Process for the recovery of copper

Abstract

Provided is a copper recovery method capable of highly selectively separating and recovering Cu from a target material containing Ni, Co, and Cu. The copper recovery method of the present disclosure includes a first ammonia leaching step of leaching a target material containing Ni, Co, and Cu in metallic form using first ammonia water having a concentration of 2.5 mol / L or less to obtain an aqueous phase containing Cu and a solid residue. The leaching of the first ammonia leaching step is performed in the presence of oxygen.

Description

Technical Field

[0001] This disclosure relates to methods for copper recovery. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in various fields, such as vehicle power supplies and portable power sources. In recent years, from the perspective of the SDGs (Safety, Government, and Goods Administration), the recycling of materials from used lithium-ion rechargeable batteries is being promoted. Various metal elements are used in lithium-ion rechargeable batteries, and technologies for separating these metal elements from used batteries are being developed for material recycling.

[0003] Representative examples of positive electrode active materials for lithium-ion secondary batteries used in automotive applications include lithium nickel cobalt manganese composite oxide (NCM) and lithium nickel cobalt aluminum composite oxide (NCA), which contain Ni and Co. On the other hand, copper foil is typically used in the negative electrode current collector of lithium-ion secondary batteries. Therefore, waste materials from lithium-ion secondary batteries mostly contain Ni, Co, and Cu.

[0004] As an example of a technique for separating metal elements from waste from lithium-ion secondary batteries, Patent Document 1 can be cited. In Patent Document 1, an acid and reducing agent are used to obtain a leachate containing Ni, Co and Cu from waste from lithium-ion secondary batteries. A hydrogen sulfide compound is used to precipitate Cu from the leachate as a sulfide (i.e., CuS), thereby separating Cu from Ni and Co.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2023-150907 Summary of the Invention

[0008] However, as shown in Patent Document 1 above, when Cu is precipitated and separated in the form of CuS from a leachate containing Ni, Co and Cu, NiS and CoS are also precipitated at the same time, which leads to a problem of reduced recovery rates of Ni and Co.

[0009] Therefore, the purpose of this disclosure is to provide a copper recovery method capable of highly selectively separating and recovering Cu from an object containing Ni, Co and Cu.

[0010] The copper recovery method disclosed herein includes: a first ammonia leaching step, in which a substance containing Ni, Co, and Cu in metallic form is leached using a first ammonia solution with a concentration of 2.5 mol / L or less, to obtain an aqueous phase containing Cu and a solid residue. The leaching in the first ammonia leaching step is carried out in the presence of oxygen.

[0011] Based on this composition, Cu can be separated and recovered with high selectivity from objects containing Ni, Co and Cu. Attached Figure Description

[0012] Figure 1 This is a summary of the copper recycling method disclosed herein and a flowchart of each step.

[0013] Figure 2 This is a longitudinal cross-sectional view schematically representing the internal structure of an example of a lithium-ion secondary battery.

[0014] Figure 3 It means Figure 2 The diagram shows an exploded view of the electrode structure of a lithium-ion secondary battery. Detailed Implementation

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. 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 drawings, components and parts that perform the same function are labeled with the same symbols. Additionally, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect 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 between the positive and negative electrodes.

[0017] Figure 1 This is a summary of the copper (Cu) recovery method of this disclosure and a flowchart of each step. The copper recovery method of this disclosure includes: a first ammonia leaching step S101 as a mandatory step: using a first ammonia solution with a concentration of 2.5 mol / L or less, leaching the object containing Ni, Co, and Cu in metallic form, to obtain an aqueous phase containing Cu and a solid residue. The leaching in the first ammonia leaching step S101 is carried out in the presence of oxygen. The copper recovery method of this disclosure may further include: a second ammonia leaching step S102 as an optional step: using a second ammonia solution in an inert gas atmosphere to leach the solid residue obtained in the first ammonia leaching step S101. Additionally, the copper recovery method of this disclosure may include the roasting step, Cu recovery step, etc., described later as optional steps.

[0018] The copper recycling method disclosed herein is applied to materials containing Ni, Co, and Cu in metallic form. The type of material is not particularly limited as long as it contains Ni, Co, and Cu in metallic form; examples include battery waste containing Ni, Co, and Cu in metallic form, and other waste containing Ni, Co, and Cu in metallic form besides battery waste. The material containing Ni, Co, and Cu is preferably 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] Illustrate the general structure of a lithium-ion secondary battery with an example. An example of the structure of a lithium-ion secondary battery is shown 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 The diagram shows an exploded view of the electrode body of a lithium-ion secondary battery. It should be noted that the following description of the lithium-ion secondary battery is for ease of understanding and does not in any way limit the copper recovery method disclosed herein.

[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 2 As 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 sealed by welding, such as laser welding. 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 configured 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 3As shown, the electrode body 20 has a strip-shaped positive electrode 50 and a strip-shaped negative electrode 60, which are formed by overlapping two strip-shaped insulating sheets 70 and wound along their long sides. Therefore, in this embodiment, the electrode body 20 is a wound electrode body. However, the electrode body 20 is not limited to this, and may also be a stacked electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked by insulating sheets.

[0025] like Figure 2 As shown, in the positive electrode 50, a positive active material layer 54 is formed on one or both sides (in this case, 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 non-formed portion 52a of the positive active material layer. A positive current collector plate 42a is bonded to the non-formed portion 52a of the positive active material layer.

[0026] Examples of the positive current collector 52 constituting the positive electrode sheet 50 include aluminum foil. The positive electrode active material layer 54 contains a positive electrode active material. The positive electrode active material is typically a lithium transition metal composite oxide containing Ni and Co. Examples of such positive electrode active materials include lithium nickel cobalt manganese composite oxides and lithium nickel cobalt aluminum composite oxides. The positive electrode active material layer 54 may contain conductive materials (e.g., carbon black, carbon nanotubes, etc.), binders (e.g., polyvinylidene fluoride, etc.), 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% by mass to 99% by mass. The content of the conductive material in the positive electrode active material layer 54 is preferably 0.1% by mass to 20% by mass, more preferably 0.3% by mass to 15% by mass. The content of the binder in the positive electrode active material layer 54 is preferably 0.4% by mass to 15% by mass, more preferably 0.5% by mass to 10% by mass.

[0028] like Figure 2 As shown, in the negative electrode sheet 60, a negative electrode active material layer 64 is formed on one or both sides (in this case, 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] The negative electrode current collector 62 constituting the negative electrode sheet 60 is typically 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, etc.) and 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), 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 such as polyethylene and polypropylene. 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] Non-aqueous electrolytes typically contain a non-aqueous solvent and a supporting salt (in other words, an electrolyte salt). Examples of non-aqueous solvents include carbonates (e.g., ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, etc.), esters, ethers, etc. 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. The non-aqueous electrolyte 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, as a power source 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 electronic devices.

[0034] As described above, Li, Ni, and Co are typically used as constituent metal elements of the positive electrode active material in lithium-ion secondary batteries. The positive electrode active material may further include Mn and Al. Al is typically used in the positive electrode current collector. Cu is typically used in the negative electrode current collector. Additionally, Li is used in the non-aqueous electrolyte in lithium-ion secondary batteries. Furthermore, Al can be used in the battery casing. The following describes in detail each step of the copper recovery method of this disclosure.

[0035] <First Ammonia Leaching Process S101>

[0036] In the first ammonia leaching step S101, ammonia water of low concentration is used to leach a substance containing Ni, Co and Cu in metallic form in the presence of oxygen.

[0037] As mentioned above, there is no particular limitation on the objects containing Ni, Co, and Cu in metallic form, but battery waste (especially waste from lithium-ion secondary batteries) is preferred. It should be noted that in this specification, "battery waste" includes not only used batteries, but also components of used batteries (e.g., electrodes), defective batteries, and components of defective batteries (e.g., electrodes). Battery waste may undergo some form of treatment (e.g., roasting).

[0038] As an object containing Ni, Co, and Cu in metallic form, black powder obtained by crushing and reducing calcining waste from lithium-ion secondary batteries (also known as calcined black powder from lithium-ion secondary batteries) is particularly preferred. In lithium-ion secondary batteries, Ni and Co are contained in the form of composite oxides as positive electrode active materials. Cu is contained in the form of metals as negative electrode current collector. In the calcined black powder from lithium-ion secondary battery waste, Ni and Co are reduced to metals during calcination, thus containing a large proportion (preferably 90 mol% or more, particularly preferably 100 mol%) of Ni and Co in metallic form. Therefore, the calcined black powder from lithium-ion secondary battery waste is particularly suitable for the recycling method disclosed herein because it contains a very large amount of Ni, Co, and Cu in metallic form.

[0039] The calcined black powder can be obtained, for example, by the following operation: crushing a lithium-ion secondary battery according to a known method, sieving it as needed, and calcining it for 1 hour to 24 hours (preferably 4 hours to 12 hours) in an atmosphere of 700°C to 1500°C (preferably 800°C to 1000°C) and an oxygen concentration of less than 5% by volume (preferably less than 1% by volume) (especially in an atmosphere of inactive gases such as argon or nitrogen). The calcined black powder can be sorted by specific metal types.

[0040] Therefore, the copper recovery method of this disclosure, as an optional step, may further include a step of roasting the waste from lithium-ion secondary batteries to obtain an object containing Ni, Co, and Cu in metallic form (i.e., roasted black powder) (hereinafter also referred to as the "roasting step"). This roasting step is performed before the first ammonia leaching step S101. The roasting conditions for this roasting step are as described above.

[0041] It should be noted that the above-mentioned roasting process can remove liquid components (such as electrolyte) from the waste of lithium-ion secondary batteries and carbonize resin components (such as adhesives, separators, etc.). In addition, roasting can stop the battery from functioning.

[0042] The object may further contain elements (especially metallic elements) other than Ni, Co, and Cu. For example, the object may contain other transition metal elements, and in particular, may further contain Mn. For example, the object may further contain metallic elements other than transition metals such as Li and Al. In addition, the object may contain a portion of Ni, Co, and Cu in a form other than metallic. For example, in addition to metallic Ni, metallic Co, and metallic Cu, the object may also contain at least one oxide selected from Ni oxide, Co oxide, and Cu oxide.

[0043] In the first ammonia leaching step S101, Cu is leached from an object containing Ni, Co, and Cu in metallic form. A first ammonia solution is used as the leaching agent.

[0044] Here, if the concentration of ammonia is too high, Ni and Co are also leached along with Cu. Therefore, for highly selective Cu leaching, the concentration of the first ammonia solution (i.e., the concentration of ammonia in the first ammonia solution) is 2.5 mol / L or less. From the viewpoint of higher Cu selectivity, the concentration of the first ammonia solution is preferably 1.0 mol / L or less, more preferably 0.7 mol / L or less, and even more preferably 0.5 mol / L or less. There is no particular limitation on the lower limit of the concentration of the first ammonia solution, but if it is too low, the leaching rate slows down, requiring a longer leaching time. Therefore, the concentration of the first ammonia solution is preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more, and even more preferably 0.3 mol / L or more.

[0045] The first ammonia solution typically contains only water and ammonia. However, the first ammonia solution may further contain components other than water and ammonia within a range that does not impair the effects of this disclosure (e.g., concentrations of less than 10%, 5%, or 1% by mass).

[0046] There is no particular limitation on the amount of ammonia solution used in the first step; it can be the same as the amount used in the well-known ammonia leaching method. For example, the amount of ammonia solution used in the first step is enough to completely submerge the object.

[0047] The dissolution of metallic Cu in ammonia water is generally related to oxygen. Therefore, the leaching in the first ammonia leaching step S101 is carried out in the presence of oxygen. It should be noted that the presence of oxygen means that oxygen is present in the atmosphere of the first ammonia leaching step S101 and dissolved in the first ammonia water. Therefore, by dissolving oxygen in the first ammonia water, Cu can be preferentially leached into the aqueous phase.

[0048] Therefore, for example, the leaching in the first ammonia leaching step S101 can be carried out in an oxygen-containing atmosphere. Here, the higher the dissolved oxygen content, the higher the leaching rate of Cu. Therefore, the oxygen concentration of the leaching atmosphere is preferably 21% by volume or more, more preferably 30% by volume or more, further preferably 50% by volume or more, particularly preferably 99% by volume or more (most preferably 100% by volume). Here, since the oxygen concentration in the atmosphere is about 21% by volume, the leaching in the first ammonia leaching step S101 can be carried out in a container or reaction tank with the atmosphere open. Alternatively, an oxygen-containing gas can be supplied to the atmosphere (i.e., the gas phase). In this case, an oxygen-containing gas can be supplied to a closed container and pressurized.

[0049] Alternatively, the leaching in the first ammonia leaching step S101 can be carried out while supplying an oxygen-containing gas to the first ammonia solution. In this case, it is advantageous that oxygen can be stably dissolved in the first ammonia solution. From the viewpoint of high Cu leaching rate, the oxygen concentration of the oxygen-containing gas is preferably high, specifically, preferably 21% by volume or more, more preferably 30% by volume or more, further preferably 50% by volume or more, particularly preferably 99% by volume or more (most preferably 100% by volume).

[0050] It should be noted that since the oxygen concentration in the atmosphere is approximately 21% by volume, the oxygen-containing atmosphere and oxygen-containing gas can be the atmosphere itself. Furthermore, the oxygen concentration of the oxygen-containing atmosphere and oxygen-containing gas can be adjusted using known methods. For example, oxygen can be mixed with an inert gas (such as nitrogen, argon, etc.) or the atmosphere to achieve a predetermined oxygen concentration, thereby adjusting the oxygen concentration. Additionally, when only oxygen is used as the oxygen-containing atmosphere and the supplied gas, i.e., when the oxygen-containing atmosphere and the supplied gas contain only oxygen, the oxygen concentration can be made to be 99% by volume or higher (especially 100% by volume).

[0051] The supply of oxygen-containing gas to the first ammonia solution can be carried out according to known methods. For example, the oxygen-containing gas can be supplied to the first ammonia solution by bubbling. Here, when only oxygen is supplied to the first ammonia solution by bubbling, the leaching rate of Cu is particularly high. In this case, the smaller the bubbles, the more effectively the dissolved oxygen content can be increased.

[0052] The first ammonia leaching process S101 can be performed as follows, for example. First, a container is prepared. The container can be a known container used in ammonia leaching. As needed, a heating mechanism such as a heater, a temperature measuring mechanism such as a thermometer and temperature sensor, a stirring mechanism such as stirring blades and a magnetic stirring rod are installed in the container. Additionally, a bubbling device is prepared. The bubbling device can be a known bubbling 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.

[0053] 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 one can be added first, or they can be added simultaneously. Meanwhile, an oxygen-containing gas is supplied to the first ammonia solution in the form of bubbles using a bubbling device.

[0054] As for the amount of oxygen supplied for utilizing the gas, it is preferable to supply an excess of the target oxidizing element (i.e., Cu) contained in the target material.

[0055] The first ammonia leaching step 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.

[0056] 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.

[0057] 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.

[0058] By performing the first ammonia leaching as described above, Cu can be preferentially leached into the aqueous phase (i.e., the first ammonia solution). Specifically, in the first ammonia leaching step S101, by using a low concentration of first ammonia solution of 2.5 mol / L or less to dissolve oxygen in the first ammonia solution, the leaching of Ni and Co can be suppressed, and Cu can be leached with a high leaching rate.

[0059] The first ammonia leaching can be completed by solid-liquid separation such as filtration. Through this solid-liquid separation, an aqueous phase containing Cu (i.e., leachate) and solid residue can be obtained. As described above, the first ammonia leaching S101 can be performed.

[0060] Cu can be separated and recovered from the leachate using known methods. For example, according to known methods, Cu can be precipitated as copper oxide (CuO) by evaporating ammonia from the leachate. The precipitate is then recovered by solid-liquid separation, thereby recovering Cu as copper oxide. Alternatively, by adding a hydroxide (e.g., LiOH, NaOH, KOH, etc.) to the leachate and then evaporating ammonia, copper can be precipitated as copper hydroxide (Cu(OH)₂). Therefore, in this case, the precipitate is recovered by solid-liquid separation, thereby recovering Cu as copper hydroxide.

[0061] Therefore, the copper recovery method disclosed herein may further include a step of recovering Cu from the Cu-containing aqueous phase obtained from the first ammonia leaching step S101 (hereinafter also referred to as the "Cu recovery step"). The Cu recovery step specifically includes: a step of evaporating ammonia from the Cu-containing aqueous phase obtained from the first ammonia leaching step S101 to recover CuO, or a step of adding sodium hydroxide to the Cu-containing aqueous phase obtained from the first ammonia leaching step S101 and then evaporating ammonia from the aqueous phase to recover Cu(OH)2, etc.

[0062] The recovered Cu can be reused as a raw material for a negative electrode current collector using known methods. Therefore, the copper recovery method disclosed herein can be applied as a method for manufacturing raw materials for a negative electrode current collector.

[0063] <Second ammonia leaching process S102>

[0064] As described above, in the first ammonia leaching step S101, a low-concentration ammonia solution is used. Therefore, the leached and dissolved Ni, Co, and Cu are unstable in the low-concentration ammonia leaching solution, and some of them redefine onto the surface of the object. This redefinement is considered to be a compound containing Ni, Co, and Cu, which is difficult to dissolve under the conditions of the first ammonia leaching. Therefore, in the first ammonia leaching step S101, this redefinement hinders the leaching of Cu from the object. As a result, Cu that cannot be completely recovered remains in the solid residue obtained in the first ammonia leaching step S101.

[0065] Therefore, the Cu recovery method of this disclosure may further include: a second ammonia leaching step S102, in which the solid residue obtained in the first ammonia leaching step S101 is leached using a second ammonia solution under an inactive gas atmosphere. According to the second ammonia leaching step S102, reprecipitates can be removed from the solid residue.

[0066] Therefore, in the second ammonia leaching step S102, the reprecipitates adhering to the surface of the solid residue obtained in the first ammonia leaching step S101 are redissolved. For this purpose, a second ammonia solution is used.

[0067] The concentration of the second ammonia solution (i.e., the concentration of ammonia in the second ammonia solution) is not particularly limited. The higher the concentration of the second ammonia solution, the higher the Cu recovery rate. Therefore, the concentration of the second ammonia solution is, for example, 0.3 mol / L or more, preferably 5.0 mol / L or more, more preferably 8.0 mol / L or more, even more preferably 10.0 mol / L or more, and particularly preferably 13.0 mol / L or more. The concentration of the second ammonia solution can be the saturation concentration of ammonia, or it can be 16.0 mol / L or less, or 15.0 mol / L or less.

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

[0069] There is no particular limitation on the amount of ammonia water used in the second ammonia solution; it can be the same as the amount used in the well-known ammonia leaching process. For example, the amount of ammonia water used is enough to completely submerge the solid residue.

[0070] Here, the oxygen in the atmosphere inhibits the dissolution of the aforementioned heavy precipitates in the second ammonia solution. Furthermore, Ni and Co are unnecessarily leached from the solid residue. Therefore, in the second ammonia leaching step S102, leaching is carried out under an inactive gas atmosphere. Thus, in the second ammonia leaching step S102, leaching is typically carried out under an oxygen-free atmosphere. This allows for the preferential and selective dissolution of the heavy precipitates on the surface of the solid residue.

[0071] Examples of inert gases include nitrogen and argon.

[0072] Here, it is advantageous to supply inactive gases to the second ammonia solution via bubbling. In this case, dissolved oxygen in the second ammonia solution can be removed.

[0073] The second ammonia leaching process S102 can be performed as follows, for example. First, a container is prepared. The container can be a known container used in ammonia leaching. As needed, a heating mechanism such as a heater, a temperature measuring mechanism such as a thermometer and temperature sensor, a stirring mechanism such as stirring blades and a magnetic stirring rod are installed in the container. Additionally, a bubbling device is prepared. The bubbling device can be a known bubbling 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.

[0074] Solid residue and 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 simultaneously. Meanwhile, an inert gas is supplied to the second ammonia solution in the form of bubbles using a bubbling device. The amount of gas supplied is at least the amount by which the atmosphere is replaced by the gas.

[0075] The second ammonia leaching step 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.

[0076] 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.

[0077] 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.

[0078] As described above, the reprecipitate can be dissolved in the aqueous phase (i.e., the second ammonia solution). That is, the second ammonia leaching process S102 can be performed. The second ammonia leaching can be completed by solid-liquid separation such as filtration. Through this solid-liquid separation, a leachate and solid residue can be obtained.

[0079] A portion of the Cu is leached into the leachate, and this Cu can be recovered using known methods. Therefore, by performing a second ammonia leaching step S102 in addition to the first ammonia leaching step S101, the Cu recovery rate can be improved. Furthermore, on the other hand, the solid residue contains Ni, Co, and partially recovered Cu in metallic form. Additionally, by removing heavy precipitates that hinder Cu leaching from the solid residue, Cu becomes readily leached.

[0080] Therefore, by using the solid residue obtained in the second ammonia leaching step S102 as the object containing Ni, Co and Cu in metallic form, and by repeating the first ammonia leaching step S101 and the second ammonia leaching step S102 in sequence, a greater amount of Cu can be recovered.

[0081] Therefore, in the copper recovery method disclosed herein, it is preferable to use the solid residue obtained in the second ammonia leaching step S102 as the target material, and to repeat the first ammonia leaching step S101 and the second ammonia leaching step S102 more than once. In this case, the Cu recovery rate can be further improved, and more than 90% or even more than 99% of Cu can be recovered.

[0082] According to the copper recovery method disclosed herein, Cu can be separated and recovered with high selectivity from a material containing Ni, Co, and Cu. Furthermore, the copper recovery method of this disclosure is simple to implement. In addition, Cu is selectively removed from the solid residue after the copper recovery method of this disclosure with a high removal rate, while most of Ni and Co remain. Therefore, in the case of recovering Ni and Co from this solid residue, the selectivity and recovery rate of Ni and Co recovery are high. Therefore, the copper recovery method of this disclosure is extremely useful in the material recovery of lithium-ion secondary batteries.

[0083] The following describes in detail test examples related to this disclosure, but it is not intended to limit this disclosure to the contents shown in these test examples.

[0084] [Examples 1-3 and Comparative Examples 1-3]

[0085] First, prepare the calcined black powder for the leaching sample according to the following steps. The sample will be coated with an aluminum (Al) foil containing a 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 sieved through a 500 μm mesh to prepare positive electrode powder. Separately, the negative electrode with a graphite-containing active material layer on copper foil was crushed. The pulverized negative electrode was sieved through a 500 μm mesh 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. This reduced Ni and Co, yielding calcined black powder containing Ni, Co, and Cu in metallic form. 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 Ni, Co, and Cu in the calcined black powder (i.e., their initial amounts) were determined.

[0086] Prepare ammonia solution of the concentrations shown in Table 1. Add the calcined black powder of the leaching sample to the ammonia solution. While supplying the ammonia solution with the gas shown in Table 1 by bubbling, leaching of ammonia was carried out at room temperature (25°C) for 3 hours with stirring at 800 rpm. Then, solid-liquid separation was performed by filtration to obtain leachate (1) and solid residue (1).

[0087] The leachate (1) was subjected to high-frequency inductively coupled plasma (ICP) emission spectroscopy analysis to determine the Ni, Co and Cu content.

[0088] The amounts of Ni, Co, and Cu were compared. Using these values, along with the initial amounts of Ni, Co, and Cu (i.e., the amounts of Ni, Co, and Cu in the calcined black powder), the leaching rates of Ni, Co, and Cu were calculated. The leaching rate of Cu was taken as the Cu recovery rate, and the average of the Ni and Co leaching rates was taken as the "Ni and Co loss rate". The results are shown in Table 1.

[0089]

[0090] A comparison of Comparative Example 1 and Comparative Example 2 shows that an oxygen supply is required to leach Cu from the leaching sample. Comparative Examples 1 and 3, and Examples 1-3, show that when the ammonia concentration is below 2.5 mol / L, the Cu recovery rate is high, and the loss rates of Ni and Co are low. Furthermore, the following trend was observed: the lower the ammonia concentration, the higher the Cu recovery rate, and the lower the loss rates of Ni and Co, i.e., the higher the selectivity of Cu leaching and the higher the Cu recovery rate.

[0091] [Examples 4-12]

[0092] The roasted black powder of the leaching sample was subjected to a first-stage ammonia leaching (first ammonia leaching) under the same conditions as the ammonia leaching in Example 3, resulting in leachate (2) and solid residue (2).

[0093] Prepare ammonia solution of the concentration shown in Table 2. Add the solid residue (2) obtained above to the ammonia solution. While supplying the ammonia solution with the gas shown in Table 2 by bubbling, carry out the second stage of ammonia leaching (second ammonia leaching) at room temperature (25°C) for 3 hours with stirring at 800 rpm. Then, perform solid-liquid separation by filtration to obtain leachate (3) and solid residue (3).

[0094] For Examples 9-12, the first and second ammonia leaching processes were repeated. That is, the solid residue (3) was subjected to the first ammonia leaching again to obtain a leachate (4) and a solid residue (4). The obtained solid residue (4) was subjected to the second ammonia leaching again, and then solid-liquid separation was performed by filtration to obtain a leachate (5) and a solid residue (5).

[0095] The leachates (2) to (5) were subjected to high-frequency inductively coupled plasma (ICP) emission spectroscopy analysis to determine the amounts of Ni, Co, and Cu. Using these values ​​and the initial amounts of Ni, Co, and Cu, the leaching rates of Ni, Co, and Cu were determined. It should be noted that the leaching rate in Examples 4 to 8 is the total leaching rate for leachates (2) to (3), and in Examples 9 to 12 it is the total leaching rate for leachates (2) to (5). The leaching rate of Cu was taken as the Cu recovery rate, and the average of the Ni leaching rate and the Co leaching rate was taken as the "Ni and Co loss rate". The results are shown in Table 2.

[0096]

[0097] A comparison of Examples 4 with Examples 5-8 shows that performing a second ammonia leaching under an inert gas atmosphere can further improve the Cu recovery rate. Furthermore, a comparison of Examples 5-8 with Examples 9-12 shows that repeating the first and second ammonia leaching processes can further improve the Cu recovery rate. Additionally, the results of Examples 5-12 indicate that the higher the concentration of the ammonia solution in the second ammonia leaching, the higher the Cu recovery rate.

[0098] [Comparative Example 4]

[0099] Ammonia solution was prepared by mixing 28% by mass ammonia solution with ammonium sulfate ((NH4)2SO4) as a pH adjuster. The calcined black powder of the leaching sample was added to this ammonia solution and heated to 80°C. Ammonia leaching was carried out by stirring at 500 rpm for 3 hours while maintaining the temperature at 80°C. Solid-liquid separation was then performed by filtration to obtain the leachate and solid residue. It should be noted that the leachate contains Ni, Co, and Cu.

[0100] Hydrogen sulfide gas was supplied to the obtained leachate while the leachate was stirred at a speed of 600 rpm. After confirming the formation of a black precipitate, solid-liquid separation was performed by filtration to obtain filtrate and precipitate.

[0101] High-frequency inductively coupled plasma (ICP) emission spectroscopy was used to analyze the leachate after ammonia leaching to determine the amounts of Ni, Co, and Cu. Furthermore, ICP emission spectroscopy was also performed on the black precipitate to determine the amounts of Ni, Co, and Cu. This confirmed that over 99% of Cu had precipitated. Additionally, using the Ni and Co amounts in the leachate and the precipitate, the average proportion of unrecoverable Ni and Co (i.e., the "Ni, Co loss rate") was calculated. The results showed that the Ni, Co loss rate was 85.8%.

[0102] Comparative Example 4 is an experimental example related to a conventional method for recovering Cu in the form of CuS. It can be seen that in the conventional method, the loss rates of Ni and Co are significantly higher compared to the example.

[0103] Therefore, as can be seen from the above, the copper recovery method of this disclosure can selectively separate and recover Cu from an object containing Ni, Co and Cu.

[0104] The specific examples of this disclosure have been described in detail above, but these are merely illustrative and do not limit the scope of patent protection. The technology described in the scope of patent protection includes technologies that have undergone various modifications and alterations to the specific examples described above.

[0105] That is, the copper recovery method disclosed herein is as follows [1] to [9].

[0106] [1] A method for recovering copper, comprising: a first ammonia leaching step, wherein a first ammonia solution with a concentration of less than 2.5 mol / L is used to leach an object containing Ni, Co and Cu in metallic form, to obtain an aqueous phase containing Cu and a solid residue.

[0107] The leaching process described above for the first ammonia leaching step is carried out in the presence of oxygen.

[0108] [2] According to the method of [1], the leaching of the first ammonia leaching step is carried out in an atmosphere with an oxygen concentration of 21% by volume or more.

[0109] [3] According to the method described in item [1], the first ammonia leaching process is carried out while gas with an oxygen concentration of 21% or more is supplied to the first ammonia water by bubbling.

[0110] [4] According to the method of [1], the leaching of the first ammonia leaching process is carried out while oxygen is supplied to the first ammonia water by bubbling.

[0111] [5] The method according to any one of [1] to [3] further includes: a second ammonia leaching step, wherein the solid residue obtained in the first ammonia leaching step is leached with a second ammonia solution under an inactive gas atmosphere.

[0112] [6] According to the method of [5], the second ammonia leaching process is carried out while nitrogen gas is supplied to the second ammonia water by bubbling.

[0113] [7] The method according to item [5] or [6], wherein the concentration of the second ammonia solution is 5 mol / L or more.

[0114] [8] The method according to any one of [5] to [7], wherein the first ammonia leaching process and the second ammonia leaching process are repeated more than once using the solid residue obtained in the second ammonia leaching process as the object.

[0115] [9] The method according to any one of [1] to [8], wherein the object is roasted black powder from waste lithium-ion secondary batteries.

Claims

1. A method for recovering copper, comprising: In the first ammonia leaching process, a first ammonia solution with a concentration of less than 2.5 mol / L is used to leach the object containing Ni, Co, and Cu in metallic form, yielding an aqueous phase containing Cu and a solid residue. The first ammonia leaching process is carried out in the presence of oxygen.

2. The method according to claim 1, wherein, The first ammonia leaching process is carried out in an atmosphere with an oxygen concentration of 21% by volume or higher.

3. The method according to claim 1, wherein, While supplying gas with an oxygen concentration of 21% or more to the first ammonia solution through bubbling, the first ammonia leaching process is carried out.

4. The method according to claim 1, wherein, While supplying oxygen to the first ammonia solution through bubbling, the first ammonia leaching process is carried out.

5. The method according to claim 1, wherein, The process further includes a second ammonia leaching step, in which the solid residue obtained in the first ammonia leaching step is leached using a second ammonia solution under an inactive gas atmosphere.

6. The method according to claim 5, wherein, Nitrogen gas is supplied to the second ammonia solution through bubbling while the second ammonia leaching process is carried out.

7. The method according to claim 5, wherein, The concentration of the second ammonia solution is above 5 mol / L.

8. The method according to claim 5, wherein, Using the solid residue obtained in the second ammonia leaching process as the object, the first ammonia leaching process and the second ammonia leaching process are repeated more than once.

9. The method according to claim 1, wherein, The object being referred to is calcined black powder from waste lithium-ion secondary batteries.

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