Lithium recovery method

Abstract

The present invention provides a lithium recovery method that can separate metal impurities during lithium ion recovery without generating hydrogen sulfide gas. [Solution] A lithium recovery method from a used lithium-ion secondary battery comprising an electrode body having a positive electrode, a sulfide solid electrolyte, and a negative electrode, comprising: a dissolution step of dissolving the solid electrolyte and lithium compound contained in the deactivated lithium-ion secondary battery in pure water to obtain a dispersion; a separation liquid recovery step of recovering the separation liquid by solid-liquid separation of the dispersion liquid; an oxidation step of oxidizing the separation liquid to generate acidic components in the separation liquid and adjust the pH of the separation liquid; a recovery stock liquid recovery step of recovering the recovery stock liquid by solid-liquid separation of the separation liquid after the oxidation treatment; and a step of extracting an aqueous lithium hydroxide solution from the recovery stock liquid by electrodialysis using a cation exchange membrane.

Description

[Technical Field]

[0001] This invention relates to a lithium recovery method. [Background technology]

[0002] In recent years, research and development has been conducted on so-called all-solid-state batteries, which use a solid electrolyte instead of a liquid electrolyte. Because all-solid-state batteries do not use organic solvents, improvements in safety are expected. Furthermore, as with conventional batteries, recycling technologies are being developed for all-solid-state batteries to ensure efficient resource utilization (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-98840 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the recycling of all-solid-state batteries, as described in Patent Document 1, a process is carried out in which the solid electrolyte and lithium are dissolved by immersion in water after deactivation treatment, and separated from solid components such as the positive electrode active material. Then, lithium is recovered from the separated liquid in which the lithium has been dissolved. One method for recovering lithium from the separated solution is electrodialysis. In electrodialysis, if the separated solution contains high concentrations of metal ions such as aluminum, copper, and nickel, these metal ions prevent the purity of the lithium extract from being increased, and the separation membrane used in electrodialysis deteriorates. Therefore, it is necessary to remove metal ions from the separated solution before performing electrodialysis.

[0005] Copper and nickel precipitate as hydroxides in alkaline conditions and can therefore be removed by precipitation. Aluminum precipitates as hydroxides in neutral conditions and can therefore be removed by solid-liquid separation. To separate aluminum as hydroxides, it is necessary to lower the pH of the strongly alkaline separation solution to a neutral level. However, if the pH of the separation solution is lowered rapidly by adding hydrochloric acid, for example, localized areas of high acid concentration may occur in the separation solution, potentially generating toxic hydrogen sulfide gas.

[0006] To solve the above-mentioned problems, this invention aims to provide a lithium recovery method that can separate metal impurities from lithium ions without generating hydrogen sulfide gas. This will ultimately contribute to a significant reduction in waste generation. [Means for solving the problem]

[0007] To solve the above problems, the present invention has the following embodiments. [1] A method for recovering lithium from a spent lithium-ion secondary battery, comprising an electrode body having a positive electrode, a sulfide solid electrolyte, and a negative electrode, A dissolution step involves dissolving the solid electrolyte and lithium compound contained in a deactivated lithium-ion secondary battery in pure water to obtain a dispersion. A separation liquid recovery step is performed to separate the dispersion liquid into solid and liquid components and recover the separated liquid, An oxidation step is performed to oxidize the separated liquid to generate acidic components in the separated liquid and adjust the pH of the separated liquid. A recovery process for recovering the recovered stock solution by performing solid-liquid separation of the separated liquid after the oxidation treatment, A lithium recovery method comprising the step of extracting an aqueous lithium hydroxide solution from the recovered stock solution by electrodialysis using a cation exchange membrane.

[0008] According to the above embodiment, by oxidizing the separated liquid to generate acidic components in the separated liquid and adjusting the pH of the separated liquid, lithium can be recovered from a solid electrolyte secondary battery that uses lithium as a charge carrier and has a sulfide solid electrolyte while suppressing the generation of hydrogen sulfide and reducing the inclusion of impurity metals.

[0009] [2] The lithium recovery method according to [1], wherein the oxidation step comprises a first oxidation step of adjusting the pH of the separated liquid to 7 to 12 and a second oxidation step of adjusting the pH of the separated liquid to 6 to 8.

[0010] According to the above embodiment, by utilizing the fact that the saturated dissolution amount of copper and nickel in the separated liquid decreases to 10 mg / L between pH 7 and 12, the pH of the separated liquid can be adjusted by oxidation treatment, thereby promoting the precipitation of hydroxides such as copper, nickel, and aluminum. Furthermore, by adjusting the pH of the separated liquid to 6 to 8, the precipitation of aluminum hydroxide can be promoted, and aluminum can be removed.

[0011] [3] The lithium recovery method according to [1] or [2], wherein the oxidation treatment includes any of the following: a treatment in which the separated liquid is left to stand in the air, a treatment in which the separated liquid is aerated with air or an oxidizing gas, and a treatment in which the separated liquid is heated.

[0012] According to the above embodiment, the pH of the separated liquid can be adjusted without releasing hydrogen sulfide.

[0013] [4] A lithium recovery method according to any one of [1] to [3], further comprising the step of removing impurity anions from the lithium hydroxide aqueous solution using an anion exchange resin.

[0014] According to the above embodiment, an aqueous lithium hydroxide solution is brought into contact with an anion exchange resin to remove trace amounts (on the order of ppm) of chlorine (Cl), bromine (Br), and sulfate ions (SO4) contained in the aqueous lithium hydroxide solution. 2- ) etc. can be removed. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a lithium recovery method capable of separating a metal that becomes an impurity in the recovery of lithium ions without generating hydrogen sulfide gas.

Brief Description of the Drawings

[0016] [Figure 1] It is a flowchart of a lithium recovery method according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing a lithium recovery device according to an embodiment of the present invention. [Figure 3] It is a diagram showing the results of measuring the pH of a LiOH·H2O solution and the saturated dissolution amounts of copper and nickel in the LiOH·H2O solution in Experimental Example 1. [Figure 4] It is a diagram showing the results of adjusting the pH of a sulfide solid electrolyte solution in Example 1 by a treatment of leaving the sulfide solid electrolyte solution standing in air, a treatment of aerating the sulfide solid electrolyte solution with air, a treatment of aerating the sulfide solid electrolyte solution with ozone, or a treatment of heating the sulfide solid electrolyte solution to 80°C.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to these contents and can be implemented with modifications within the scope of the gist.

[0018] [Lithium Recovery Method] A lithium recovery method according to an embodiment of the present invention is a method for recovering lithium from a used lithium-ion secondary battery including an electrode body having a positive electrode, a sulfide solid electrolyte, and a negative electrode.

[0019] A lithium recovery method according to one embodiment of the present invention includes: a dissolution step of dissolving a solid electrolyte and lithium compound contained in a deactivated lithium-ion secondary battery in pure water to obtain a dispersion; a separation liquid recovery step of recovering the separation liquid by solid-liquid separation of the dispersion liquid; an oxidation step of oxidizing the separation liquid to generate acidic components in the separation liquid and adjust the pH of the separation liquid; a recovery stock liquid recovery step of recovering the recovery stock liquid by solid-liquid separation of the separation liquid after the oxidation treatment; and a step of extracting an aqueous lithium hydroxide solution from the recovery stock liquid by electrodialysis using a cation exchange membrane.

[0020] Figure 1 is a flowchart of the lithium recovery method according to this embodiment.

[0021] "Dissolution process" In the dissolution step S1, after deactivating the used lithium-ion secondary battery, the components of the deactivated lithium-ion secondary battery are stirred in pure water to dissolve the solid electrolyte and lithium compound contained in the components in the pure water and prepare a dispersion. The components to be treated refer to the components that make up the deactivated lithium-ion secondary battery. Deactivation of used lithium-ion secondary batteries can be carried out by known methods (see, for example, Japanese Patent Publication No. 2023-124857, International Publication No. 2021 / 201151, etc.). The components to be processed include positive electrode active material, positive electrode materials other than the positive electrode active material (conductive additives, binders, etc.), copper of the negative electrode current collector, sulfur and phosphorus derived from the electrolyte, current collector tabs, current collectors, etc. For example, a positive electrode including a current collector and a positive electrode active material layer formed on the current collector is crushed and dispersed in fragments of a desired size, a filtrate, a post-extraction separation liquid, or a mixture thereof to prepare a dispersion. The resulting dispersion contains positive electrode active material, positive electrode materials other than the positive electrode active material, current collector tabs, current collectors, etc. as solid components.

[0022] The positive electrode active material is not particularly limited and may be any material known as a positive electrode active material for lithium-ion secondary batteries. Examples of positive electrode active materials include LiCoO2, LiNiO2, and NCM(Li(Ni x Co y Mnz )ternary cathode materials such as O2, (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1)), layered cathode active material particles such as LiVO2 and LiCrO2, and spinel-type cathode active materials such as LiMn2O4, Li(Ni 0.25 Mn 0.75 )2O4, LiCoMnO4, Li2NiMn3O8, and olivine-type cathode active materials such as LiCoPO4, LiMnPO4, and LiFePO4 can be mentioned.

[0023] In the dissolution step S1, the reason for using pure water is that natural water, tap water, etc. contain alkali metals and alkaline earth metals such as sodium, potassium, calcium, and magnesium as mineral components, which impair the separability of the cation exchange membrane. Alkali metals and alkaline earth metals become contaminants in the recovered lithium.

[0024] In the dissolution step S1, since the dispersion contains a solid electrolyte containing lithium, the pH of the dispersion becomes 11 or more and 14 or less. To achieve a lithium recovery rate of 80% or more, it is necessary for 0.4 mol / L or more, preferably 0.7 mol / L or more of lithium to be dissolved in the dispersion.

[0025] "Separation liquid recovery step" In the separation liquid recovery step S2, solid components such as the cathode active material, cathode materials other than the cathode active material, current collector tabs, and current collectors contained in the dispersion are filtered, separated, and removed to recover the separation liquid. Here, the water-insoluble solid components of the lithium-ion secondary battery are removed. Examples of the water-insoluble solid components include the cathode active material, binder, conductive assistant, tab, and electrode.

[0026] The separation liquid obtained in the separation liquid recovery step S2 contains, for example, chlorine (Cl), bromine (Br), phosphorus (P), sulfur (S), aluminum (Al), nickel (Ni), copper (Cu), etc.

[0027] "Oxidation step" In oxidation step S3, the separated liquid is oxidized to generate acidic components and adjust the pH of the separated liquid. In oxidation step S3, the pH of the separated liquid is adjusted. Preferably, the pH of the separated liquid is between 7 and 12. The pH value is adjusted by treatments such as letting the separated liquid stand in the air, aerating (bubbling) the separated liquid with air, aerating (bubbling) the separated liquid with an oxidizing gas such as ozone, oxygen gas, or active oxygen gas, or heating the separated liquid. These treatments promote the reaction in which phosphorus (P) in the separated liquid becomes PO4 and the reaction in which sulfur (S) in the separated liquid becomes S2O3 or SO4, thereby adjusting the pH of the separated liquid. Active oxygen gases include superoxide, hydroxyl radicals, etc. In processes where the separated liquid is left to stand in the air, for example, the separated liquid is left to stand for more than 10 hours but less than 100 days. In the process of aerating the separated liquid with air, for example, the separated liquid is aerated with air for more than 4 hours but less than 10 days. In the process of aerating the separated liquid with an oxidizing gas, for example, the separated liquid is aerated with ozone for 2 to 5 hours. In the process of heating the separated liquid, for example, the separated liquid is heated to a temperature between 40°C and 90°C. This causes hydroxides such as copper, nickel, and aluminum to precipitate.

[0028] The oxidation step S3 preferably includes a first oxidation step S4 and a second oxidation step S6.

[0029] "First oxidation process" In the first oxidation step S4, the pH of the separated liquid obtained in the separated liquid recovery step S2 is adjusted to 7-12. By utilizing the fact that the saturation dissolution amount of copper and nickel in the separated solution decreases to 10 mg / L between pH 7 and 12, the pH of the separated solution is adjusted through oxidation treatment to promote the precipitation of hydroxides such as copper, nickel, and aluminum. The pH of the dispersion immediately after dissolving the solid electrolyte reaches around 12, which is due to the dissolution of lithium ions in the lithium-ion secondary battery. Furthermore, due to sulfide reactions caused by hydrogen sulfide gas generated when the solid electrolyte is dissolved in water, the content of contaminants such as copper, nickel, and aluminum in the separated solution reaches several hundred mg / L. Therefore, it is desirable to lower the pH of the separated solution to 10 or below in order to stabilize the ionic state in the separated solution. If the pH of the separated solution falls below 7, the dissolution concentration of copper and nickel will increase because they are soluble in acid.

[0030] While it is possible to adjust the pH of the separated liquid using acidic liquids (such as sulfuric acid or hydrochloric acid), this process is burdensome because it involves the release of hydrogen sulfide, a harmful, flammable, and corrosive gas. Since large amounts of phosphorus and sulfur are leached into the separated liquid, it is desirable to oxidize these substances in the separated liquid to bring its pH to the neutral range. Therefore, in the lithium recovery method of this embodiment, the pH of the separated liquid is adjusted without using acidic liquids by processes such as letting the separated liquid stand in the air, aerating (bubbling) the separated liquid with air, aerating (bubbling) the separated liquid with an oxidizing gas such as ozone, or heating the separated liquid.

[0031] "Separation process" The lithium recovery method of this embodiment may include a separation step S5. In the separation step S5, solid components (aluminum-containing compounds, nickel-containing compounds, copper-containing compounds, etc.) are separated and removed from the separated liquid after the first oxidation step S4 by filtration.

[0032] "Second oxidation process" In the second oxidation step S6, the pH of the separated liquid obtained in the first separation step S5 is adjusted to 6-8. Since aluminum in the separated liquid is amphoteric, it dissolves in both acids and alkalis. However, in the neutral range, aluminum hydroxide (Al(OH)3) precipitates and is known to function as a flocculant. Therefore, to remove aluminum, it is effective to adjust the pH of the separated liquid to 6-8 to promote the precipitation of aluminum hydroxide. The method for adjusting the pH of the separated liquid is the same as in the first oxidation step.

[0033] "Recovery process for the recovered concentrate" In the recovered raw material recovery process S7, the separated liquid after oxidation treatment is subjected to solid-liquid separation to recover the recovered raw material. In the recovered raw material recovery process S7, solid components (aluminum-containing compounds, nickel-containing compounds, copper-containing compounds, etc.) are filtered, separated, and removed from the separated liquid that has gone through the oxidation process S3 (first oxidation process S4, second oxidation process S6).

[0034] "Extraction process" In extraction step S8, an aqueous lithium hydroxide solution is extracted from the recovered stock solution by electrodialysis using a cation exchange membrane.

[0035] In extraction step S8, examples of materials for the cation exchange membrane include sodium sulfonate and polyolefin. As lithium concentration progresses in the lithium hydroxide aqueous solution, the pH exceeds 12, and the recovery stock solution undergoes strong oxidation to around pH 1 due to the decrease in lithium and the progression of oxidation of anionic components. Therefore, the cation exchange membrane requires a wide pH tolerance.

[0036] In electrodialysis using a cation exchange membrane, lithium ions contained in the recovered stock solution permeate through the cation exchange membrane, where they react with water to form lithium hydroxide. In other words, an aqueous solution of lithium hydroxide is produced on the side that has permeated the cation exchange membrane. As an example of an electrodialysis method, one could use a constant current treatment of 0.3A, and stop the process when the voltage between electrodes reaches the membrane's breakdown voltage limit. Alternatively, as an example of an electrodialysis method, one could use a constant voltage treatment, where the voltage is set below the membrane's breakdown voltage, and the process stops when the current value falls below a certain value.

[0037] In the extraction step S8, if copper (Cu), nickel (Ni), aluminum (Al), phosphate ions (PO4 3- ) etc. are at a concentration of several tens of ppm or less in the recovered stock solution, they do not permeate through the cation exchange membrane. Chlorine (Cl), bromine (Br), sulfate ions (SO4 2- ) etc. hardly permeate through the cation exchange membrane. Therefore, in the extraction step S8, these substances and lithium are separated.

[0038] "Ion exchange step" The lithium recovery method of this embodiment may include an ion exchange step S9. In the ion exchange step S9, the lithium hydroxide aqueous solution obtained in the extraction step S8 is brought into contact with an anion exchange resin to remove impurity anions such as chlorine (Cl), bromine (Br), sulfate ions (SO4 2- ) etc. contained in trace amounts (ppm order) in the lithium hydroxide aqueous solution.

[0039] In the ion exchange step S9, it is preferable that the temperature at which the lithium hydroxide aqueous solution is brought into contact with the anion exchange resin is 10°C or higher and 40°C or lower.

[0040] Through the above steps, a high-purity lithium hydroxide aqueous solution can be obtained.

[0041] According to the lithium recovery method of this embodiment, lithium can be recovered alone from the solid electrolyte aqueous solution by electrodialysis using a cation exchange membrane without adding a preparation solution to adjust the pH.

[0042] [Lithium recovery device] The lithium recovery device according to an embodiment of the present invention is a device for recovering lithium from a used lithium ion secondary battery.

[0043] FIG. 2 is a cross-sectional view schematically showing the lithium recovery device of this embodiment.

[0044] The lithium recovery device 1 includes a treatment tank 10, a cation exchange membrane 20, a first electrode 30, a second electrode 40, and a power source 50.

[0045] The processing tank 10 has a first space 11 and a second space 12 separated by a cation exchange membrane 20 installed inside the processing tank 10. In the first space 11, the inner surface facing the cation exchange membrane 20 at a distance is defined as one main surface 10a of the processing tank 10. In the second space 12, the inner surface facing the cation exchange membrane 20 at a distance is defined as the other main surface 10b of the processing tank 10.

[0046] The treatment tank 10 is a tank that processes a dispersion obtained by dispersing the water-soluble solid electrolyte contained in the components of a deactivated lithium-ion secondary battery to be treated in pure water, using electrodialysis.

[0047] The cation exchange membrane 20 is positioned in the center of the processing tank 10, along the height direction of the processing tank 10, so as to separate the first space 11 and the second space 12 of the processing tank 10. As the cation exchange membrane 20, the same type as that used in the lithium recovery method of the above-described embodiment can be used.

[0048] The first electrode 30 is positioned within the first space 11 on one main surface 10a side of the processing tank 10. The second electrode 40 is positioned within the second space 12 on the other main surface 10b side of the processing tank 10.

[0049] The power supply 50 is connected to the first electrode 30 and the second electrode 40. The power supply 50 applies the voltage required for electrodialysis to the first electrode 30 and the second electrode 40.

[0050] The lithium recovery method using the lithium recovery device 1 of this embodiment will be described. The lithium recovery method of the above embodiment is prepared by going through the dissolution step S1, the separation liquid recovery step S2, the oxidation step S3, and the recovery stock liquid recovery step S7. In the lithium recovery apparatus 1 of this embodiment, the extraction step S8 of the lithium recovery method of the above-described embodiment is performed.

[0051] The separation liquid is injected into the first space 11 of the processing tank 10, and a dilute lithium hydroxide solution is injected as the recovery liquid into the second space 12 of the processing tank 10 to ensure conductivity. In this state, when a voltage is applied from the power supply 50 to the first electrode 30 and the second electrode 40, electrodialysis begins, and lithium ions contained in the separated liquid in the first space 11 permeate the cation exchange membrane and move to the recovered liquid in the second space 12. The lithium ions that have permeated the cation exchange membrane react with water in the second space 12 to form lithium hydroxide. In other words, an aqueous solution of lithium hydroxide is generated in the second space 12. Note that trace amounts (on the order of ppm) of chlorine (Cl), bromine (Br), and sulfate ions (SO4) are present. 2- Because ) permeates the cation exchange membrane, the lithium hydroxide aqueous solution contains trace amounts (on the order of ppm) of chlorine (Cl), bromine (Br), and sulfate ions (SO4). 2- ) is included.

[0052] According to the lithium recovery apparatus of this embodiment, lithium can be recovered independently from a solid electrolyte aqueous solution by electrodialysis using a cation exchange membrane, without adding a compounding solution to adjust the pH.

[0053] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Examples]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0055] [Experimental Example 1] The pH of the LiOH·H2O solution and the saturation dissolution amounts of copper and nickel in the LiOH·H2O solution were measured. LiOH·H2O powder was dissolved in pure water, and 0.5 g of copper hydroxide or nickel hydroxide was added to 25 mL of the pH-adjusted solution and stirred. After 12 hours or more, the solution was filtered through a 0.45 μm filter, and the amounts of copper and nickel in the solution were analyzed by inductively coupled plasma spectroscopy (ICP). The results are shown in Figure 3. As shown in Figure 3, copper and nickel have low alkali solubility. The saturated solubility of copper and nickel in the LiOH·H2O solution decreased to 10 mg / L between pH 7 and 12, resulting in the precipitation of copper hydroxide and nickel hydroxide. Furthermore, aluminum is amphoteric, meaning it dissolves well in both acids and alkalis. However, aluminum hydroxide precipitates between pH 6 and 8, and is known to function as a flocculant. Based on the above, by adjusting the pH of the LiOH·H2O solution and performing solid-liquid separation of the LiOH·H2O solution, metal components such as copper and nickel contained in the LiOH·H2O solution can be removed.

[0056] [Example 1] The pH of the sulfide solid electrolyte solution was adjusted by either leaving the solution standing in the air, aerating it with air, aerating it with ozone, or heating it to 80°C. The results are shown in Figure 4. As shown in Figure 4, it was found that heating the sulfide solid electrolyte solution to 80°C caused a rapid change in the pH of the solution. It was found that the change in pH of the solution became more gradual in the following order: heating the sulfide solid electrolyte solution to 80°C, aerating the sulfide solid electrolyte solution with ozone, aerating the sulfide solid electrolyte solution with air, and letting the sulfide solid electrolyte solution stand in the air.

[0057] [Example 2] After deactivating used lithium-ion secondary batteries, the components of the deactivated lithium-ion secondary batteries were stirred in pure water, and the positive electrode active material and lithium compounds contained in the components were dissolved in pure water to prepare a dispersion. The obtained dispersion was left to stand in the air at room temperature (25°C). Table 1 shows the results of ICP (inductively coupled plasma) analysis of the dispersion three days after the start of standing, and the pH measurement results of the dispersion. Table 1 also shows the results of ICP (inductively coupled plasma) analysis of the dispersion two months after the start of standing, and the pH measurement results of the dispersion. For the analysis of aluminum in the dispersion, an ICP emission spectrometer ICPS-8100 (Shimadzu Corporation) was used. For the analysis of copper and nickel, an ICP mass spectrometer 7700x (Agilent Technologies) was used. LAQUA-PH-SE (manufactured by Horiba, Ltd.) was used to measure the pH of the dispersion.

[0058] [Table 1]

[0059] In the dispersion, over time, hydrogen sulfide ions (HS) are produced. - The oxidation of ) proceeds slowly, leading to sulfate ions (SO4 2- It was found that ) is generated, oxidation of the dispersion proceeds, and the separated solution becomes neutral. When the separated solution becomes neutral, hydroxides of polyvalent metals with low solubility precipitate, and the amount of polyvalent metals dissolved in the separated solution decreases. [Explanation of Symbols]

[0060] 1. Lithium recovery device 10 Processing tanks 11 1st space 12 Second space 20 Cation exchange membrane 30 1st electrode 40 2nd electrode 50 power supply

Claims

1. A method for recovering lithium from a used lithium-ion secondary battery, comprising an electrode body having a positive electrode, a sulfide solid electrolyte, and a negative electrode, A dissolution step involves dissolving the solid electrolyte and lithium compound contained in a deactivated lithium-ion secondary battery in pure water to obtain a dispersion. A separation liquid recovery step is performed to separate the dispersion liquid into solid and liquid components and recover the separated liquid, An oxidation step is performed to oxidize the separated liquid to generate acidic components in the separated liquid and adjust the pH of the separated liquid. A recovery liquid stock step is performed to recover the recovered liquid stock by separating the separated liquid after the oxidation treatment into solid and liquid components, A lithium recovery method comprising the step of extracting an aqueous lithium hydroxide solution from the recovered stock solution by electrodialysis using a cation exchange membrane.

2. The lithium recovery method according to claim 1, wherein the oxidation step comprises a first oxidation step of adjusting the pH of the separated liquid to 7 to 12 and a second oxidation step of adjusting the pH of the separated liquid to 6 to 8.

3. The lithium recovery method according to claim 1, wherein the oxidation treatment includes any of the following: a treatment of letting the separated liquid stand in the air; a treatment of aerating the separated liquid with air or an oxidizing gas; and a treatment of heating the separated liquid.

4. Furthermore, the lithium recovery method according to claim 1, comprising the step of removing impurity anions from the lithium hydroxide aqueous solution using an anion exchange resin.

Images