Method for treating lithium-ion battery waste and method for recovering metal

Abstract

This method for treating lithium-ion battery waste includes a discharge step for bringing lithium-ion battery waste into contact with a liquid containing at least one solution among the following (1) to (3). (1) An inorganic acid sodium salt aqueous solution derived from a back-extraction solution obtained by performing a manganese and / or aluminum extraction step on a metal-containing aqueous solution obtained by leaching metals including manganese and / or aluminum in a battery powder of the lithium-ion battery waste. (2) An inorganic acid sodium salt aqueous solution as a post-extraction solution obtained by sequentially performing, on a metal-containing aqueous solution obtained by leaching metals including cobalt in the battery powder of the lithium-ion battery waste, first-stage cobalt ion extraction, back extraction, and second-stage cobalt-ion extraction in a cobalt extraction step. (3) An inorganic acid lithium salt aqueous solution as a desalination solution obtained by performing an electrodialysis step on a metal-containing aqueous solution obtained by leaching metals including lithium in the battery powder of the lithium-ion battery waste.

Description

Method for Treating Lithium Ion Battery Waste and Method for Recovering Metals

[0001] This specification describes a method for treating lithium ion battery waste and a method for recovering metals.

[0002] In recent years, recovery of valuable metals from battery waste such as lithium ion battery waste discarded due to product life, manufacturing defects or other reasons has been widely studied from the perspective of effective utilization of resources.

[0003] To recover valuable metals from lithium ion battery waste, wet treatment is sometimes performed on battery powder obtained by subjecting lithium ion battery waste to heat treatment or other predetermined dry pretreatment.

[0004] In wet treatment, for example, metals such as cobalt, nickel, manganese, lithium, aluminum, and iron in the battery powder are leached with an acid to obtain a metal-containing aqueous solution in which the metals are dissolved. Then, aluminum, iron, manganese, and the like are removed, and cobalt, nickel, and the like are separated from the metal-containing aqueous solution by pH adjustment or solvent extraction.

[0005] Regarding pretreatment, Patent Document 1 discloses, in "a method for inactivating a used lithium-cobalt secondary battery, characterized in that an organic solvent containing an electrolyte in the battery is leached into a solution by opening the cobalt-containing battery and then immersing it in a solution, or by opening the battery in the solution", that "an aqueous solution containing at least one selected from the group consisting of sodium chloride, sodium sulfate and ammonium sulfate as an electrolyte is used as the solution".

[0006] Patent Document 2 states that, "In the discharge process, in order to recover valuable metals from used lithium-ion batteries, the batteries are discharged before dismantling the used batteries. This is because it is dangerous to dismantle the batteries by crushing and dismantling them in the crushing and disintegration process described later, and the batteries are discharged to render them harmless." It also states that, "In this discharge process, a discharge solution such as an aqueous solution of sodium sulfate or an aqueous solution of sodium chloride is used, and the used batteries are discharged by immersing them in the aqueous solution."

[0007] Patent Document 3 states, "In one embodiment of the present invention, an aqueous solution containing an electrolyte can be stored in the inlet tank, and water can be stored in the outlet tank. In this case, the electrical energy of the LIB can be removed in the inlet tank before introducing the LIB into the heat treatment furnace, thereby suppressing discharge in the furnace, preventing lithium ignition, and enabling stable processing. Furthermore, when removing the roasted LIB from the furnace, the electrolyte adhering to the roasted material can be removed in the outlet tank, preventing the electrolyte from being mixed into the subsequent valuable material." Patent Document 3 also states, "General-purpose electrolytes can be used as the above-mentioned electrolyte, for example, sodium chloride, sodium sulfate, and calcium chloride."

[0008] Japanese Patent Publication No. 10-223264, Japanese Patent Publication No. 2012-41621, Japanese Patent Publication No. 2021-142475

[0009] In the pretreatment of lithium-ion battery waste, it is sometimes preferable to immerse the waste in an electrolyte solution to promote discharge. However, purchasing commercially available electrolytes for discharge increases processing costs. This has a significant impact on costs, especially when processing large quantities of lithium-ion battery waste.

[0010] This specification provides a method for processing lithium-ion battery waste and a method for recovering metals from lithium-ion battery waste, which allows for the discharge of lithium-ion battery waste at a relatively low processing cost.

[0011] The method for processing lithium-ion battery waste disclosed in this specification includes a discharge step in which the lithium-ion battery waste is brought into contact with a liquid containing at least one of the following solutions (1) to (3): (1) An aqueous solution of inorganic sodium acid obtained by performing a manganese and / or aluminum extraction step on a metal-containing aqueous solution obtained by leaching out metals containing manganese and / or aluminum from the battery powder of lithium-ion battery waste. (2) An aqueous solution of inorganic sodium acid obtained as an extraction solution by sequentially performing a first-stage cobalt ion extraction and back-extraction and a second-stage cobalt ion extraction in a cobalt extraction step on a metal-containing aqueous solution obtained by leaching out metals containing cobalt from the battery powder of lithium-ion battery waste. (3) An aqueous solution of inorganic lithium acid obtained as a desalting solution by performing an electrodialysis step on a metal-containing aqueous solution obtained by leaching out metals containing lithium from the battery powder of lithium-ion battery waste.

[0012] The metal recovery method disclosed in this specification is a method for recovering metal from lithium-ion battery waste, and includes the lithium-ion battery waste treatment method described above.

[0013] According to the lithium-ion battery waste processing method described above, lithium-ion battery waste can be discharged at a relatively low processing cost.

[0014] This is a flowchart showing an example of a metal recovery method including a method for processing lithium-ion battery waste according to one embodiment. This is a schematic cross-sectional view showing an example of a bipolar membrane electrodialysis apparatus usable in the electrodialysis process included in the metal recovery method of Figure 1. This is a graph showing the change in voltage over time during a discharge test in the embodiment.

[0015] The following describes in detail embodiments of a method for processing lithium-ion battery waste (hereinafter also simply referred to as the "processing method"). One embodiment of the method for processing lithium-ion battery waste includes a discharge step in which the lithium-ion battery waste is brought into contact with a liquid containing a predetermined solution.

[0016] The specified solution refers to at least one of the following: (1) an aqueous solution of inorganic sodium acid derived from the back-extracted liquid obtained by performing a manganese and / or aluminum extraction step on an aqueous metal-containing aqueous solution obtained by leaching metals including manganese and / or aluminum from battery powder of lithium-ion battery waste (hereinafter also referred to as "Solution A"), (2) an aqueous solution of inorganic sodium acid obtained as the extracted liquid by sequentially performing a first-stage cobalt ion extraction and back-extraction and a second-stage cobalt ion extraction in a cobalt extraction step on an aqueous metal-containing aqueous solution obtained by leaching metals including cobalt from battery powder of lithium-ion battery waste (hereinafter also referred to as "Solution B"), and (3) an aqueous solution of inorganic lithium acid obtained as a desalted liquid obtained by performing an electrodialysis step on an aqueous metal-containing aqueous solution obtained by leaching metals including lithium from battery powder of lithium-ion battery waste (hereinafter also referred to as "Solution C").

[0017] Solutions A to C are all generated during the wet treatment of metals in lithium-ion battery waste (from the acid leaching process to the electrodialysis process described later) and are often discarded. However, since each contains a specific electrolyte, they can be effectively utilized by being included in the liquid to which the lithium-ion battery waste is contacted for discharge during the discharge process. Therefore, processing costs can be reduced compared to using only commercially available substances as electrolytes added to the liquid. However, in the discharge process, it is sufficient that one or more of solutions A to C are included in the liquid to which the lithium-ion battery waste is contacted, and if necessary, commercially available sulfates, etc., may be added to this liquid.

[0018] The processing method for obtaining at least one of solutions A to C does not need to be the same as or performed at the same time as the processing method in the embodiment that includes a discharge step. For example, at least one of solutions A to C obtained in a predetermined step of a previously performed processing method may be stored and used later when performing a discharge step in the processing method of the embodiment. In other words, the processing method of the embodiment may not include a step for obtaining at least one of solutions A to C.

[0019] (Lithium-ion battery waste) The lithium-ion battery waste covered by this initiative consists of lithium-ion secondary batteries used in vehicles or consumer electronics that have been discarded due to the end of their lifespan, manufacturing defects, or other reasons. Examples of lithium-ion secondary batteries used in vehicles include those contained in battery packs installed in hybrid vehicles and electric vehicles. Examples of lithium-ion secondary batteries used in consumer electronics include those used in mobile phones and various other electronic devices. Recovering cobalt, nickel, and other valuable metals from such lithium-ion battery waste is required from the perspective of effective resource utilization.

[0020] An automotive battery pack, including a lithium-ion secondary battery for use in a vehicle, generally comprises a metal case that forms the surrounding enclosure, and a battery, such as a lithium-ion secondary battery having multiple battery cells, and other components housed inside the case. Multiple battery cells may be bundled together and included in the automotive battery pack as a battery module. Automotive battery packs come in various shapes depending on the space constraints of the vehicle in which they are installed, but some have an elongated, vertical shape that is roughly rectangular in plan view, such as a rectangular parallelepiped.

[0021] Lithium-ion battery waste typically consists of a positive electrode material, which is made of one or more single metal oxides or two or more composite metal oxides from lithium, nickel, cobalt, and manganese, coated and fixed onto an aluminum foil (positive electrode substrate) with an organic binder such as polyvinylidene fluoride (PVDF); a negative electrode material made of carbon-based materials; and an organic electrolyte such as ethylene carbonate or diethyl carbonate. In addition, lithium-ion battery waste may also contain copper, iron, and other materials.

[0022] Lithium-ion battery waste includes not only automotive battery packs but also battery cells removed from automotive battery packs and the like. Battery modules, which are bundles of battery cells, may also be considered lithium-ion battery waste. Battery cells may contain electrolyte and resin.

[0023] (Pretreatment) Pretreatment should involve at least a discharge process for lithium-ion battery waste, but typically, the discharge process, heat treatment process, crushing process, and physical sorting process are performed in this order.

[0024] In the discharge process, lithium-ion battery waste is brought into contact with a liquid containing at least one of solutions A to C. As will be described in detail later, solution A is an aqueous solution of inorganic sodium acid derived from the back-extraction solution of the manganese and / or aluminum extraction process, solution B is an aqueous solution of inorganic sodium acid as the extraction solution of the cobalt extraction process, and solution C is an aqueous solution of inorganic lithium acid as the desalination solution of the electrodialysis process. All of these solutions contain either an inorganic sodium acid or an inorganic lithium acid electrolyte. Therefore, by having the liquid brought into contact with the lithium-ion battery waste contain solutions A, B and / or C, the discharge of the lithium-ion battery waste can be effectively performed. Specific examples of aqueous solutions of inorganic sodium acid include aqueous sodium sulfate, aqueous sodium chloride, and aqueous sodium nitrate, while specific examples of aqueous solutions of inorganic lithium acid include aqueous lithium sulfate, aqueous lithium chloride, and aqueous lithium nitrate.

[0025] Typically, lithium-ion battery waste can be brought into contact with the liquid by immersing it in the liquid. However, lithium-ion battery waste may have terminals or wiring extending from the cells, and if these come into contact with the liquid, discharge can occur. Therefore, in the discharge process, it is sufficient for at least a portion of the lithium-ion battery waste to be in contact with the liquid, and immersion in the liquid is not always necessary.

[0026] If the liquid contains an aqueous solution of sodium sulfate among the aqueous solutions of inorganic sodium acid salts of solution A and / or B, it is preferable to adjust the sodium sulfate concentration in the liquid to 1% to 15% by mass, and more preferably to 4% to 10% by mass. If the liquid contains an aqueous solution of lithium sulfate among the aqueous solutions of inorganic lithium acid salts of solution C, it is preferable to adjust the lithium sulfate concentration in the liquid to 1% to 20% by mass, and more preferably to 3% to 10% by mass. If the concentration is too low, the discharge may take a long time, and if it is too high, there is a concern that crystals may precipitate.

[0027] If aqueous solutions of hydrochloride salts such as sodium chloride or potassium chloride are used to discharge lithium-ion battery waste, it can lead to corrosion of the metals contained in the lithium-ion battery waste and leakage of the electrolyte, raising concerns about safety and environmental impact. To address these concerns, it is preferable to use sulfate solutions, such as sodium sulfate or lithium sulfate, among the inorganic sodium salt aqueous solutions and inorganic lithium salt aqueous solutions, respectively, for solutions A to C. Furthermore, using sulfate solutions allows for faster discharge of lithium-ion battery waste compared to using carbonate solutions such as sodium carbonate, thus enabling the discharge to be completed in a shorter time.

[0028] The inorganic sodium acid aqueous solutions of Solution A and Solution B are preferred over the inorganic lithium acid aqueous solution of Solution C because they have a faster discharge rate. However, the inorganic lithium acid aqueous solution of Solution C is preferred because it does not lead to the inclusion of sodium, which becomes an impurity in the subsequent wet treatment. When lithium-ion battery waste is immersed in a liquid containing the inorganic sodium acid aqueous solutions of Solution A or Solution B and discharged, it is desirable to perform a washing step to remove the sodium adhering to the lithium-ion battery waste before the subsequent acid leaching step. Furthermore, when the inorganic lithium acid aqueous solution of Solution C is used in the discharge step, the lithium contained therein can adhere to the lithium-ion battery waste, which has the advantage of maintaining a high lithium ion concentration in the wet treatment and recovering lithium from Solution C.

[0029] The pH of the liquid containing solutions A, B, and / or C is preferably 6 to 10, and more preferably 7 to 9. If the pH is too low, there is a risk that metals such as aluminum and iron used in the casing may dissolve, and if it is too high, there is a concern that the aluminum may dissolve.

[0030] The liquid temperature while the lithium-ion battery waste is immersed in the liquid may be set to 10°C to 50°C. The immersion time of the lithium-ion battery waste in the liquid can be, for example, 24 to 72 hours if the liquid contains solution A, 24 to 72 hours if the liquid contains solution B, and 24 to 72 hours if the liquid contains solution C. This allows the lithium-ion battery waste to be sufficiently discharged while suppressing the lengthening of the lead time.

[0031] After the discharge process, a heat treatment process may be performed. In the heat treatment process, the lithium-ion battery waste described above is heated. Heat treatment decomposes and removes the electrolyte and organic binder, and metals such as lithium and cobalt contained in the lithium-ion battery waste can be changed into a form that is easily soluble in the acid leaching solution in the acid leaching process. Although the composition of the positive electrode active material changes due to heat treatment, it is referred to as the positive electrode active material here even after heat treatment. During heating, the lithium-ion battery waste can be held at a temperature range of, for example, 100°C to 800°C for 0.5 to 6 hours. The heat treatment can be performed in an atmospheric atmosphere or an inert atmosphere such as nitrogen, and the heat treatment in these atmospheres may be performed in this order or in the reverse order. As the heat treatment furnace, for example, a batch-type stationary furnace or a continuous-type rotary kiln furnace or various other types of furnaces can be used.

[0032] Subsequently, the lithium-ion battery waste can be crushed in the crushing process. In the crushing process, the lithium-ion battery waste's case is crushed, exposing the interior, and it can be broken down into somewhat fine fragments, granules, or powder. Various known devices or equipment can be used in the crushing process, but it is particularly preferable to use an impact-type crusher that can crush the lithium-ion battery waste by applying impact while cutting it. Examples of such impact-type crushers include sample mills, hammer mills, pin mills, wing mills, tornado mills, and hammer crushers.

[0033] After crushing the lithium-ion battery waste, a physical sorting process may be performed, for example, by sieving using a sieve with an appropriate mesh size. After the physical sorting process, a positive electrode material with aluminum foil may be obtained. In this case, the positive electrode material with aluminum foil may be treated with a solvent to dissolve the binder and separate the positive electrode material components from the aluminum foil.

[0034] By performing the pretreatment described above, lithium-ion battery waste becomes battery powder with concentrated positive electrode material components. Alternatively, to extract essentially only lithium from the battery powder, the battery powder may be brought into contact with water before the acid leaching process described later, allowing the lithium in the battery powder to leach into the water. In this case, the acid leaching process is performed on the battery powder as a residue after the water leaching. However, the battery powder may also be subjected to the acid leaching process without water leaching. If water leaching is omitted, it becomes easier to maintain a high lithium ion concentration in the liquid during the subsequent wet processing.

[0035] The battery powder obtained by pretreatment, if it contains nickel, has a nickel content of, for example, 1% to 30% by mass, typically 5% to 20% by mass. If it contains cobalt, the cobalt content in the battery powder is, for example, 1% to 30% by mass, typically 5% to 20% by mass. The battery powder may also contain, for example, 2% to 8% by mass of lithium, 1% to 30% by mass of manganese, 1% to 10% by mass of aluminum, 1% to 5% by mass of iron, and 1% to 10% by mass of copper.

[0036] (Acid Leaching) In the acid leaching process, the battery powder is brought into contact with an acidic leaching solution containing mineral or inorganic acids such as sulfuric acid, hydrochloric acid, or nitric acid to leach the battery powder. This dissolves mainly the metals in the battery powder, and a post-leaching solution containing these metals as metal ions is obtained. Here, the solution containing the metals in the battery powder as metal ions is referred to as a metal-containing aqueous solution. The metal-containing aqueous solution includes the post-leaching solution obtained in the acid leaching process and sent to the next process, as well as solutions obtained during or between the pH raising process and each extraction process.

[0037] Regarding pH, the acidic leachate during leaching is preferably -0.5 to 3.0, while the post-leaching solution after leaching is complete may have a pH of 0.5 to 2.0. During leaching, for example, the acidic leachate may be stirred at 100 rpm to 400 rpm using a stirrer as needed, and the liquid temperature may be set to 50°C to 80°C, and further to 65°C to 70°C.

[0038] The metal-containing aqueous solution (post-leaching solution) obtained in the acid leaching process may have, for example, a cobalt ion concentration of 10 g / L to 50 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a manganese ion concentration of 0 g / L to 50 g / L, an aluminum ion concentration of 1.0 g / L to 20 g / L, an iron ion concentration of 0.1 g / L to 5.0 g / L, and a copper ion concentration of 0.005 g / L to 0.2 g / L. The metal ion concentration in the solution can be confirmed by analysis using an ICP emission spectrometer.

[0039] (pH increase) In the pH increase step, the pH of the metal-containing aqueous solution is increased, causing at least some of the aluminum ions and / or at least some of the iron ions in the metal-containing aqueous solution to precipitate and separate them from the metal-containing aqueous solution.

[0040] The pH raising process may include, for example, a dealuminizing process in which at least some of the aluminum ions are precipitated and removed by raising the pH of the metal-containing aqueous solution, and a deirradiating process in which an oxidizing agent is then added to oxidize the iron ions, and the pH is further raised as needed to precipitate and remove the iron ions. However, if the metal-containing aqueous solution is substantially free of iron ions, the deirradiating process may be omitted.

[0041] In each of the aluminum removal process and the iron removal process, the pH may be adjusted within the range of 3.0 to 4.5. In the iron removal process, the ORP value during oxidation may be set to 300 mV to 900 mV. After precipitating aluminum in the aluminum removal process and after precipitating iron in the iron removal process, solid-liquid separation such as filtration can be performed using known apparatuses and methods such as a filter press or a thickener, thereby removing the neutralization residue as the precipitate.

[0042] In the aluminum removal process and the iron removal process, for example, lithium hydroxide, sodium hydroxide, sodium carbonate, ammonia, or the like can be used as an alkaline pH adjuster for increasing the pH of the metal-containing aqueous solution. Among these, from the viewpoint of cost reduction, it is preferable to use lithium hydroxide produced from lithium recovered by wet processing, such as a lithium hydroxide solution obtained after the electrodialysis step or the hydroxylation step described later. The pH increasing step may be included in at least a part of the steps in which lithium hydroxide is used as a pH adjuster in wet processing. The oxidizing agent used in the iron removal process is not particularly limited as long as it can oxidize iron, but is preferably hydrogen peroxide, manganese dioxide, a positive electrode active material, and / or a manganese-containing leaching residue obtained by leaching the positive electrode active material.

[0043] (Solvent Extraction) After the above pH extraction step, one or more extraction steps by solvent extraction can be performed according to the types of metal ions contained in the metal-containing aqueous solution. This extraction step may include, for example, a manganese and / or aluminum extraction step, a cobalt extraction step, and a nickel extraction step in this order.

[0044] In the manganese and / or aluminum extraction step, manganese ions and / or the remaining aluminum ions remaining in the solution without being precipitated in the pH increasing step can be extracted and removed by solvent extraction. In this case, after manganese ions and aluminum ions are extracted into a solvent, a post-extraction solution from which these ions have been removed can be obtained.

[0045] For extracting manganese ions and / or aluminum ions, a phosphate ester-based extractant (such as di-2-ethylhexyl phosphoric acid (abbreviation: D2EHPA or trade name: DP-8R)), or a mixture of a phosphate ester-based extractant and an aldoxime or an oxime-based extractant mainly composed of aldoxime (such as 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecylsalicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), 5-nonylsalicylaldoxime (trade name: ACORGAM5640)) can be used. The extractant is typically diluted with a hydrocarbon organic solvent such as aromatic, paraffin, or naphthene solvent and used as a solvent.

[0046] When extracting manganese ions and / or aluminum ions, the equilibrium pH is preferably set to 2.3 to 3.5, more preferably 2.5 to 3.0. From the viewpoint of cost reduction, lithium hydroxide generated from lithium obtained by wet processing (such as the lithium hydroxide solution obtained after the electrodialysis step described later) is preferably used as the alkaline pH adjuster used in this step, but separately prepared lithium hydroxide or the like may also be used.

[0047] For extraction, it is desirable to perform extraction by countercurrent multi-stage extraction in which the flow directions of the aqueous phase and the solvent supplied for each extraction are opposite. By this method, the extraction of other metal ions such as cobalt ions, nickel ions, and lithium ions can be suppressed, and the extraction rate of manganese ions can be increased. In the case of countercurrent multi-stage extraction, for example, it is effective to set the equilibrium pH during the first-stage extraction within the above range, and increase the equilibrium pH during extraction as the number of stages increases. Countercurrent multi-stage extraction is also preferable for the cobalt extraction step and nickel extraction step described later.

[0048] The back-extraction solution obtained in the manganese and / or aluminum extraction process contains manganese ions and / or aluminum ions and inorganic acid anions. Previously, this back-extraction solution could not be discarded directly. Therefore, sodium hydroxide was added to the back-extraction solution to precipitate and remove manganese and aluminum as hydroxides before disposal. By using this waste liquid as solution A in the discharge process, it can be effectively utilized, contributing to cost reduction.

[0049] In the cobalt extraction process, cobalt ions are separated from the metal-containing aqueous solution obtained as a post-extraction solution after the manganese extraction process by solvent extraction. The cobalt extraction process may include a first-stage extraction and back-extraction of cobalt ions, followed by a second-stage extraction and back-extraction of cobalt ions, in this order.

[0050] For the first stage of cobalt ion extraction, it is preferable to use a solvent containing a phosphonic acid ester extractant such as 2-ethylhexyl 2-ethylhexylphosphonic acid (trade names: PC-88A, Ionquest 801). During extraction, the equilibrium pH can be preferably set to 5.0 to 6.0, more preferably to 5.0 to 5.5. In this case, from the viewpoint of cost reduction, lithium hydroxide produced from lithium extracted by wet processing (such as the lithium hydroxide solution obtained after the electrodialysis process described later) may be used as the pH adjuster, but a commercially available product of relatively high purity lithium hydroxide prepared separately may also be used.

[0051] The solvent containing the extracted cobalt ions may be scrubbed one or more times as needed. The scrubbing solution can be, for example, a sulfuric acid solution, with an equilibrium pH of 3.5 to 5.5. Then, using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, the pH can be adjusted to, for example, 2.0 to 4.0, and the cobalt ions can be back-extracted from the solvent from which the cobalt ions were extracted to obtain the back-extracted solution.

[0052] The back-extracted solution obtained from the first stage of cobalt ion extraction and back-extraction may contain magnesium ions in addition to cobalt ions. To separate these magnesium ions, a second stage of cobalt ion extraction and back-extraction can be performed on the back-extracted solution.

[0053] In the second stage of cobalt ion extraction, carboxylic acid-based extractants such as neodecanoic acid and naphthenic acid can be used, but among them, neodecanoic acid-based carboxylic acid extractants, specifically Versatic Acid 10 (also known as VA-10) manufactured by Shell Chemical Corporation, are preferred. The equilibrium pH during extraction is preferably 6.0 to 7.0.

[0054] If sulfuric acid is used in the first stage of back-extraction of cobalt ions, the post-extract solution obtained after the second stage of cobalt ion extraction will contain sulfate ions. Also, for example, if a pH adjusting agent containing sodium hydroxide is used to adjust the equilibrium pH during the second stage of cobalt ion extraction, the sodium ions of the sodium hydroxide tend to be easily distributed into the aqueous phase, so the post-extract solution may contain sodium ions. In this case, the post-extract solution becomes an aqueous solution of an inorganic acid sodium salt containing inorganic acid anions and sodium ions, and can be effectively used as solution B in the discharge step described above.

[0055] For the solvent from which cobalt ions have been extracted, scrubbing is performed to an equilibrium pH of 5.5 to 6.5, if necessary. Then, back-extraction is performed using a back-extract solution containing sulfuric acid, hydrochloric acid, or nitric acid, for example, to a pH of 1.0 to 4.0. To obtain cobalt salts such as cobalt sulfate from this back-extract solution, crystallization can be performed by heating and concentrating the back-extract solution.

[0056] In the nickel extraction process, nickel ions are separated from the metal-containing aqueous solution obtained as a post-extraction solution in the first stage of the cobalt extraction process by solvent extraction. As the solvent, those containing carboxylic acid-based extractants such as neodecanoic acid and naphthenic acid can be used. At this time, it is preferable to set the equilibrium pH to 6.0 to 8.0, and for adjustment, lithium hydroxide produced from lithium extracted by wet treatment (such as the lithium hydroxide solution obtained after the electrodialysis process described later) may be used, but relatively high-purity lithium hydroxide such as commercially available products prepared separately may also be used.

[0057] After scrubbing the solvent from which nickel ions have been extracted, if necessary, back-extraction can be performed using a back-extract solution containing sulfuric acid, hydrochloric acid, or nitric acid, for example, with a pH of 1.0 to 3.0. Subsequently, the back-extracted solution can be heated and concentrated to crystallize the nickel ions as nickel salts such as nickel sulfate.

[0058] The metal-containing aqueous solution remaining after nickel ions have been extracted mainly contains lithium ions. At least a portion of this metal-containing aqueous solution may be mixed with the acidic leachate in the acid leaching step. This allows the lithium ions contained in the metal-containing aqueous solution to be circulated throughout the series of steps from acid leaching to extraction. Preferably, after the lithium ion concentration in the metal-containing aqueous solution has increased to a certain extent by circulating the lithium ions in this way, the electrodialysis step described below can be performed.

[0059] (Electrodialysis) After the extraction process, the metal-containing aqueous solution is subjected to electrodialysis after removing impurities such as nickel ions, cobalt ions, manganese ions, and magnesium ions as needed. The term "impurities" used here is used to distinguish them from lithium ions, which are the main component of the metal-containing aqueous solution subjected to electrodialysis, but these are also metals that can be recovered.

[0060] To remove impurities from a metal-containing aqueous solution before electrodialysis, for example, a pH adjusting agent can be added to the metal-containing aqueous solution, which may have a pH of 3.0 to 6.0, to raise the pH of the metal-containing aqueous solution, preferably to 8.0 to 13.0. This allows for the selective deposition and precipitation of impurity metal ions from among the lithium ions and impurity metal ions in the metal-containing aqueous solution. From the viewpoint of cost reduction, lithium hydroxide produced from lithium extracted by wet treatment (such as a lithium hydroxide solution obtained after the electrodialysis process) may be used as the pH adjusting agent, but a commercially available product of relatively high purity lithium hydroxide may also be used.

[0061] Furthermore, when removing impurities from a metal-containing aqueous solution, resins such as cation exchange resins and / or chelate resins may be used. A cation exchange resin is a synthetic resin that binds to cations by having acidic groups on its surface. A chelate resin is a resin that has functional groups that form complexes with metal ions. By pre-adsorbing lithium ions as exchange ions onto the cation exchange resin or chelate resin, ion exchange occurs between the metal ions of impurities in the metal-containing aqueous solution and the lithium ions when the resin is brought into contact with the metal-containing aqueous solution.

[0062] In electrodialysis, for example, a commercially available bipolar membrane electrodialysis apparatus is used to prepare a lithium hydroxide solution from a metal-containing aqueous solution. As an example, the bipolar membrane electrodialysis apparatus 1 shown in Figure 2 (hereinafter also simply referred to as "electrodialysis apparatus 1") has an anode 2 and a cathode 3 in its cell, and a bipolar membrane 4, an anion exchange membrane 5, a cation exchange membrane 6, and a bipolar membrane 7 arranged sequentially between the anode 2 and cathode 3 from the anode 2 side to the cathode 3 side. As a result, the inside of the cell is divided into a desalination chamber R1 between the anion exchange membrane 5 and the cation exchange membrane 6, an acid chamber R2 between the bipolar membrane 4 and the anion exchange membrane 5, and an alkali chamber R3 between the cation exchange membrane 6 and the bipolar membrane 7. The bipolar membranes 4 and 7 are each constructed by overlapping a cation exchange layer and an anion exchange layer.

[0063] To perform electrodialysis with the electrodialysis apparatus 1 shown in the figure, a metal-containing aqueous solution is placed in the desalination chamber R1, and pure water is placed in the acid chamber R2 and alkali chamber R3 respectively, and a predetermined voltage is applied between the anode 2 and the cathode 3. Then, lithium ions (Li) in the metal-containing aqueous solution in the desalination chamber R1 are removed. + ) passes through the cation exchange membrane 6 and moves to the alkaline chamber R3. In the alkaline chamber R3, water (H2O) is decomposed by the bipolar membrane 7 and hydroxide ions (OH) are formed. - Since ) is present, a lithium hydroxide solution is obtained as the post-dialysis fluid.

[0064] Meanwhile, the anions of the inorganic acid in the metal-containing aqueous solution in the desalination chamber R1 pass through the anion exchange membrane 5 and move to the acid chamber R2. In the acid chamber R2, these anions and hydrogen ions (H₂O) generated from water (H₂O) by the bipolar membrane 4 are exchanged. + This generates an acid solution such as sulfuric acid solution. As a result, the post-dialysis solution (lithium hydroxide solution) obtained in alkaline chamber R3 contains almost no inorganic acid anions. Note that the inorganic acid anions are sulfate ions (SO4) in the example shown. 2- However, depending on the type of acid used in the acid leaching process, nitrate ions (NO3) may be present. - ) or chloride ions (Cl - ) This may be the case.

[0065] In desalination chamber R1, the lithium salt is separated from the metal-containing aqueous solution as described above, resulting in a desalination solution. The anion concentration of the inorganic acid tends to be higher in the acid solution than in the post-dialysis solution (lithium hydroxide solution), and also higher in the desalination solution than in the post-dialysis solution (lithium hydroxide solution).

[0066] The desalination solution may contain residual anions of inorganic acids and lithium ions, as lithium salts are not completely separated by electrodialysis, resulting in an aqueous solution of inorganic acid lithium salt. This desalination solution can be effectively used as the aqueous solution of inorganic acid lithium salt in solution C in the discharge process described above. The desalination solution may not contain sodium ions. When using the desalination solution as solution C, it is preferable that it does not contain sodium, as sodium can be an impurity.

[0067] The post-dialysis solution (lithium hydroxide solution) obtained by electrodialysis can be effectively used as a pH adjuster in at least some steps of the wet treatment process. After electrodialysis, if necessary, the lithium ion concentration of the lithium hydroxide solution may be increased by heating or other means before it is used as a pH adjuster.

[0068] (Crystallization) The lithium hydroxide solution obtained as a post-dialysis solution in the electrodialysis process can be subjected to a crystallization process. For example, as described above, if the lithium hydroxide solution is returned to the wet treatment as a pH adjuster, the lithium ion concentration in the solution may gradually increase due to the lithium in the battery powder newly added to the wet treatment. Depending on the lithium ion concentration, a crystallization process may be performed to recover the lithium hydroxide.

[0069] In the crystallization process, crystallization operations such as heating and concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heating and concentration, a higher temperature during crystallization is preferable as it speeds up the process. However, after crystallization, the temperature at which the precipitate is dried should preferably be below 60°C to prevent the desorption of crystal water. This is because anhydrous lithium hydroxide from which crystal water has been desorbed is hygroscopic and difficult to handle. The lithium hydroxide produced in the crystallization process may be subjected to pulverization or other treatments to adjust its physical properties to the required level.

[0070] (Potential Contribution to SDGs) According to the embodiment described above, lithium-ion battery waste can be discharged at a relatively low processing cost, which may contribute to reducing costs in the recovery of metals from lithium-ion battery waste. For this reason, this embodiment may contribute to Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," and Goal 12, "Ensure sustainable consumption and production patterns," of the United Nations-led Sustainable Development Goals (SDGs).

[0071] Next, we conducted tests related to the lithium-ion battery waste disposal method described above, which are explained below. However, this explanation is for illustrative purposes only and is not intended to be an exhaustive list.

[0072] To simulate the desalination solution obtained after the electrodialysis step in the metal recovery method shown in Figure 1, we prepared an aqueous lithium sulfate solution with a concentration of approximately 4% by mass (Solution S1), a 10% by mass sodium sulfate aqueous solution prepared by dissolving sodium sulfate (Solution S2), and a 10% by mass sodium carbonate aqueous solution prepared by dissolving sodium carbonate (Solution S3). Solution S1 simulates a liquid containing Solution C, and Solution S2 simulates a liquid containing Solutions A and B. Solution S3 was prepared to compare the discharge characteristics of Solution S1 (lithium sulfate aqueous solution) and Solution S2 (sodium sulfate aqueous solution) with those of a sodium carbonate aqueous solution.

[0073] A test was conducted in which lithium-ion battery waste was immersed in each of the above solutions S1 to S3 as a discharge fluid and discharged. In each test, the conductivity and pH of the discharge fluid were measured before and after use. The results are shown in Table 1. Conductivity was measured using a multi-water quality meter MM-43X and an electrical conductivity cell CT58101B. pH was measured using a portable pH meter DM-32P and a composite electrode GST-2739C manufactured by Toa DKK Corporation. The lithium-ion battery waste used in the test was a tool battery consisting of four cylindrical cells connected in series.

[0074]

[0075] Furthermore, the voltage was measured while the lithium-ion battery waste was immersed in the discharge solution. The voltage was measured by removing the battery from the discharge solution and using a voltmeter to measure the voltage between the terminals. The results are shown in Figure 3.

[0076] As can be seen from Figure 3, solution S3 could only be discharged to 2V or less, whereas solutions S1 and S2 were both able to reduce the voltage to a sufficiently low level. Therefore, it was found that the desalted solution of solution C, simulated with solution S1, and the back-extracted solution of solution A and the extracted solution of solution B, simulated with solution S2, can also be effectively used in the discharge process. Furthermore, it was found that solutions A and B, which are sodium sulfate aqueous solutions, and solution C, which is lithium sulfate aqueous solution, have superior discharge characteristics compared to sodium carbonate aqueous solution.

[0077] Based on the above, it can be said that, according to the lithium-ion battery waste processing method described earlier, it is possible to discharge lithium-ion battery waste at a relatively low processing cost.

[0078] 1. Bipolar membrane electrodialysis machine 2. Anode 3. Cathode 4., 7. Bipolar membrane 5. Anion exchange membrane 6. Cation exchange membrane

Claims

1. A method for treating lithium-ion battery waste, comprising a discharge step of contacting the lithium-ion battery waste with a liquid containing at least one of the following solutions (1) to (3): (1) An aqueous solution of inorganic sodium acid obtained by performing a manganese and / or aluminum extraction step on a metal-containing aqueous solution obtained by leaching out metals containing manganese and / or aluminum from the battery powder of lithium-ion battery waste. (2) An aqueous solution of inorganic sodium acid obtained as an extraction solution by sequentially performing a first-stage cobalt ion extraction and back-extraction and a second-stage cobalt ion extraction in a cobalt extraction step on a metal-containing aqueous solution obtained by leaching out metals containing cobalt from the battery powder of lithium-ion battery waste. (3) An aqueous solution of inorganic lithium acid obtained as a desalting solution by performing an electrodialysis step on a metal-containing aqueous solution obtained by leaching out metals containing lithium from the battery powder of lithium-ion battery waste.

2. The method for treating lithium-ion battery waste according to claim 1, wherein the liquid comprises at least an aqueous solution of an inorganic sodium salt derived from the back-extracted liquid of (1), the back-extracted liquid comprises manganese ions and / or aluminum ions and sulfate ions, and the aqueous solution of an inorganic sodium salt derived from the back-extracted liquid is obtained by adding sodium hydroxide to the back-extracted liquid.

3. The method for treating lithium-ion battery waste according to claim 1, wherein the liquid comprises at least an aqueous solution of inorganic sodium acid as the post-extraction solution of (2), and the sodium ions in the aqueous solution of inorganic sodium acid as the post-extraction solution originate from a pH adjuster containing sodium hydroxide used in the second stage extraction of cobalt ions.

4. A method for treating lithium-ion battery waste according to claim 1, comprising: an acid leaching step of leaching metals including cobalt, lithium, manganese and / or aluminum from battery powder obtained by pretreatment including the discharge step to obtain a metal-containing aqueous solution; a manganese and / or aluminum extraction step of which the extraction and back-extraction of manganese ions and / or aluminum ions from the metal-containing aqueous solution are included in this order; a cobalt extraction step of which, after the manganese and / or aluminum extraction step, the extraction and back-extraction of cobalt ions from the metal-containing aqueous solution in a first stage and the extraction of cobalt ions in a second stage are included in this order; and an electrodialysis step of which, after the cobalt extraction step, electrodialysis is performed on the metal-containing aqueous solution to obtain a desalted solution.

5. A method for recovering metal from lithium-ion battery waste, comprising performing the lithium-ion battery waste treatment method described in any one of claims 1 to 4.

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