Methods for recycling valuable metals

Abstract

This invention provides a novel method for recovering Ni, Co, and Cu from battery waste containing Ni, Co, and Cu with a high recovery rate, and for using a leaching agent that is suitable for reuse. [Solution] The method for recycling valuable metals according to the present disclosure includes a Cu leaching step in which Cu is leached from battery waste containing Ni, Co, and Cu into ammonia water using ammonia water, and a Ni,Co leaching step in which Ni and Co are leached from the solid residue obtained in the Cu leaching step into the ammonia aqueous solution using ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate.

Description

Technical Field

[0001] The present disclosure relates to a method for recycling valuable metals.

Background Art

[0002] Lithium-ion secondary batteries are widely used in various fields as power sources for vehicle driving, portable power sources, etc. In recent years, from the perspective of SDGs, the material recycling of used lithium-ion secondary batteries has been promoted. In lithium-ion secondary batteries, various metal elements are used, and for material recycling, the development of technologies for separating metal elements contained in used lithium-ion secondary batteries has been carried out.

[0003] Representative examples of the positive electrode active material of lithium-ion secondary batteries that have been put into practical use in in-vehicle applications include lithium nickel cobalt manganese-based composite oxides (NCM) and lithium nickel cobalt aluminum-based composite oxides (NCA), which contain Ni and Co. Therefore, the waste of lithium-ion secondary batteries using these positive electrode active materials contains Ni and Co. On the other hand, copper foil is usually used for the negative electrode current collector of lithium-ion secondary batteries. Therefore, the waste of lithium-ion secondary batteries usually contains Cu.

[0004] Regarding the technology for separating metal elements from the waste of lithium-ion secondary batteries, for example, in Patent Document 1, a leachate containing Ni, Co, and Cu is obtained from the waste of lithium-ion secondary batteries using an acid and a reducing agent. Further, in Patent Document 1, Cu is precipitated as a sulfide (that is, CuS) using a hydrogen sulfide compound from the leachate, thereby separating Ni and Co from Cu. In Non-Patent Document 1, using a leachate containing ammonia and ammonium sulfate, Ni and Co are selectively leached and separated from Ni, Co, Mn, and Al contained in the positive electrode waste of used lithium-ion secondary batteries.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-150907 [Non-patent literature]

[0006] [Non-Patent Document 1] Waste Management, February 2017, vol.60, p.680-688 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, as described in Patent Document 1 above, when separating metal elements from lithium-ion secondary battery waste by acid leaching (i.e., using acid as the leaching agent), there is a problem that the acid becomes contaminated as it is reused. In other words, there is a problem that the acid is unfavorable for the reuse of the leaching agent. Furthermore, in Non-Patent Document 1, if the lithium-ion secondary battery waste also contains Cu, Cu is leached out along with Ni and Co, similar to Patent Document 1. When separating Cu from a leaching solution containing Ni, Co, and Cu by precipitating it as CuS, NiS and CoS are also precipitated at the same time, which leads to a problem of reduced recovery rates for Ni and Co.

[0008] Therefore, the present disclosure aims to provide a novel method for recovering Ni, Co, and Cu from battery waste containing Ni, Co, and Cu with a high recovery rate, and for which the leaching agent is suitable for reuse. [Means for solving the problem]

[0009] The method for recycling valuable metals according to this disclosure includes a Cu leaching step of leaching Cu from battery waste containing Ni, Co, and Cu into ammonia water using ammonia water, and a Ni,Co leaching step of leaching Ni and Co from the solid residue obtained in the Cu leaching step into the ammonia aqueous solution using ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate.

[0010] With this configuration, Ni, Co, and Cu can be recovered from battery waste containing Co and Cu with a high recovery rate. In addition, the ammonia used as a leaching agent when separating Cu is suitable for reuse. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a flowchart showing each step of the valuable metal recycling method related to this disclosure. [Figure 2] Figure 2 is a schematic diagram showing the movement of valuable metals in the method for recycling valuable metals according to this disclosure. [Figure 3] Figure 3 is a schematic longitudinal cross-sectional view showing the internal structure of an example of a lithium-ion secondary battery. [Figure 4] Figure 4 is a schematic exploded view showing the configuration of the electrode body of the lithium-ion secondary battery shown in Figure 3. [Modes for carrying out the invention]

[0012] Embodiments relating to this disclosure will be described below with reference to the drawings. Matters not mentioned herein but necessary for the implementation of this disclosure can be understood as design matters for those skilled in the art based on prior art in the relevant field. This disclosure can be implemented based on the contents disclosed herein and common technical knowledge in the relevant field. In the following drawings, members and parts that perform the same function are denoted by the same reference numerals. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. In this specification, the numerical range expressed as "A~B" includes A and B.

[0013] In this specification, "secondary battery" refers to an energy storage device that can be repeatedly charged and discharged. Furthermore, in this specification, "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and achieves charging and discharging through the transfer of charge associated with lithium ions between the positive and negative electrodes.

[0014] Figure 1 is a flowchart showing each step of the valuable metal recycling method according to this disclosure. Figure 2 is a schematic diagram showing the movement of valuable metals in the valuable metal recycling method according to this disclosure. The valuable metal recycling method according to this disclosure includes, as essential steps, a Cu leaching step S101 in which Cu is leached from battery waste containing Ni, Co, and Cu into ammonia water using ammonia water, and a Ni, Co leaching step S102 in which Ni and Co are leached from the solid residue obtained in the Cu leaching step S101 into ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate. The valuable metal recycling method according to this disclosure may include optional steps such as the roasting step and ammonia recovery step described later.

[0015] <Lithium-ion rechargeable battery> First, the method for recycling valuable metals according to the present disclosure relates to the material recycling of secondary batteries (especially lithium-ion secondary batteries). First, a general configuration example of a lithium-ion secondary battery will be described. Examples of the structure of a lithium-ion secondary battery are shown in FIGS. 3 and 4. FIG. 3 is a longitudinal sectional view schematically showing the internal structure of an example of a lithium-ion secondary battery. FIG. 4 is an exploded view schematically showing the electrode body of the lithium-ion secondary battery shown in FIG. 3. Note that the following description of the lithium-ion secondary battery is for convenience of understanding and does not limit the method for recycling valuable metals according to the present disclosure in any way.

[0016] As shown in FIG. 3, the lithium-ion secondary battery 100 is a sealed battery in which a flat electrode body 20 and a non-aqueous electrolyte (not shown) are housed inside a battery case 30. As shown in FIG. 3, the battery case 30 is composed of an exterior body 32 that houses the electrode body 20 and a lid body 34 that seals the opening of the exterior body 32. The exterior body 32 and the lid body 34 are welded and sealed by laser welding or the like. As the material of the battery case 30, for example, aluminum, an aluminum alloy, resin, or the like is used.

[0017] In the illustrated example, the battery case 30 is rectangular. However, the shape of the battery case 30 is not limited thereto, and for example, it may be cylindrical. Alternatively, the battery case 30 may be a laminate case having a gas barrier layer such as an aluminum layer and a sealant layer containing a thermoplastic resin.

[0018] The battery case 30 includes a positive electrode terminal 42 and a negative electrode terminal 44 for external connection. Further, the battery case 30 is provided with a safety valve 36 that is set to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. The battery case 30 is provided with an injection port (not shown) for injecting a non-aqueous electrolyte. The positive electrode terminal 42 is electrically connected to a positive electrode current collector plate 42a. The negative electrode terminal 44 is electrically connected to a negative electrode current collector plate 44a.

[0019] As shown in FIGS. 3 and 4, the electrode body 20 has a form in which a long positive electrode sheet 50 and a long negative electrode sheet 60 are overlapped via two long separator sheets 70 and wound in the longitudinal direction. Therefore, in the present embodiment, the electrode body 20 is a wound electrode body. However, the electrode body 20 is not limited to this, and may be a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated via a separator.

[0020] As shown in FIG. 3, in the positive electrode sheet 50, a positive electrode active material layer 54 is formed along the longitudinal direction on one side or both sides (here, both sides) of the positive electrode current collector 52. The positive electrode sheet 50 has a positive electrode active material layer non-formation portion 52a which is a portion where the positive electrode current collector 52 is exposed without the positive electrode active material layer 54 being formed. A positive electrode current collecting plate 42a is joined to the positive electrode active material layer non-formation portion 52a.

[0021] Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil and the like. 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 the positive electrode active material include lithium nickel cobalt manganese-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, and the like. The positive electrode active material layer 54 may contain a conductive material (e.g., carbon black, carbon nanotubes, etc.), a binder (e.g., polyvinylidene fluoride, etc.), and the like.

[0022] The content of the positive electrode active material in the positive electrode active material layer 54 is preferably 70% by mass or more, and more preferably 85% by mass or more and 99% by mass or less. The content of the conductive material in the positive electrode active material layer 54 is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 0.3% by mass or more and 15% by mass or less. The content of the binder in the positive electrode active material layer 54 is preferably 0.4% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 10% by mass or less.

[0023] In the negative electrode sheet 60, a negative electrode active material layer 64 is formed along the longitudinal direction on one or both sides (in this case, both sides) of the negative electrode current collector 62. The negative electrode sheet 60 has a portion 62a where the negative electrode active material layer 64 is not formed and the negative electrode current collector 62 is exposed. A negative electrode current collector plate 44a is bonded to the portion 62a where the negative electrode active material layer is not formed.

[0024] 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 also contain a binder (e.g., styrene-butadiene rubber (SBR), etc.) and a thickener (e.g., carboxymethylcellulose (CMC), etc.).

[0025] The graphite content in the negative electrode active material layer 64 is preferably 90% by mass or more, and more preferably 95% by mass or more and 99% by mass or less. The binder content in the negative electrode active material layer 64 is preferably 0.1% by mass or more and 8% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less. The thickener content in the negative electrode active material layer 64 is preferably 0.3% by mass or more and 3% by mass or less, and more preferably 0.5% by mass or more and 2% by mass or less.

[0026] Examples of separators 70 include porous resin sheets such as polyethylene and polypropylene. The porous sheet may have a single-layer structure or a multi-layer structure. A heat-resistant layer (HRL) may be provided on the surface of the separator 70.

[0027] The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (or electrolyte salt). Examples of non-aqueous solvents include carbonates (e.g., EC, ethyl methyl carbonate, dimethyl carbonate, etc.), esters, ethers, and the like. 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 a gas generating agent and a film forming agent. In this embodiment, a non-aqueous electrolyte is used as the electrolyte, but the electrolyte may be a solid electrolyte.

[0028] The lithium-ion secondary battery 100 is used, for example, for in-vehicle applications (i.e., as a driving power source for vehicles such as battery electric vehicles (BEV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.) and power supply applications for electronic devices.

[0029] As described above, in the positive electrode of a lithium-ion secondary battery, Li, Ni, and Co are typically used as the constituent metal elements of the positive electrode active material. The positive electrode active material may further contain Mn or Al. Al is generally used for the positive electrode current collector. Cu is typically used for the negative electrode current collector. In addition, in a lithium-ion secondary battery, Li is used in the non-aqueous electrolyte. Also, Al may be used for the battery case. Hereinafter, each step of the method for recycling valuable metals of the present disclosure will be described in detail.

[0030] <Cu Leaching Step S101> In the Cu leaching step S101, battery waste containing Ni, Co, and Cu is used. Ni and Co contained in the battery waste typically originate from the positive electrode active material (particularly, a lithium transition metal composite oxide containing Ni and Co). Cu contained in the battery waste typically originates from the copper foil of the negative electrode current collector. However, Ni, Co, and Cu contained in the battery waste are not limited to these.

[0031] Battery waste includes, for example, used lithium-ion secondary batteries, defective lithium-ion secondary batteries, electrodes from used lithium-ion secondary batteries, and electrodes from defective lithium-ion secondary batteries. Battery waste may also be lithium-ion secondary batteries that have undergone processing (e.g., discharge processing, crushing processing, sieving processing after crushing, etc.). Therefore, battery waste may be crushed lithium-ion secondary battery material (so-called black mass).

[0032] Since the selectivity of Cu in leaching is increased, it is preferable that battery waste contains Ni and Co as oxides and Cu as a metal. From this viewpoint, it is preferable that the battery waste is roasted so that the roasted material contains Ni and Co as oxides and Cu as a metal.

[0033] Therefore, the method for producing valuable metals of this disclosure may further include, prior to the Cu leaching step S101, a step of roasting the battery waste so that it contains Ni and Co as oxides and Cu as a metal (hereinafter also referred to as the "roasting step").

[0034] The roasting can be carried out by heat-treating battery waste (preferably pulverized lithium-ion secondary batteries) at 150°C to 400°C under an inert gas atmosphere. Furthermore, if the molar ratio of carbon to oxygen in the waste is less than 1 / 2, the roasting can be carried out at 150°C to 600°C under an inert gas atmosphere. Alternatively, the roasting can be carried out at 150°C to 400°C (preferably 200°C to 320°C) under an air atmosphere. The roasting time is not particularly limited, for example, 1 to 24 hours, preferably 3 to 12 hours, and more preferably 4 to 8 hours.

[0035] The roasting process removes liquid components (e.g., electrolyte) from lithium-ion secondary batteries and carbonizes resin components (e.g., binder, separator). Furthermore, roasting can disable the battery's function.

[0036] Battery waste may further contain elements other than Ni, Co, and Cu (especially metallic elements). For example, in addition to Ni, Co, and Cu, battery waste may further contain Li, Mn, Al, etc. Battery waste may further contain transition metal elements other than Ni and Co.

[0037] In the Cu leaching process S101, Cu is first extracted from battery waste containing Ni, Co, and Cu. To do this, ammonia is used as a leaching agent in the form of aqueous ammonia (see Figure 2).

[0038] The concentration of ammonia in the ammonia solution is not particularly limited as long as it allows for the leaching of Cu. Since a higher ammonia concentration results in higher leaching ability, the ammonia concentration in the ammonia solution is preferably 10% by mass or more, and more preferably 15% by mass or more. 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 ability and ease of handling, an ammonia concentration of 15% by mass to 25% by mass is particularly preferred. Furthermore, to further enhance the selectivity of Cu during leaching, the pH of the ammonia solution at 20°C is preferably 12 or higher.

[0039] Ammonia water may contain only water and ammonia. Ammonia water may further contain components other than water and ammonia, within limits that do not impair the effects of this disclosure (for example, at concentrations of less than 10% by mass, 5% by mass or less, or 1% by mass or less).

[0040] The amount of ammonia water used is not particularly limited and may be similar to the amount used in known ammonia leaching methods. For example, the amount of ammonia water used should be enough to completely immerse the battery waste.

[0041] The Cu leaching process S101 can be carried out, for example, as follows: First, a container is prepared. The container may be a known container used for ammonia leaching. If necessary, heating means such as a heater, temperature measuring means such as a thermometer or temperature sensor, stirring means such as a stirring blade or magnetic stirring bar are attached to the container.

[0042] Place the battery waste and ammonia water into the container. There is no particular order in which you add them; you can add them in either order or at the same time.

[0043] The leaching temperature in the Cu leaching process S101 is not particularly limited and may be at room temperature (i.e., 25±10℃), under heating, or under cooling. From the viewpoint of energy saving and preventing ammonia volatilization, the leaching temperature is preferably greater than 0℃ and 45℃ or less, more preferably 10℃ or more and 40℃ or less, and even more preferably 15℃ to 35℃.

[0044] The leaching time can be determined according to the leaching temperature. It is preferable to select a longer leaching time when the leaching temperature is low. The leaching time is, for example, 0.5 hours to 48 hours, preferably 1 hour to 24 hours, and more preferably 1.5 hours to 12 hours.

[0045] Stirring is preferable during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 300 rpm or higher, and even more preferably 400 rpm or higher. The stirring speed may be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0046] The dissolution of metallic Cu in aqueous ammonia typically involves oxygen. This oxygen can be either dissolved oxygen in the aqueous ammonia or oxygen from the atmosphere. Therefore, the Cu leaching process S101 may be carried out in the atmosphere, but from the viewpoint of a high leaching rate, it is preferable to supply oxygen to the aqueous ammonia during leaching. The amount of oxygen supplied is preferably equimolar or more relative to the element to be oxidized (i.e., Cu) contained in the battery waste, and preferably 1.5 molar times or more.

[0047] Oxygen can be supplied according to known methods. For example, oxygen can be supplied by introducing an oxygen-containing gas (e.g., oxygen gas, air, etc.) into ammonia water by bubbling. In this case, the smaller the bubbles, the more efficiently the amount of dissolved oxygen can be increased. Alternatively, for example, oxygen can be supplied by sealing a container and pressurizing it while introducing oxygen into it.

[0048] Leaching can be terminated by solid-liquid separation, such as by performing a filtrate separation. This solid-liquid separation yields a Cu-containing aqueous phase (i.e., Cu-containing ammonia water) and a solid residue containing Ni and Co, as shown in Figure 2. Thus, Cu, a constituent element of the negative electrode current collector, and Ni and Co, constituent elements of the positive electrode active material, can be separated.

[0049] As described above, the Cu leaching step S101 can be carried out. Furthermore, Cu can be recovered from the Cu-containing aqueous phase according to known methods. Ammonia can also be recovered from the Cu-containing aqueous phase. Therefore, the method for recycling valuable metals according to this disclosure may further include a step of recovering ammonia from the Cu-containing aqueous phase obtained in the Cu leaching step S101 (hereinafter also referred to as the "ammonia recovery step").

[0050] <Ammonia recovery process> The ammonia recovery process can be carried out in accordance with known methods. Specifically, for example, it can be carried out as follows: Prepare an open container (i.e., a container that is not sealed and is open to the atmosphere). The open container may be one of known types. Attach heating means such as a heater, temperature measuring means such as a thermometer or temperature sensor, stirring means such as a stirring blade or magnetic stirring bar to the open container.

[0051] On the other hand, an ammonia collection device is prepared. Known ammonia collection devices can be used. For example, an ammonia collection device comprises a suction hood and an ammonia collection unit. The suction hood is installed, for example, above an open container. The ammonia collection unit cools the aspirated ammonia gas and recovers it as ammonia water. Alternatively, the ammonia collection unit contains, for example, an ammonia collection liquid (for example, an acidic aqueous solution with a pH of less than 7, especially a sulfuric acid solution with a pH of less than 7), and is configured so that the gas aspirated from the suction hood can pass through the ammonia collection liquid. The ammonia collection device may also have an ammonia separation unit and an ammonia recovery unit. The ammonia separation unit is configured to separate ammonia from the collection liquid by distillation, adsorption with an adsorbent, membrane separation, etc. The ammonia recovery unit is a tank, etc., connected to the ammonia separation unit by piping, etc., and is configured to recover the ammonia separated in the ammonia separation unit. Note that the configuration of the ammonia collection device is not limited to the above.

[0052] The aqueous phase obtained in the Cu leaching step S101 is added to an open container, and the aqueous phase is heated. This allows ammonia to volatilize from the aqueous phase. The heating temperature is not particularly limited as long as ammonia volatilizes, but is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher. On the other hand, the heating temperature may be below the boiling point of water (i.e., 100°C).

[0053] The heating time can be appropriately determined according to the heating temperature. The higher the heating temperature, the shorter the heating time can be. The heating time is, for example, 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. The heating time is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 8 hours or less.

[0054] Stirring may be performed during heating. The stirring speed is not particularly limited, but is preferably 200 rpm or more, more preferably 400 rpm or more, and even more preferably 600 rpm or more. The stirring speed may be 2000 rpm or less, 1000 rpm or less, or 800 rpm or less.

[0055] Ammonia that has evaporated due to heating is recovered by an ammonia collection device. Specifically, for example, ammonia that has evaporated is sucked in from a suction hood and captured in the collection liquid of the ammonia collection unit. In this way, the ammonia recovery process can be carried out.

[0056] The ammonia recovered in the ammonia recovery step can be reused in the Cu leaching step S101 and the Ni,Co leaching step S102. Therefore, if the method for recovering valuable metals according to this disclosure further includes an ammonia recovery step, the ammonia used in the Ni,Co leaching step S102 may be the ammonia recovered in the ammonia recovery step. If the method for recovering valuable metals according to this disclosure further includes an ammonia recovery step, the ammonia recovered in the ammonia recovery step may be reused in the Cu leaching step S101.

[0057] The ammonia recovery process may be performed before the Ni,Co leaching process S102, in parallel with the Ni,Co leaching process S102, or after the Ni,Co leaching process S102.

[0058] On the one hand, Cu can be recovered as CuO from the aqueous phase after the ammonia recovery process. Alternatively, by adding sodium hydroxide to the aqueous phase, Cu can be recovered as Cu(OH)2. Therefore, the valuable metal recycling method of the present disclosure may further include a step of recovering CuO from the aqueous phase containing Cu obtained in the Cu leaching step S101, or a step of adding sodium hydroxide to the aqueous phase containing Cu to recover Cu as Cu(OH)2.

[0059] The recovered Cu can be reused as a raw material for the negative electrode current collector according to a known method. Therefore, the valuable metal recycling method of the present disclosure can be applied as a method for manufacturing a raw material for the negative electrode current collector.

[0060] <Ni,Co leaching step S102> The solid residue obtained in the Cu leaching step S101 contains Ni and Co. In the Ni,Co leaching step S102, ammonia leaching is performed on the solid residue obtained in the Cu leaching step S101 using an ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate, to leach Ni and Co into the ammonia aqueous solution (i.e., the aqueous phase).

[0061] In the Ni,Co leaching step S102, an ammonia aqueous solution containing ammonia (NH3) and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate ((NH4)2SO4) and ammonium carbonate ((NH4)2CO3) is used as the leaching agent for ammonia leaching.

[0062] In an aqueous ammonia solution, the concentration of ammonia is not particularly limited, but a higher concentration results in higher leaching ability. Therefore, the concentration of ammonia in the aqueous 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. 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 ability and ease of handling, an ammonia concentration of 15% by mass to 25% by mass is particularly preferred.

[0063] Inorganic ammonium salts act as pH adjusters. The amount of inorganic ammonium salt in the ammonia aqueous solution is such that the pH of the ammonia aqueous solution is, for example, 9 to 12, preferably 10 to 11. The concentration of inorganic ammonium salt in the ammonia aqueous solution is preferably 0.5 mol / L or higher, more preferably 1 mol / L or higher, and even more preferably 1.5 mol / L or higher. On the other hand, the concentration of inorganic ammonium salt in the ammonia aqueous solution may be 3 mol / L or lower, or 2.5 mol / L or lower. Here, since Ni and Co can be reused as constituent metal elements of the positive electrode active material, and sulfates are generally used as raw materials for positive electrode active materials, ammonium sulfate is preferred as the inorganic ammonium salt.

[0064] The ammonia aqueous solution may contain only water, ammonia, and an inorganic ammonium salt. The ammonia aqueous solution may further contain components other than water, ammonia, and an inorganic ammonium salt, within limits that do not impair the effects of the present disclosure (for example, at concentrations of less than 10% by mass, 5% by mass or less, or 1% by mass or less).

[0065] The amount of aqueous ammonia solution used is not particularly limited and may be similar to the amount used in known ammonia leaching methods. For example, the amount of aqueous ammonia solution used should be enough to completely immerse the solid residue.

[0066] The Ni,Co leaching process S102 can be carried out, for example, as follows: First, a container is prepared. The container may be a known container used for ammonia leaching. If necessary, heating means such as a heater, temperature measuring means such as a thermometer or temperature sensor, stirring means such as a stirring blade or magnetic stirring bar are attached to the container.

[0067] The solid residue and ammonia solution are placed in a container. The order in which these are added is not particularly limited; they can be added either first or simultaneously.

[0068] The Ni,Co leaching process S102 may be carried out at room temperature (i.e., 25±10℃), and may be carried out under heating or cooling. From the viewpoint of leaching rate, it is preferable to carry out the Ni,Co leaching process S102 under heating. Therefore, the leaching temperature is preferably 45℃ or higher, and more preferably 60℃ or higher. The leaching temperature may be 90℃ or lower, 85℃ or lower, or 80℃ or lower.

[0069] The leaching time can be appropriately determined according to leaching conditions such as 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. From the viewpoint of operational efficiency, the leaching time is, for example, 48 hours or less, preferably 24 hours or less, and more preferably 12 hours or less.

[0070] Stirring is preferable during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 300 rpm or higher, and even more preferably 400 rpm or higher. The stirring speed may be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0071] As described above, Ni and Co can be leached into the aqueous phase (i.e., an aqueous ammonia solution). In other words, the Ni,Co leaching process S102 can be performed. The ammonia leaching can be terminated by solid-liquid separation, such as by filtrate separation. As shown in Figure 2, this solid-liquid separation yields the leachate (i.e., the aqueous phase from which Ni and Co have leached) and a solid residue.

[0072] Ni and Co extracted into the aqueous phase can be recovered according to known methods. Here, sulfates are generally used as the Ni and Co sources for the positive electrode active material. Therefore, it is advantageous to recover the Ni and Co extracted into the aqueous phase by converting them to nickel sulfate and cobalt sulfate according to known methods (for example, by volatilizing ammonia from the aqueous phase and adding sulfuric acid to the aqueous phase). In this case, when ammonium sulfate is used as the inorganic ammonium salt of the aqueous ammonia solution, ammonium sulfate is SO4 2- It can be a source and does not become an impurity, which is advantageous.

[0073] According to the valuable metal recycling method of this disclosure, Ni, Co, and Cu can be recovered from battery waste containing Ni, Co, and Cu with a high recovery rate. Furthermore, the leaching agent used to extract Ni, Co, and Cu can be recovered and reused, making it suitable for recycling. In addition, the valuable metal recycling method of this disclosure can be implemented simply. Therefore, the valuable metal recycling method of this disclosure is extremely useful in the material recycling of lithium-ion secondary batteries.

[0074] The following describes in detail some test examples related to this disclosure, but this disclosure is not intended to be limited to those shown in such test examples.

[0075] [Test Example 1] First, the black mass of leaching samples was prepared using the following procedure: Lithium nickel cobalt manganese composite oxide (LiNi) was placed on an aluminum (Al) foil. 0.6 Co 0.2 Mn 0.2A positive electrode having a positive electrode active material layer containing O2 was crushed. The crushed positive electrode material was sieved through a 500 μm mesh sieve to produce positive electrode powder. A negative electrode having a negative electrode active material layer containing graphite on a copper foil was also crushed. The crushed negative electrode material was sieved through a 500 μm mesh sieve to produce negative electrode powder. The obtained positive electrode powder and negative electrode powder were mixed to obtain black mass. This black mass was roasted at 300°C for 6 hours in a low-oxygen atmosphere to obtain roasted black mass containing Ni and Co as oxides and Cu as metal.

[0076] Next, an aqueous ammonia solution was prepared by mixing 28% by mass aqueous ammonia with ammonium sulfate ((NH4)2SO4) as a pH adjuster. The resulting roasted black muss was added to this aqueous ammonia solution and stirred at a stirring speed of 500 rpm for 3 hours while maintaining a temperature of 80°C to extract ammonia. After that, solid-liquid separation was performed by filtration to obtain the leachate and solid residue. The leachate contained Ni, Co, and Cu.

[0077] The obtained leachate was stirred at a stirring speed of 600 rpm while supplying hydrogen sulfide gas to it. After confirming that a black precipitate had been obtained, solid-liquid separation was performed by filtration to obtain the filtrate and precipitate.

[0078] The amounts of Ni, Co, and Cu were determined by inductively coupled plasma (ICP) emission spectroscopy of the leachate after ammonia leaching. Furthermore, the amounts of Ni, Co, and Cu were also determined by ICP emission spectroscopy of the black precipitate. This confirmed that more than 99% of the precipitate was Cu. In addition, the average percentage of Ni and Co that could not be recovered (hereinafter also referred to as the "Ni, Co loss rate") was calculated using the amounts of Ni and Co in the leachate and the precipitate. The results are shown in Table 1.

[0079] [Test Example 2] Roasted black muss was obtained in the same manner as in Test Example 1. Next, a 28% by mass concentration of ammonia water was prepared, and the obtained roasted black muss was added to this ammonia water. While maintaining the temperature of the ammonia water at room temperature (25°C to 35°C), the mixture was stirred at a stirring speed of 600 rpm for 1.5 hours to allow leaching. After that, solid-liquid separation was performed by filtration to obtain the leachate and solid residue.

[0080] On the other hand, 1 g of roasted black mass was dissolved in acid, and ICP emission spectroscopy was performed on the solution. From the analysis results, the amounts of Ni, Co, and Cu in the roasted black mass were determined. The amounts of these metals correspond to the initial amounts before ammonia leaching.

[0081] Next, ICP emission spectroscopy was performed on the obtained leachate to determine the amounts of Ni, Co, and Cu in the leachate. The leaching rates of Ni, Co, and Cu were determined from the ratio (percentage) of the amount of these metals in the leachate to the initial amount of these metals in the roasted black mass. This confirmed that more than 99% of the Cu had leached out. Furthermore, the Ni and Co loss rates were determined by calculating the average of the leaching rates of Ni and Co.

[0082] [Test Example 3] Roasted black muss was obtained in the same manner as in Test Example 1. Next, a 28% by mass concentration of ammonia water was prepared, and the obtained roasted black muss was added to this ammonia water. This was then stirred at a stirring speed of 600 rpm for 1 hour and 30 minutes while bubbling with oxygen gas to allow leaching. The oxygen gas supply rate was 0.4 mol / L relative to the ammonia water. The temperature of the ammonia water during stirring was 25°C to 30°C. After that, solid-liquid separation was performed by filtration to obtain leachate and solid residue.

[0083] The leaching rates (mass%) of Ni, Co, and Cu were determined in the same manner as in Test Example 2. This confirmed that more than 99% of Cu had leached out. The Ni and Co loss rates were also determined in the same manner as in Test Example 2. The results are shown in Table 1.

[0084] Next, the leachate containing the extracted copper was heated to 90°C while being stirred, and the volatile components were collected, confirming that ammonia water was obtained. A precipitate was also observed in the solution. This precipitate is believed to be copper oxide.

[0085] The obtained ammonia solution was mixed with the solid residue, and ammonium sulfate was added. This brought the ammonia solution containing ammonia and ammonium sulfate into contact with the solid residue. The ammonia solution was then heated to 80°C, and while maintaining the temperature at 80°C, the mixture was stirred at a stirring speed of 500 rpm for 8 hours to allow leaching. After that, solid-liquid separation was performed by filtration to obtain the leachate and the solid residue.

[0086] ICP emission spectroscopy was also performed on this leachate to determine the amounts of Ni and Co in the leachate. Using these values ​​and the initial amounts in the roasted black mass described above, the Ni and Co leaching rates were calculated. The results are shown in Table 2.

[0087] [Table 1]

[0088] [Table 2]

[0089] Test Example 1 followed the prior art method, leaching Ni, Co, and Cu, and then separating Cu as CuS. As shown in Table 1, the Ni and Co loss rate during Cu separation was very high at 85.8% in Test Example 1. Test Example 2 is an example of the Cu leaching process of the valuable metal recycling method of this disclosure. As shown in Table 1, Cu leaching with ammonia water reduced the Ni and Co loss rate during Cu separation to 10.3%. In Test Example 3, the Cu leaching process using ammonia water was also performed, but oxygen was supplied to the ammonia water. As a result, as shown in Table 1, the Ni and Co loss rate during Cu separation was reduced to 3.1%.

[0090] Furthermore, in Test Example 3, the Ni and Co leaching process of the valuable metal regeneration method disclosed herein was also performed. As a result, as shown in Table 2, Ni and Co could be leached with a high leaching rate. In addition, in Test Example 3, the Ni and Co leaching process utilized recycled ammonia water from the Cu leaching process.

[0091] Therefore, from the above, it can be seen that, according to the valuable metal recycling method of this disclosure, Ni, Co, and Cu can be recovered from battery waste containing Ni, Co, and Cu with a high recovery rate. Furthermore, it can be seen that, in the valuable metal recycling method of this disclosure, the ammonia used as a leaching agent when separating Cu is suitable for reuse.

[0092] The specific examples of this disclosure have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples described above.

[0093] In other words, the method for recycling valuable metals described herein is as described in the following sections [1] to [7]. [1] A Cu leaching step in which Cu is leached into ammonia water from battery waste containing Ni, Co and Cu, From the solid residue obtained in the Cu leaching step, a Ni,Co leaching step is performed in which Ni and Co are leached into the ammonia aqueous solution using an ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate. A method for recycling valuable metals, including [specific metals]. [2] The method according to item [1], wherein, in the Cu leaching step, an oxygen-containing gas is supplied to the ammonia water during the leaching. [3] The method according to item [1] or [2], further comprising the step of recovering ammonia from the Cu-containing aqueous phase obtained in the Cu leaching step. [4] The method according to item [3], wherein the ammonia used in the Ni,Co leaching step is the ammonia recovered in the ammonia recovery step. [5] The method according to item [3], wherein the ammonia recovered in the ammonia recovery step is reused in the Cu leaching step. [6] The method according to any one of the items [1] to [5], wherein the battery waste contains Ni and Co as oxides and Cu as a metal. [7] The method according to any one of claims [1] to [6], further comprising the step of roasting the battery waste so that it contains Ni and Co as oxides and Cu as a metal, prior to the Cu leaching step. [Explanation of symbols]

[0094] 20 Electrode body 30 Battery Cases 32 Exterior 34 Lid 36 Safety valve 42 Positive terminal 42a Positive electrode current collector plate 44 Negative terminal 44a Negative current collector plate 50 positive electrode 52 Positive electrode current collector 52a Portion where positive electrode active material layer is not formed 54 Cathode active material layer 60 negative electrode 62 Negative electrode current collector 62a Part where negative electrode active material layer is not formed 64 Negative electrode active material layer 70 Separators 100 Lithium-ion rechargeable batteries

Claims

1. A Cu leaching step is performed in which Cu is leached into ammonia water from battery waste containing Ni, Co, and Cu, From the solid residue obtained in the Cu leaching step, a Ni, Co leaching step is performed in which Ni and Co are leached into the ammonia aqueous solution using an ammonia aqueous solution containing ammonia and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate. A method for recycling valuable metals, including [specific metals].

2. The method according to claim 1, wherein, in the Cu leaching step, an oxygen-containing gas is supplied to the ammonia water during the leaching.

3. The method according to claim 1, further comprising the step of recovering ammonia from the Cu-containing aqueous phase obtained in the Cu leaching step.

4. The method according to claim 3, wherein the ammonia used in the Ni,Co leaching step is the ammonia recovered in the ammonia recovery step.

5. The method according to claim 3, wherein the ammonia recovered in the ammonia recovery step is reused in the Cu leaching step.

6. The method according to claim 1, wherein the battery waste contains Ni and Co as oxides and Cu as a metal.

7. The method according to claim 1, further comprising the step of roasting the battery waste before the Cu leaching step so that Ni and Co are contained as oxides and Cu is contained as a metal.

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