Lithium recovery method, lithium recovery device

Abstract

The present invention provides a lithium recovery method and lithium recovery apparatus that can recover lithium independently and eliminate the need to add a compounding solution to adjust the pH. [Solution] A lithium recovery method comprising the steps of: stirring a deactivated lithium-ion secondary battery component to be processed in pure water; dispersing the water-soluble solid electrolyte contained in the component to be processed in pure water, a filtrate, a post-extraction separation solution, or a mixture thereof to prepare a dispersion; separating the solid components contained in the dispersion and recovering the separation solution; and extracting an aqueous lithium hydroxide solution from the separation solution by electrodialysis using a cation exchange membrane.

Description

[Technical Field]

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

[0002] In recent years, efforts to significantly reduce waste generation through waste prevention, reduction, recycling, and reuse have become more active. To achieve this, research and development are being conducted on recycling methods for used lithium-ion secondary batteries. One known recycling method for lithium-ion secondary batteries involves disassembling used batteries to separate and recover the battery materials.

[0003] A method for recovering lithium by electrodialysis using a solid electrolyte membrane is known. For example, a lithium recovery method is known that includes a first mixing of an aqueous solution containing lithium and at least one element other than lithium and a base in a reaction vessel, adjusted to a pH of 6 to 10, and a second mixing of the aqueous solution adjusted to a pH of 12 or higher, and removing the hydroxides of the elements other than lithium generated by the first and second mixing to obtain a lithium ion extract, recovering only lithium ions from the lithium ion extract into a recovery solution using an electrochemical apparatus equipped with a Li-selective permeable membrane, and performing the pH adjustment by returning the lithium ion extract from which lithium ions have been recovered by the electrochemical apparatus back to the reaction vessel (see, for example, Patent Document 1).

[0004] Another method for recovering lithium is known, for example, a method in which lithium ions are transferred from a lithium ion extract containing lithium ions extracted from a component of a lithium secondary battery to a recovery solution, using a lithium selective permeable membrane (solid electrolyte membrane), and the temperature of at least one of the lithium ion extract and the lithium selective permeable membrane is adjusted to 30°C or higher and 100°C or lower, thereby recovering lithium in the recovery solution (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2022 / 203055 [Patent Document 2] Japanese Patent Publication No. 2022-75618 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the methods described in Patent Documents 1 and 2 have the problem that lithium cannot be recovered on its own. Furthermore, in the methods described in Patent Documents 1 and 2, lithium recovery by electrodialysis using a solid electrolyte membrane is inefficient unless the pH of the recovered stock solution is between 12 and 14 due to the characteristics of the solid electrolyte membrane, so treatment such as concentrating the lithium is necessary. In order to make the pH of the recovered stock solution between 12 and 14, it is necessary to add a compounding solution, but this compounding solution can cause side reactions, which presents a problem.

[0007] Furthermore, in the methods described in Patent Documents 1 and 2, the ion permeability of the solid electrolyte membrane decreases at or near room temperature, requiring heating of the recovered raw material, which presents challenges in terms of equipment and energy burden.

[0008] This invention aims to provide a lithium recovery method and apparatus that can recover lithium independently and eliminate the need to add a compounding solution to adjust the pH, thereby contributing to a significant reduction in waste generation. [Means for solving the problem]

[0009] To solve the above problems, the present invention has the following embodiments. [1] A step of preparing a dispersion by stirring the deactivated lithium-ion secondary battery component to be treated in pure water and dispersing the water-soluble solid electrolyte contained in the component to be treated in pure water, filtrate, post-extraction separation liquid, or a mixture thereof, A step of separating the solid components contained in the dispersion and recovering the separated liquid, A lithium recovery method comprising the step of extracting an aqueous lithium hydroxide solution from the separated liquid by electrodialysis using a cation exchange membrane.

[0010] According to the above embodiment, lithium can be recovered alone from a dispersion containing a positive electrode active material by electrodialysis using a cation exchange membrane, without adding a compounding solution to adjust the pH, and without heating the recovered stock solution with a heating device.

[0011] [2] A lithium recovery apparatus for extracting an aqueous lithium hydroxide solution by electrodialysis from a dispersion obtained by dispersing a water-soluble solid electrolyte contained in a component of a deactivated lithium-ion secondary battery in pure water, a filtrate, a post-extraction separation solution, or a mixture thereof, A treatment tank for treating the dispersion by electrodialysis, A cation exchange membrane is installed in the treatment tank so as to separate the dispersion and the lithium hydroxide aqueous solution, with the dispersion on one main surface and the lithium hydroxide aqueous solution on the other main surface. A first electrode positioned on one of the main surfaces of the cation exchange membrane, A lithium recovery apparatus comprising: a second electrode disposed on the other main surface side of the cation exchange membrane.

[0012] According to the above embodiment, lithium can be recovered alone from a dispersion containing a positive electrode active material by electrodialysis using a cation exchange membrane, without adding a compounding solution to adjust the pH. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a lithium recovery method and a lithium recovery device that can recover lithium alone and do not require the addition of a preparation solution to adjust the pH.

Brief Description of the Drawings

[0014] [Figure 1] It is a flowchart of a lithium recovery method according to an embodiment of the present invention. [Figure 2A] It is a cross-sectional view schematically showing a lithium recovery device according to an embodiment of the present invention. [Figure 2B] In the cross-sectional view schematically showing a lithium recovery device according to an embodiment of the present invention, it is an enlarged view of a part around the cation exchange membrane. [Figure 3] It is a diagram showing the result of measuring the voltage of a solution in Experimental Example 1. [Figure 4] It is a diagram showing the result of evaluating the sulfur permeability of the cation exchange membrane in Experimental Example 2. [Figure 5] It is a diagram showing the result of evaluating the lithium permeability of the cation exchange membrane in Experimental Example 3. [Figure 6] It is a diagram showing the result of evaluating the lithium recovery rate by electrodialysis using a cation exchange membrane in Experimental Example 4.

Modes for Carrying Out the Invention

[0015] 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.

[0016] [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.

[0017] A lithium recovery method according to one embodiment of the present invention includes the steps of: stirring a member of a deactivated lithium-ion secondary battery to be processed in pure water and dispersing the water-soluble solid electrolyte contained in the member to be processed in pure water, a filtrate, a post-extraction separation solution, or a mixture thereof to prepare a dispersion (hereinafter referred to as the "solution preparation step"); separating the solid components contained in the dispersion and recovering the separation solution (hereinafter referred to as the "recovery step"); and extracting an aqueous lithium hydroxide solution from the separation solution by electrodialysis using a cation exchange membrane (hereinafter referred to as the "extraction step").

[0018] Examples of lithium-ion secondary batteries include all-solid-state batteries that use water-soluble electrolytes such as sulfides.

[0019] Figure 1 is a flowchart of the lithium recovery method according to this embodiment.

[0020] "Solution preparation process" In solution preparation step S1, after deactivating the used lithium-ion secondary battery, the components of the deactivated lithium-ion secondary battery to be treated are stirred in pure water, and the water-soluble solid electrolyte contained in the components to be treated is dispersed in the pure water to prepare a dispersion. The components to be treated refer to the components that make up the deactivated lithium-ion secondary battery. The 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.

[0021] The positive electrode active material is not particularly limited and may be a material known as a positive electrode active material for a lithium-ion secondary battery. Examples of the positive electrode active material include, for example, LiCoO2, LiNiO2, NCM (Li(Ni x Co y Mn z )O2, (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1)) and other ternary cathode materials, layered cathode active material particles such as LiVO2 and LiCrO2, spinel cathode active materials such as LiMn2O4, Li(Ni 0.25 Mn 0.75 )2O4, LiCoMnO4, Li2NiMn3O8, olivine cathode active materials such as LiCoPO4, LiMnPO4, LiFePO4, and the like.

[0022] In the solution preparation 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, magnesium, etc. as mineral components, which will impair the separation performance of the cation exchange membrane. Alkali metals and alkaline earth metals will contaminate the recovered lithium. Also, the filtrate or the separated liquid after extraction does not contain these contaminants, which enables the improvement of the lithium concentration in the dispersion liquid and reduces the amount of pure water used.

[0023] In the solution preparation step S1, since the dispersion liquid contains a solid electrolyte containing lithium, the pH of the dispersion liquid is 11 or more and 14 or less. In order to achieve a lithium recovery rate of 80% or more, it is necessary that 0.4 mol / L or more, preferably 0.7 mol / L or more of lithium is dissolved in the dispersion liquid.

[0024] "Recovery step" In the recovery step S2, the positive electrode active material, the positive electrode material other than the positive electrode active material, the current collecting tab, the current collector, etc. contained in the dispersion liquid are filtered to separate and remove the solid content, and the separated liquid is recovered. Here, the water-insoluble solid content of the lithium-ion secondary battery is removed. Examples of the water-insoluble solid content include the positive electrode active material, the binder, the conductive aid, the tab, the electrode, etc.

[0025] The separated liquid obtained in recovery step S2 contains, for example, chlorine (Cl), bromine (Br), phosphorus (P), sulfur (S), aluminum (Al), nickel (Ni), copper (Cu), etc.

[0026] "pH adjustment process" The lithium recovery method of this embodiment may include a pH adjustment step S3. In the pH adjustment step S3, the pH of the separated liquid is adjusted. The pH of the separated liquid is preferably between 7 and 10. The pH value is adjusted by sulfating dissolved hydrogen sulfide by bubbling or by a neutralization reaction by adding an acid solution such as sulfuric acid.

[0027] In pH adjustment step S3, the pH of the separated liquid is adjusted to the above range to remove metallic components such as aluminum (Al), nickel (Ni), and copper (Cu) contained in the dispersion.

[0028] "Filtration process" The lithium recovery method of this embodiment may include a filtration step S4. In the filtration step S4, solid components (aluminum-containing compounds, nickel-containing compounds, copper-containing compounds, etc.) are filtered and separated and removed from the separated liquid after the pH adjustment step S3.

[0029] "Extraction process" In extraction step S5, an aqueous lithium hydroxide solution is extracted from the separated liquid by electrodialysis using a cation exchange membrane.

[0030] In extraction step S5, 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 separated liquid from which the recovered material is recovered undergoes strong oxidation to a pH of around 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.

[0031] In electrodialysis using a cation exchange membrane, lithium ions contained in the separated liquid 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. One example of an electrodialysis method is to use a constant current of 0.3A and stop the process when the voltage between the electrodes reaches the membrane's breakdown voltage limit. Another example of an electrodialysis method is to use a constant voltage process, where the voltage is set below the membrane's breakdown voltage, and the process stops when the current value falls below a certain value.

[0032] In extraction step S5, copper (Cu), nickel (Ni), aluminum (Al), and phosphate ions (PO4) are extracted. 3- ) and others do not permeate the cation exchange membrane. Chlorine (Cl), bromine (Br), sulfate ions (SO4 2- These substances hardly permeate the cation exchange membrane. Therefore, in extraction step S5, these substances are separated from lithium.

[0033] "Ion exchange process" The lithium recovery method of this embodiment may include an ion exchange step S6. In the ion exchange step S6, the lithium hydroxide aqueous solution obtained in the extraction step S5 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 lithium hydroxide aqueous solution. 2- Remove ) etc.

[0034] In the ion exchange step S6, it is preferable that the temperature at which the lithium hydroxide aqueous solution is brought into contact with the anion exchange resin is between 10°C and 40°C.

[0035] Through the above process, a high-purity aqueous lithium hydroxide solution is obtained.

[0036] According to the lithium recovery method of this embodiment, lithium can be recovered alone from an aqueous solution containing a positive electrode active material by electrodialysis using a cation exchange membrane, without adding a compounding solution to adjust the pH.

[0037] [Lithium recovery device] A lithium recovery device according to one embodiment of the present invention is a device for recovering lithium from used lithium-ion secondary batteries.

[0038] Figure 2A is a schematic cross-sectional view of the lithium recovery apparatus of this embodiment. Figure 2B is an enlarged view of a portion of the area around the cation exchange membrane in the schematic cross-sectional view of the lithium recovery apparatus of this embodiment.

[0039] The lithium recovery device 1 comprises a processing tank 10, a cation exchange membrane 20, a first electrode 30, a second electrode 40, and a power supply 50.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The power supply 50 is connected to the first electrode 30 and the second electrode 40. The power supply 50 applies the voltage required in electrodialysis to the first electrode 30 and the second electrode 40.

[0045] A lithium recovery method by the lithium recovery device 1 of the present embodiment will be described. Prepare a separation liquid that has passed through the solution preparation step S1, the recovery step S2, the pH adjustment step S3, and the filtration step S4 in the lithium recovery method of the above-described embodiment. In the lithium recovery device 1 of the present embodiment, the extraction step S5 in the lithium recovery method of the above-described embodiment is performed.

[0046] Inject the separation liquid into the first space 11 of the treatment tank 10, and inject a dilute lithium hydroxide solution as a recovery liquid into the second space 12 of the treatment 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 starts, and lithium ions contained in the separation liquid in the first space 11 permeate through the cation exchange membrane 20 and move to the recovery liquid in the second space 12. The lithium ions that have permeated through the cation exchange membrane 20 react with water in the second space 12 to become lithium hydroxide. That is, an aqueous lithium hydroxide solution is generated in the second space 12. In addition, trace amounts (on the order of ppm) of chlorine (Cl), bromine (Br), and sulfate ions (SO4 2- ) permeate through the cation exchange membrane 20, so the aqueous lithium hydroxide solution contains trace amounts (on the order of ppm) of chlorine (Cl), bromine (Br), and sulfate ions (SO4 2- ).

[0047] According to the lithium recovery device of the present embodiment, lithium can be recovered alone from an aqueous solution containing a positive electrode active material by electrodialysis using a cation exchange membrane without adding a preparation liquid to adjust the pH.

[0048] As described above, the embodiments of the present invention have been described in detail, but 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 described in the claims.

Example

[0049] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[0050] [Experimental Example 1] A solid electrolyte membrane made of a Li2O-Al2O3-SiO2-P2O5-TiO2 system material, a cation exchange membrane made of sodium sulfonate, a cation exchange membrane made of polyolefin (A), a cation exchange membrane made of polyolefin (B), a cation exchange membrane made of polyolefin (C), a cation exchange membrane made of fluorinated sulfonic acid, and a cation exchange membrane made of hydrocarbons were used as cation exchange membranes in a lithium recovery device, and an electric current was passed through the solution in the processing tank of the lithium recovery device, and the voltage between the cathode and anode terminals was measured. The ambient temperature of the lithium recovery system was set to 20°C, 40°C, 60°C, 80°C, and 90°C, and the voltage was measured at each temperature. The measurement results are shown in Figure 3. The results shown in Figure 3 indicate that the solid electrolyte membrane has low ion permeability at or near room temperature and requires heating treatment.

[0051] [Experimental Example 2] The permeability of sulfur (S) through cation exchange membranes made of sodium sulfonate, polyolefin (A), polyolefin (B), polyolefin (C), fluorinated sulfonic acid, and hydrocarbons was investigated. To evaluate the permeability of each membrane, the components of lithium aqueous solution after electrodialysis were analyzed. Cr, Br, PO4, SO4, etc., were analyzed by ion chromatography (IC), and the total sulfur and total phosphorus content were analyzed by inductively coupled plasma spectroscopy (ICP). The evaluation was conducted at temperatures of 20°C, 40°C, 60°C, and 80°C. The measurement results are shown in Figure 4. The results shown in Figure 4 indicate that cation exchange membranes made of fluorinated sulfonic acid and cation exchange membranes made of hydrocarbons exhibit increased sulfur permeability as the temperature rises, making it desirable to use them at temperatures below 40°C.

[0052] [Experimental Example 3] The permeability of lithium (Li) to cation exchange membranes made of sodium sulfonate, polyolefin (A), polyolefin (B), and polyolefin (C) was investigated. To evaluate the permeability of each membrane, the components of lithium aqueous solution after electrodialysis were analyzed. Cr, Br, PO4, SO4, etc., were analyzed by ion chromatography (IC), and the total sulfur and total phosphorus content were analyzed by inductively coupled plasma spectroscopy (ICP). The evaluation was conducted at temperatures of 25°C, 40°C, and 60°C. The measurement results are shown in Figure 5. As shown in Figure 5, the lithium permeability increased in the order of polyolefin (A) < polyolefin (B) < polyolefin (C) ≈ sodium sulfonate salt.

[0053] [Experimental Example 4] In electrodialysis using a cation exchange membrane made of sodium sulfonate, the effect of changes in the amount of lithium contained in the separated solution on the lithium recovery rate was investigated. In evaluating the lithium recovery rate, the amount of lithium in the separated solution before and after electrodialysis was analyzed using inductively coupled plasma spectroscopy (ICP). The measurement results are shown in Figure 6. The results shown in Figure 6 indicate that the lithium recovery rate increases with higher lithium concentrations in the separated solution, and that a lithium concentration of 0.4 mol / L or higher, preferably 0.7 mol / L or higher, is necessary to achieve a lithium recovery rate of 80% or higher. [Explanation of Symbols]

[0054] 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. The process involves stirring the deactivated lithium-ion secondary battery component to be treated in pure water, and dispersing the water-soluble solid electrolyte contained in the component to be treated in pure water, filtrate, post-extraction separation liquid, or a mixture thereof to prepare a dispersion. A step of separating the solid components contained in the dispersion and recovering the separated liquid, A lithium recovery method comprising the step of extracting an aqueous lithium hydroxide solution from the separated liquid by electrodialysis using a cation exchange membrane.

2. A lithium recovery apparatus for extracting an aqueous lithium hydroxide solution by electrodialysis from a dispersion obtained by dispersing a water-soluble solid electrolyte contained in a component of a deactivated lithium-ion secondary battery in pure water, a filtrate, a post-extraction separation solution, or a mixture thereof, A treatment tank for treating the dispersion by electrodialysis, A cation exchange membrane is installed in the treatment tank so as to separate the dispersion and the lithium hydroxide aqueous solution, with the dispersion on one main surface and the lithium hydroxide aqueous solution on the other main surface. A first electrode positioned on one of the main surfaces of the cation exchange membrane, A lithium recovery apparatus comprising: a second electrode disposed on the other main surface side of the cation exchange membrane.

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