Method for recovering metals from lithium ion battery waste

Abstract

A method for recovering metals from lithium ion battery waste includes a wet process of reaching metals including lithium in lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved therein, wherein lithium hydroxide is produced from part of the lithium extracted by the wet process, lithium carbonate is produced from at least part of the remainder of the lithium, and wherein, when lithium hydroxide is used as a pH adjusting agent in at least one step in the wet process, and an amount of lithium hydroxide produced is determined depending on an amount of lithium hydroxide required in the at least one step.

Description

METHOD FOR RECOVERING METALS FROM LITHIUM ION BATTERY WASTE

[0001] This specification discloses a method for recovering metals from lithium ion battery waste.

[0002] In recent years, it has been widely studied for recovery of valuable metals from battery waste such as lithium ion battery waste discarded for expired product life, manufacturing defects or other reasons, in terms of effective utilization of resources.

[0003] In order to recover valuable metals from lithium ion battery waste, wet processes are subjected to powder of batteries (“battery powder”) that is obtained through dry preprocessing such as heating processes of lithium ion battery waste.

[0004] For example, in the wet processes, metals such as cobalt, nickel, manganese, lithium, aluminum, and iron in the battery powder are leached with an acid to obtain a metal-containing solution containing the metals dissolved therein. Aluminum, iron, manganese, and the like, among respective elements contained the metal-containing solution, are then sequentially or simultaneously removed by neutralization or solvent extraction. Cobalt and nickel in the metal-containing solution are then separated by solvent extraction and concentrated. The separation of the nickel by solvent extraction results in a lithium-containing solution in which lithium dissolves and remains. The lithium-containing solution thus obtained may be subjected to concentration of lithium ions by repeating solvent extraction, and then subjected to carbonation by adding a carbonate salt or blowing a carbon dioxide gas, thereby recovering the lithium ions in the lithium-containing solution as lithium carbonate.

[0005] As a related technique, for example, Patent Literature 1 proposes, “to efficiently recover highly pure lithium contained in lithium ion batteries”, "a method for processing lithium ion batteries, including: a crushing and classifying step of crushing and classifying lithium ion batteries to obtain an electrode material containing at least lithium; a leaching step of immersing the electrode material in an acid to obtain a leached solution; a pH adjusting step of adding lithium hydroxide to the leached solution to adjust the pH; a metal recovering step of recovering metals other than lithium from the leached solution to obtain a lithium-containing solution; and a lithium hydroxide recovering step of recovering lithium from the lithium-containing solution as lithium hydroxide, wherein the lithium hydroxide recovered in the lithium hydroxide recovering step is used in the pH adjusting step".

[0006] Further, Patent Literature 2 discloses, "to provide a method for suppressing the use of sodium hydroxide as a pH adjusting agent to efficiently recover metals from lithium ion battery waste”, “a method for recovering metals from lithium ion battery waste, the method including a wet process of leaching metals containing lithium in the lithium ion battery waste with an acid and removing the metals from a metal-containing solution having the metals dissolved therein, wherein the lithium removed in the wet process is used as a pH adjusting agent used in the wet process”. Patent Literature 2 discloses that, in this "method for recovering metals", "the lithium is removed as an aqueous lithium hydroxide solution by the wet process, and the aqueous lithium hydroxide solution is used as the pH adjusting agent”.

[0007] [PTL 1] Japanese Patent Application Publication No. 2023-135553 A [PTL 2] Japanese Patent Application Publication No. 2023-100197 A

[0008] As described in Patent Literatures 1 and 2, if the lithium removed in the wet process is lithium hydroxide and the lithium hydroxide is used as a pH adjusting agent in the wet process, the processing cost can be reduced as compared to the case where a pH adjusting agent such as sodium hydroxide is separately prepared and used.

[0009] Here, if the total amount of the lithium removed in the wet process was converted to lithium hydroxide, the cost of excess lithium hydroxide could be higher when the amount of lithium hydroxide obtained exceeded the amount required as a pH adjusting agent in the wet process. On the other hand, it is difficult to say that an indicator of how much of the lithium removed in the wet process should be converted to lithium hydroxide has been sufficiently studied. Therefore, there is room for improvement or refinement of the methods described in Patent Literature 1 and 2 from the viewpoint of further cost reduction.

[0010] This specification provides a method for recovering metals from lithium ion battery waste that can contribute to reduction of processing costs.

[0011] One method for recovering metals from lithium ion battery waste described in this specification includes a wet process of reaching metals containing lithium in lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved therein, wherein lithium hydroxide is produced from part of the lithium extracted by the wet process, lithium carbonate is produced from at least part of the remainder of the lithium, and wherein, when lithium hydroxide is used as a pH adjusting agent in at least one step in the wet process, an amount of the lithium hydroxide produced is determined depending on an amount of lithium hydroxide required in the at least one step.

[0012] Another method for recovering metals from lithium ion battery waste described in this specification includes a wet process of reaching metals containing lithium in lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved therein, wherein lithium hydroxide is produced from part of the lithium extracted by the wet process, lithium carbonate is produced from at least part of the remainder of the lithium, and wherein, when lithium hydroxide is used as a pH adjusting agent in at least one step in the wet process, an amount of the lithium hydroxide produced is 0.8 to 1.3 molar equivalents of an amount of lithium hydroxide required in the at least one step.

[0013] According to the method for recovering metals from lithium ion battery waste, it is possible to contribute to reduction of processing costs.

[0014] Fig. 1 is a flow chart showing an example of a method for recovering metals according to an embodiment.Fig. 2 is a flow chart showing an example of a method for recovering metals according to another embodiment.Fig. 3 is a flow chart illustrating an example of a preprocessing step for obtaining battery powder from lithium ion battery waste.Fig. 4 is a cross-sectional view schematically illustrating an example of a bipolar membrane electrodialysis device that can be used in an electrodialysis step included in the method for recovering metals in Fig. 1.

[0015] Hereinafter, embodiments of the above method for recovering metals from lithium ion battery waste will be described in detail. One embodiment of the method for recovering metals includes a wet process of leaching metals containing lithium in the lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved therein. The lithium extracted in the wet process is then used to produce lithium hydroxide from a part thereof and lithium carbonate from at least part of the remainder thereof. The lithium hydroxide to be produced from part of the lithium extracted by the wet process may be in either solution or solid form. Lithium hydroxide as used herein includes a solution and / or a solid.

[0016] In producing lithium hydroxide from the part of the lithium extracted by the wet process, when lithium hydroxide is used as a pH adjusting in at least one step in the wet process, an amount of lithium hydroxide produced can be determined depending on an amount of lithium hydroxide required in the at least one step. In such a way, whether or not the amount of lithium hydroxide produced is determined depending on the amount of lithium hydroxide required in at least one step in the above process, the amount of lithium hydroxide produced may be 0.8 to 1.3 molar equivalents relative to the amount of lithium hydroxide required in the at least one step. The lithium hydroxide produced in the given amount accordingly can be used as a pH adjusting agent required in the at least one step. As a result, any excessive production of lithium hydroxide can be suppressed, and the relevant increase in processing costs can be reduced.

[0017] Figures 1 and 2 show one embodiment and another embodiment of the method for recovering metals, respectively. The methods for recovering metals in Figures 1 and 2 each includes an acid leaching step, a pH increasing step, a manganese extracting step, a cobalt extracting step, and a nickel extracting step in this order. In the illustrated embodiment, the wet process includes an acid leaching step, a pH increasing step, a manganese extracting step, a cobalt extracting step, and a nickel extracting step.

[0018] In Figure 1, a part of the lithium-containing solution as an extracted solution obtained in the nickel extracting step is subjected to an electrodialysis step to prepare a lithium hydroxide solution, and the remainder of the lithium-containing solution is subjected to a carbonation step to prepare lithium carbonate. In Figure 2, the lithium-containing solution obtained in the nickel extracting step is subjected to the carbonation step to obtain lithium carbonate once, and then part of the lithium carbonate is converted to a lithium hydroxide solution in a hydroxylation step, while the remainder remains lithium carbonate. In both Figures 1 and 2, all of the remainders of the lithium-containing solution or lithium carbonate are lithium carbonate, but it is not necessary that all of the remainders be lithium carbonate; at least part of the remainders may be extracted as lithium carbonate.

[0019] In addition, the battery powder can be obtained by subjecting the lithium ion battery waste to the preprocessing step, as illustrated in Figure 3. Here, the descriptions will be given with reference to Figures 1 and 2, however Figures 1 and 2 are merely examples and are not limited to such specific flows.

[0020] (Lithium Ion Battery Waste) The lithium ion battery waste of interest is lithium ion batteries which can be used in various electronic devices such as mobile phones and which have been discarded due to the expired life of the product, manufacturing defects or other reasons. The recovery of valuable metals from such lithium ion battery waste is preferred in terms of effective utilization of resources.

[0021] The lithium ion battery waste has housings containing aluminum and may contain, in the housings, cathode active materials composed of single metal oxide containing lithium and one selected from the group consisting of nickel, cobalt and manganese, or composite metal oxides containing lithium and two or more of those, or the like, and aluminum foils (cathode substrates) to which the cathode active materials are applied and fixed by, for example, polyvinylidene fluoride (PVDF) or other organic binders. In addition, the lithium ion battery waste may contain copper, iron, or the like. Further, the above housings may generally contain an electrolytic solution having an electrolyte such as lithium hexafluorophosphate dissolved in an organic solvent such as ethylene carbonate and diethyl carbonate.

[0022] (Preprocessing Step) In many cases, the lithium ion battery waste is subjected to a preprocessing step. The preprocessing step may include at least one of heating, crushing and sieving. The lithium ion battery waste becomes battery powder through the preprocessing step. The heating, crushing, and sieving in the preprocessing step may optionally be performed, respectively, or they may be performed in any order. The battery powder means a powder obtained by subjecting the lithium ion battery waste to any preprocessing to concentrate cathode material components. The battery powder may be obtained as a powder by crushing and sieving the lithium ion battery waste with or without a heat treatment to concentrate the cathode material components.

[0023] In the heating, the above lithium ion battery waste is heated. The heating decomposes and removes the electrolyte and organic binder, and can also convert metals such as lithium and cobalt contained in the lithium ion battery waste into a form that is easily soluble in the acid leaching solution during the acid leaching step. Although the heating changes the composition of the cathode active material, the heated material is also referred to as the cathode active material. During the heating, the lithium ion battery waste is preferably heated, for example, maintained in a temperature range of 600°C to 800°C for 0.5 to 6 hours. The heating can be carried out in either an air atmosphere or an inert atmosphere such as nitrogen, and the heating in their atmospheres in that order or vice versa. As a heating furnace, for example, a batch type stationary furnace or a continuous type rotary kiln furnace, or other various types of furnaces can be used.

[0024] The crushing selectively separates the cathode active materials from the aluminum foils to which the cathode active materials are applied, while destroying the housings of the lithium ion battery waste. Various known apparatuses or devices can be used in the crushing. In particular, it is preferable to use an impact-type crusher that can crush lithium ion battery waste by applying an impact while cutting it. Examples of the impact-type crusher include a sample mill, a hammer mill, a pin mill, a wing mill, a tornado mill, and a hammer crusher.

[0025] After crushing the lithium ion battery waste, the sieving is performed by sieving it using a sieve having appropriate openings. Thus, aluminum or copper remains on the sieve, and the battery powder that has removed Al or Cu to some extent is obtained under the sieve. If the battery powder contains nickel, the nickel content is, for example, 1% by mass to 30% by mass, and typically 5% by mass to 20% by mass. If it contains cobalt, the cobalt content in the battery powder is, for example, 1% by mass to 30% by mass, typically 5% by mass 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.

[0026] In order to extract substantially only lithium from the battery powder, the battery powder can be brought into contact with water prior to an acid leaching step as described below to leach the lithium in the battery powder into water. In this case, the battery powder as the water leached residue is subjected to the acid leaching step. However, the battery powder may be subjected to the acid leaching step without the water leaching. When the water leaching is not carried out, the lithium ion concentration in the liquid can be easily maintained at a higher level in wet processes after the acid leaching step.

[0027] (Acid Leaching Step) In the acid leaching step, the metals in the battery powder are brought into contact with an acid leaching solution containing a mineral or inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid to leach the metals. This dissolves the metals in the battery powder to provide a leached solution that contains those metals as metal ions. As used herein, the solution containing metals in the battery powder as metal ions is referred to as a metal containing solution. The metal containing solution includes the above leached solution obtained in the acid leaching step and sent to the next metal separation step, and a solution in the middle of the metal separation step.

[0028] For a pH, it may preferably be -0.5 to 3.0 in the acid leaching solution during leaching, and may be 0.5 to 2.0 in the leached solution after leaching is completed. During leaching, for example, the acidic leaching solution may be stirred at 100 rpm to 400 rpm using an agitator if necessary, and a temperature of the solution may be 50°C to 80°C, or further 65°C to 70°C.

[0029] The metal containing solution obtained in the acid leaching step may have 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 concentrations of the metal ions in the solution can be confirmed by analysis using an ICP optical emission spectrometer.

[0030] (pH Increasing Step) In the pH increasing step, the pH of the metal-containing solution is increased to deposit at least part of the aluminum ions and / or at least part of the iron ions in the metal-containing solution, which are then separated from the metal-containing solution.

[0031] The pH increasing step includes, for example, an aluminum removal process of depositing and removing at least a part of the aluminum ions by increasing the pH of the metal-containing solution, and, after that, an iron removal process of adding an oxidizing agent to oxidize the iron ions, and optionally further increasing the pH, thereby depositing and removing the iron ions. However, if the metal containing solution is substantially free of iron ions, the iron removal process may be omitted.

[0032] In each of the aluminum removal step and the iron removal step, the pH may be in the range of 3.0 to 4.5. In the iron removal step, the ORP value during oxidation may be 300 mV to 900 mV. After aluminum is precipitated in the aluminum removal process and iron is precipitated in the iron removal process, each neutralization residue as the precipitates can be removed by solid-liquid separation such as filtration using known device and method such as filter presses and thickener.

[0033] In the aluminum removal process and iron removal process, as an alkaline pH adjusting agent for increasing the pH of the metal-containing solution, lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia can be used, for example. In particular, it is preferable to use lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step described below) as lithium hydroxide from the viewpoint of cost reduction. The pH increasing step may be included in at least part of steps that use lithium hydroxide as a pH adjusting agent in the wet process. It should be noted that the oxidizing agent used in the iron removal process is not particularly limited as long as it can oxidize iron, but it may preferably be hydrogen peroxide, manganese dioxide, a cathode active material, and / or a manganese-containing leached residue obtained by leaching a cathode active material.

[0034] (Manganese Extracting Step) For the metal-containing solution after the pH increasing step, the remainders of manganese and possibly aluminum ions can also be extracted and removed by solvent extraction. In this case, the remainders of manganese and aluminum ions are extracted, resulting in a manganese extracted solution that have removed them.

[0035] Here, a phosphate ester-based extracting agent (di-2-ethylhexyl phosphate (abbreviated as D2EHPA or product name: DP-8R), and the like), or a mixture of the phosphate ester-based extracting agent and an oxime-based extracting agent made of aldoxime or mainly based on aldoxime (2-hydroxy-5-nonylacetophenone oxime (trade name: LIX 84), 5-dodecyl salicylaldoxime (trade name: LIX 860), a mixture of LIX 84 and LIX 860 (trade name: LIX984), 5-nonyl salicylaldoxime (trade name: ACORGAM 5640) and the like) can be used.

[0036] During extraction, an equilibrium pH is preferably 2.3 to 3.5, and more preferably 2.5 to 3.0. For the alkaline pH adjusting agent used herein, it is preferable to use lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step described below) from the viewpoint of cost reduction, but lithium hydroxide or the like separately prepared may be used. The manganese extracting step may be included in at least part of steps that use lithium hydroxide as a pH adjusting agent in the wet process.

[0037] At the time of extraction, it is desirable to carry out extraction by countercurrent type multistage extraction in which directions of the flow of the aqueous phase and the solvent used for each extraction are opposite to each other. By doing so, 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 the countercurrent type multistage extraction, it is effective to set the equilibrium pH at the first stage of extraction to a value in the above range, and increase the equilibrium pH at the time of extraction through successive stages. The cobalt extracting step and the nickel extracting step as described below are also desirable to carry out the countercurrent type multistage extraction.

[0038] (Cobalt Extracting Step) In the cobalt extracting step, cobalt ions are separated from a metal-containing solution as an extracted solution obtained after the manganese extracting step, using solvent extraction. In this case, the magnesium ions that may be contained in the metal containing solution may also be extracted and removed.

[0039] Here, it is preferable to use a solvent containing a phosphonate ester-based extracting agent such as 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest 801).

[0040] During extraction, an equilibrium pH can preferably be 5.0 to 6.0, and more preferably 5.0 to 5.5. In this case, as a pH adjusting agent, the lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step described below) may be used from the viewpoint of cost reduction. The cobalt extracting step may be included in at least part of steps that use lithium hydroxide as a pH adjusting agent in the wet process. However, impurities contained in the pH adjusting agent used herein may cause a decrease in the quality of the cobalt salt finally obtained, so depending on the purity of the lithium hydroxide, it may be preferable to use a relatively high-purity lithium hydroxide such as a separately prepared commercial product as the above pH adjusting agent.

[0041] The solvent that has extracted the cobalt ions can be scrubbed as necessary and then stripped with a stripping solution containing sulfuric acid, hydrochloric acid, or nitric acid, for example, at a pH of 2.0 to 4.0. The stripped solution can be then heated and concentrated to crystallize the cobalt ions as cobalt salts such as cobalt sulfate.

[0042] (Nickel Extracting Agent) In the nickel extracting step, nickel ions are separated from a metal-containing solution as a cobalt extracted solution obtained after the cobalt extracting step, using solvent extraction. The solvent that can be used herein includes carboxylic acid-based extracting agent such as neodecanoic acid and naphthenic acid.

[0043] In this case, an equilibrium pH is preferably 6.0 to 8.0, and more preferably 6.8 to 7.2. Although the pH adjusting agent used for adjusting the equilibrium pH may also employ lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step described below) from the viewpoint of cost reduction, for the purpose of suppressing a decrease in the purity of the nickel salts, it may be preferable to use a commercially available lithium hydroxide or the like having a relatively high purity. The nickel extracting step may be included in at least part of steps that use lithium hydroxide as a pH adjusting agent in the wet process.

[0044] The solvent that has extracted the nickel ions can be scrubbed as necessary and then stripped with a stripping solution containing sulfuric acid, hydrochloric acid, or nitric acid, for example, at a pH of 1.0 to 3.0. Thereafter, the stripped solution may be electrolyzed and dissolved as necessary, and then heated to concentrate it, so that the nickel ions can be crystallized as nickel salts such as nickel sulfate.

[0045] At least a part of the lithium containing solution after the nickel ions have been extracted may be mixed with the acid leaching solution and the mixture may be used in the acid leaching step. This allows the lithium ions contained in the lithium-containing solution to be circulated in a series of steps from the acid leaching step and nickel extracting step. Preferably, after the lithium ion concentration of the lithium containing solution has been increased to some extent by thus circulating the lithium ions, the electrodialysis step and the carbonation step as described below are carried out.

[0046] (Electrodialysis Step) In the embodiment of Figure 1, electrodialysis is performed on part of the above lithium-containing solution (lithium extracted by the wet process) after impurities such as nickel, cobalt, manganese, and magnesium ions are removed as necessary. The impurities as used herein are referred to as impurities with the intention of distinguishing them from lithium ions that are the main components of the lithium containing solution used for electrodialysis, but they are also metals that can be recovered.

[0047] To remove the impurity in the lithium-containing solution prior to electrodialysis, for example, a pH adjusting agent can be added to a lithium containing solution that may have a pH of 3.0 to 6.0 to increase the pH of the lithium containing solution, preferably to 8.0 to 13.0. As a result, the impurity metal ions of the lithium ions and impurity metal ions in the lithium containing solution can be selectively deposited and precipitated. Although the pH adjusting agent may employ lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step) from the viewpoint of cost reduction, it may be preferable to use a commercially available lithium hydroxide or the like with relatively high purity that is separately prepared, from the viewpoint of preventing impurities from being contaminated into the lithium-containing solution due to the pH adjusting agent.

[0048] In addition, a cation exchange resin and / or a chelating resin may be used to remove impurities from the lithium-containing solution. The cation exchange resin is a synthetic resin that bind to cations by having an acidic group(s) on its surface. The chelating resin is a resin with a functional group(s) that will form a complex with metal ions. By allowing the lithium ions to be adsorbed in advance as exchange ions onto the cation exchange resin or the chelating resin, when the resin is brought into contact with the lithium-containing solution, ion exchange takes place between the lithium ions and the metal ions of the impurities in the lithium-containing solution. For the pH adjustment in this case, the lithium hydroxide produced from lithium extracted by the wet process (such as a lithium hydroxide solution obtained after the electrodialysis step or hydroxylation step) may be used as a pH adjusting agent from the viewpoint of cost reduction, as well as commercially available lithium hydroxide may also be used. The impurity removal step before electrodialysis may be included in at least part of steps that use lithium hydroxide as a pH adjusting agent in the wet process.

[0049] In the electrodialysis, the lithium hydroxide solution is prepared from the lithium-containing solution, for example, using a commercially available bipolar membrane electrodialysis device. As an example, the bipolar membrane electrodialysis device 1 (hereinafter simply referred to as an “electrodialysis device 1”) illustrated in Figure 4. As an example, a bipolar membrane electrodialysis device 1 (hereinafter, also referred to as an “electrodialysis device”) shown in Figure 3 has, in a cell, an anode 2 and a cathode 3; and a bipolar membrane 4, an anion exchange membrane 5, a cation exchange membrane 6, and a bipolar membrane 7, which are arranged in this order between the anode 2 and the cathode 3 from the anode 2 side to the cathode 3 side. These separate the interior of the cell into a desalination chamber R1 between the anion exchange membrane 5 and the cation exchange membrane 6, an acidic chamber R2 between the bipolar membrane 4 and the anion exchange membrane 5, and an alkaline chamber R3 between the cation exchange membrane 6 and the bipolar membrane 7. The bipolar membranes 4 and 7 are constructed by laminating a cation exchange layer and an anion exchange layer, respectively.

[0050] In order to carry out electrodialysis by the illustrated electrodialysis device 1, the lithium-containing solution is placed in the desalination chamber R1, and pure water is also placed in each of the acidic chamber R2 and the alkaline chamber R3, and a predetermined voltage is applied to the positive electrode 2 and the negative electrode 3. Then, lithium ions (Li+) in the lithium-containing solution in the desalination chamber R1 pass through the cation exchange membrane 6 and move to the alkaline chamber R3. In the alkaline chamber R3, water (H2O) is decomposed by the bipolar membrane 7 and hydroxide ions (OH-) are present, so that a lithium hydroxide solution is obtained as a dialyzed solution.

[0051] On the other hand, the anions of the inorganic acid in the lithium-containing solution in the desalination chamber R1 pass through the anion exchange membrane 5 and move to the acidic chamber R2. In the acidic chamber R2, an acidic solution such as a sulfuric acid solution is generated by the anions and hydrogen ions (H+) generated from water (H2O) by the bipolar membrane 4. As a result, the dialyzed solution (lithium hydroxide solution) obtained in the alkaline chamber R3 contains substantially no anions of inorganic acid. It should be noted that the anions of the inorganic acid are sulfate ions (SO42-) in the illustrated example, but they may be nitrate ions (NO3-) or chloride ions (Cl-) depending on the type of the acid used in the acid leaching step.

[0052] In the desalination chamber R1, the lithium salt is separated from the lithium-containing solution as described above, and a desalinated solution remains. The anion concentration of the inorganic acid tends to be higher in the acidic solution than in the dialyzed solution (lithium hydroxide solution), and tends to be higher in the desalinated solution than in the dialyzed solution (lithium hydroxide solution).

[0053] The dialyzed solution (lithium hydroxide solution) obtained by the electrodialysis as described above can be effectively used as a pH adjusting agent in at least one step in the wet process. After the electrodialysis, the lithium hydroxide solution may optionally be used as a pH adjusting agent after increasing the lithium ion concentration of the lithium hydroxide solution by heat concentration or the like.

[0054] (Carbonation Step) In the embodiment of Figure 1, the remainder of the lithium-containing solution obtained in the nickel extracting step (lithium extracted by the wet process) is at least partially fed to the carbonation step. The remainder of the lithium-containing solution after removal of impurities in the electrodialysis step may be used for the carbonation step. In the embodiment of Figure 2, the carbonation step is performed on the lithium-containing solution obtained in the nickel extracting step to obtain lithium carbonate.

[0055] In both Figures 1 and 2, impurities such as nickel, cobalt, manganese, and magnesium ions may be removed from the lithium-containing solution as necessary before carbonation. This removal of impurities can be substantially the same as the removal of impurities prior to electrodialysis (adjustment of pH, use of resins, etc.) described above. Prior to carbonation, it is possible to perform heating concentration, decompression concentration, membrane concentration using a semipermeable membrane such as a reverse osmosis membrane, or other concentration.

[0056] In the carbonation step, carbonation is performed such as by adding a carbonate salt or blowing a carbon dioxide gas into the lithium-containing solution, and a liquid temperature is preferably maintained in the range of 50°C to 90°C for a predetermined time, such as 0.5 hours to 2 hours, with stirring as necessary.

[0057] When the carbonate salts are added to the lithium-containing solution, sodium carbonate or the like can be used as the carbonate salts. The amount of carbonate added can be, for example, 1.0 to 2.0 molar equivalents, preferably 1.0 to 1.2 molar equivalents, relative to Li in the lithium-containing solution in the assumed reaction of Li2SO4+ Na2CO3→ Li2CO3+ Na2SO4. However, from the viewpoint of preventing an increase in impurities, the blowing of the carbon dioxide gas is preferable.

[0058] If the lithium grade of the lithium carbonate thus obtained is lower than the target grade, the lithium carbonate can be purified to obtain a higher grade lithium carbonate, if necessary. In addition, the target lithium grade of lithium carbonate can be 16% or more, preferably 17% or more.

[0059] Specifically, the purification of lithium carbonate involves repulping the above lithium carbonate and blowing a carbon dioxide gas into it to dissolve carbonic acid in the liquid, followed by solid-liquid separation to separate the lithium hydrogen carbonate solution from calcium, magnesium, and other substances. Then, after deacidification and concentration, it is separated into purified lithium carbonate and a filtrate by solid-liquid separation. If the impurity grade in this purified lithium carbonate is higher, further washing can be performed.

[0060] If the wet process is repeated, it is not necessary to perform the carbonation step in each wet process in the repetition. The carbonation step may be performed in at least one of the repeated wet processes. This allows the cost increase due to excess lithium hydroxide in the wet process that has performed the carbonation step to be suppressed. Therefore, a method in which the carbonation step is performed in at least one wet process can be said to produce lithium hydroxide from part of the lithium extracted in that wet process and to produce lithium carbonate from the at least part of the remainder of lithium, and thus can correspond to the method for recovering the metals described herein. In the wet process without the carbonation step, all of the lithium extracted in that wet process may be used as lithium hydroxide, which may be used as a pH adjusting agent in the subsequent wet process, although this is not shown in the figure.

[0061] By the way, the battery powder may contain sodium. The sodium is leached out in the acid leaching step and contained in the metal-containing solution, and is not separated in the wet process together with lithium and contained in the subsequent lithium-containing solution. In this case, as in the embodiment described herein, when the lithium in the lithium-containing solution is lithium hydroxide, which is used as a pH adjusting agent to repeat the wet process, not only the lithium concentration in the solution but also the sodium concentration will increase during the repetition. In contrast, the carbonation step reduces an increase in a sodium concentration in the solution of the wet process because part of the sodium circulated in the repeated wet processes is mixed into the lithium carbonate obtained in the carbonation step. Therefore, producing lithium carbonate from at least part of the remainder of the lithium extracted by the wet process also has an advantage of reducing the increase in the sodium concentration in the solution circulating in the wet process.

[0062] (Hydroxylation Step) In the embodiment of Figure 2, the hydroxylation step is performed on part of the lithium carbonate (lithium extracted by the wet process) obtained in the carbonation step.

[0063] In the hydroxylation step, for example, lithium carbonate is allowed to react with calcium hydroxide in the liquid to obtain a lithium hydroxide solution under the reaction formula: Li2CO3+ Ca(OH)2→ 2LiOH + CaCO3. Calcium hydroxide is preferably added 1.05 to 1.10 times, to lithium hydroxide in molar equivalents in the above reaction formula. The pH during the reaction may be 9.0 or higher.

[0064] Most of the calcium carbonate produced in the above reaction can be removed after the reaction by solid-liquid separation using a thickener or filter press, or the like. Calcium ions and / or barium ions that may remain in the lithium hydroxide solution after solid-liquid separation can be removed with a cation exchange resin, a chelate resin, or the like.

[0065] As described above, lithium hydroxide is produced from part of the lithium extracted by the wet process, and lithium carbonate is produced from at least part of the remainder. The lithium hydroxide thus produced can be used as a pH adjusting agent, so that the amount of lithium hydroxide produced can be determined depending on the amount of lithium hydroxide required to be used as a pH adjusting agent in at least one step in the wet process. This means, for example, that based on the amount of lithium hydroxide required, it may be determined how much of the lithium extracted by the wet process is converted to lithium hydroxide in the electrodialysis step and / or the hydroxylation step described above.

[0066] The amount of lithium hydroxide required as described above is further described now. The amount of lithium hydroxide required can be set as follows: First, the implementation of each step in the wet process is determined based on the respective metal grades and amount of battery powder to be processed in the wet process. Since the implementation of each step can be changed depending on the purpose, the amount of pH adjusting agent required is also set depending on the purpose. For example, the amount of pH adjusting agent required may be set based on the amount of liquid and pH to be processed in each step. In the pH increasing step, the amount of pH adjusting agent required may be set based on the type and amount of neutralized residue to be produced. In addition, each extraction step may set the amount of pH adjusting agent required, based on the type of metal to be extracted and its amount. Thus, the amount of pH adjusting agent required is a theoretical amount of a pH adjusting agent set according to the implementation of the wet process. The same applies to the use of lithium hydroxide as a pH adjusting agent in at least one step in the wet process, and the amount of lithium hydroxide required is also a theoretical amount of lithium hydroxide set according to the implementation of the wet process.

[0067] In most cases, the amount of lithium hydroxide produced may preferably be 0.8 to 1.3 molar equivalents of the amount of lithium hydroxide required in at least one step described above, 1.0 to 1.3 molar equivalents, especially 1.1 to 1.3 molar equivalents, and most preferably 1.2 to 1.3 molar equivalents. If the amount of lithium hydroxide produced is more than or equal to 0.8 molar equivalents of the required amount, the amount of pH adjusting agent to be purchased separately can be reduced because most of the amount of lithium hydroxide required can be provided by the produced lithium hydroxide, thus contributing to cost reduction. If the amount of lithium hydroxide produced is more than or equal to 1.0 molar equivalent of the required amount, the amount of lithium hydroxide produced is sufficiently provided by the amount of lithium hydroxide required, and the amount of pH adjusting agent to be separately purchased can be further reduced or eliminated, further contributing to cost reduction. If the amount of pH adjusting agent to be separately purchased is zero, the amount of lithium hydroxide produced is typically more than or equal to 1.0 molar equivalent. This is because, operationally, the lithium hydroxide used as a pH adjusting agent is not all consumed in the target reaction. In this regard, the amount of lithium hydroxide produced may be more than or equal to 1.1 molar equivalents of the amount of lithium hydroxide required, or more than or equal to 1.2 molar equivalents. On the other hand, if the amount of lithium hydroxide generated is less than or equal to 1.3 molar equivalents of the required amount, it is possible to suppress a larger amount of lithium hydroxide than the amount actually used in the at least one step, thus contributing to cost reduction.

[0068] Lithium hydroxide, i.e., lithium derived from part of the lithium extracted in the wet process in the amount described above, it is preferably used for all pH adjusting agents used in at least one step described above.

[0069] As an example, Table 1 illustrates the steps where the pH adjusting agents can be used in the wet process in the method for recovering metals in Figure 1.

[0070] The amount of lithium hydroxide required was calculated assuming that lithium hydroxide was used as a pH adjusting agent in each step, and the amount of lithium hydroxide that was desirable to be ensured for that required amount was determined. The results are also shown in Table 1. The amount of lithium hydroxide required was determined from the implementation of each step in Table 1. The proportion of the amount of lithium hydroxide that was desirable to be ensured for the required amount (double molar equivalents) was determined from previously obtained results.

[0071] For example, the amount of lithium hydroxide required for the Al removal process is obtained as follows: (1) pH adjustment (pH 3.0 → 3.5): (10-3- 10-3.5) x liquid volume x 23.95 (LiOH molecular weight); (2) formation of (Mn, Co, Ni), Al, Fe, and Mg neutralized products: The amounts of lithium hydroxide required for producing each metal neutralized product are calculated, and add up. The following is an example of how to calculate the amount of lithium hydroxide required for obtaining Mn neutralized product. Using the same method, the amount of lithium hydroxide required for obtaining neutralized products of Co, Ni, Al, Fe, and Mg is calculated. Weight of metal in Mn neutralized product / 54.94 (Mn atomic mass) x 2 (valence) x 23.95 (LiOH molecular weight) The amount of lithium hydroxide that is desirable to be ensured can be calculated by multiplying the total amount of lithium hydroxide required obtained in (1) and (2) by double molar equivalents (1.24).

[0072] Further, the amount of lithium hydroxide required for the Mn extraction is obtained as follows: In Mn extraction, Co, Ni, Al, Cu, Ca, and Mg are extracted in addition to Mn. The amounts of lithium hydroxide required for extracting these metals are calculated and add up. The following is an example of how to calculate the amount of lithium hydroxide required for extracting Mn. Using the same method, the amount of lithium hydroxide required for extracting Co, Ni, Al, Cu, Ca and Mg is calculated. Weight of Mn to be extracted / 54.94 (Mn atomic mass) x 2 (valence) x 23.95 (LiOH molecular weight) Then, the amount of lithium hydroxide that is desirable to be ensured can be calculated by multiplying the total amount of lithium hydroxide required obtained by double molar equivalents (1.20).

[0073]

[0074] When lithium hydroxide was used as a pH adjusting agent in each step of the wet process, it was found from Table 1 that the amount of lithium hydroxide produced from part of the lithium extracted by the wet process was desirably 0.8 to 1.3 molar equivalents relative to the amount of lithium hydroxide required in the step.

[0075] (Possibility of Contribution to SDGs) The embodiments described above can contribute to reducing the processing costs required for recovering metals from lithium ion battery waste. Thus, the embodiments may contribute to Goal 9 of the Sustainable development goals led by the United Nations (SDGs), which is to “build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation”, by promoting waste recycling and improving resource efficiency, and Goal 12 “responsible consumption and production”.Description of Reference Numerals

[0076] 1. bipolar membrane electrodialysis device 2 anode 3 cathode 4, 7 bipolar membrane 5 anion exchange membrane 6 cation exchange membrane R1 desalination chamber R2 Acidic chamber R3 alkaline chamber

Claims

1. A method for recovering metals from lithium ion battery waste, the method comprising: a wet process of leaching metals containing lithium in the lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved, wherein lithium hydroxide is produced from part of the lithium extracted by the wet process, lithium carbonate is produced from at least part of the remainder of the lithium, and wherein, when lithium hydroxide is used as a pH adjusting agent in at least one step in the wet process, an amount of the lithium hydroxide produced is determined depending on an amount of lithium hydroxide required in the at least one step.

2. A method for recovering metals from lithium ion battery waste, the method comprising: a wet process of leaching metals containing lithium in the lithium ion battery waste with an acid and extracting the metals from a metal-containing solution having the metals dissolved, wherein lithium hydroxide is produced from part of the lithium extracted by the wet process, lithium carbonate is produced from at least part of the remainder of the lithium, and wherein, when lithium hydroxide is used as a pH adjusting agent in at least one step in the wet process, an amount of the lithium hydroxide produced is 0.8 to 1.3 molar equivalents relative to an amount of lithium hydroxide required in the at least one step.

3. The method for recovering metals according to claim 2, wherein the amount of the lithium hydroxide produced is 1.0 to 1.3 molar equivalents of the amount of lithium hydroxide required in the at least one step.

4. The method for recovering metals according to any one of claims 1 to 3, wherein the at least one step comprises: a pH increasing step of increasing a pH of the metal-containing solution to deposit and separate at least part of aluminum ions and / or at least part of iron ions in the metal-containing solution, and / or a manganese extracting step of extracting and separating manganese ions in the metal-containing solution by solvent extraction.

5. The method for recovering metals according to any one of claims 1 to 3, wherein the lithium hydroxide derived from lithium extracted by the wet process is used as all pH adjusting agents used in the at least one step.

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