Method for recovering metals

Abstract

Provided is a method for recovering Co and Mn from an object containing Ni, Co, and Mn with high recovery rates using ammonia and ammonium carbonate. The metal recovery method of the present disclosure includes: a Mn leaching step in which an object containing Ni, Co, and Mn is subjected to leaching using a first aqueous ammonia solution containing ammonia and ammonium carbonate to leach Mn into a first aqueous phase; and a Ni, Co leaching step in which a solid residue obtained in the Mn leaching step is subjected to leaching using a second aqueous ammonia solution containing ammonia and ammonium carbonate to leach Ni and Co into a second aqueous phase. The amount of dissolved oxygen in the first aqueous ammonia solution in the leaching in the Mn leaching step is less than the amount of dissolved oxygen in the second aqueous ammonia solution in the leaching in the Ni, Co leaching step.

Description

Technical Field

[0001] This disclosure relates to a method for recycling metals. It should be noted that this application claims priority to Japanese Patent Application No. 2025-064485, filed April 9, 2025, the entire contents of which are incorporated herein by reference. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in various fields, including vehicle power supplies and portable power sources. In recent years, from the perspective of the SDGs (Safety, Government, and Goods Administration), the reuse of materials from used lithium-ion rechargeable batteries has been progressing. Various metal elements are used in lithium-ion rechargeable batteries, and for the purpose of material reuse, technologies are being developed to separate the metal elements contained in used lithium-ion rechargeable batteries.

[0003] As a representative example of positive electrode active materials for lithium-ion secondary batteries practically used in automotive applications, lithium nickel cobalt manganese composite oxides (NCMs) can be cited, which contain Ni, Co, and Mn. Therefore, waste from lithium-ion secondary batteries using these positive electrode active materials contains Ni, Co, and Mn. In Non-Patent Literature 1, Ni and Co are selectively separated from the Ni, Co, Mn, and Al contained in the positive electrode waste of used lithium-ion secondary batteries by ammonia leaching.

[0004] Existing technical documents

[0005] Non-patent literature

[0006] Non-patent literature 1: Waste Management, February 2017, vol.60, pp.680-688 Summary of the Invention

[0007] In ammonia leaching, pH adjusters are used to selectively leach specific metals. The inventors conducted in-depth research and discovered the following: In ammonia leaching of materials containing Ni, Co, and Mn, when ammonium carbonate is used as the pH adjuster, unlike when other pH adjusters (e.g., ammonium sulfate used in Non-Patent Document 1) are used, after Co dissolves in the aqueous phase, a portion of Co precipitates along with Mn as a poorly soluble compound. As a result, the recovery rate of Co decreases.

[0008] Therefore, the purpose of this disclosure is to provide a method for recovering Co and Mn from an object containing Ni, Co and Mn with high recovery rates using ammonia and ammonium carbonate.

[0009] The metal recovery method disclosed herein comprises: a Mn leaching step, wherein a sample containing Ni, Co, and Mn is leached using a first ammonia solution containing ammonia and ammonium carbonate, such that Mn is leached to a first aqueous phase; and a Ni and Co leaching step, wherein the solid residue obtained in the Mn leaching step is leached using a second ammonia solution containing ammonia and ammonium carbonate, such that Ni and Co are leached to a second aqueous phase. The dissolved oxygen content in the first ammonia solution during the Mn leaching step is less than the dissolved oxygen content in the second ammonia solution during the Ni and Co leaching step.

[0010] Based on this composition, ammonia and ammonium carbonate can be used to recover Co and Mn from objects containing Ni, Co and Mn with high recovery rates. Attached Figure Description

[0011] Figure 1 This is a summary of the metal recycling method disclosed herein and a flowchart of each step.

[0012] Figure 2 This is a longitudinal cross-sectional view schematically representing the internal structure of an example of a lithium-ion secondary battery.

[0013] Figure 3 It means Figure 2 The diagram shows an exploded view of the electrode structure of a lithium-ion secondary battery.

[0014] Figure 4 yes Figure 2 The diagram shows a schematic cross-sectional view of the positive electrode of a lithium-ion secondary battery. Detailed Implementation

[0015] The following is a reference to the appendix. Figure 1 The embodiments of this disclosure will be described below. It should be noted that matters not mentioned in this specification but necessary for the implementation of this disclosure can be grasped by those skilled in the art based on existing technology in the field. This disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the field. Furthermore, in the following figures, components that perform the same function are... The same symbols are used to indicate the same parts. Additionally, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. It should be noted that the numerical range represented as "A~B" in this specification includes both A and B.

[0016] It should be noted that in this specification, "secondary battery" refers to an energy storage device capable of repeated charging and discharging. Furthermore, in this specification, "lithium-ion secondary battery" refers to a secondary battery that utilizes lithium ions as charge carriers and achieves charging and discharging through the movement of lithium ions' charge between the positive and negative electrodes.

[0017] Figure 1 This is a summary of the metal recovery method of this disclosure and a flowchart of each step. The metal recovery method of this disclosure includes: a Mn leaching step S101, in which a sample containing Ni, Co, and Mn is leached using a first ammonia solution containing ammonia and ammonium carbonate, so that Mn is leached to a first aqueous phase; and a Ni and Co leaching step S102, in which the solid residue obtained in the Mn leaching step S101 is leached using a second ammonia solution containing ammonia and ammonium carbonate, so that Ni and Co are leached to a second aqueous phase. The dissolved oxygen content of the first ammonia solution in the Mn leaching step S101 is less than the dissolved oxygen content of the second ammonia solution in the Ni and Co leaching step S102.

[0018] The metal recycling method disclosed herein is applicable to materials containing Ni, Co, and Mn. The type of material is not particularly limited as long as it contains Ni, Co, and Mn; examples include minerals containing Ni, Co, and Mn, battery waste containing Ni, Co, and Mn, and other waste materials besides batteries. The preferred material containing Ni, Co, and Mn is battery waste, more preferably waste from secondary batteries, and particularly preferably waste from lithium-ion secondary batteries. Therefore, lithium-ion secondary batteries will be specifically described first.

[0019] <Lithium-ion secondary batteries>

[0020] Examples illustrating the general structure of a lithium-ion secondary battery are provided below. Figure 2 and Figure 3 . Figure 2 This is a longitudinal cross-sectional view schematically representing the internal structure of an example of a lithium-ion secondary battery. Figure 3 It is a schematic representation Figure 2 An exploded view of the electrode body of a lithium-ion secondary battery is shown. Figure 4 It is along Figure 2 The diagram shows a schematic cross-sectional view of the positive electrode of a lithium-ion secondary battery along its thickness. It should be noted that the following description of the lithium-ion secondary battery is for illustrative purposes only and does not limit the metal recycling method disclosed herein in any way.

[0021] like Figure 2 As shown, the lithium-ion secondary battery 100 is a sealed battery in which a flat electrode 20 and a non-aqueous electrolyte (not shown) are housed inside the battery casing 30. Figure 2As shown, the battery casing 30 consists of an outer body 32 that houses the electrode body 20 and a cover 34 that seals the opening of the outer body 32. The outer body 32 and the cover 34 are welded and sealed by means of laser welding or the like. Materials used for the battery casing 30 include, for example, aluminum, aluminum alloy, and resin.

[0022] In the example shown, the battery casing 30 is square. However, the shape of the battery casing 30 is not limited to this; for example, it can be cylindrical. Alternatively, the battery casing 30 can be a laminated casing having a gas barrier layer such as an aluminum layer and a sealing layer containing a thermoplastic resin.

[0023] The battery casing 30 includes a positive terminal 42 and a negative terminal 44 for external connection. Additionally, the battery casing 30 is equipped with a safety valve 36 designed to release internal pressure when the internal pressure of the battery casing 30 rises above a predetermined level. The battery casing 30 also has an injection port (not shown) for injecting a non-aqueous electrolyte. The positive terminal 42 is electrically connected to the positive current collector 42a. The negative terminal 44 is electrically connected to the negative current collector 44a.

[0024] like Figure 2 and Figure 3 As shown, the electrode body 20 has a shape in which a strip-shaped positive electrode 50 and a strip-shaped negative electrode 60 are formed by overlapping two strip-shaped separators 70 and being wound along the long side. Therefore, in this embodiment, the electrode body 20 is a wound electrode body. However, the electrode body 20 is not limited to this, and can be a stacked electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked by separators.

[0025] like Figure 2 and Figure 4 As shown, in the positive electrode 50, a positive active material layer 54 is formed on one or both sides (here, both sides) of the positive current collector 52 along the long side direction. The positive electrode 50 has a portion where the positive active material layer 54 is not formed and the positive current collector 52 is exposed, namely the positive active material layer non-formed portion 52a. A positive current collector plate 42a is bonded to the positive active material layer non-formed portion 52a.

[0026] Examples of positive current collectors 52 constituting the positive electrode sheet 50 include aluminum foil. The positive electrode active material layer 54 contains a positive electrode active material. Typically, a lithium nickel cobalt manganese composite oxide is used as the positive electrode active material. The positive electrode active material layer 54 may contain conductive materials (e.g., carbon black, carbon nanotubes), binders (e.g., polyvinylidene fluoride), etc.

[0027] The content of the positive electrode active material in the positive electrode active material layer 54 is preferably 70% by mass or more, more preferably 85% to 99% by mass. The content of the conductive material in the positive electrode active material layer 54 is preferably 0.1% to 20% by mass, more preferably 0.3% to 15% by mass. The content of the binder in the positive electrode active material layer 54 is preferably 0.4% to 15% by mass, more preferably 0.5% to 10% by mass.

[0028] like Figure 3 As shown, in the negative electrode sheet 60, a negative electrode active material layer 64 is formed on one or both sides (here, both sides) of the negative electrode current collector 62 along the long side direction. The negative electrode sheet 60 has a portion where the negative electrode active material layer 64 is not formed and the negative electrode current collector 62 is exposed, namely the non-formed portion 62a of the negative electrode active material layer. A negative electrode current collector plate 44a is bonded to the non-formed portion 62a of the negative electrode active material layer.

[0029] Examples of negative electrode current collector 62 constituting negative electrode sheet 60 include copper foil. The negative electrode active material layer 64 contains a negative electrode active material. Examples of negative electrode active materials include carbon-based negative electrode active materials (e.g., graphite, hard carbon, soft carbon), silicon-based negative electrode active materials (e.g., silicon, silicon oxide), etc. The negative electrode active material layer 64 may contain binders (e.g., styrene-butadiene rubber (SBR), etc.), thickeners (e.g., carboxymethyl cellulose (CMC), etc.).

[0030] The graphite content in the negative electrode active material layer 64 is preferably 90% by mass or more, more preferably 95% by mass to 99% by mass. The binder content in the negative electrode active material layer 64 is preferably 0.1% by mass to 8% by mass, more preferably 0.5% by mass to 3% by mass. The thickener content in the negative electrode active material layer 64 is preferably 0.3% by mass to 3% by mass, more preferably 0.5% by mass to 2% by mass.

[0031] Examples of spacer 70 include porous resin sheets made of polyethylene, polypropylene, etc. The porous sheet can be a single-layer or multi-layer structure. A heat-resistant layer (HRL) can be provided on the surface of spacer 70.

[0032] Regarding non-aqueous electrolytes, typically, they contain a non-aqueous solvent and a supporting salt (in other words, an electrolyte salt). Examples of non-aqueous solvents include carbonates (such as ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, etc.), esters, and ethers. Examples of supporting salts include lithium salts such as LiPF6. The concentration of the supporting salt is not particularly limited, but is preferably 0.7 mol / L to 1.3 mol / L. Non-aqueous electrolytes may contain various additives such as gas generators and film-forming agents. It should be noted that in this embodiment, a non-aqueous electrolyte is used as the electrolyte, but the electrolyte can be a solid electrolyte.

[0033] The lithium-ion secondary battery 100 is used, for example, for automotive applications (i.e., as a drive power source for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs)) and as a power source for electronic devices.

[0034] As mentioned above, in the positive electrode of a lithium-ion secondary battery, the typical constituent metal elements used as the active material are Li, Ni, Co, and Mn. Al is generally used as the positive current collector, and Cu is generally used as the negative current collector. In addition, Li is used as the non-aqueous electrolyte in lithium-ion secondary batteries. Furthermore, Al can be used for the battery casing.

[0035] Therefore, waste from lithium-ion secondary batteries can primarily originate from lithium nickel-cobalt-manganese composite oxides of the positive electrode active material, containing Ni, Co, and Mn. Waste from lithium-ion secondary batteries can also originate from materials different from lithium nickel-cobalt-manganese composite oxides (e.g., electrode terminal materials), containing at least one of Ni, Co, and Mn. Next, the various steps of the metal recycling method disclosed herein will be described.

[0036]

[0037] In the Mn leaching process S101, the object containing Ni, Co and Mn is subjected to ammonia leaching of Mn.

[0038] As described above, the objects containing Ni, Co, and Mn can be minerals containing Ni, Co, and Mn, battery waste containing Ni, Co, and Mn, or waste other than batteries containing Ni, Co, and Mn, preferably battery waste (especially waste from lithium-ion secondary batteries). It should be noted that in this specification, "battery waste" includes not only used batteries but also structural components of used batteries, defective batteries, and structural components of defective batteries. Waste can be waste that has undergone some form of treatment (e.g., roasting).

[0039] Specific examples of waste from lithium-ion secondary batteries include black powder from used lithium-ion secondary batteries (especially black powder obtained by crushing and roasting used lithium-ion secondary batteries), positive electrode waste from used lithium-ion secondary batteries, electrode body waste from used lithium-ion secondary batteries, waste from positive electrodes judged to be defective, waste from electrode bodies judged to be defective, and positive electrode active materials judged to be defective.

[0040] Ni, Co, and Mn are contained in the object in the form of metals, oxides, etc. The oxide can be a composite oxide containing two or more metals. Preferably, Ni and Co are contained in the object in metallic form. From this viewpoint, the object is preferably subjected to reduction calcination. As the object, black powder obtained by pulverizing and reducing calcining used lithium-ion secondary batteries (also known as calcined black powder of lithium-ion secondary batteries) is preferred. Typically, Ni and Co are contained in the calcined black powder in metallic form. Generally, Mn is contained in the black powder in the form of an oxide, but Mn can also be contained as a metal.

[0041] Specifically, calcined black powder can be obtained, for example, by crushing lithium-ion secondary batteries according to known methods, sieving as needed, and calcining at 400°C to 1500°C (preferably 700°C to 1000°C) in an atmosphere with an oxygen concentration of 5% by volume or less (preferably 1% by volume or less) (especially in an atmosphere of inactive gases such as argon or nitrogen) for 1 hour to 24 hours (preferably 4 hours to 12 hours). Calcined black powder can be a substance obtained by removing specific metals (such as Cu) through sieving.

[0042] The object may further contain elements (especially metallic elements) other than Ni, Co, and Mn. For example, in addition to Ni, Co, and Mn, the object may further contain Li, Al, etc. The object may further contain transition metal elements other than Ni, Co, and Mn.

[0043] In the Mn leaching process S101, a first ammonia solution containing ammonia (NH3) and ammonium carbonate ((NH4)2CO3) is used as the leaching agent.

[0044] In the first ammonia solution, the concentration of ammonia is not particularly limited, but a higher concentration results in higher leaching energy. Therefore, the concentration of ammonia in the first ammonia solution is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, the upper limit of the ammonia concentration is the saturation concentration of ammonia in water, which is approximately 35% by mass. From the viewpoint of leaching energy and ease of operation, the ammonia concentration is particularly preferably 15% to 25% by mass.

[0045] Ammonium carbonate functions as a pH adjuster. Here, the pH of the first ammonia solution at 25°C is preferably 9 to 12, more preferably 10 to 11. Therefore, the amount of ammonium carbonate in the first ammonia solution is preferably such that the pH (at 25°C) of the first ammonia solution is 9 to 12, more preferably 10 to 11. The concentration of ammonium carbonate in the first ammonia solution is preferably 0.5 mol / L or more, more preferably 1 mol / L or more, and even more preferably 1.5 mol / L or more. On the other hand, the concentration of ammonium carbonate in the first ammonia solution can be 3 mol / L or less, or 2.5 mol / L or less.

[0046] The first ammonia solution may contain only water, ammonia, and ammonium carbonate. The first ammonia solution may further contain components other than water, ammonia, and ammonium carbonate to a extent that does not impair the effects of this disclosure (e.g., concentrations of less than 10%, 5%, or 1% by mass).

[0047] There is no particular limitation on the amount of ammonia solution used in the first ammonia solution, and it can be the same as the amount of ammonia solution used in known ammonia leaching methods. For example, the amount of ammonia solution used in the first ammonia solution is enough to completely submerge the object.

[0048] In the Mn leaching process S101, the dissolved oxygen content in the first ammonia solution (i.e., the first aqueous phase) is less than that in the second ammonia solution (i.e., the second aqueous phase) in the Ni and Co leaching process S102. In the Mn leaching process S101, the lower dissolved oxygen content in the first ammonia solution allows for preferential leaching of Mn. In the Ni and Co leaching process S102, the higher dissolved oxygen content in the second ammonia solution increases the leaching rate of Ni and Co.

[0049] From the viewpoint of setting the dissolved oxygen content as described above, in the Mn leaching process S101, leaching is preferably carried out in an atmosphere with an oxygen concentration of 21% by volume or less. The lower the oxygen concentration in the atmosphere, the higher the selectivity of Mn leaching. Therefore, the oxygen concentration of the atmosphere is preferably 18% by volume or less, more preferably 10% by volume or less, further preferably 5% by volume or less, particularly preferably 1% by volume or less (most preferably 0% by volume). Here, the oxygen concentration in the atmosphere is approximately 21% by volume, so, for example, the leaching in the Mn leaching process S101 can be carried out in a container or reaction tank open to the atmosphere. Alternatively, a gas with an oxygen concentration of 21% by volume or less can be supplied to the atmosphere (i.e., the gas phase). In this case, the oxygen-containing gas can be supplied to a closed container and pressurized.

[0050] Advantageously, leaching is performed while supplying a gas with an oxygen concentration of 21% by volume or less to the first ammonia solution. By operating in this way, the amount of oxygen dissolved in the first ammonia solution (i.e., the aqueous phase) can be easily adjusted so that Mn is preferentially leached while Mn and Co do not precipitate. From the viewpoint of higher selectivity for Mn leaching, the oxygen concentration of the supplied gas is preferably 18% by volume or less, more preferably 10% by volume or less, further preferably 5% by volume or less, particularly preferably 1% by volume or less (most preferably 0% by volume).

[0051] It should be noted that the oxygen concentration in the atmosphere is approximately 21% by volume, therefore the atmosphere and the supplied gas described above can be the atmosphere. Furthermore, it should be noted that the oxygen concentration of the supplied gas can be adjusted using known methods. For example, oxygen can be mixed with an inert gas (e.g., nitrogen, argon, etc.) to achieve a predetermined oxygen concentration, thereby adjusting the oxygen concentration. Additionally, when only an inert gas is used as the supplied gas, i.e., when the supplied gas contains only an inert gas (e.g., nitrogen, argon, etc.), the oxygen concentration can be made to be 1% by volume or less (especially 0% by volume).

[0052] The supply of a gas with an oxygen concentration of 21% by volume or less to the first ammonia solution can be carried out using known methods. For example, it can be done by bubbling to supply the gas with an oxygen concentration of 21% by volume or less to the first ammonia solution. Here, when an inactive gas is supplied to the first ammonia solution by bubbling, the selectivity of Mn leaching becomes extremely high.

[0053] It should be noted that the method for adjusting the dissolved oxygen content in the first ammonia solution during the Mn leaching process S101 is not limited to the above. For example, the first ammonia solution can be degassed under vacuum to reduce the dissolved oxygen content.

[0054] The Mn leaching process S101 can be carried out, for example, as follows: First, a container is prepared. The container can be a known container used for ammonia leaching. Heating means such as a heater, temperature measuring means such as a thermometer and temperature sensor, and stirring means such as stirring blades and magnetic stir bar are installed in the container as needed. Next, a bubbling device is prepared. The bubbling device can be a known device used in leaching. The bubbling device can be installed in the container before or after the addition of the target substance and the first ammonia solution.

[0055] The target substance and the first ammonia solution are added to the container. The order in which they are added is not particularly important; either can be added first, or they can be added simultaneously. Meanwhile, using a bubbling device, a gas with an oxygen concentration of 21% by volume or less is supplied as bubbles to the first ammonia solution.

[0056] The supply amount of gas with an oxygen concentration of 21% by volume or less can be appropriately determined based on the amount of the target material and the first ammonia solution.

[0057] The Mn leaching process S101 can be carried out at room temperature (i.e., 25±10°C) or under heating. The leaching temperature is preferably above 0°C and below 80°C. More preferably, it is 10°C to 50°C, and even more preferably, it is 15°C to 35°C.

[0058] The leaching time can be appropriately determined based on the leaching temperature. The higher the leaching temperature, the shorter the leaching time can be. The leaching time is, for example, 1 hour or more, preferably 2 hours or more, and more preferably 4 hours or more. On the other hand, from the viewpoint of operational efficiency, the leaching time is, for example, 48 hours or less, preferably 24 hours or less, and more preferably 10 hours or less.

[0059] Stirring is preferably performed during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 400 rpm or higher, and even more preferably 500 rpm or higher. The stirring speed can be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0060] By performing ammonia leaching as described above, Mn can be preferentially leached into the first aqueous phase (i.e., the first ammonia solution). That is, the Mn leaching process S101 can be performed. In the ammonia leaching of the Mn leaching process S101, by reducing the dissolved oxygen content of the first ammonia solution, the precipitation of Mn and Co is suppressed, while Mn is selectively leached into the first aqueous phase. The ammonia leaching can be completed by solid-liquid separation such as filtration. Through this solid-liquid separation, a leachate (i.e., the first aqueous phase from which Mn has been leached) and a solid residue can be obtained. The leachate obtained in the Mn leaching process S101 contains Mn, and the solid residue contains Ni and Co.

[0061] Mn can be separated and recovered from the leachate using known methods. The recovered Mn can be used in the manufacture of positive electrode active materials. Alternatively, the recovered Mn can be used for other purposes. Furthermore, the leachate containing Mn can be used directly in the manufacture of positive electrode active materials. In this case, it is possible to suppress the reduction in output characteristics that may occur in the conventional manufacture of positive electrode active materials due to the contamination of the active material with sulfuric acid source.

[0062] It should be noted that if the leachate containing Mn is stored in a state where ammonia evaporates and the oxygen concentration of the leachate is high, Mn precipitation may occur. Therefore, the leachate containing Mn is preferably stored in an environment where the oxygen concentration is preferably 10% by volume or less, more preferably 5% by volume or less, further preferably 2% by volume or less, and most preferably 0%. Furthermore, the leachate containing Mn is preferably stored in a closed system. In one preferred example, the leachate containing Mn is stored in a closed container filled with an inert gas (e.g., nitrogen, argon).

[0063] <Ni and Co leaching process S102>

[0064] In the Ni and Co leaching process S102, the solid residue obtained in the Mn leaching process S101 is subjected to ammonia leaching of Ni and Co.

[0065] In the Ni and Co leaching process S102, a second ammonia solution containing ammonia (NH3) and ammonium carbonate ((NH4)2CO3) is used as the leaching agent.

[0066] In the second ammonia solution, the concentration of ammonia is not particularly limited, but a higher concentration results in higher leaching energy. Therefore, the concentration of ammonia in the second ammonia solution is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, the upper limit of the ammonia concentration is the saturation concentration of ammonia in water, and therefore approximately 35% by mass. From the viewpoint of leaching energy and ease of operation, the ammonia concentration is particularly preferably 15% to 25% by mass.

[0067] Ammonium carbonate functions as a pH adjuster. Here, the pH of the second ammonia solution at 25°C is preferably 9 to 12, more preferably 10 to 11. Therefore, the amount of ammonium carbonate in the second ammonia solution is preferably such that the pH (at 25°C) of the second ammonia solution is 9 to 12, more preferably 10 to 11. The concentration of ammonium carbonate in the second ammonia solution is preferably 0.5 mol / L or more, more preferably 1 mol / L or more, and even more preferably 1.5 mol / L or more. On the other hand, the concentration of ammonium carbonate in the second ammonia solution can be 3 mol / L or less, or 2.5 mol / L or less.

[0068] The second ammonia solution may contain only water, ammonia, and ammonium carbonate. The second ammonia solution may further contain components other than water, ammonia, and ammonium carbonate to a extent that does not impair the effects of this disclosure (e.g., concentrations of less than 10%, 5%, or 1% by mass).

[0069] The second ammonia solution can be a solution with the same composition as the first ammonia solution (i.e., the same components and concentration), or a solution with a different composition can be used. For ease of management during implementation, the composition of the second ammonia solution is preferably the same as that of the first ammonia solution.

[0070] There is no particular limitation on the amount of ammonia solution used in the second ammonia solution, and it can be the same as the amount of ammonia solution used in known ammonia leaching methods. For example, the amount of ammonia solution used in the second ammonia solution is enough to completely submerge the solid residue.

[0071] In the Ni and Co leaching process S102, the dissolved oxygen content in the second ammonia solution (i.e., the second aqueous phase) is greater than that in the first ammonia solution (i.e., the first aqueous phase) in the Mn leaching process S101. The higher dissolved oxygen content in the second ammonia solution during the Ni and Co leaching process S102 increases the leaching rate of Ni and Co.

[0072] From the viewpoint of setting the dissolved oxygen content as described above, in the Ni and Co leaching process S102, leaching is preferably carried out in an atmosphere with an oxygen concentration of 50% by volume or more. The higher the oxygen concentration in the atmosphere, the higher the leaching rate of Ni and Co becomes. Therefore, the oxygen concentration of the atmosphere is preferably 60% by volume or more, more preferably 75% by volume or more, further preferably 90% by volume or more, particularly preferably 99% by volume or more (most preferably 100% by volume).

[0073] During leaching, a gas with an oxygen concentration of 50% by volume or higher can be supplied to the atmosphere (i.e., the gas phase). At this time, the oxygen-containing gas can be supplied to a closed container and pressurized.

[0074] Advantageously, in the Ni and Co leaching step S102, leaching is carried out while a gas with an oxygen concentration of 50% by volume or more is supplied to the second ammonia solution. By operating in this way, the amount of oxygen dissolved in the second ammonia solution can be easily adjusted to enable rapid leaching of Ni and Co. From the viewpoint of achieving higher leaching rates for Ni and Co, the oxygen concentration of the supplied gas is preferably 60% by volume or more, more preferably 75% by volume or more, further preferably 90% by volume or more, particularly preferably 99% by volume or more (most preferably 100% by volume).

[0075] The oxygen concentration of the supplied gas can be adjusted using known methods. For example, oxygen can be mixed with an inert gas (such as nitrogen, argon, etc.) to achieve a predetermined oxygen concentration, thereby adjusting the oxygen concentration. Furthermore, when only oxygen is used as the supplied gas, that is, when the supplied gas contains only oxygen, it is possible to achieve an oxygen concentration of 99% by volume or more (especially 100% by volume).

[0076] The supply of gas with an oxygen concentration of 50% by volume or higher to the second ammonia solution can be carried out using known methods. For example, it can be done by bubbling to supply gas with an oxygen concentration of 50% by volume or higher to the second ammonia solution. Here, when only oxygen is supplied to the second ammonia solution by bubbling, the leaching rate and selectivity of Ni and Co become extremely high. At this time, the smaller the bubbles, the more efficiently the dissolved oxygen content can be increased. Alternatively, for example, the supply of gas with an oxygen concentration of 50% by volume or higher to the second ammonia solution can be carried out by pressurizing a closed container while supplying it with gas with an oxygen concentration of 50% by volume or higher.

[0077] It should be noted that the method for adjusting the dissolved oxygen content in the second ammonia solution during the Ni and Co leaching process S102 is not limited to the above.

[0078] The Ni and Co leaching process S102 can be performed as follows, for example. First, a container is prepared. The container can be a known container used for ammonia leaching. Heating means such as a heater, temperature measuring means such as a thermometer and temperature sensor, and stirring means such as stirring blades and magnetic stir bar are installed in the container as needed. Next, a bubbling device is prepared. The bubbling device can be a known device used in leaching. The bubbling device can be installed in the container before or after the addition of the solid residue and the second ammonia solution.

[0079] The solid residue and the second ammonia solution are added to the container. The order in which they are added is not particularly important; either can be added first, or they can be added simultaneously. Meanwhile, a gas with an oxygen concentration of 50% by volume or more is supplied as bubbles to the second ammonia solution via a bubbling device.

[0080] The amount of gas supplied with an oxygen concentration of 50% by volume or more can be appropriately determined based on the amounts of the solid residue and the second ammonia solution. Regarding the amount of gas supplied, the amount of oxygen supplied relative to potentially oxidizable elements (especially Ni and Co) contained in the solid residue is preferably equimolar or more, more preferably 2 times molar or more, and even more preferably 3 times molar or more. The amount of oxygen supplied relative to potentially oxidizable elements contained in the solid residue can be 100 times molar or less.

[0081] The Ni and Co leaching process S102 can be carried out at room temperature (i.e., 25±10°C) or under heating. The leaching temperature is preferably above 0°C and below 80°C. More preferably, it is 10°C to 50°C, and even more preferably, it is 15°C to 35°C.

[0082] The leaching time can be appropriately determined based on the leaching temperature. The higher the leaching temperature, the shorter the leaching time can be. The leaching time is, for example, 1 hour or more, preferably 2 hours or more, and more preferably 4 hours or more. On the other hand, from the viewpoint of operational efficiency, the leaching time is, for example, 48 hours or less, preferably 24 hours or less, and more preferably 10 hours or less.

[0083] Stirring is preferably performed during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 400 rpm or higher, and even more preferably 500 rpm or higher. The stirring speed can be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0084] By performing ammonia leaching as described above, Ni and Co can be preferentially leached into the second aqueous phase (i.e., the second ammonia solution). That is, the Ni and Co leaching process S102 can be performed. In the ammonia leaching of the Ni and Co leaching process S102, by increasing the dissolved oxygen content of the second ammonia solution, Ni and Co are selectively leached into the second aqueous phase. The ammonia leaching can be completed by solid-liquid separation such as filtration. Through this solid-liquid separation, a leachate (i.e., the second aqueous phase from which Ni and Co have been leached) and solid residue can be obtained. The leachate obtained in the Ni and Co leaching process S102 contains Ni and Co.

[0085] Ni and Co can be separated and recovered from the leachate using known methods. The recovered Ni and Co can be used in the manufacture of positive electrode active materials. Alternatively, the recovered Ni and Co can be used for other purposes. Furthermore, the leachate containing Ni and Co can be used directly in the manufacture of positive electrode active materials. In this case, it is possible to suppress the reduction in output characteristics that may occur in the conventional manufacture of positive electrode active materials due to the contamination of the active material with sulfuric acid source.

[0086] As described above, according to the metal recovery method of this disclosure, through a two-stage ammonia leaching process that alters the oxygen concentration of the gas supplied to the aqueous phase, Co and Mn can be recovered from materials containing Ni, Co, and Mn with high recovery rates. Furthermore, the recovery rate of Ni is also high. Ni, Co, and Mn can be used for various applications according to known methods. The metal recovery method of this disclosure is easy to implement and is useful in the field of metal extraction. In addition, Ni, Co, and Mn can be recovered from battery waste containing Ni, Co, and Mn according to the metal recovery method of this disclosure and reused in the manufacture of positive electrode active materials. Therefore, the metal recovery method of this disclosure is useful in metal recycling, and is particularly useful in the recycling of materials for lithium-ion secondary batteries.

[0087] The embodiments relating to this disclosure will be described in detail below, but are not intended to limit this disclosure to the scope shown in the above embodiments.

[0088] [Examples 1-2 and Comparative Examples 1-7]

[0089] First, prepare the calcined black powder for the leaching sample according to the following steps. On aluminum (Al) foil, prepare the sample containing lithium nickel cobalt manganese composite oxide (LiNi). 0.6 Co 0.2 Mn 0.2 The positive electrode with an active material layer containing O2 was crushed. The crushed positive electrode was passed through a sieve with 500 μm aperture to prepare positive electrode powder. Separately, the negative electrode with a graphite-containing active material layer was crushed on copper foil. The crushed negative electrode was passed through a sieve with 500 μm aperture to prepare negative electrode powder. The obtained positive and negative electrode powders were mixed to obtain black powder. This black powder was calcined at 750°C for 6 hours under a low-oxygen atmosphere to obtain calcined black powder with most of the metal reduced. 1 g of this calcined black powder was dissolved in acid and subjected to high-frequency inductively coupled plasma (ICP) emission spectroscopy analysis. Based on the analysis results, the amounts of Co and Mn in the calcined black powder were determined.

[0090] An ammonia solution is prepared by dissolving ammonium carbonate, which has a total molar amount of Ni and Co relative to the calcined black powder of 1.5 moles, in an ammonia solution with a concentration of 13 mol / L (approximately 25% by mass).

[0091] The first stage of ammonia leaching was carried out as follows: Roasted black powder was added to the ammonia solution. Ammonia leaching was performed for 6 hours at room temperature (25°C) with stirring at 800 rpm while the gas shown in Table 1 was supplied to the ammonia solution via bubbling. Then, solid-liquid separation was performed by filtration to obtain leachate (1) and solid residue (1).

[0092] Next, the second stage of ammonia leaching was carried out as follows. The obtained solid residue (1) was added to the above ammonia solution. While the gas shown in Table 1 was supplied to the ammonia solution by bubbling, ammonia leaching was carried out at room temperature (25°C) for 6 hours with stirring at 800 rpm. Then, solid-liquid separation was performed by filtration to obtain leachate (2) and solid residue (2).

[0093] [Leaching Rate Evaluation]

[0094] ICP emission spectroscopy analysis was performed on the leachates (1) and (2) obtained in each embodiment and comparative example to determine the amounts of Co and Mn in leachate (1) and leachate (2). Using the determined values ​​and the initial amounts in the calcined black powder mentioned above, the Co leaching rate and Mn leaching rate in the first and second stages of ammonia leaching were determined. Furthermore, the sum of the Co leaching rates in the first and second stages was taken as the Co recovery rate, and the sum of the Mn leaching rates in the first and second stages was taken as the Mn recovery rate. The results are shown in Table 1.

[0095] Table 1

[0096]

[0097] As shown in Table 1, when oxygen is supplied during the first stage of ammonia leaching, Co is preferentially leached. On the other hand, Mn is precipitated. As a result, the recovery rates of both Co and Mn are insufficient. When atmospheric or nitrogen gas is supplied during the first stage of ammonia leaching, Mn is preferentially leached. Furthermore, when oxygen is supplied during the second stage of ammonia leaching, Co is preferentially leached. Based on these results, it can be concluded that the leaching selectivity can be controlled according to the oxygen concentration of the gas supplied to the aqueous phase.

[0098] Furthermore, in Examples 1 and 2, where the oxygen concentration of the gas supplied in the first stage of ammonia leaching is below the atmospheric oxygen concentration and the oxygen concentration of the gas supplied in the second stage of ammonia leaching is increased, the Co recovery rate and Mn recovery rate are both above 90%.

[0099] As can be seen from the above, the metal recovery method disclosed herein can recover Co and Mn from objects containing Ni, Co and Mn with high recovery rates using ammonia and ammonium carbonate.

[0100] The specific examples of this disclosure have been described in detail above, but these are merely illustrative and do not limit the scope of protection of the claims. The technology described in the scope of protection of the claims includes technologies that have undergone various modifications and alterations to the specific examples illustrated above.

[0101] That is, the metal recycling method disclosed herein is as follows [1] to [9].

[0102] [1] A method for recovering a metal, comprising: a Mn leaching step, wherein a first ammonia solution containing ammonia and ammonium carbonate is used to leach a substance containing Ni, Co and Mn, thereby leaching Mn to a first aqueous phase, and

[0103] In the Ni and Co leaching process, a second ammonia solution containing ammonia and ammonium carbonate is used to leach the solid residue obtained in the Mn leaching process above, so that Ni and Co are leached into the second aqueous phase;

[0104] The dissolved oxygen content in the first ammonia solution during the Mn leaching process is less than the dissolved oxygen content in the second ammonia solution during the Ni and Co leaching processes.

[0105] [2] According to the method of [1], wherein in the above-mentioned Mn leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 21% by volume or less to the first ammonia solution.

[0106] In the above-mentioned Ni and Co leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 50% by volume or more to the above-mentioned second ammonia solution.

[0107] [3] According to the method of [1], wherein in the above-mentioned Mn leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 10% by volume or less to the first ammonia aqueous solution.

[0108] In the above-mentioned Ni and Co leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 90% by volume or more to the above-mentioned second ammonia solution.

[0109] [4] According to the method of [1], wherein, in the above-mentioned Mn leaching process, the leaching is carried out while nitrogen gas is supplied to the first ammonia solution.

[0110] In the above-mentioned Ni and Co leaching process, the leaching is carried out while oxygen is supplied to the above-mentioned second ammonia solution.

[0111] [5] The method according to any one of [1] to [4], wherein the object contains Ni and Co as metals.

[0112] [6] The method according to any one of [1] to [5], wherein the object is waste from a lithium-ion secondary battery.

[0113] [7] According to the method described in item [6], wherein the aforementioned waste is calcined black powder from lithium-ion secondary batteries.

[0114] [8] The method according to any one of [1] to [7], wherein the ammonia concentration of the first ammonia solution and the ammonia concentration of the second ammonia solution are in the range of 15% by mass to 25% by mass.

[0115] [9] The method according to any one of [1] to [8], wherein the pH of the first ammonia solution at 25°C and the pH of the second ammonia solution at 25°C are in the range of 9 to 12.

Claims

1. A method for recycling metal, comprising: In the Mn leaching process, a first ammonia solution containing ammonia and ammonium carbonate is used to leach the object containing Ni, Co, and Mn, so that Mn is leached into the first aqueous phase. In the Ni and Co leaching process, a second ammonia solution containing ammonia and ammonium carbonate is used to leach the solid residue obtained in the Mn leaching process, so that Ni and Co are leached into the second aqueous phase; The dissolved oxygen content in the first ammonia solution during the Mn leaching process is less than the dissolved oxygen content in the second ammonia solution during the Ni and Co leaching process.

2. The method according to claim 1, wherein, In the Mn leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of less than 21% by volume to the first ammonia solution. In the Ni and Co leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 50% by volume or more to the second ammonia solution.

3. The method according to claim 1, wherein, In the Mn leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of less than 10% by volume to the first ammonia solution. In the Ni and Co leaching process, the leaching is carried out while supplying a gas with an oxygen concentration of 90% by volume or more to the second ammonia solution.

4. The method according to claim 1, wherein, In the Mn leaching process, the leaching is carried out while nitrogen gas is supplied to the first ammonia solution. In the Ni and Co leaching process, the leaching is carried out while oxygen is supplied to the second ammonia solution.

5. The method according to claim 1, wherein, The object contains Ni and Co as metals.

6. The method according to claim 1, wherein, The object in question is waste material from lithium-ion secondary batteries.

7. The method according to claim 6, wherein, The waste material is calcined black powder from lithium-ion secondary batteries.

8. The method according to claim 1, wherein, The ammonia concentration of the first ammonia solution and the ammonia concentration of the second ammonia solution are in the range of 15% to 25% by mass.

9. The method according to claim 1, wherein, The pH of the first ammonia solution at 25°C and the pH of the second ammonia solution at 25°C are both in the range of 9 to 12.

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