Lithium recovery methods

Abstract

A lithium recovery method is disclosed, which involves recovering lithium from a deactivated lithium-ion secondary battery having an electrode body comprising a positive electrode, a sulfide solid electrolyte, and a negative electrode. The lithium recovery method includes: a dissolution step, in which the solid electrolyte and lithium compounds contained in the deactivated lithium-ion secondary battery are dissolved in pure water to obtain a dispersion; a separation liquid recovery step, in which the dispersion is subjected to solid-liquid separation to recover the separation liquid; an oxidation step, in which the separation liquid is oxidized to generate an acidic component and the pH of the separation liquid is adjusted; an aeration step, in which the oxidized separation liquid is aerated with air or an oxidizing gas to adjust the pH of the separation liquid; a recovery stock solution recovery step, in which the aerated separation liquid is subjected to solid-liquid separation to recover the recovery stock solution; and a step of extracting an aqueous lithium hydroxide solution from the recovery stock solution using electrodialysis via a cation exchange membrane.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2024-232127, filed on December 27, 2024, the contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to lithium recovery methods. Background Technology

[0003] In recent years, research and development have been conducted on so-called all-solid-state batteries, which use solid electrolytes instead of liquid electrolytes. All-solid-state batteries do not use organic solvents, thus promising improved safety. Furthermore, like conventional batteries, all-solid-state batteries are also undergoing recycling technology development from the perspective of efficient resource utilization (see, for example, Japanese Patent Application Publication No. 2024-98840). Summary of the Invention

[0004] In the recycling of all-solid-state batteries, as described in Japanese Patent Application Publication No. 2024-98840, the following process is performed: after deactivation treatment, the solid electrolyte and lithium are dissolved by immersion in water, and separated from solid components such as the positive electrode active material. Then, lithium is recovered from the separated liquid containing dissolved lithium. One method for lithium recovery from the separated liquid is electrodialysis. The separated liquid contains sulfur and phosphorus ions, which are components of the solid electrolyte. These ions react with dissolved oxygen in an alkaline pH region to generate S₂O₃. 2- (Thiosulfate ion), PO4 3- (Phosphate ions). S2O3 2- During electrodialysis, the thiosulfate ion undergoes an oxidation reaction to produce SO4. 2- (Sulfate ions) and sulfur particles, deterioration of liquid circulation, and degradation of membranes used in electrodialysis. PO4 3- When phosphate ions reach saturation concentration, they combine with lithium to form Li3PO4 (lithium phosphate), leading to deterioration of the liquid's recyclability and a decrease in lithium recovery rate.

[0005] S2O3 2- During electrodialysis, the oxidation reaction of thiosulfate ions proceeds, generating sulfur particles, and therefore needs to be removed before electrodialysis. This is to prevent the separation of S2O3 from the solution. 2- (Thiosulfate ions) are oxidized to form SO4 before electrodialysis. 2- Sulfate ions and sulfur particles are removed by means of filtration.

[0006] From PO4 3-The Li3PO4 (lithium phosphate) produced by (phosphate ions) dissolves in strong acids below pH 2, thus acidifying the separation liquid, which is a strong alkali, through oxidation containing ions, thereby redissolving lithium and preventing a decrease in recovery rate.

[0007] As a method to promote the oxidation of the separation liquid, it is desirable to force oxidation by aerating the separation liquid with ozone. By adjusting the pH of the separation liquid to around 2, more than 90% of the sulfur components contained in the separation liquid are oxidized, which can suppress the formation of sulfur particles during lithium recovery, and restore the lithium recovery rate by redissolving Li3PO4 (lithium phosphate).

[0008] The present application provides a lithium recovery method that can suppress the obstacles to recovery caused by sulfur particles, the obstacles to lithium recovery caused by lithium phosphate precipitation, and the reduction in lithium recovery rate. Furthermore, the present application's solution contributes to a significant reduction in waste generation.

[0009] The present invention has the following solution.

[0010] [1] A lithium recovery method, which is a lithium recovery method for recovering lithium from a used lithium-ion secondary battery having an electrode body, wherein the electrode body has a positive electrode, a sulfide solid electrolyte and a negative electrode, wherein,

[0011] The lithium recovery method includes:

[0012] The dissolution process involves dissolving the solid electrolyte and lithium compounds contained in the deactivated lithium-ion secondary battery in pure water to obtain a dispersion.

[0013] The separation liquid recovery process involves performing solid-liquid separation on the dispersion to recover the separation liquid;

[0014] The oxidation process involves oxidizing the separation liquid to generate acidic components and adjusting the pH of the separation liquid.

[0015] The aeration process involves aerating the oxidized separation liquid with air or an oxidizing gas to adjust the pH of the separation liquid.

[0016] The raw liquid recovery process involves solid-liquid separation of the separated liquid after aeration treatment to recover the raw liquid; and

[0017] The process of extracting an aqueous solution of lithium hydroxide from the recovered stock solution by electrodialysis using a cation exchange membrane.

[0018] [2] Based on the lithium recovery method described in [1], the pH of the separation liquid is adjusted to 7-12 through the oxidation process, and the pH of the separation liquid is adjusted to below 2 through the aeration process.

[0019] [3] Based on the lithium recovery method described in [1] or [2], there is also a step of using anion exchange resin to remove impurity anions from the lithium hydroxide aqueous solution.

[0020] According to the present invention, a lithium recovery method is provided that can suppress the formation of sulfur particles from hindering recovery, the precipitation of lithium phosphate from hindering lithium recovery, and the reduction of lithium recovery rate. Attached Figure Description

[0021] Figure 1 This is a flowchart of a lithium recovery method according to one embodiment of the present invention.

[0022] Figure 2 This is a schematic cross-sectional view illustrating a lithium recovery apparatus according to one embodiment of the present invention. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below. However, the following description is only one example of the embodiments of the present invention. The present invention is not limited to these contents and can be modified and implemented within the scope of its spirit.

[0024] [Lithium Recovery Methods]

[0025] One embodiment of the present invention relates to a lithium recovery method for recovering lithium from a used lithium-ion secondary battery having an electrode body, the electrode body having a positive electrode, a sulfide solid electrolyte, and a negative electrode.

[0026] An embodiment of the present invention relates to a lithium recovery method comprising: a dissolution step, wherein a solid electrolyte and lithium compound contained in a deactivated lithium-ion secondary battery are dissolved in pure water to obtain a dispersion; a separation liquid recovery step, wherein the dispersion is subjected to solid-liquid separation to recover the separation liquid; an oxidation step, wherein the separation liquid is oxidized to generate an acidic component in the separation liquid and the pH of the separation liquid is adjusted; an aeration step, wherein the oxidized separation liquid is aerated with air or an oxidizing gas to adjust the pH of the separation liquid; a recovery stock liquid recovery step, wherein the aerated separation liquid is subjected to solid-liquid separation to recover the recovery stock liquid; and a step of extracting an aqueous solution of lithium hydroxide from the recovery stock liquid by electrodialysis using a cation exchange membrane.

[0027] Figure 1 This is a flowchart of the lithium recovery method according to this embodiment.

[0028] "Dissolving process"

[0029] In the dissolution step S1, after the used lithium-ion secondary battery is deactivated, the deactivated lithium-ion secondary battery component to be treated is stirred in pure water to dissolve the solid electrolyte and lithium compound contained in the component and prepare a dispersion. It should be noted that the component to be treated refers to the component that constitutes the lithium-ion secondary battery that has undergone deactivation treatment.

[0030] The deactivation of used lithium-ion secondary batteries can be carried out by known methods (e.g., see Japanese Patent Application Publication No. 2023-124857, International Publication No. 2021 / 201151, etc.).

[0031] The components being processed include positive electrode active material, positive electrode materials other than the positive electrode active material (conductive additives, binders, etc.), copper for the negative electrode current collector, sulfur or phosphorus derived from the electrolyte, current collector tabs, current collectors, etc. For example, the current collector and the positive electrode containing the positive electrode active material layer formed on the current collector are crushed to form fragments of the desired size and dispersed in a filtrate, a post-extraction separation liquid, or a mixture thereof to prepare a dispersion. The resulting dispersion contains, as solid components, the positive electrode active material, positive electrode materials other than the positive electrode active material, current collector tabs, current collectors, etc.

[0032] The positive electrode active material is not particularly limited; any known material can be used as the positive electrode active material in a lithium-ion secondary battery. Examples of positive electrode active materials include LiCoO2, LiNiO2, and NCM(Li(NiO2)2). x Co y Mn z 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, LiMn2O4, and Li(Ni) 0.25 Mn 0.75 Spinel-type positive electrode active materials such as Li₂O₄, LiCoMnO₄, and Li₂NiMn₃O₈, and olivine-type positive electrode active materials such as LiCoPO₄, LiMnPO₄, and LiFePO₄.

[0033] The reason for using pure water in the dissolution process S1 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 separation performance of the cation exchange membrane. Alkali metals and alkaline earth metals become contaminants in lithium recovery.

[0034] In the dissolution step S1, the dispersion contains a lithium-containing solid electrolyte, therefore the pH of the dispersion is 11 or higher and 14 or lower. To achieve a lithium recovery rate of over 80%, it is necessary to dissolve more than 0.4 mol / L of lithium in the dispersion, ideally more than 0.7 mol / L.

[0035] "Separation liquid recovery process"

[0036] In the separation liquid recovery process S2, the solid components contained in the dispersion, such as the positive electrode active material, positive electrode materials other than the positive electrode active material, current collector tabs, and current collectors, are filtered, separated, and removed, and the separation liquid is recovered. Here, the non-water-soluble solid components of the lithium-ion secondary battery are removed. Examples of non-water-soluble solid components include positive electrode active material, binder, conductive additives, tabs, and electrodes.

[0037] The separated liquid obtained in the separation liquid recovery process S2 contains, for example, chlorine (Cl), bromine (Br), phosphorus (P), sulfur (S), aluminum (Al), nickel (Ni), and copper (Cu).

[0038] "Oxidation process"

[0039] In oxidation step S3, the separation liquid is oxidized to generate acidic components, thus adjusting the pH of the separation liquid. The pH of the separation liquid is preferably 7 or higher and 12 or lower. The pH is adjusted by treating the separation liquid by allowing it to stand in air, aerating it with air (foaming), aerating it with oxidizing gases such as ozone, oxygen, or active oxygen (SO4), or heating the separation liquid. These treatments promote the reaction of phosphorus (P) in the separation liquid to form PO4, and the reaction of sulfur (S) in the separation liquid to form S2O3 and SO4, thereby adjusting the pH of the separation liquid. Active oxygen includes superoxide and hydroxyl radicals.

[0040] In the process of leaving the separated liquid to stand in the air, for example, leaving the separated liquid to stand for more than 10 hours and less than 100 days.

[0041] In the treatment of aerating the separated liquid with air, for example, aerating the separated liquid with air for more than 4 hours and less than 10 days.

[0042] In the treatment of aerating the separated liquid with oxidizing gases, for example, aerating the separated liquid with ozone for more than 2 hours but less than 5 hours.

[0043] In the process of heating the separated liquid, for example, the separated liquid is heated to above 40°C and below 90°C.

[0044] This causes hydroxides of copper, nickel, aluminum, etc., to precipitate out.

[0045] Taking advantage of the fact that the saturated solubility of copper and nickel in the separation solution is reduced to 10 mg / L within the pH range of 7-12, the pH of the separation solution is adjusted through oxidation treatment to promote the precipitation of hydroxides of copper, nickel, and aluminum. The pH of the dispersion immediately after the solid electrolyte is dissolved reaches about 12 due to the water solubility of lithium ions in the lithium-ion secondary battery. In addition, the sulfide reaction caused by hydrogen sulfide gas generated during the water solubility of the solid electrolyte results in the content of contaminants such as copper, nickel, and aluminum in the separation solution reaching several hundred mg / L. Therefore, to stabilize the ionic state in the separation solution, it is desirable to lower the pH of the separation solution to below 10. When the pH of the separation solution is below 7, copper and nickel are soluble in acid, thus leading to an increase in their solubility concentration.

[0046] Acidic liquids (sulfuric acid, hydrochloric acid, etc.) can also be used to adjust the pH of the separation liquid, but this is accompanied by the release of hydrogen sulfide, a harmful, flammable, and corrosive gas, thus incurring a significant burden. Since phosphorus and sulfur dissolve in large quantities in the separation liquid, it is desirable to oxidize them in the separation liquid to bring its pH to a neutral range. Therefore, in the lithium recovery method of this embodiment, acidic liquids are not used. Instead, the pH of the separation liquid is adjusted by treating it by allowing it to stand in air, aerating it with air (foaming), aerating it with an oxidizing gas such as ozone (foaming), or heating it.

[0047] "Separation process"

[0048] The lithium recovery method of this embodiment may also include a separation step S4. In the separation step S4, solid components (compounds containing aluminum, compounds containing nickel, compounds containing copper, etc.) are filtered and removed from the separation liquid after the oxidation step S3.

[0049] "Aeration process"

[0050] In aeration step S5, the separated liquid obtained from oxidation step S3 is aerated with air or an oxidizing gas. This further adjusts the pH of the separated liquid. Preferably, the pH of the separated liquid is 2 or lower. The pH value is adjusted by aeration (foaming) of the separated liquid with air or by aeration (foaming) with an oxidizing gas such as ozone, oxygen, or active oxygen. Through these treatments, the H₂S contained in the separated liquid is reduced. - (hydrogen sulfide ions), S2O3 2- The sulfur (thiosulfate ion) oxidizes the separation liquid strongly (below pH 2), thereby enabling the acid-soluble Li3PO4 (lithium phosphate) to be redissolved, inhibiting the precipitation of lithium phosphate from hindering lithium recovery and reducing the lithium recovery rate.

[0051] "Recycled raw material recovery process"

[0052] In the raw liquid recovery process S6, the oxidized separation liquid is subjected to solid-liquid separation to recover the raw liquid. In the raw liquid recovery process S6, the solid components (sulfur particles) are filtered and removed from the separation liquid after the aeration process S5.

[0053] "Extraction process"

[0054] In extraction step S7, an aqueous solution of lithium hydroxide is extracted from the recovered stock solution by electrodialysis using a cation exchange membrane.

[0055] In extraction step S7, materials used as cation exchange membranes include, for example, sodium sulfonate and polyolefins. When lithium concentration in an aqueous lithium hydroxide solution increases to pH 12 or higher, the recovery solution from the recovery source experiences strong oxidation at around pH 1 due to lithium reduction and the oxidation of anionic components. Therefore, the cation exchange membrane needs to be pH-tolerant over a wide range.

[0056] Electrodialysis using a cation exchange membrane recovers lithium ions from the feed solution. These ions pass through the cation exchange membrane, and on the permeate side, they react with water to form lithium hydroxide. In other words, an aqueous solution of lithium hydroxide is generated on the side after permeation through the cation exchange membrane. One example of an electrodialysis method is a constant current treatment of 0.3 A, triggered by the inter-electrode voltage reaching the membrane's withstand voltage limit. Another example of an electrodialysis method is a constant voltage treatment where the voltage is set below the membrane's withstand voltage, and the process stops when the current value falls below a certain value.

[0057] In extraction step S7, if copper (Cu), nickel (Ni), aluminum (Al), and phosphate ions (PO4) are present... 3- Concentrations of ions such as chloride (Cl), bromine (Br), and sulfate (SO4) in the recycled solution below tens of ppm do not permeate the cation exchange membrane. 2- These substances, such as lithium, hardly permeate the cation exchange membrane. Therefore, in the extraction step S7, these substances are separated from lithium.

[0058] "Ion exchange process"

[0059] The lithium recovery method of this embodiment may also include an ion exchange step S8. In the ion exchange step S8, the lithium hydroxide aqueous solution obtained by the extraction step S7 is contacted with an anion exchange resin to remove trace amounts (ppm level) of chloride (Cl), bromine (Br), and sulfate (SO4) ions contained in the lithium hydroxide aqueous solution. 2- Impurity anions such as )

[0060] In the ion exchange process S8, it is preferable that the temperature at which the lithium hydroxide aqueous solution comes into contact with the anion exchange resin is 10°C or higher and 40°C or lower.

[0061] Through the above process, a high-purity lithium hydroxide aqueous solution can be obtained.

[0062] The lithium recovery method according to this embodiment can suppress the obstacles to recovery caused by the formation of sulfur particles, the obstacles to lithium recovery caused by the precipitation of lithium phosphate, and the reduction of lithium recovery rate, and can recover lithium separately from the aqueous solution of solid electrolyte by using electrodialysis performed through a cation exchange membrane.

[0063] [Lithium recovery device]

[0064] One embodiment of the present invention relates to a lithium recovery device that recovers lithium from used lithium-ion secondary batteries.

[0065] Figure 2 This is a schematic cross-sectional view illustrating the lithium recovery apparatus of this embodiment.

[0066] The lithium recovery device 1 includes a processing tank 10, a cation exchange membrane 20, a first electrode 30, a second electrode 40, and a power supply 50.

[0067] The treatment tank 10 has a first space 11 and a second space 12 separated by a cation exchange membrane 20 disposed in the treatment tank 10. The inner surface of the first space 11 that is separated from the cation exchange membrane 20 is designated as the main surface 10a of one side of the treatment tank 10. The inner surface of the second space 12 that is separated from the cation exchange membrane 20 is designated as the main surface 10b of the other side of the treatment tank 10.

[0068] The treatment tank 10 is a tank for treating a dispersion obtained by dispersing the water-soluble solid electrolyte contained in the treated component of a deactivated lithium-ion secondary battery in pure water through electrodialysis.

[0069] The cation exchange membrane 20 is disposed in the center of the treatment tank 10 along the height direction of the treatment tank 10 in such a way that it separates the first space 11 and the second space 12 of the treatment tank 10.

[0070] As the cation exchange membrane 20, the same cation exchange membrane as the lithium recovery method described in the above embodiments can be used.

[0071] The first electrode 30 is disposed in the first space 11 on one of the main surfaces 10a of the processing tank 10.

[0072] The second electrode 40 is disposed in the second space 12 on the main surface 10b side of the processing tank 10.

[0073] A 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.

[0074] The lithium recovery method performed by the lithium recovery device 1 of this embodiment is explained.

[0075] Prepare the separated liquid after the dissolution step S1, the separation liquid recovery step S2, the oxidation step S3, the aeration step S5, and the recovery raw liquid recovery step S7 in the lithium recovery method of the above-described embodiments.

[0076] In the lithium recovery apparatus 1 of this embodiment, the extraction step S7 of the lithium recovery method of the above embodiment is performed.

[0077] Separation liquid is injected into the first space 11 of the treatment tank 10, and a dilute lithium hydroxide solution is injected into the second space 12 of the treatment tank 10 as a recovery liquid to ensure conductivity.

[0078] In this state, when a voltage is applied from the power source 50 to the first electrode 30 and the second electrode 40, electrodialysis begins. Lithium ions contained in the separation solution in the first space 11 pass through the cation exchange membrane and move to the recovery solution in the second space 12. The lithium ions that have passed through the cation exchange membrane react with water in the second space 12 to form lithium hydroxide. That is, an aqueous solution of lithium hydroxide is generated in the second space 12. It should be noted that trace amounts (ppm level) of chloride (Cl), bromine (Br), and sulfate ions (SO42-) are present. 2- Through the cation exchange membrane, trace amounts (in the ppm range) of chloride (Cl), bromine (Br), and sulfate ions (SO42-) are present in aqueous lithium hydroxide solution. 2- ).

[0079] The lithium recovery apparatus according to this embodiment can recover lithium separately from an aqueous solid electrolyte solution without the need to add a conditioning solution to adjust the pH, by using electrodialysis performed through a cation exchange membrane.

[0080] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Various modifications and alterations can be made within the scope of the spirit of the present invention as described in the technical solution.

[0081] The present invention has the following solution.

[0082] [1] A lithium recovery method, which is a lithium recovery method for recovering lithium from a used lithium-ion secondary battery having an electrode body, wherein the electrode body has a positive electrode, a sulfide solid electrolyte and a negative electrode, wherein,

[0083] The lithium recovery method includes:

[0084] The dissolution process involves dissolving the solid electrolyte and lithium compounds contained in the deactivated lithium-ion secondary battery in pure water to obtain a dispersion.

[0085] The separation liquid recovery process involves performing solid-liquid separation on the dispersion to recover the separation liquid;

[0086] The oxidation process involves oxidizing the separation liquid to generate acidic components and adjusting the pH of the separation liquid.

[0087] The aeration process involves aerating the oxidized separation liquid with air or an oxidizing gas to adjust the pH of the separation liquid.

[0088] The raw liquid recovery process involves solid-liquid separation of the separated liquid after aeration treatment to recover the raw liquid; and

[0089] The process of extracting an aqueous solution of lithium hydroxide from the recovered stock solution by electrodialysis using a cation exchange membrane.

[0090] According to the above scheme, the separation liquid is oxidized to generate acidic components. After adjusting the pH of the separation liquid, it is further aerated with air or oxidizing gas. This can suppress the generation of sulfur particles that hinders recovery, redissolve the acid-soluble Li3PO4 (lithium phosphate), suppress the precipitation of lithium phosphate that hinders lithium recovery, and reduce the lithium recovery rate.

[0091] [2] Based on the lithium recovery method described in [1], the pH of the separation liquid is adjusted to 7-12 through the oxidation process, and the pH of the separation liquid is adjusted to below 2 through the aeration process.

[0092] According to the above scheme, the saturated solubility of copper and nickel in the separation solution can be reduced to 10 mg / L within the pH range of 7-12. This allows for pH adjustment of the separation solution through oxidation treatment, promoting the precipitation of hydroxides of copper, nickel, and aluminum. Furthermore, the oxidation treatment reduces the amount of H₂S contained in the separation solution. - (hydrogen sulfide ions), S2O3 2- (Thiosulfate ions) are oxidized by sulfur, thereby suppressing the obstacles to recovery by removing sulfur particles after precipitation before electrodialysis and by filtration, and by strongly oxidizing the separation liquid (pH 2~5) to redissolve the acid-soluble Li3PO4 (lithium phosphate), thereby suppressing the precipitation of lithium phosphate from hindering lithium recovery and reducing the lithium recovery rate.

[0093] [3] Based on the lithium recovery method described in [1] or [2], there is also a step of using anion exchange resin to remove impurity anions from the lithium hydroxide aqueous solution.

[0094] According to the above scheme, lithium hydroxide aqueous solution can be contacted with anion exchange resin to remove trace amounts (ppm level) of chloride (Cl), bromine (Br), and sulfate (SO4) ions contained in the lithium hydroxide aqueous solution. 2- )wait.

Claims

1. A lithium recovery method for recovering lithium from a used lithium-ion secondary battery having an electrode body, wherein the electrode body has a positive electrode, a sulfide solid electrolyte, and a negative electrode, wherein... The lithium recovery method includes: The dissolution process involves dissolving the solid electrolyte and lithium compounds contained in the deactivated lithium-ion secondary battery in pure water to obtain a dispersion. The separation liquid recovery process involves performing solid-liquid separation on the dispersion to recover the separation liquid; The oxidation process involves oxidizing the separation liquid to generate acidic components and adjusting the pH of the separation liquid. The aeration process involves aerating the oxidized separation liquid with air or an oxidizing gas to adjust the pH of the separation liquid. The raw liquid recovery process involves solid-liquid separation of the separated liquid after aeration treatment to recover the raw liquid; and The process of extracting an aqueous solution of lithium hydroxide from the recovered stock solution using electrodialysis via a cation exchange membrane.

2. The lithium recovery method according to claim 1, wherein, The pH of the separated liquid is adjusted to 7-12 through the oxidation process, and the pH of the separated liquid is adjusted to below 2 through the aeration process.

3. The lithium recovery method according to claim 1, wherein, The lithium recovery method also includes a step of removing impurity anions from the lithium hydroxide aqueous solution using anion exchange resin.

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