Disposal methods for lithium-ion secondary batteries

Abstract

To provide a treatment method of a lithium ion secondary battery capable of recovering lithium contained in the lithium ion secondary battery at good efficiency and high purity.SOLUTION: There is provided a treatment method of a lithium ion secondary battery, including: a pulverization and classification step of pulverizing and classifying a lithium ion secondary battery to obtain an electrode material containing at least lithium; a leaching step of immersing the electrode material in an acid to obtain a leachate; a pH adjustment step of adding lithium hydroxide to the leachate to adjust the pH; a metal recovery step of recovering metals other than lithium in the leachate to obtain a lithium-containing liquid; and a lithium hydroxide recovery step of recovering lithium in the lithium-containing liquid as lithium hydroxide, wherein the lithium hydroxide recovered in the lithium hydroxide recovery step is used in the pH adjustment step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for processing lithium-ion secondary batteries. [Background technology]

[0002] Lithium-ion rechargeable batteries use valuable metals such as lithium, copper, aluminum, cobalt, nickel, manganese, and iron. Therefore, efforts are being made to recover these valuable metals from discarded lithium-ion rechargeable batteries and reuse them.

[0003] A known method for recovering valuable metals from lithium-ion secondary batteries involves immersing the electrodes of the lithium-ion secondary battery in acid to obtain a leachate, and then recovering the metals from the resulting leachate. Methods for recovering metals from the leachate include adjusting the pH of the leachate to precipitate metal ions, followed by solid-liquid separation of the precipitated metals, and solvent extraction. Alkalis such as sodium hydroxide, sodium carbonate, and ammonia are used as pH adjusting agents to adjust the pH of the leachate (Patent Document 1). As a method for recovering lithium ions from a leachate containing sodium ions (due to pH adjusting agents, etc.) and lithium ions, a method is being investigated in which a solvent containing lithium ions and sodium ions is scrubbed with a lithium solution, and then the lithium ions are back-extracted (Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-40035 [Patent Document 2] Japanese Patent Publication No. 2020-164969 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Sodium hydroxide and sodium carbonate are useful as pH adjusters for leachate because they are odorless and easy to handle. However, in order to recover lithium in high purity, it is necessary to separate the sodium, as described in Patent Document 2, which reduces efficiency.

[0006] This invention has been made in view of the circumstances described above, and aims to provide a method for processing lithium-ion secondary batteries that can efficiently recover lithium contained in lithium-ion secondary batteries with high purity. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a lithium-ion secondary battery processing method comprising: a crushing and sorting step of crushing and classifying a lithium-ion secondary battery to obtain an electrode material containing at least lithium; a leaching step of immersing the electrode material in acid to obtain a leaching solution; a pH adjustment step of adding lithium hydroxide to the leaching solution to adjust the pH; a metal recovery step of recovering metals other than lithium in the leaching solution to obtain a lithium-containing solution; and a lithium hydroxide recovery step of recovering lithium in the lithium-containing solution as lithium hydroxide. The acid is one selected from sulfuric acid, hydrochloric acid, or nitric acid. The lithium hydroxide recovery step is as follows: The process further comprises the steps of: supplying the lithium-containing liquid to a desalination chamber, generating an acid-containing solution and a lithium hydroxide-containing solution by electrodialysis, thereby recovering lithium from the lithium-containing liquid as lithium hydroxide and recovering the acid; in the lithium hydroxide recovery step, evaporating and concentrating the delithiation-treated water discharged from the desalination chamber to obtain a concentrated solution, and combining the obtained concentrated solution with the lithium-containing liquid; and purifying and removing cations other than lithium ions and anions other than sulfate ions if the acid is sulfuric acid, anions other than chloride ions if the acid is hydrochloric acid, and anions other than nitrate ions if the acid is nitric acid, from the liquid containing the concentrated solution that has been combined with the lithium-containing liquid. The lithium hydroxide recovered in the lithium hydroxide recovery step is used in the pH adjustment step And in both the metal recovery process, as a pH adjuster (alkali) Use, The acid recovered in the lithium hydroxide recovery step is used in the leaching step and also as a pH adjuster (acid) in the metal recovery step. It is characterized by the following.

[0008] According to the lithium-ion secondary battery processing method of the present invention, since lithium hydroxide is used as a pH adjusting agent (alkali) in the pH adjustment step, the lithium-containing liquid obtained in the metal recovery step substantially contains no sodium. Therefore, in the lithium hydroxide recovery step, when recovering lithium as lithium hydroxide from the lithium-containing liquid, the sodium removal step is unnecessary, making lithium recovery easier and improving work efficiency. In addition, since the sodium removal step is unnecessary, no wastewater discharged with sodium is generated, reducing the burden on wastewater treatment. Furthermore, since the lithium hydroxide recovered in the lithium hydroxide recovery step is used as a pH adjusting agent (alkali) in the pH adjustment step, the need to prepare alkali separately is reduced, further improving work efficiency and reducing chemical costs. It should be noted that in the metal recovery step, it is not necessary to recover all metals other than lithium; it is sufficient to reduce the content of other metals to a level that does not significantly affect the recovery of lithium and other metals in the lithium hydroxide recovery step.

[0009] In the lithium-ion secondary battery processing method of the present invention, the lithium-containing liquid may be separated and recovered in the lithium hydroxide recovery step into a solution containing lithium hydroxide and a solution containing acid using electrodialysis, and the acid recovered in the lithium hydroxide recovery step may be used in the leaching step. In this case, since the acid recovered in the lithium hydroxide recovery process is used in the leaching process, work efficiency is further increased and chemical costs are further reduced. In addition, by recovering the acid in the lithium-containing solution in the lithium hydroxide recovery process, the amount of wastewater discharged along with the acid is reduced, further reducing the burden on wastewater treatment.

[0010] Furthermore, in the lithium-ion secondary battery processing method of the present invention, the acid may be sulfuric acid. In this case, since sulfuric acid is used as the acid, nickel and cobalt contained in the electrode material can be recovered as sulfates. Since sulfates such as nickel sulfate and cobalt sulfate are used as the battery electrode material, the recycling of nickel and cobalt is facilitated by recovering nickel and cobalt as sulfates.

Advantages of the Invention

[0011] According to the present invention, it becomes possible to provide a method for treating a lithium-ion secondary battery that can efficiently recover lithium contained in the lithium-ion secondary battery with high purity.

Brief Description of the Drawings

[0012] [Figure 1] It is a flowchart showing a method for treating a lithium-ion secondary battery according to an embodiment of the present invention. [Figure 2] It is a block diagram showing an example of a lithium recovery device that can be used in the method for treating a lithium-ion secondary battery according to an embodiment of the present invention. [Figure 3] It is a schematic cross-sectional view showing another example of an electrodialysis device that can be used in the lithium recovery device shown in FIG. 2. [Figure 4] It is a schematic cross-sectional view showing yet another example of an electrodialysis device that can be used in the lithium recovery device shown in FIG. 2. [Figure 5] It is a schematic cross-sectional view showing yet another example of an electrodialysis device that can be used in the lithium recovery device shown in FIG. 2.

Modes for Carrying Out the Invention

[0013] Hereinafter, a method for treating a lithium-ion secondary battery according to an embodiment of the present invention will be described with reference to the drawings. Note that each of the embodiments shown below is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0014] FIG. 1 is a flowchart showing a method for treating a lithium-ion secondary battery according to an embodiment of the present invention. As shown in FIG. 1, the method for treating a lithium-ion secondary battery of this embodiment includes a heat treatment step S01, a pulverization and separation step S02, a leaching step S03, a pH adjustment step S04, a metal recovery step S05, and a lithium hydroxide recovery step S06.

[0015] (Heat treatment step S01) In the heat treatment step S01, a discarded lithium-ion secondary battery (hereinafter referred to as a waste LIB) is heat treated. The heat treatment temperature is, for example, within the range of 400°C or higher and 660°C or lower. The heat treatment may be vacuum heating or atmospheric pressure heating. Due to the presence of the binder, the adhesion between the positive electrode active material and the negative electrode active material and the current collectors, which are aluminum foil and copper foil, is strong in the waste LIB. Therefore, by performing the heat treatment step, the separation of these active materials and the current collectors can be facilitated. Further, by performing the heat treatment step, combustible substances such as the separator and the organic solvent contained in the electrolyte of the lithium secondary battery can be thermally decomposed and removed.

[0016] (Pulverization and separation step S02) In the pulverization and separation step S02, the waste LIB heat treated in the heat treatment step S01 is pulverized and classified to obtain an electrode material containing lithium. The pulverization of the waste LIB can be performed, for example, using a shear crusher such as a twin-shaft crusher or an impact crusher such as a hammer mill alone or in combination of two or more types. The classification of the pulverized waste LIB can be performed, for example, using a sieve. By using a sieve, coarse crushed materials including the battery exterior material, the metal tab terminal, the positive electrode current collector, and the negative electrode current collector can be recovered as the oversize product on the sieve, and the electrode material can be recovered as the undersize product on the sieve. The electrode material mainly consists of the positive electrode active material and the negative electrode active material, but also contains a small amount of fine powder of the residue of the electrolyte and over-pulverized coarse crushed materials.

[0017] (Leaching step S03) In the leaching process S03, the electrode material (black mass) obtained in the crushing and sorting process S02 is immersed in acid to obtain a leached solution. As the acid, for example, mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid can be used. In this embodiment, sulfuric acid is used as the acid. In this embodiment, the electrode material and sulfuric acid are mixed, and the resulting mixture is stirred for 1 to 3 hours while adjusting the temperature to 50 to 80°C to dissolve the metal in the electrode material and obtain a leached solution. Furthermore, the leaching can be accelerated by introducing hydrogen peroxide or dissolved oxygen during the leaching process.

[0018] There are no particular restrictions on the pH of the leachate, but for example, it should be 2 or less. The metals contained in the leachate vary depending on the materials used in the waste lithium-ion battery (LIB), but for example, they may be lithium, cobalt, nickel, manganese, iron, aluminum, or copper. Lithium is found, for example, in the positive electrode active material, negative electrode active material, and electrolyte residue of the waste LIB. Cobalt, nickel, and manganese are found, for example, in the positive electrode active material of the waste LIB. Aluminum is found, for example, in the positive electrode current collector of the waste LIB. Copper is found, for example, in the negative electrode current collector of the waste LIB. Iron is found, for example, in the battery casing material of the waste LIB.

[0019] If the leachate contains insoluble matter, it is preferable to remove it. Methods for removing insoluble matter include solid-liquid separation methods such as decantation, pressure filtration, and centrifugation. Insoluble matter is, for example, carbon material. Carbon material is found, for example, in the positive electrode active material and negative electrode active material of waste lithium-ion batteries (LIBs).

[0020] (pH adjustment step S04) In the pH adjustment step S04, lithium hydroxide is added to the leachate obtained in the leaching step S03 to adjust the pH. The pH of the leaachate is adjusted, for example, by adding lithium hydroxide to the leaachate while stirring it. The pH of the leaachate is adjusted to a range of, for example, 3.0 to 6.0, preferably 4.0 to 5.0. As a result, aluminum in the leaachate precipitates as aluminum hydroxide, and iron precipitates as iron hydroxide.

[0021] (Metal recovery process S05) In the metal recovery step S05, metals other than lithium are recovered from the leachate to obtain a lithium-containing solution (lithium sulfate-containing solution). First, the precipitates (aluminum hydroxide, iron hydroxide) that precipitated in the pH adjustment step S04 are recovered. As a method for recovering the precipitates, solid-liquid separation methods such as decantation, pressure filtration, and centrifugation can be used.

[0022] Next, cobalt, nickel, manganese, and copper are recovered from the leachate. These metals can be selectively recovered by solvent extraction. There are no particular limitations on the method of recovering the above metals by solvent extraction, and known methods can be used. For example, manganese and copper may be recovered first, then cobalt, and finally nickel. When recovering the above metals by solvent extraction, lithium hydroxide (alkali) and sulfuric acid (acid) can be used to adjust the pH of the leachate.

[0023] Manganese and copper can be recovered by solvent extraction by stirring and mixing the leachate and the extraction solvent, extracting the manganese and copper from the leachate into the extraction solvent, then separating the leachate and the extraction solvent by standing, and finally separating the extraction solvent. The manganese and copper in the extraction solvent can be recovered by washing the extraction solvent, stirring and mixing the extraction solvent with an aqueous sulfuric acid solution, and then back-extracting the manganese and copper into the aqueous sulfuric acid solution. A mixed solvent containing a phosphate ester extractant and an oxime extractant can be used as the extraction solvent. Using this mixed solvent allows for the simultaneous recovery of iron and aluminum remaining in the leachate.

[0024] Cobalt can be recovered by solvent extraction by stirring and mixing the leachate and the extraction solvent, extracting the cobalt from the leachate into the extraction solvent, then separating the leachate and the extraction solvent by standing, and finally separating the extraction solvent. The cobalt in the extraction solvent can be recovered by washing the extraction solvent, stirring and mixing the extraction solvent with an aqueous sulfuric acid solution, and back-extracting the cobalt in the extraction solvent into the aqueous sulfuric acid solution. As the extraction solvent, for example, a phosphate ester extractant such as PC-88A can be used. When recovering cobalt from a leachate containing cobalt and nickel using PC-88A, the pH of the leachate is adjusted to, for example, within the range of 2 to 5 to extract the cobalt and some nickel, and then the nickel is washed off from the extraction solvent with a dilute acid.

[0025] Nickel can be recovered by solvent extraction by stirring and mixing the leachate and the extraction solvent, extracting the nickel from the leachate into the extraction solvent, then separating the leachate and the extraction solvent by standing, and finally separating the extraction solvent. Nickel in the extraction solvent can be recovered by washing the extraction solvent, stirring and mixing the extraction solvent with an aqueous sulfuric acid solution, and back-extracting the nickel in the extraction solvent into the aqueous sulfuric acid solution. As the extraction solvent, for example, a phosphate ester extractant such as PC-88A can be used. When recovering nickel using PC-88A, the pH of the leachate should be adjusted to, for example, within the range of 4 to 7. If the leachate contains cobalt, the method described above for recovering cobalt by solvent extraction should be carried out, and nickel should be recovered by solvent extraction of the leachate after cobalt extraction.

[0026] (Lithium hydroxide recovery process S06) In the lithium hydroxide recovery step S06, lithium is recovered as lithium hydroxide from the lithium-containing solution (lithium sulfate-containing solution) obtained in the metal recovery step S05, and sulfuric acid is also recovered. The recovered lithium hydroxide is used as a pH adjusting agent (alkali) in the pH adjustment step S04 and the metal recovery step S05. The recovered sulfuric acid is used as an acid in the leaching step S03 and as a pH adjusting agent (acid) in the metal recovery step S05. Electrodialysis can be used as a method to recover lithium as lithium hydroxide and sulfuric acid from the lithium sulfate-containing solution.

[0027] Figure 2 is a block diagram showing an example of a lithium recovery device that can be used in a lithium-ion secondary battery processing method according to one embodiment of the present invention. As shown in Figure 2, the lithium recovery apparatus 1 includes an electrodialysis apparatus 10. The lithium recovery apparatus 1 further includes a purification apparatus 20, a lithium sulfate circulation tank 30, a sulfuric acid circulation tank 40, a lithium hydroxide circulation tank 50, an evaporator 60, and a condenser 70.

[0028] The electrodialysis apparatus 10 includes a container 11, an anode 12 and a cathode 13 placed inside the container 11, and an anion exchange membrane A1 and a cation exchange membrane C1 placed between the anode 12 and the cathode 13. The anion exchange membrane A1 is located on the anode 12 side, and the cation exchange membrane C1 is located on the cathode 13 side. The anode 12 and the anion exchange membrane A1 form an anode chamber AE, the anion exchange membrane A1 and the cation exchange membrane C1 form a desalination chamber D, and the cathode 13 and the cation exchange membrane C1 form a cathode chamber CE. The lithium sulfate-containing solution is supplied to the desalination chamber D. When a voltage is applied between the anode 12 and the cathode 13, lithium ions (Li) in the desalination chamber D are released. + ) moves through the cation exchange membrane C1 to the cathode chamber CE, where sulfate ions (SO4 2- ) moves through the anion exchange membrane A1 to the anode chamber AE. At anode 12, hydrogen ions (H + ) is generated, and sulfuric acid concentrate is formed in the anode chamber AE. Hydroxide ions (OH-) are generated at cathode 13, and lithium hydroxide concentrate is formed in the cathode chamber CE.

[0029] The delithiumated water, from which lithium has been removed in the desalination chamber D, is sent to the evaporator 60 or the lithium sulfate circulation tank 30. In the evaporator 60, the delithiumated water is heated and concentrated by the evaporation of water. The resulting concentrate, along with the lithium sulfate-containing liquid, is sent to the purification unit 20. Meanwhile, the evaporated water (water vapor) is sent to the condenser 70 where it is liquefied.

[0030] The purification apparatus 20 removes cations other than lithium ions and anions other than sulfate ions contained in the lithium sulfate-containing mixture, which is a mixture of lithium sulfate-containing liquid and concentrated liquid, by ion exchange or solvent extraction. As a method for removing cations by ion exchange, for example, a method can be used in which the lithium sulfate-containing mixture is brought into contact with a lithium-substituted cation exchange resin or a chelate resin that forms a chelate with lithium. Similarly, as a method for removing anions by ion exchange, for example, a method can be used in which the lithium sulfate-containing mixture is brought into contact with an anion exchange resin substituted with sulfuric acid or a chelate resin that forms a chelate with sulfuric acid. The lithium sulfate-containing mixture purified in the purification apparatus 20 is sent to the lithium sulfate circulation tank 30.

[0031] The lithium sulfate-containing mixture sent to the lithium sulfate circulation tank 30 is temporarily stored in the lithium sulfate circulation tank 30 before being sent to the desalination chamber D of the electrodialysis machine 10. The lithium sulfate concentration in the lithium sulfate-containing mixture is preferably within the range of 1% by mass to 20% by mass. If the concentration of the lithium sulfate-containing mixture sent from the purification device 20 is high, it is diluted with delithiated water. If the lithium sulfate concentration in the lithium sulfate-containing mixture is less than 1% by mass, the voltage during electrolysis will be high, making proper operation difficult, and if it is greater than 20% by mass, the concentration will be close to the solubility of lithium sulfate, making handling difficult.

[0032] A portion of the sulfuric acid concentrate generated in the anode chamber AE is removed and used as an acid in the leaching process or as a pH adjuster (acid) in the metal recovery process. The remaining sulfuric acid concentrate is sent to the sulfuric acid circulation tank 40. Water is also supplied to the sulfuric acid circulation tank 40. The water used can be water liquefied in the condenser 70.

[0033] The sulfuric acid concentrate and water sent to the sulfuric acid circulation tank 40 are mixed within the sulfuric acid circulation tank 40, temporarily stored as sulfuric acid diluent, and then sent to the anode chamber AE of the electrodialysis machine 10. The sulfuric acid concentration of the sulfuric acid diluent is preferably 1% by mass or higher. If the sulfuric acid concentration of the sulfuric acid diluent is less than 1% by mass, the voltage during electrolysis will increase, making proper operation difficult.

[0034] A portion of the lithium hydroxide concentrate produced in the cathode chamber CE is removed and used as a pH adjuster (alkali) in the pH adjustment process or the metal recovery process. Another portion of the removed lithium hydroxide concentrate is used as lithium hydroxide (product). The remaining lithium hydroxide concentrate is sent to the lithium hydroxide circulation tank 50. Water is also supplied to the lithium hydroxide circulation tank 50. The water used can be water liquefied in the condenser 70.

[0035] The lithium hydroxide concentrate and water sent to the lithium hydroxide circulation tank 50 are mixed within the lithium hydroxide circulation tank 50 and, after being temporarily stored as lithium hydroxide diluent, are sent to the cathode chamber CE of the electrodialysis machine 10. The lithium hydroxide concentration of the lithium hydroxide diluent is preferably within the range of 1% by mass or more and 10% by mass or less. If the lithium hydroxide concentration of the lithium hydroxide diluent is less than 1% by mass, the voltage during electrolysis will be high, which may make proper operation difficult, and if it is greater than 20% by mass, lithium ions may have difficulty moving from the desalination chamber D to the cathode chamber CE.

[0036] The operating conditions of the electrodialysis device 10 vary depending on conditions such as the size of the device and the lithium sulfate concentration in the lithium sulfate-containing mixed solution. For example, the applied voltage between the anode 12 and the cathode 13 is within the range of 1 V or more and 3 V or less, and the current density is 0.3 mA / dm 2 or more and 50 mA / dm 2 or less, preferably within the range of 1 mA / dm 2 or more and 20 mA / dm 2 or less. The liquid temperatures of the lithium sulfate-containing mixed solution, the sulfuric acid dilution solution, and the lithium hydroxide dilution solution of the electrodialysis device 10 are, for example, 100°C or less, preferably 30°C or more and 60°C or less. Further, the concentrations and flow rates of the lithium sulfate-containing mixed solution, the sulfuric acid dilution solution, and the lithium hydroxide dilution solution are adjusted so that the production rate of lithium hydroxide is 140 g / m 2 (effective area of the ion exchange membrane) / hour or more and 900 g / m 2 (effective area of the ion exchange membrane) / hour or less. Note that the effective area of the ion exchange membrane is the area of the portion where the anion exchange membrane and the cation exchange membrane face each other.

[0037] In the lithium recovery device 1 shown in FIG. 2, the electrodialysis device 10 is configured such that one anion exchange membrane A1 and one cation exchange membrane C1 are respectively arranged between the anode 12 and the cathode 13, but the configuration of the electrodialysis device 10 is not limited thereto. For example, a configuration in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged may be used, or a configuration in which a plurality of anion exchange membranes, cation exchange membranes, and bipolar membranes are arranged in this order may be used. Examples of the electrodialysis device 10 are shown in FIGS. 3 to 5.

[0038] The electrodialysis apparatus 10a shown in Figure 3 has cation exchange membranes C21 and C22 and anion exchange membranes A21 and A22 alternately arranged between the anode 12 and the cathode 13. Cation exchange membrane C21 is located at the end on the anode 12 side, and anion exchange membrane A22 is located at the end on the cathode 13 side. The anode 12 and cation exchange membrane C21 form the anode chamber AE, cation exchange membrane C21 and anion exchange membrane A21 form the sulfuric acid concentration chamber AC, anion exchange membrane A21 and cation exchange membrane C22 form the desalination chamber D, cation exchange membrane C22 and anion exchange membrane A22 form the lithium concentration chamber CC, and anion exchange membrane A22 and cathode 13 form the cathode chamber CE. Water is supplied to the anode chamber AE and the cathode chamber CE. The desalination chamber D is connected to a lithium sulfate circulation tank 30, and a lithium sulfate-containing mixed solution is supplied to it. The sulfuric acid concentration chamber AC is connected to the sulfuric acid circulation tank 40 and is supplied with sulfuric acid diluent. The lithium concentration chamber CC is connected to the lithium hydroxide circulation tank 50 and is supplied with lithium hydroxide diluent.

[0039] When a voltage is applied between the anode 12 and cathode 13 of the electrodialysis machine 10a, lithium ions in the desalination chamber D move to the lithium concentration chamber CC through the cation exchange membrane C22, and sulfate ions move to the sulfuric acid concentration chamber AC through the anion exchange membrane A21. Hydrogen ions in the anode chamber AE move to the sulfuric acid concentration chamber AC through the cation exchange membrane C21. Hydroxide ions in the cathode chamber CE move to the lithium concentration chamber CC through the anion exchange membrane A22. As a result, sulfuric acid concentrate is produced in sulfuric acid concentration chamber AC. Additionally, lithium hydroxide concentrate is produced in lithium concentration chamber CC.

[0040] In the electrodialysis apparatus 10b shown in Figure 4, cation exchange membranes C31-C36 and anion exchange membranes A31-A36 are alternately arranged between the anode 12 and the cathode 13. Cation exchange membrane C31 is located at the end of the anode 12, and anion exchange membrane A36 is located at the end on the cathode 13 side. The anode 12 and cation exchange membrane C31 form the anode chamber AE. Sulfuric acid concentration chambers AC are formed between cation exchange membrane C31 and anion exchange membrane A31, between cation exchange membrane C33 and anion exchange membrane A33, and between cation exchange membrane C35 and anion exchange membrane A35. Desalination chambers D are formed between anion exchange membrane A31 and cation exchange membrane C32, between anion exchange membrane A33 and cation exchange membrane C34, and between anion exchange membrane A35 and cation exchange membrane C36. A lithium concentration chamber CC is formed between the cation exchange membrane C32 and the anion exchange membrane A32, between the cation exchange membrane C34 and the anion exchange membrane A34, and between the cation exchange membrane C36 and the anion exchange membrane A36. A water electrolysis chamber WE is formed between the anion exchange membrane A32 and the cation exchange membrane C33, and between the anion exchange membrane A34 and the cation exchange membrane C35. A cathode chamber CE is formed between the anion exchange membrane A36 and the cathode 13. Water is supplied to the anode chamber AE, the cathode chamber CE, and the water electrolysis chamber WE. The desalination chamber D is connected to the lithium sulfate circulation tank 30 and supplied with a lithium sulfate-containing mixed solution. The sulfuric acid concentration chamber AC is connected to the sulfuric acid circulation tank 40 and supplied with a sulfuric acid diluent. The lithium concentration chamber CC is connected to the lithium hydroxide circulation tank 50 and supplied with a lithium hydroxide diluent.

[0041] When a voltage is applied between the anode 12 and cathode 13 of the electrodialysis machine 10b, lithium ions in the desalination chamber D move to the lithium concentration chamber CC through cation exchange membranes C32, C34, and C36, and sulfate ions move to the sulfuric acid concentration chamber AC through anion exchange membranes A31, A33, and A35. Hydrogen ions in the anode chamber AE move to the sulfuric acid concentration chamber AC through cation exchange membrane C31. Hydroxide ions in the cathode chamber CE move to the lithium concentration chamber CC through anion exchange membrane A36. Hydrogen ions in the water electrolysis chamber WE move to the sulfuric acid concentration chamber AC through cation exchange membranes C33 and C35, and hydroxide ions move to the lithium concentration chamber CC through anion exchange membranes A32 and A34. As a result, sulfuric acid concentrate is produced in the sulfuric acid concentration chamber AC. In addition, lithium hydroxide concentrate is produced in the lithium concentration chamber CC.

[0042] In the electrodialysis apparatus 10c shown in Figure 5, bipolar membranes B41-B43, cation exchange membranes C41-C43, and anion exchange membranes A41-A43 are arranged between the anode 12 and the cathode 13 in the order of bipolar membrane, cation exchange membrane, and anion exchange membrane, respectively, from the anode 12. A bipolar membrane B44 is positioned between the anion exchange membrane A43 at the cathode 13 end and the cathode 13. Sulfuric acid concentration chambers AC are formed between bipolar membrane B41 and anion exchange membrane A31, between bipolar membrane B42 and anion exchange membrane A42, and between bipolar membrane B43 and anion exchange membrane A43. Desalination chambers D are formed between anion exchange membrane A41 and cation exchange membrane C41, between anion exchange membrane A42 and cation exchange membrane C42, and between anion exchange membrane A43 and cation exchange membrane C43. A lithium concentration chamber CC is formed between the cation exchange membrane C41 and the bipolar membrane B42, between the cation exchange membrane C42 and the bipolar membrane B43, and between the cation exchange membrane C43 and the bipolar membrane B44. A cathode chamber CE is formed between the bipolar membrane B44 and the cathode 13. Water is supplied to the anode chamber AE and the cathode chamber CE. The desalination chamber D is connected to the lithium sulfate circulation tank 30 and supplied with a lithium sulfate-containing mixed solution. The sulfuric acid concentration chamber AC is connected to the sulfuric acid circulation tank 40 and supplied with a sulfuric acid diluent. The lithium concentration chamber CC is connected to the lithium hydroxide circulation tank 50 and supplied with a lithium hydroxide diluent.

[0043] When a voltage is applied between the anode 12 and cathode 13 of the electrodialysis machine 10c, lithium ions in the desalination chamber D move to the lithium concentration chamber CC through the cation exchange membranes C41-C43, and sulfate ions move to the sulfuric acid concentration chamber AC through the anion exchange membranes A41-A43. Hydrogen ions generated in the bipolar membranes B41-B43 move to the sulfuric acid concentration chamber AC, and hydroxide ions generated in the bipolar membranes B42-B44 move to the lithium concentration chamber CC. As a result, sulfuric acid concentrate is generated in the sulfuric acid concentration chamber AC. In addition, lithium hydroxide concentrate is generated in the lithium concentration chamber CC.

[0044] All of the above electrodialysis machines 10a to 10c can be advantageously used as electrodialysis machines for the lithium recovery device 1.

[0045] In the lithium-ion secondary battery processing method of this embodiment, configured as described above, lithium hydroxide is used as the pH adjusting agent (alkali) in the pH adjustment step S04, so the lithium-containing liquid obtained in the metal recovery step S05 is substantially sodium-free. Therefore, in the lithium hydroxide recovery step, when recovering lithium from the lithium-containing liquid as lithium hydroxide, the sodium removal step is unnecessary, making lithium recovery easier and improving work efficiency. Also, since the sodium removal step is unnecessary, no wastewater discharged with sodium is generated, reducing the burden on wastewater treatment. Furthermore, since the lithium hydroxide recovered in the lithium hydroxide recovery step S06 is used as the pH adjusting agent (alkali) in the pH adjustment step S04, the need to prepare alkali separately is reduced, further improving work efficiency and reducing chemical costs. Note that in the metal recovery step S05, it is not necessary to recover all metals other than lithium; it is sufficient to reduce the content of other metals to an extent that does not significantly affect the recovery of lithium and sulfuric acid in the lithium hydroxide recovery step S06.

[0046] Furthermore, in the lithium-ion secondary battery processing method of this embodiment, in the lithium hydroxide recovery step S06, the lithium-containing liquid is separated and recovered into a solution containing lithium hydroxide and a solution containing sulfuric acid using electrodialysis, and the sulfuric acid recovered in the lithium hydroxide recovery step S06 is used in the leaching step S03, thus further increasing work efficiency and further reducing chemical costs. In addition, by recovering the sulfuric acid in the lithium sulfate-containing liquid in the lithium hydroxide recovery step S06, the amount of wastewater discharged along with the sulfuric acid is reduced, further reducing the burden on wastewater treatment.

[0047] Furthermore, in the lithium-ion secondary battery processing method of this embodiment, sulfuric acid is used as the acid, so nickel and cobalt contained in the electrode material can be recovered as sulfates. Since sulfates such as nickel sulfate and cobalt sulfate are used as battery electrode materials, recovering nickel and cobalt as sulfates makes it easier to recycle nickel and cobalt.

[0048] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0049] For example, in the lithium-ion secondary battery processing method of this embodiment, a heat treatment step S01 is performed before the crushing and sorting step S02, but the heat treatment step S01 may be omitted. However, in this case, separators may be mixed into the electrode material obtained in the crushing and sorting step S02. If separators are mixed into the electrode material, it is preferable to remove the separators after the electrode material has been converted into a leachate in the leaching step S03.

[0050] Furthermore, in the lithium-ion secondary battery processing method of this embodiment, sulfuric acid is used in the leaching step S03, but hydrochloric acid or nitric acid may be used instead of sulfuric acid. When hydrochloric acid is used, chloride ions are recovered instead of sulfate ions in the lithium hydroxide recovery step S06. When nitric acid is used, nitrate ions are recovered instead of sulfate ions in the lithium hydroxide recovery step S06.

[0051] Furthermore, in the lithium-ion secondary battery processing method of this embodiment, electrodialysis is used as the lithium recovery method in the lithium hydroxide recovery step S06, but the lithium recovery method is not limited to this. As a lithium recovery method, a method may be used in which lithium is recovered as lithium carbonate and a lithium hydroxide solution is prepared using the obtained lithium carbonate. As a method for recovering lithium as lithium carbonate, a method can be used in which impurities are removed from the lithium-containing solution and purified, then a carbonate such as sodium carbonate or sodium bicarbonate, or carbon dioxide is added to the lithium-containing solution to precipitate lithium carbonate, and the precipitated lithium carbonate is recovered. At this time, sodium hydroxide can be added to adjust the pH in order to promote the formation of lithium carbonate. As a method for purifying the lithium-containing solution, ion exchange or solvent extraction can be used. As a method for precipitating lithium carbonate, if the lithium-containing solution is a lithium sulfate-containing solution, for example, a method of reacting lithium sulfate with sodium carbonate (Li2SO4 + Na2CO3 → Li2CO3↓ + Na2SO4) can be used. As a method for recovering the precipitated lithium carbonate, solid-liquid separation methods such as decantation, pressure filtration, and centrifugation can be used.

[0052] For example, the following method can be used to prepare a lithium hydroxide solution using lithium carbonate. First, water and lithium carbonate are mixed to obtain a lithium carbonate solution. Next, calcium hydroxide (slaked lime) is added to the lithium carbonate solution, and the lithium carbonate and calcium hydroxide react (Li2CO3 + Ca(OH)2 → 2LiOH + CaCO3↓) to produce lithium hydroxide and precipitate calcium carbonate. Then, the calcium carbonate is removed from the lithium hydroxide solution by solid-liquid separation. [Explanation of Symbols]

[0053] 1. Lithium recovery device 10, 10a, 10b, 10c Electrodialysis machine 11 Container 12 Anodes 13 Cathode 20 Purification equipment 30. Lithium sulfate circulation tank 40 Sulfuric acid circulation tank 50 Lithium hydroxide circulation tank 60 Evaporator 70 Condenser

Claims

1. A crushing and sorting step of crushing and classifying lithium-ion secondary batteries to obtain electrode material containing at least lithium, A leaching step in which the electrode material is immersed in acid to obtain a leachate, A pH adjustment step involves adding lithium hydroxide to the aforementioned leachate to adjust the pH, A metal recovery step to recover metals other than lithium from the leachate to obtain a lithium-containing solution, The process includes a lithium hydroxide recovery step for recovering lithium from the lithium-containing liquid as lithium hydroxide, The acid is one selected from sulfuric acid, hydrochloric acid, or nitric acid. The lithium hydroxide recovery step involves supplying the lithium-containing liquid to a desalination chamber and generating an acid-containing solution and a lithium hydroxide-containing solution by electrodialysis, thereby recovering the lithium in the lithium-containing liquid as lithium hydroxide and recovering the acid. The lithium hydroxide recovery process further comprises the steps of: evaporating and concentrating the delithiated water discharged from the desalination chamber to obtain a concentrated solution, and combining the obtained concentrated solution with the lithium-containing solution; and purifying and removing cations other than lithium ions and, if the acid is sulfuric acid, anions other than sulfate ions, if the acid is hydrochloric acid, anions other than chloride ions, and if the acid is nitric acid, anions other than nitrate ions from the solution containing the concentrated solution combined with the lithium-containing solution. The lithium hydroxide recovered in the lithium hydroxide recovery step is used as a pH adjusting agent (alkali) in both the pH adjustment step and the metal recovery step. A method for processing a lithium-ion secondary battery, characterized in that the acid recovered in the lithium hydroxide recovery step is used in the leaching step and also used as a pH adjusting agent (acid) in the metal recovery step.

2. The method for processing a lithium-ion secondary battery according to claim 1, wherein the acid is sulfuric acid.

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