limited. The divalent iron ions may be oxidized by adding an oxidizing agent to the first solution. Examples of the oxidizing agent include an oxygen-containing gas (e.g., air) and aqueous hydrogen peroxide. In step (2), the divalent iron ions may be oxidized by air oxidation or an aqueous hydrogen peroxide solution. Air oxidation may be performed by bubbling air through the first solution.

[0022] (Step (3)) In step (3), the pH of the first solution that has been subjected to step (2) is adjusted to a range of 3.0 to 5.0 to obtain a first precipitate containing an iron compound and an aluminum compound and a second solution. That is, in step (3), the pH of the first solution is increased. The adjustment of the pH produces a first precipitate in the first solution. As a result, the first solution changes into a second solution and the first precipitate in the second solution. The metal in the second solution is less than the metal in the first solution by the amount of the first precipitate produced. After the second solution and the first precipitate are separated, the second solution is used in step (4).

[0023] In the recovery method (M), the step of obtaining a precipitate and a solution may include a step of precipitating the precipitate by a predetermined operation and a step of separating the precipitate from the solution in which the precipitate has been precipitated. The separation step of separating the solution from the precipitate is not particularly limited. The separation step may be performed by a known method. Examples of the separation method include separation by filtration and centrifugation.

[0024] The pH of the first solution may be adjusted by adding an alkaline agent to the first solution. In this case, the pH of the first solution is adjusted to a range of 3.0 to 5.0 (e.g., a range of 4.0 to 4.2) so that a first precipitate (e.g., iron compound, aluminum compound) is produced. This allows at least a portion of the iron ions to precipitate as iron hydroxide (e.g., iron(III) oxide hydroxide). Furthermore, at least a portion of the aluminum ions to precipitate as hydroxide.

[0025] The alkaline agent is not particularly limited. In step (3), the pH of the first solution may be adjusted by adding at least one alkaline agent selected from the group consisting of calcium hydroxide, calcium carbonate, and sodium hydroxide to the first solution. For example, in step (3), the pH of the first solution may be adjusted by adding at least one alkaline agent selected from the group consisting of calcium hydroxide and calcium carbonate to the first solution. That is, calcium hydroxide and / or calcium carbonate may be used as the alkaline agent in step (3). These calcium compounds are preferred because calcium can be removed as calcium sulfate in a subsequent step, making it easier to reuse hydrochloric acid. Therefore, the above-mentioned calcium compounds may also be used as alkaline agents in other steps.

[0026] The alkaline agent may be added to the solution in the form of an aqueous solution or in the form of a powder (the same applies to other steps in which an alkaline agent is used). Adding the alkaline agent in the form of a powder is preferable in that it can prevent the volume of the solution from increasing and allows the hydrochloric acid to be reused.

[0027] (Step (4)) In step (4), a sulfurizing agent is added to the second solution and the pH of the second solution is adjusted to a range of 4.0 to 5.0, thereby precipitating copper ions in the second solution as copper sulfide, and a second precipitate containing copper sulfide and a third solution are obtained. As a result of the formation of the second precipitate in the second solution, the second solution changes into a third solution and the second precipitate in the third solution. The amount of copper in the third solution is less than that in the second solution by the amount of the second precipitate formed. After the third solution and the second precipitate are separated, the third solution is used in step (5). The amount of sulfurizing agent added is preferably in the range of 1.0 to 1.1 times, and more preferably in the range of 1.0 to 1.02 times, the equivalent of the copper dissolved in the second solution. If the sulfurizing agent is added in an amount exceeding the equivalent amount, sulfur components become impurities.

[0028] The sulfiding agent used in step (4) may be any agent capable of producing copper sulfide. The sulfiding agent may be at least one selected from the group consisting of sodium hydrogen sulfide, sodium sulfide, and sulfide gas. For example, any one of sodium hydrogen sulfide, sodium sulfide, and sulfide gas may be used as the sulfiding agent.

[0029] The pH of the second solution may be adjusted by adding an alkaline agent to the second solution. The alkaline agent may be any of the alkaline agents described above. In one example of step (4), the sulfiding agent is at least one selected from the group consisting of sodium hydrogen sulfide, sodium sulfide, and sulfide gas, and the alkaline agent is at least one selected from the group consisting of calcium hydroxide and calcium carbonate.

[0030] (Step (5)) In step (5), the pH of the third solution is adjusted to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution. That is, in step (5), the pH of the third solution is increased. As a result of the formation of the third precipitate in the third solution, the third solution changes into a fourth solution and the third precipitate in the fourth solution. The nickel and cobalt in the fourth solution are less than the nickel and cobalt in the third solution by the amount of the third precipitate formed. The third precipitate is a mixed hydroxide containing nickel hydroxide and cobalt hydroxide and also contains nickel-cobalt composite hydroxide (Mixed Hydroxide Precipitate: MHP), which is an intermediate raw material for nickel production. After the fourth solution and the third precipitate are separated, the fourth solution is used in step (5). The third precipitate may be washed with water and then dried until its water content is 60% by mass or less. By washing and drying the third precipitate, impurities are removed, facilitating transportation to the next step. If the water content is 30% by mass or less, it may be difficult to loosen the third precipitate in an aqueous solution during the step of treating the third precipitate. Therefore, it is desirable to set the water content of the third precipitate to be in the range of 35 to 55% by mass.

[0031] The pH of the third solution may be adjusted by adding an alkaline agent to the third solution, such as the alkaline agents described above.

[0032] (Step (6)) In step (6), the fourth solution is concentrated while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution. As a result of the formation of the fourth precipitate in the fourth solution, the fourth solution changes into a fifth solution and a fourth precipitate in the fifth solution. The amount of lithium in the fifth solution is less than that in the fourth solution by the amount of the fourth precipitate formed. By concentrating the fourth solution in step (6), the amount of the fourth precipitate can be increased. The concentration is preferably performed until the volume of the solution is 50% or less (more preferably 20% or less) of the volume of the solution before concentration. The concentration can be performed by heating the fourth solution. To simplify the concentration by heating, the fourth solution may be pre-concentrated using an RO membrane (reverse osmosis membrane) before the heat concentration. After the fifth solution and the fourth precipitate are separated, the fifth solution can be used in the next step.

[0033] The fourth precipitate contains lithium carbonate as the lithium compound. The heating and concentration of the fourth solution may be performed in the atmosphere. For more efficient heating and concentration, the heating and concentration may be accompanied by bubbling of carbon dioxide gas.

[0034] (Step (A)) In at least one step selected from the group consisting of steps (3), (4), and (5), a calcium compound may be used to adjust the pH. Specifically, a calcium compound (alkaline agent) may be added to at least one solution selected from the group consisting of the first solution, the second solution, and the third solution to adjust the pH of the solution. In this case, the recovery method (M) may further include, after step (6), step (A) of adding sulfuric acid to the fifth solution to obtain a calcium sulfate-containing precipitate Xa and a solution Ya. Examples of calcium compounds include alkaline agents such as calcium carbonate and calcium hydroxide. Using only a calcium compound as the alkaline agent in the recovery method (M) facilitates the reuse of acids (e.g., hydrochloric acid). The pH adjustment in steps (3), (4), and (5) may be performed using a calcium compound without using an alkali metal hydroxide (e.g., sodium hydroxide or potassium hydroxide).

[0035] As a result of the formation of precipitate Xa in the fifth solution, the fifth solution changes into solution Ya and precipitate Xa in solution Ya. According to step (A), calcium can be recovered and sulfate ions (SO ４ ２－ ) can be recovered. By recovering the sulfate radical, the acid (e.g., hydrochloric acid) in the solution Ya can be easily reused. After the solution Ya and the precipitate Xa are separated, the solution Ya can be used as an acidic aqueous solution.

[0036] The acidic aqueous solution in step (1) may be hydrochloric acid. In this case, the hydrochloric acid contained in solution Ya may be used for the acidic aqueous solution in step (1). By reusing the hydrochloric acid, the cost of recovering metal elements can be reduced.

[0037] (Step (7)) When the crushed material contains manganese, the recovery method (M) may further include, after step (6), step (7) of adjusting the pH of the fifth solution to a range of 9.0 to 11.0 to obtain a fifth precipitate containing a manganese compound and a sixth solution. That is, in step (7), the pH of the fifth solution is increased. According to step (7), manganese can be recovered. The pH of the fifth solution may be adjusted by adding an alkaline agent to the fifth solution. The alkaline agent may be any of the alkaline agents described above.

[0038] As a result of the formation of the fifth precipitate in the fifth solution, the fifth solution changes into a sixth solution and the fifth precipitate in the sixth solution. The manganese in the sixth solution is less than that in the fifth solution by the amount of the fifth precipitate formed. After the sixth solution and the fifth precipitate are separated, the sixth solution can be used in the next step.

[0039] (Step (B)) In the recovery method (M), a calcium compound may be used to adjust the pH in at least one step selected from the group consisting of steps (3), (4), (5), and (7). Specifically, a calcium compound (alkali agent) may be added to at least one solution selected from the group consisting of the first solution, the second solution, the third solution, and the fifth solution in order to adjust the pH of the solution. In this case, the recovery method (M) may further include, after step (7), step (B) of adding sulfuric acid to the sixth solution to obtain a calcium sulfate-containing precipitate Xb and a solution Yb. A calcium compound may be used instead of an alkali metal hydroxide to adjust the pH in steps (3), (4), (5), and (7).

[0040] As a result of the formation of precipitate Xb in the sixth solution, the sixth solution changes into solution Yb and precipitate Xb in solution Yb. According to step (B), calcium can be recovered and sulfate ions (SO ４ ２－ ) can be recovered. By recovering the sulfate radical, the acid (e.g., hydrochloric acid) in the solution Yb can be easily reused. After the seventh solution and the sixth precipitate are separated, the seventh solution can be used as an acidic aqueous solution.

[0041] The acidic aqueous solution in step (1) may be hydrochloric acid. In this case, the hydrochloric acid contained in the solution Yb may be used for the acidic aqueous solution in step (1). By reusing the hydrochloric acid, the cost of recovering the metal elements can be reduced.

[0042] The total number of moles of iron, aluminum, and copper in the crushed material used in step (1), Mfac, is preferably smaller than the total number of moles of nickel and cobalt in the crushed material, Mnc. This configuration allows the proportions of nickel and cobalt contained in the first and second precipitates by coprecipitation to be reduced. This facilitates the recovery of nickel and cobalt. By setting the ratio Mfac / Mnc to less than 1.0, the recovery of nickel and cobalt is particularly facilitated.

[0043] The recovery method (M) may further include a step (a) of dissolving aluminum in the first precipitate as tetrahydroxidealuminate(III) ions in an alkaline aqueous solution to obtain an aqueous solution containing tetrahydroxidealuminate(III) ions and a seventh precipitate. Step (a) allows the aluminum in the first precipitate to be recovered.

[0044] The recovery method (M) may further include, after the step (a), a step (b) of adding the seventh precipitate to boiling water to obtain an eighth precipitate containing iron. By adding the seventh precipitate to boiling water, the iron compound contained in the seventh precipitate is converted into hematite (Fe ２ O ３ According to step (b), the iron in the seventh precipitate can be recovered.

[0045] The recovered metal elements can be reused as needed. The metal elements recovered as metal compounds can be converted into a form that can be reused as needed. Lithium, cobalt, nickel, and manganese are particularly valuable and therefore offer great benefits for reuse.

[0046] An example of this embodiment will be specifically described below with reference to the drawings. The example method described below can be modified based on the above description. The matters described below may also be applied to the above embodiment. Furthermore, components that are not essential to the method described below and the method according to the present disclosure may be omitted.

[0047] (Embodiment 1) A flowchart of a recovery method according to embodiment 1 is shown in Figure 1. In embodiment 1, hydrochloric acid is used as the acidic aqueous solution in step (1). Furthermore, in embodiment 1, a calcium compound is used as an alkaline agent for adjusting the pH.

[0048] In the recovery method of the first embodiment, metals in the crushed lithium-ion batteries are first dissolved in hydrochloric acid to obtain an acidic first solution containing the dissolved metals (step S1). Next, iron (II) ions (divalent iron ions) in the first solution are oxidized to iron (III) ions (trivalent iron ions) (step S2).

[0049] Next, the pH of the first solution is adjusted to a range of 3.0 to 5.0 to obtain a first precipitate containing iron compounds and aluminum compounds and a second solution (step S3). In the first embodiment, the pH of the first solution is adjusted by adding a calcium compound (alkaline agent) to the first solution. Next, the first precipitate is separated from the solution (second solution) (step S3a).

[0050] Next, a sulfurizing agent is added to the second solution and the pH of the second solution is adjusted to a range of 4.0 to 5.0, thereby precipitating the copper ions in the second solution as copper sulfide, thereby obtaining a second precipitate containing copper sulfide and a third solution (step S4). The pH adjustment is performed by adding a calcium compound (alkaline agent) to the second solution. Next, the second precipitate is separated from the solution (third solution) (step S4a).

[0051] Next, the pH of the third solution is adjusted to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution (step S5). The pH adjustment is performed by adding a calcium compound (alkaline agent) to the third solution. Next, the third precipitate is separated from the solution (fourth solution) (step S5a).

[0052] Next, the fourth solution is concentrated while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution (step S6). Next, the fourth precipitate is separated from the solution (fifth solution) (step S6a). In this way, the metal elements in the battery (element metals, alloys, and metal elements in metal compounds) are recovered in the form of metal compounds.

[0053] 1 shows an example of recovering and reusing hydrochloric acid. In this case, after step S6a, sulfuric acid is added to the fifth solution to obtain a precipitate Xa containing calcium sulfate and a solution Ya (step SA). Next, the precipitate Xa is separated from the solution (solution Ya) (step SAa). The solution Ya contains hydrochloric acid. The solution Ya can be reused as the acidic aqueous solution (hydrochloric acid) in step S1.

[0054] As described above, step (7), step (B), step (a), and step (b) may be performed. A flowchart of an example in which step (7) and step (B) are performed is shown in Figure 2.

[0055] Steps 1 to S6a are the same as those shown in FIG. 1. After step S6a, the pH of the fifth solution is adjusted to a range of 9.0 to 11.0 to obtain a fifth precipitate containing a manganese compound and a sixth solution (step S7). The pH adjustment is performed by adding a calcium compound (alkaline agent) to the fifth solution. Next, the fifth precipitate is separated from the solution (sixth solution) (step S7a).

[0056] Next, sulfuric acid is added to the sixth solution to obtain a precipitate Xb containing calcium sulfate and a solution Yb (step SB). Next, the precipitate Xb is separated from the solution (solution Yb) (step SBa). The solution Yb contains hydrochloric acid. The solution Yb is reused as the hydrochloric acid in step S1.

[0057] The relationship between pH and solubility varies depending on the metal compound. Therefore, in the metal element recovery method (M), it is possible to recover a predetermined metal compound by adjusting the pH of a predetermined solution to a predetermined value.

[0058] (Additional Note) The above description discloses the following technology: (Technology 1) A method for recovering metal elements from crushed lithium-ion batteries, comprising the steps of: (1) dissolving the metals in the crushed lithium-ion batteries in an acidic aqueous solution to obtain an acidic first solution in which the metals are dissolved; (2) oxidizing divalent iron ions in the first solution to trivalent iron ions; (3) adjusting the pH of the first solution to a range of 3.0 to 5.0 to obtain a first precipitate containing an iron compound and an aluminum compound and a second solution; (4) adding a sulfiding agent to the second solution and adjusting the pH of the second solution to a range of 4.0 to 5.0 to precipitate copper ions in the second solution as copper sulfide, thereby obtaining a second precipitate containing copper sulfide and a third solution; and (5) adjusting the pH of the third solution to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution. A metal element recovery method comprising step (6) of concentrating the fourth solution while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution. (Technology 2) The metal element recovery method according to Technology 1, wherein a calcium compound is used to adjust the pH in at least one step selected from the group consisting of steps (3), (4), and (5), and further comprising step (A) after step (6) of adding sulfuric acid to the fifth solution to obtain a precipitate Xa containing calcium sulfate and a solution Ya. (Technology 3) The metal element recovery method according to Technology 2, wherein the acidic aqueous solution is hydrochloric acid, and the hydrochloric acid contained in solution Ya is used for the acidic aqueous solution in step (1). (Technology 4) The metal element recovery method according to Technology 1, wherein the crushed material contains manganese, and further comprising step (7) after step (6) of adjusting the pH of the fifth solution to a range of 9.0 to 11.0 to obtain a fifth precipitate and a sixth solution containing a manganese compound.(Technology 5) The metal element recovery method according to Technology 4, wherein a calcium compound is used to adjust the pH in at least one step selected from the group consisting of steps (3), (4), (5), and (7), and further comprising step (B) after step (7) of adding sulfuric acid to the sixth solution to obtain a calcium sulfate-containing precipitate Xb and a solution Yb. (Technology 6) The metal element recovery method according to Technology 5, wherein the acidic aqueous solution is hydrochloric acid, and the hydrochloric acid contained in solution Yb is used for the acidic aqueous solution in step (1). (Technology 7) The metal element recovery method according to any one of Technology 1 to 6, wherein the total number of moles of iron, aluminum, and copper in the crushed material, Mfac, is smaller than the total number of moles of nickel and cobalt, Mnc, in the crushed material. (Technology 8) The metal element recovery method according to any one of Technology 1 to 7, wherein divalent iron ions are oxidized using air oxidation or an aqueous hydrogen peroxide solution in step (2). (Technology 9) The metal element recovery method according to any one of Technologies 1 to 8, wherein in the step (3), at least one selected from the group consisting of calcium hydroxide and calcium carbonate is added to the first solution as an alkaline agent to adjust the pH of the first solution. (Technology 10) The metal element recovery method according to any one of Technologies 1 to 9, wherein the sulfiding agent is at least one selected from the group consisting of sodium hydrogen sulfide, sodium sulfide, and sulfide gas. (Technology 11) The metal element recovery method according to any one of Technologies 1 to 10, further comprising a step (a) of dissolving aluminum in the first precipitate as tetrahydroxide aluminum(III) ions in an alkaline aqueous solution to obtain an aqueous solution containing tetrahydroxide aluminum(III) ions and a seventh precipitate. (Technology 12) The metal element recovery method according to Technology 11, further comprising a step (b) of adding the seventh precipitate to boiling water after the step (a) to obtain an eighth precipitate containing iron.

[0059] The metal element recovery method according to the present disclosure will be described in more detail with reference to the following examples. The present disclosure is not limited to the following examples. In these examples, metal elements were recovered in the form of metal compounds from crushed lithium-ion batteries.

[0060] First, crushed lithium-ion batteries (black mass) were prepared. The crushed lithium-ion batteries contained at least lithium, iron, aluminum, copper, nickel, cobalt, and manganese as metal elements.

[0061] (1) Step (1): 20 g of crushed lithium-ion battery material was immersed in 100 mL of hydrochloric acid (concentration: 20% by mass) for 3 hours. The temperature of the hydrochloric acid was maintained at 85°C. In this way, the metals in the crushed material were dissolved in the hydrochloric acid. Next, carbon, Si-based Li compounds, and the like were separated as solids using a membrane filter. The separated solution was diluted with water to a total volume of 100 mL. In this way, an acidic first solution in which the metals were dissolved was obtained.

[0062] (2) Step (2) Next, air was blown into the first solution (100 mL) for 3 hours or more using an air pump, thereby oxidizing the divalent iron ions in the first solution to trivalent iron ions.

[0063] (3) Step (3) Next, calcium carbonate powder was added to the first solution to adjust the pH of the first solution to 4.6. This resulted in the formation of a first precipitate containing iron hydroxide and aluminum hydroxide in the first solution. The first solution was transformed into the first precipitate and a second solution containing the first precipitate. Next, the first precipitate was separated from the second solution using a membrane filter. The separated solution was diluted with water to a total volume of 100 mL, thereby obtaining 100 mL of the second solution.

[0064] (4) Step (4): Next, calcium carbonate powder was added to the second solution (100 mL) to adjust the pH of the second solution to a range of 4.0 to 5.0, and an aqueous solution of sodium hydrogen sulfide was added to the second solution. As a result, the copper ions in the second solution precipitated as copper sulfide. In this way, the second solution changed into a second precipitate containing copper sulfide and a third solution in which the second precipitate had precipitated. Next, the second precipitate was separated from the third solution using a membrane filter. The separated solution was diluted with water to a total volume of 100 mL, thereby obtaining 100 mL of a third solution.

[0065] (5) Step (5) Next, calcium carbonate powder was added to the third solution (100 mL) to adjust the pH of the third solution to 7.6. As a result, a third precipitate containing nickel hydroxide and cobalt hydroxide was formed in the third solution. The third solution changed into a third precipitate and a fourth solution in which the third precipitate had precipitated. Next, the third precipitate was separated from the fourth solution using a membrane filter. The separated solution was diluted with water to a total volume of 100 mL, thereby obtaining 100 mL of the fourth solution.

[0066] (6) Step (6) Next, the fourth solution (100 mL) was boiled by heating while injecting carbon dioxide gas, and the fourth solution was concentrated until the volume was approximately 20 mL. Heating was performed while stirring the fourth solution using a stirrer. As a result, a fourth precipitate containing a lithium compound (lithium carbonate) was produced in the fourth solution. The fourth solution changed into the fourth precipitate and a fifth solution in which the fourth precipitate had precipitated. Next, the fourth precipitate was separated from the fifth solution using a membrane filter. Because the solubility of lithium carbonate decreases at high temperatures, the fourth precipitate was washed away with water at 90°C or higher. The separated solution was diluted with water to a total volume of 100 mL, thereby obtaining 100 mL of the fifth solution.

[0067] (7) Step (7) Next, a calcium carbonate aqueous solution was added to the fifth solution (100 mL) to adjust the pH of the fifth aqueous solution to 10.8. As a result, a fifth precipitate containing a manganese compound (manganese hydroxide) was formed in the fifth solution. The fifth solution changed into the fifth precipitate and a sixth solution in which the fifth precipitate had precipitated. Next, the fifth precipitate was separated from the sixth solution using a membrane filter. The separated solution was diluted with water to a total volume of 100 mL, thereby obtaining 100 mL of the sixth solution.

[0068] (8) Step (B) Next, sulfuric acid (concentration: 95% by mass) was added to the sixth solution (100 mL), thereby generating a precipitate Xb containing calcium sulfate in the sixth solution. The sixth solution was transformed into a precipitate Xb and a solution Yb containing the precipitate Xb. Next, the precipitate Xb was separated from the solution Yb using a membrane filter. Water was added to the obtained solution Yb to make it approximately 100 mL. In this way, hydrochloric acid with a concentration of 18.1% by mass was obtained. The obtained hydrochloric acid can be reused.

[0069] The contents of metal elements in the above solutions were analyzed by ICP atomic emission spectroscopy. The analysis results are shown in Table 1. The values ​​in Table 1 indicate relative values ​​when the content of each metal element in the first solution is set to 100. For example, the content of iron (Fe) in the second solution was 0.06% of the iron content in the first solution. In Table 1, "-" indicates that the amount was below the detection limit.

[0070]

[0071] As shown in Table 1, each treatment resulted in the separation of specific metals. One of the reasons for the decrease in the content of other metals during the separation of specific metal compounds is coprecipitation. To prevent this, it is important to set the pH within the above-mentioned range.

[0072] The present disclosure can be used for a metal element recovery method for recovering metal elements from crushed lithium-ion batteries. Although the present invention has been described with reference to presently preferred embodiments, such disclosure should not be construed as limiting. Various modifications and variations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Therefore, the appended claims should be construed to cover all modifications and variations that do not depart from the true spirit and scope of the present invention.

Claims

1. A method for recovering metal elements from crushed lithium-ion batteries, comprising the steps of: (1) dissolving the metals in the crushed lithium-ion batteries in an acidic aqueous solution to obtain an acidic first solution in which the metals are dissolved; (2) oxidizing divalent iron ions in the first solution to trivalent iron ions; (3) adjusting the pH of the first solution to a range of 3.0 to 5.0 to obtain a first precipitate containing iron compounds and aluminum compounds and a second solution; (4) adding a sulfiding agent to the second solution and adjusting the pH of the second solution to a range of 4.0 to 5.0 to precipitate copper ions in the second solution as copper sulfide, thereby obtaining a second precipitate containing copper sulfide and a third solution; and (5) adjusting the pH of the third solution to a range of 7.0 to 8.5 to obtain a third precipitate containing nickel hydroxide and cobalt hydroxide and a fourth solution. and (6) concentrating the fourth solution while injecting carbon dioxide gas to obtain a fourth precipitate containing a lithium compound and a fifth solution.

2. The method for recovering metal elements according to claim 1, wherein a calcium compound is used to adjust the pH in at least one step selected from the group consisting of steps (3), (4), and (5), and further comprising, after step (6), step (A) of adding sulfuric acid to the fifth solution to obtain a precipitate Xa containing calcium sulfate and a solution Ya.

3. The metal element recovery method according to claim 2, wherein the acidic aqueous solution is hydrochloric acid, and the hydrochloric acid contained in the solution Ya is used for the acidic aqueous solution in step (1).

4. The metal element recovery method according to claim 1, wherein the crushed material contains manganese, and further comprising, after step (6), a step (7) of adjusting the pH of the fifth solution to a range of 9.0 to 11.0 to obtain a fifth precipitate and a sixth solution containing a manganese compound.

5. The method for recovering metal elements according to claim 4, wherein a calcium compound is used to adjust the pH in at least one step selected from the group consisting of steps (3), (4), (5), and (7), and further comprising, after step (7), step (B) of adding sulfuric acid to the sixth solution to obtain a precipitate Xb containing calcium sulfate and a solution Yb.

6. The method for recovering metal elements according to claim 5, wherein the acidic aqueous solution is hydrochloric acid, and the hydrochloric acid contained in the solution Yb is used for the acidic aqueous solution in step (1).

7. A method for recovering metal elements according to any one of claims 1 to 6, wherein the total number of moles of iron, aluminum, and copper in the crushed material, Mfac, is smaller than the total number of moles of nickel and cobalt in the crushed material, Mnc.

8. A method for recovering metal elements according to any one of claims 1 to 6, wherein in step (2), the divalent iron ions are oxidized by air oxidation or using an aqueous hydrogen peroxide solution.

9. The method for recovering metal elements according to any one of claims 1 to 6, wherein in step (3), the pH of the first solution is adjusted by adding at least one alkaline agent selected from the group consisting of calcium hydroxide and calcium carbonate to the first solution.

10. A method for recovering metal elements according to any one of claims 1 to 6, wherein the sulfiding agent is at least one selected from the group consisting of sodium hydrogen sulfide, sodium sulfide, and sulfide gas.

11. The method for recovering metal elements according to any one of claims 1 to 6, further comprising a step (a) of dissolving aluminum in the first precipitate as tetrahydroxide aluminate (III) ions in an alkaline aqueous solution, thereby obtaining an aqueous solution containing tetrahydroxide aluminate (III) ions and a seventh precipitate.

12. The method for recovering metal elements according to claim 11, further comprising, after step (a), step (b) of adding the seventh precipitate to boiling water to obtain an eighth precipitate containing iron.

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