Methods for recovering valuable metals

Abstract

This invention provides a method for easily separating water-soluble Li compounds, Ni, Co, and Cu from a material containing these elements, and for reusing the leaching agent. [Solution] The method for recovering valuable metals according to the present disclosure includes: a Li, Cu leaching step in which Li and Cu are leached into a first aqueous phase by ammonia leaching from a target material containing a water-soluble Li compound, Ni, Co, and Cu; a separation step in which Li and Cu are separated by evaporating ammonia from the first aqueous phase; and a Ni, Co leaching step in which Ni and Co are leached into a second aqueous phase from the solid residue obtained in the Li, Cu leaching step by ammonia leaching.

Description

TECHNICAL FIELD

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

BACKGROUND ART

[0002] Lithium ion secondary batteries are widely used in various fields as power sources for vehicle driving, portable power supplies, and the like. In recent years, material recycling of spent lithium ion secondary batteries has been promoted from the perspective of SDGs. Various metal elements are used in lithium ion secondary batteries, and for the purpose of material recycling, technologies for separating the metal elements contained in spent lithium ion secondary batteries are being developed.

[0003] Representative examples of positive electrode active materials for lithium ion secondary batteries that have been put to 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 Li, Ni, and Co. Therefore, the waste of lithium ion secondary batteries using these positive electrode active materials contains Li, Ni and Co. On the other hand, a copper foil is usually used for the negative electrode current collector of a lithium ion secondary battery. For this reason, 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, Li, Ni, Co, and Cu are separated from the waste of lithium ion secondary batteries by the following method. Spent lithium ion secondary batteries are pretreated to obtain battery powder containing Li, Ni, Co, and Cu, and aluminum slag, and the battery powder is subjected to roasting treatment. Water is added to the roasted battery powder to prepare an aqueous slurry, and Li is leached into the aqueous phase using a metal chloride. After solid-liquid separation, the solid residue is subjected to acid leaching to leach Ni, Co, and Cu into the aqueous phase. Aluminum slag is added to the aqueous phase, and a copper reduction reaction is performed to separate copper. Thereafter, the pH of the aqueous phase is adjusted to remove the aluminum slag.

PRIOR ART DOCUMENTS

[0005] [Patent Document 1] International Publication No. 2023 / 024599 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the method described in Patent Document 1 involves acid leaching, and the acid has the problem of contamination as it is reused. In other words, the acid is unfavorable for the reuse of the leaching agent. Furthermore, the process involves adding aluminum slag, reducing the copper, and removing the aluminum slag in order to separate the copper, which is a cumbersome process.

[0007] Therefore, the present disclosure aims to provide a method for easily separating Li, Ni, Co, and Cu from a material containing water-soluble Li compounds, Ni, Co, and Cu, and for which the leaching agent is suitable for reuse. [Means for solving the problem]

[0008] The method for recovering valuable metals according to this disclosure includes a Li, Cu leaching step in which Li and Cu are leached into a first aqueous phase by ammonia leaching from a target material containing a water-soluble Li compound, Ni, Co, and Cu; a separation step in which Li and Cu are separated by evaporating ammonia from the first aqueous phase; and a Ni, Co leaching step in which Ni and Co are leached into a second aqueous phase from the solid residue obtained in the Li, Cu leaching step by ammonia leaching.

[0009] This configuration allows for the easy separation of water-soluble Li compounds, Ni, Co, and Cu from a material containing these elements, and provides a method for reusing the leaching agent. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a flowchart showing each step of the valuable metal recovery method related to this disclosure. [Figure 2] Figure 2 is a schematic diagram showing the movement of valuable metals in the method for recovering 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]

[0011] 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.

[0012] 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.

[0013] Figure 1 is a flowchart showing each step of the valuable metal recovery method according to this disclosure. Figure 2 is a schematic diagram showing the movement of valuable metals in the valuable metal recovery method according to this disclosure. The valuable metal recovery method of this disclosure includes a Li,Cu leaching step S101 in which Li and Cu are leached into a first aqueous phase by ammonia leaching from a target material containing a water-soluble Li compound, Ni, Co, and Cu; a separation step S102 in which ammonia is evaporated from the first aqueous phase to separate Li and Cu; and a Ni,Co leaching step S103 in which Ni and Co are leached into a second aqueous phase from the solid residue obtained in the Li,Cu leaching step by ammonia leaching.

[0014] The method for recovering valuable metals described herein is applied to materials containing water-soluble Li compounds, Ni, Co, and Cu. The type of material is not particularly limited as long as it contains water-soluble Li compounds, Ni, Co, and Cu. Typically, the material is roasted black mass of lithium-ion secondary battery waste. For this reason, lithium-ion secondary batteries will be described in detail first.

[0015] <Lithium-ion rechargeable battery> The general configuration of a lithium-ion secondary battery will be explained with examples. An example of the general structure of a lithium-ion secondary battery is shown in Figures 2 and 3. Figure 2 is a schematic longitudinal cross-sectional view showing the internal structure of an example of a lithium-ion secondary battery. Figure 3 is a schematic exploded view showing the electrode body of the lithium-ion secondary battery shown in Figure 2. Figure 4 is a schematic cross-sectional view along the thickness direction of the positive electrode of the lithium-ion secondary battery shown in Figure 2. Note that the following explanation of lithium-ion secondary batteries is for the sake of understanding and does not in any way limit the method of recovering valuable metals in this disclosure.

[0016] As shown in Figure 3, the lithium ion secondary battery 100 is a sealed battery in which a flat-shaped electrode body 20 and a non-aqueous electrolyte (not shown) are housed inside a battery case 30. As shown in Figure 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, aluminum alloy, resin, and the like are used.

[0017] In the illustrated example, the battery case 30 has a rectangular shape. However, the shape of the battery case 30 is not limited to this, and may be, for example, a cylindrical shape. 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, for example.

[0018] The battery case 30 is provided with 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 configured to release the internal pressure of the battery case 30 when the internal pressure rises to a predetermined level or higher. The battery case 30 is provided with an injection port (not shown) for injecting the non-aqueous electrolyte. The positive electrode terminal 42 is electrically connected to the positive electrode current collector plate 42a. The negative electrode terminal 44 is electrically connected to the negative electrode current collector plate 44a.

[0019] As shown in Figure 3 and Figure 4, the electrode body 20 has a form in which an elongated positive electrode sheet 50 and an elongated negative electrode sheet 60 are superimposed with two elongated separator sheets 70 interposed therebetween 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 stacked electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween.

[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 a 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 active material layer 54 is not formed and the positive electrode current collector 52 is exposed. A positive electrode current collector 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 include 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 mass% or more, and more preferably 85 mass% or more and 99 mass% or less. The content of the conductive material in the positive electrode active material layer 54 is preferably 0.1 mass% or more and 20 mass% or less, and more preferably 0.3 mass% or more and 15 mass% or less. The content of the binder in the positive electrode active material layer 54 is preferably 0.4 mass% or more and 15 mass% or less, and more preferably 0.5 mass% or more and 10 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 side or both sides (here, both sides) of a negative electrode current collector 62. The negative electrode sheet 60 has a negative electrode active material layer non-formation portion 62a, which is a portion 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 joined to the negative electrode active material layer non-formation portion 62a.

[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] 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., EC, 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. Non-aqueous electrolytes may also contain various additives such as gas generating agents and film-forming agents. 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, in in-vehicle applications (that is, as a drive power source for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEV)), and power supply applications for electronic devices and the like.

[0029] As described above, in the positive electrode of a lithium-ion secondary battery, Li, Ni and Co are typically used as 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 lithium-ion secondary batteries, Li is used in non-aqueous electrolytes. Further, Al may be used for the battery case. Hereinafter, each step of the valuable metal recovery method of the present disclosure will be described in detail.

[0030] <Li, Cu leaching step S101> In the Li, Cu leaching step S101, ammonia leaching of Li and Cu is performed on a target object containing a water-soluble Li compound, Ni, Co and Cu.

[0031] The type of water-soluble Li compound contained in the target object is not particularly limited as long as it is a water-soluble Li compound. Examples of water-soluble Li compounds include Li2CO3, LiCl, LiOH and the like.

[0032] As described above, the target object containing the water-soluble Li compound, Ni, Co and Cu is typically a roasted black mass of lithium-ion secondary battery waste. In the present specification, "lithium-ion secondary battery waste" includes not only used lithium-ion secondary batteries, but also constituent members of used lithium-ion secondary batteries (e.g., electrode bodies, etc.), defective lithium-ion secondary batteries, and constituent members of defective lithium-ion secondary batteries (e.g., electrode bodies, etc.).

[0033] Lithium-ion secondary batteries contain Li, Ni, and Co in the form of composite oxides as positive electrode active materials. Li is also present in the form of an electrolyte salt. Cu is present in the form of a metal as a negative electrode current collector. In the roasted black mass of lithium-ion secondary battery waste, Li is converted mainly into water-soluble Li compounds (e.g., Li2CO3) through reactions such as carbonation during the roasting process. Therefore, the roasted black mass of lithium-ion secondary battery waste contains water-soluble Li compounds, Ni, Co, and Cu.

[0034] Furthermore, Ni and Co in oxide form contained in lithium-ion secondary batteries can be reduced by roasting. Also, Cu contained in lithium-ion secondary batteries can be oxidized by roasting. For this reason, the roasted black mass of lithium-ion secondary battery waste may contain Ni, Co, and Cu in metallic or oxide form. Since the leaching rates of Ni, Co, and Cu in metallic form are higher than those of Ni, Co, and Cu in oxide form, it is preferable that the roasted black mass of lithium-ion secondary battery waste contains Ni, Co, and Cu in metallic form.

[0035] The roasted black mass can be obtained, for example, by crushing lithium-ion secondary battery waste according to a known method, sieving it if necessary, separating specific metal species if necessary, and roasting it at 650°C to 1500°C (preferably 750°C to 1000°C) for 1 to 24 hours (preferably 4 to 12 hours). Here, by using an atmosphere with an oxygen concentration of 5% by volume or less (preferably 1% by volume or less) (particularly an inert gas atmosphere such as argon gas or nitrogen gas) as the roasting atmosphere, the roasted black mass of lithium-ion secondary battery waste can contain Li in the form of water-soluble Li compounds, as well as Ni, Co, and Cu in metallic forms. On the other hand, if air or an oxygen atmosphere with a higher oxygen concentration than air is selected as the roasting atmosphere, Li, Ni, Co, and Cu may be contained in the roasted black mass in the form of oxides. Therefore, it is particularly preferable that the material is roasted black mass obtained by roasting lithium-ion secondary battery waste in an atmosphere with an oxygen concentration of 5% by volume or less (especially in an inert gas atmosphere such as argon gas or nitrogen gas).

[0036] The roasting atmosphere may contain gases other than oxygen, typically inert gases such as argon and nitrogen. However, the roasting atmosphere may also contain gases other than oxygen and inert gases. Here, the type of water-soluble Li compound can be changed depending on the type of gas contained in the roasting atmosphere. Specifically, if the roasting atmosphere is an inert gas atmosphere such as argon or nitrogen, the roasted black mass contains Li2CO3 as the water-soluble Li compound. If the roasting atmosphere contains chlorine gas (for example, if the atmosphere is a mixed gas atmosphere of chlorine gas and an inert gas), the roasted black mass contains LiCl. In this case, it is preferable that the concentration of chlorine gas in the atmosphere be 5% by volume or less so that metals other than Li do not form chlorides. If the roasting atmosphere contains hydrogen gas (for example, if the atmosphere is a mixed gas atmosphere of hydrogen gas and an inert gas), the roasted black mass contains LiOH. If the roasting atmosphere contains hydrogen gas, metal elements such as Ni and Co maintain their metallic state, so their concentrations are not particularly limited.

[0037] Therefore, the method for recovering valuable metals according to this disclosure may further include, as an optional step, a step of roasting lithium-ion secondary battery waste to obtain a material containing water-soluble Li compounds, Ni, Co, and Cu (i.e., roasted black mass) (hereinafter also referred to as the "roasting step"). The roasting step is performed before the Li, Cu leaching step S101. The roasting conditions in the roasting step are as described above.

[0038] Furthermore, the roasting process described above removes liquid components (e.g., electrolyte) from the lithium-ion secondary battery waste and carbonizes resin components (e.g., binder, separator). Roasting also disables the battery's functionality.

[0039] The substance may further contain elements other than water-soluble Li compounds, Ni, Co, and Cu (especially metallic elements). For example, the substance may further contain other transition metal elements, and in particular, Mn. For example, the substance may further contain Al.

[0040] In the Li,Cu leaching process S101, a first aqueous ammonia solution containing at least water and ammonia is used as the leaching agent in order to leach ammonia from the target material.

[0041] The concentration of ammonia in the first aqueous ammonia solution is not particularly limited as long as it can leach Li and Cu. From the viewpoint of suppressing the dissolution of metals other than Li and Cu, the concentration of ammonia in the first aqueous ammonia solution is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more. Furthermore, the upper limit of the ammonia concentration is preferably 5% by mass or less, and more preferably 2% by mass or less. From the viewpoint of leaching ability and ease of handling, an ammonia concentration of 0.1% by mass to 2% by mass is particularly preferred.

[0042] The first ammonia aqueous solution may contain only water and ammonia. In other words, the first ammonia aqueous solution may be ammonia water.

[0043] On the other hand, the primary ammonia aqueous solution may further contain other components. For example, the primary ammonia aqueous solution may further contain ammonium carbonate. The amount of ammonium carbonate in the primary ammonia aqueous solution is preferably 0.5 to 1.5 molar times, more preferably 0.8 to 1.2 molar times, and even more preferably equimolar times, of the amount of Cu contained in the target substance. On the other hand, ammonium carbonate promotes the leaching of Ni and Co. The amount of ammonium carbonate in the primary ammonia aqueous solution is preferably 0.20 molar times or less, more preferably 0.10 molar times or less, and even more preferably 0.05 molar times or less, of the total amount of Ni and Co contained in the target substance.

[0044] The first aqueous ammonia solution may contain only water, ammonia, and ammonium carbonate. The first aqueous ammonia solution may further contain components other than water, ammonia, and ammonium carbonate, within a range that does not impair the effects of the disclosure (for example, at concentrations of less than 10% by mass, 5% by mass or less, or 1% by mass or less).

[0045] The amount of the first ammonia solution used is not particularly limited and may be about the same as the amount of ammonia solution used in known ammonia leaching methods. For example, the amount of the first ammonia solution used is enough to completely immerse the object.

[0046] Normally, oxygen is involved in the dissolution of Cu in aqueous ammonia. This oxygen can be the dissolved oxygen in the first aqueous ammonia solution or oxygen from the atmosphere. Therefore, although the Li,Cu leaching process S101 may be carried out in the atmosphere, it is preferable to supply oxygen to the first aqueous ammonia solution during leaching from the viewpoint of a high leaching rate. The amount of oxygen supplied is preferably equimolar or more relative to the element to be oxidized (i.e., Cu) contained in the target material, 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] The Li,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. Also, if necessary, a bubbling device is prepared. The bubbling device may be a known device used in leaching. The bubbling device may be attached to the container before adding the material and the first ammonia aqueous solution, or it may be attached to the container after adding the material and the first ammonia aqueous solution.

[0049] The target substance and the first ammonia aqueous solution are placed in the container. The order in which these are placed is not particularly limited; they may be placed in any order or simultaneously. If necessary, oxygen-containing gas is supplied to the first ammonia aqueous solution as bubbles using a bubbling device.

[0050] The Li,Cu leaching process S101 may be carried out at room temperature (i.e., 25±10℃) or under heating. The leaching temperature is preferably greater than 0℃ and 80℃ or less, more preferably between 10℃ and 50℃, and even more preferably between 15℃ and 35℃.

[0051] 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.

[0052] Stirring is preferable during ammonia 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.

[0053] Ammonia leaching can be terminated by solid-liquid separation, such as by performing a filtrate separation. This solid-liquid separation yields an aqueous phase containing Li and Cu (i.e., a first aqueous ammonia solution containing Li and Cu) and a solid residue containing Ni and Co, as shown in Figure 2. In this manner, the Li, Cu leaching process S101 can be carried out.

[0054] <Separation process S102> Next, the separation process S102 will be described. The order in which the separation process S102 and the Ni,Co leaching process S103 are carried out is not particularly limited, as long as they are carried out after the Li,Cu leaching process 101. The separation process S102 may be carried out before the Ni,Co leaching process S103, or the Ni,Co leaching process S103 may be carried out before the separation process S102. Alternatively, the separation process S102 and the Ni,Co leaching process S103 may be carried out in parallel.

[0055] In separation step S102, ammonia is evaporated from the first aqueous phase. When ammonia is evaporated from the first aqueous phase, Cu precipitates as a copper compound. Thus, Li and Cu can be separated into an aqueous phase containing Li and a solid phase containing Cu.

[0056] When ammonia is simply evaporated from the first aqueous phase, the precipitated copper compound is copper oxide (CuO).

[0057] When a hydroxide (e.g., LiOH, NaOH, KOH, etc.) is added to the first aqueous phase before evaporating ammonia, the precipitated copper compound is copper hydroxide (Cu(OH)2). Here, adding a hydroxide to the first aqueous phase before evaporating ammonia is advantageous because it increases the precipitation rate of Cu. Lithium hydroxide (LiOH) is preferred as the hydroxide because it does not contain metal elements that would be impurities.

[0058] In separation step S102, it is preferable to recover the evaporated ammonia. Reusing the recovered ammonia in at least one of the Li,Cu leaching step S101 and the Ni,Co leaching step S103 is advantageous in a reagent recycling system that does not generate waste.

[0059] The separation step S102 can be carried out in accordance with a known method. 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.

[0060] When recovering ammonia, an ammonia collection device is prepared. Known devices can be used as ammonia collection devices. 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 aqueous 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.

[0061] The first aqueous phase obtained in the Li,Cu leaching step S101 is added to an open container. If copper hydroxide is to be produced using hydroxide, the hydroxide is added to the first aqueous phase and dissolved. Then the first aqueous phase is heated. This allows ammonia to evaporate from the first aqueous phase. The heating temperature is not particularly limited as long as the ammonia evaporates, 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).

[0062] 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.

[0063] During heating, stirring may be performed. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 400 rpm or higher, and even more preferably 600 rpm or higher. The stirring speed may be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0064] When recovering ammonia, the ammonia evaporated by heating is recovered by an ammonia collection device. Specifically, for example, the evaporated ammonia is sucked from a suction hood, and the ammonia is captured by the collection liquid in the ammonia collection unit.

[0065] As shown in Figure 2, when ammonia is evaporated from the first aqueous phase, Cu precipitates as a copper compound, and Li remains in the first aqueous phase. Therefore, Cu and Li can be separated. Furthermore, by performing solid-liquid separation such as filtration, Li and Cu can be recovered separately.

[0066] The recovered Li can be used as a raw material for a positive electrode active material according to a known method, and may also be used for other applications. The recovered Cu can be used as a raw material for a negative electrode current collector according to a known method, and may also be used for other applications.

[0067] <Ni, Co leaching step S103> The solid residue obtained in the above Li, Cu leaching step S101 contains Ni and Co. In the Ni, Co leaching step S103, ammonia leaching is performed on the solid residue obtained in the Li, Cu leaching step S101, to leach Ni and Co contained in the solid residue into the second aqueous phase.

[0068] In the Ni, Co leaching step S103, as the leaching agent used for ammonia leaching, a second aqueous ammonia solution containing water, ammonia (NH₃), and an inorganic ammonium salt which is a pH adjuster is used. The inorganic ammonium salt is preferably at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate ((NH₄)₂SO₄) and ammonium carbonate ((NH₄)₂CO₃).

[0069] In the second 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 second 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, and therefore 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.

[0070] The inorganic ammonium salt used is a pH adjuster. Here, the pH of the secondary ammonia aqueous solution at 25°C is preferably 9 to 12, and more preferably 10 to 11. Therefore, the amount of inorganic ammonium salt in the secondary ammonia aqueous solution is such that the pH of the secondary ammonia aqueous solution is, for example, 9 to 12, preferably 10 to 11. The concentration of the inorganic ammonium salt in the secondary ammonia aqueous solution is preferably 0.5 mol / L or more, more preferably 1 mol / L or more, and even more preferably 1.5 mol / L or more. On the other hand, the concentration of the inorganic ammonium salt in the secondary ammonia aqueous solution may be 3 mol / L or less, or 2.5 mol / L or less.

[0071] The second aqueous ammonia solution may contain only water, ammonia, and an inorganic ammonium salt. The second aqueous ammonia solution may further contain components other than water, ammonia, and an inorganic ammonium salt, within a range that does 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).

[0072] The amount of secondary ammonia solution used is not particularly limited and may be similar to the amount of ammonia solution used in known ammonia leaching methods. For example, the amount of secondary ammonia solution used is enough to completely immerse the solid residue.

[0073] In the Ni,Co leaching process S103, it is advantageous to carry out the leaching while supplying an oxygen-containing gas to the second ammonia aqueous solution. In this case, the selectivity for Ni and Co and the leaching rate can be increased.

[0074] The higher the oxygen concentration of the supplied gas, the higher the leaching rate and selectivity of Ni and Co. Therefore, the oxygen concentration of the supplied gas is preferably 21% by volume or higher, more preferably 30% by volume or higher, even more preferably 50% by volume or higher, particularly preferably 90% by volume or higher, and most preferably 99% by volume or higher.

[0075] The oxygen concentration of the supplied gas can be adjusted according to known methods. For example, the oxygen concentration can be adjusted by mixing oxygen gas with an inert gas (e.g., nitrogen gas, argon gas, etc.) to achieve a predetermined oxygen concentration. Furthermore, if only oxygen gas is used as the supplied gas, that is, if the supplied gas contains only oxygen gas, the oxygen concentration can be set to 99% by volume or higher (especially 100% by volume). Also, since the oxygen concentration of the atmosphere is 21% by volume, the atmosphere may be used as the oxygen-containing gas.

[0076] The supply of oxygen-containing gas to the second ammonia aqueous solution can be carried out according to known methods. For example, it can be done by bubbling the oxygen-containing gas into the second ammonia aqueous solution. When only oxygen gas is supplied to the second ammonia aqueous solution by bubbling, the leaching rate and selectivity of Ni and Co become extremely high. In this case, the smaller the bubbles, the more efficiently the amount of dissolved oxygen can be increased. Alternatively, for example, the supply of oxygen-containing gas can be carried out by sealing a container and pressurizing it while supplying the oxygen-containing gas into it.

[0077] The Ni,Co leaching process S103 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. Also, if necessary, a bubbling device is prepared. The bubbling device may be a known device used in leaching. The bubbling device may be attached to the container before adding the solid residue and the second ammonia aqueous solution, or it may be attached to the container after adding the solid residue and the second ammonia aqueous solution.

[0078] The solid residue and the second ammonia aqueous solution are added to the container. The order in which these are added is not particularly limited; they may be added either first or simultaneously. If necessary, oxygen-containing gas is supplied to the second ammonia aqueous solution as bubbles using a bubbling device.

[0079] The amount of oxygen-containing gas supplied can be appropriately determined according to the amounts of solid residue and the 2Ammonia aqueous solution. Regarding the amount of gas supplied, it is preferable that the amount of oxygen supplied be equimolar or greater than the amount of potentially oxidizable elements (particularly Ni and Co) contained in the solid residue, more preferably 2 molar times or more, and even more preferably 3 molar times or more. The amount of oxygen supplied may be 100 molar times or less of the potentially oxidizable elements contained in the solid residue.

[0080] The Ni,Co leaching process S103 may be carried out at room temperature (i.e., 25±10℃) or under heating. The leaching temperature is preferably greater than 0℃ and 80℃ or less, more preferably between 10℃ and 50℃, and even more preferably between 15℃ and 35℃.

[0081] The leaching time can be appropriately determined according to the leaching conditions, such as the leaching temperature. The higher the leaching temperature, the shorter the time required to complete the leaching. Therefore, it is preferable to carry out the Ni,Co leaching process S103 at a temperature of 80°C or higher for 2 hours or more (more preferably 6 hours or more, and especially preferably 10 hours or more). Alternatively, it is preferable to carry out the Ni,Co leaching process S103 at a temperature of 70°C or higher for 4 hours or more (more preferably 9 hours or more). Alternatively, it is preferable to carry out the Ni,Co leaching process S103 at a temperature of 60°C or higher for 6 hours or more (more preferably 12 hours or more). The leaching time for the Ni,Co leaching process S103 may be 24 hours or less, or 48 hours or less, at any of these temperatures.

[0082] 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.

[0083] As described above, Ni and Co can be leached into the second aqueous phase (i.e., the second aqueous ammonia solution). In other words, the Ni,Co leaching process S103 can be performed. The ammonia leaching can be terminated by solid-liquid separation of the filtrate, etc. As shown in Figure 2, this solid-liquid separation yields the second aqueous phase in which Ni and Co have leached (i.e., the second aqueous ammonia solution in which Ni and Co have leached) and a solid residue.

[0084] The Ni and Co extracted into the second aqueous phase can be recovered according to known methods. The recovered Ni and Co can be used as raw materials for the positive electrode active material according to known methods, or they can be used for other purposes. For example, it is advantageous to recover Ni and Co by evaporating ammonia from the second aqueous phase and converting them into nickel carbonate and cobalt carbonate. Alternatively, they can be recovered by adding sulfuric acid to the aqueous phase and converting them into nickel sulfate and cobalt sulfate. In this case, if the evaporated ammonia is recovered, it can be reused in at least one of the Li,Cu leaching process S101 and the Ni,Co leaching process S103, which is advantageous.

[0085] The valuable metal recovery method of this disclosure allows for the recovery of Ni and Co, and Li and Cu, with high recovery rates from materials containing water-soluble Li compounds, Ni, Co, and Cu (particularly roasted black mass of lithium-ion secondary battery waste). Furthermore, in the valuable metal recovery method of this disclosure, ammonia, a component of the leaching agent used to extract Li and Cu, can be recovered and reused, making the leaching agent suitable for reuse. In addition, the valuable metal recovery method of this disclosure can be easily implemented. Moreover, the valuable metal recovery method of this disclosure can be used as a method for recycling cathode materials. Therefore, the valuable metal recovery method of this disclosure is extremely useful in the material recycling of lithium-ion secondary batteries.

[0086] 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.

[0087] [Preparation of the material to be leached] First, the roasted black mass of the material to be leached was prepared using the following procedure: Lithium nickel cobalt manganese composite oxide (LiNi) was placed on 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 750°C for 6 hours in a low-oxygen atmosphere to obtain roasted black mass in which most of the metal was reduced. This roasted black mass contained Li as Li2CO3, and Ni, Co, and Cu as metals. 1 g of this roasted black mass was dissolved in acid, and high-frequency inductively coupled plasma (ICP) emission spectroscopy was performed on it. From the analysis results, the amounts of Li, Ni, Co, and Cu in the roasted black mass were determined.

[0088] [Li, Cu leaching study] [Test Example 1] Roasted black muss was added to a sufficient amount of water. While supplying oxygen gas to the water by bubbling, leaching was carried out at room temperature (25°C) for 3 hours under stirring at 800 rpm. After that, solid-liquid separation was performed by filtration to obtain leachate and solid residue.

[0089] [Test Example 2] Roasted black muss was added to a 0.5 mol / L (approximately 0.9 mass%) ammonia solution. While supplying oxygen gas to the ammonia solution by bubbling, ammonia leaching was carried out at room temperature (25°C) for 3 hours under stirring at 800 rpm. Subsequently, solid-liquid separation was performed by filtration to obtain the leachate and solid residue.

[0090] [Test Example 3] An aqueous ammonia solution was obtained by dissolving ammonium carbonate in a 0.5 mol / L (approximately 0.9 mass%) solution of ammonia, in an amount equivalent to the Cu contained in the roasted black trout. The amount of ammonium carbonate was 0.05 molar times the total amount of Ni and Co contained in the roasted black trout. Roasted black trout was added to this aqueous ammonia solution. While supplying oxygen gas to the aqueous ammonia solution by bubbling, ammonia leaching was carried out at room temperature (25°C) for 3 hours under stirring at 800 rpm. After that, solid-liquid separation was performed by filtration to obtain the leachate and solid residue.

[0091] [Evaluation of leaching rate] ICP emission spectroscopy was performed on the leachates obtained in Test Examples 1-3 to determine the amounts of Li, Ni, Co, and Cu in the leachates. Using these values ​​and the initial amounts in the roasted black mass described above, the leaching rates (%) of Li, Ni, Co, and Cu were calculated. The average of the Ni leaching rate (%) and the Co leaching rate (%) was defined as the "Ni, Co loss rate (%)". The results are shown in Table 1.

[0092] [Table 1]

[0093] [Li, Cu separation study] [Test Example 4] The leachate obtained in Test Example 3 was heated to 80°C and stirred at 800 rpm for 6 hours while maintaining the temperature at 80°C. This evaporated the ammonia. Subsequently, solid-liquid separation was performed by filtration to obtain the aqueous phase and solid residue.

[0094] [Test Example 4] In the leachate obtained in Test Example 3, lithium hydroxide (LiOH) in a molar amount greater than the amount of Li contained in the leachate was dissolved. This was heated to 80°C and stirred at 800 rpm for 6 hours while maintaining the temperature at 80°C. This evaporated the ammonia. Subsequently, solid-liquid separation was performed by filtration to obtain the aqueous phase and solid residue.

[0095] [Li, Cu recovery rate evaluation] ICP emission spectroscopy was performed on the aqueous phases obtained in Test Examples 4 and 5 to determine the amounts of Li and Cu in the aqueous phase. Using these values ​​and the initial amounts of Li and Cu in the roasted black mass described above, the remaining percentage of Li and Cu in the aqueous phase were calculated. The remaining percentage of Li was defined as the Li recovery rate, and the value obtained by subtracting the remaining percentage of Cu from 100% was defined as the Cu recovery rate. The results are shown in Table 2.

[0096] [Table 2]

[0097] [Ni,Co leaching study] [Test Example 6] An aqueous ammonia solution was prepared by dissolving ammonium carbonate in a 13 mol / L (approximately 24.3% by mass) aqueous ammonia solution at an amount equal to 1.5 molars relative to the total amount of Ni and Co contained in the solid residue obtained in Test Example 3. The solid residue obtained in Test Example 3 was added to this aqueous ammonia solution. Ammonia leaching was carried out at room temperature (25°C) for 3 hours while stirring at 800 rpm and supplying oxygen gas to the aqueous ammonia solution by bubbling. Subsequently, solid-liquid separation was performed by filtration to obtain the leachate and the solid residue.

[0098] [Test Example 7] Except for changing the amount of ammonium carbonate used from 1.5 molars to 2.0 molars, the same procedure as in Test Example 6 was performed to obtain leachate and solid residue.

[0099] [Test Example 8] Except for changing the amount of ammonium carbonate used from 1.5 molars to 2.5 molars, the same procedure as in Test Example 6 was performed to obtain leachate and solid residue.

[0100] [Ni,Co recovery rate evaluation] ICP emission spectroscopy was performed on the leachates obtained in Test Examples 6-8 to determine the amounts of Ni and Co in the leachate. Using these values ​​and the initial amounts of Ni and Co in the roasted black mass described above, the Ni leaching rate (%) and Co leaching rate (%) in the aqueous phase were determined, and the average of the Ni leaching rate (%) and Co leaching rate (%) was defined as the "Ni, Co recovery rate (%)". The results are shown in Table 3.

[0101] [Table 3]

[0102] The results in Table 1 show that the Li, Cu leaching step of the valuable metal recovery method of this disclosure can separate Li and Cu from a target material containing water-soluble Li compounds, Ni, Co, and Cu. Furthermore, the results in Table 2 show that the separation step of the valuable metal recovery method of this disclosure can separate Li and Cu from an aqueous phase containing Li and Cu. In addition, the results in Table 3 show that the Ni, Co leaching step of the valuable metal recovery method of this disclosure can separate Ni and Co.

[0103] Furthermore, as the above test examples demonstrate, the valuable metal recovery method of this disclosure allows for the easy separation of Li, Ni, Co, and Cu from materials containing water-soluble Li compounds, Ni, Co, and Cu. In addition, the ammonia used as a leaching agent when separating Li and Cu in the valuable metal recovery method of this disclosure is suitable for reuse.

[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 the claims. The technologies described in the claims include various modifications and changes to the specific examples described above.

[0105] In other words, the method for recovering valuable metals in this disclosure is as described in the following sections [1] to

[10] . [1] A Li, Cu leaching step in which Li and Cu are leached into the first aqueous phase by ammonia leaching from a target material containing a water-soluble Li compound, Ni, Co, and Cu, A separation step is performed to evaporate ammonia from the first aqueous phase and separate Li and Cu, From the solid residue obtained in the Li, Cu leaching step, Ni and Co are leached into the second aqueous phase by ammonia leaching in a Ni, Co leaching step. A method for recovering valuable metals, including [specific metals]. [2] In the separation step, the evaporated ammonia is recovered, The method according to item [1], wherein the recovered ammonia is reused in at least one of the Li,Cu leaching step and the Ni,Co leaching step. [3] The method according to item [1] or [2], wherein the ammonia leaching in the Li,Cu leaching step is carried out using a first aqueous ammonia solution containing water and ammonia. [4] The first aqueous ammonia solution further contains ammonium carbonate, The method according to item [3], wherein the amount of ammonium carbonate in the first aqueous ammonia solution is 0.5 to 1.5 molar times the amount of Cu contained in the object. [5] The method according to item [3], wherein the ammonia leaching in the Li,Cu leaching step is carried out while supplying an oxygen-containing gas to the first ammonia aqueous solution. [6] The method according to any one of items [1] to [5], wherein lithium hydroxide is added to the first aqueous phase in the separation step, and then ammonia is evaporated. [7] The method according to any one of items [1] to [6], wherein the ammonia leaching in the Ni,Co leaching step is carried out using a second aqueous ammonia solution containing water, ammonia, and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate. [8] The method according to item [7], wherein the ammonia leaching in the Ni,Co leaching step is carried out while supplying an oxygen-containing gas to the second aqueous ammonia solution. [9] The method according to any one of the items [1] to [8], wherein the object contains Ni, Co, and Cu in metallic form.

[10] The method according to any one of items [1] to [9], wherein the object is roasted black mass of waste lithium-ion secondary batteries. [Explanation of Symbols]

[0106] 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 Li, Cu leaching step is performed in which Li and Cu are leached into the first aqueous phase by ammonia leaching from a target object containing a water-soluble Li compound, Ni, Co, and Cu. A separation step is performed to evaporate ammonia from the first aqueous phase and separate Li and Cu, From the solid residue obtained in the Li, Cu leaching step, Ni and Co are leached into the second aqueous phase by ammonia leaching in a Ni, Co leaching step. A method for recovering valuable metals, including [specific metals].

2. In the separation step, the evaporated ammonia is recovered. The method according to claim 1, wherein the recovered ammonia is reused in at least one of the Li, Cu leaching step and the Ni, Co leaching step.

3. The method according to claim 1, wherein the ammonia leaching in the Li, Cu leaching step is carried out using a first aqueous ammonia solution containing water and ammonia.

4. The first aqueous ammonia solution further contains ammonium carbonate, The method according to claim 3, wherein the amount of ammonium carbonate in the first aqueous ammonia solution is 0.5 to 1.5 molar times the amount of Cu contained in the target substance.

5. The method according to claim 3, wherein the ammonia leaching in the Li, Cu leaching step is carried out while supplying an oxygen-containing gas to the first ammonia aqueous solution.

6. The method according to claim 1, wherein lithium hydroxide is added to the first aqueous phase in the separation step, and then ammonia is evaporated.

7. The method according to claim 1, wherein the ammonia leaching in the Ni,Co leaching step is carried out using a second aqueous ammonia solution containing water, ammonia, and at least one inorganic ammonium salt selected from the group consisting of ammonium sulfate and ammonium carbonate.

8. The method according to claim 7, wherein the ammonia leaching in the Ni,Co leaching step is carried out while supplying an oxygen-containing gas to the second ammonia aqueous solution.

9. The method according to claim 1, wherein the object contains Ni, Co, and Cu in metallic form.

10. The method according to claim 1, wherein the object is roasted black mass of waste lithium-ion secondary batteries.

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