Method for regenerating positive electrode materials

Abstract

This invention provides a novel method for recovering Ni and Co from battery waste containing Ni and Co, while adjusting the Ni / Co ratio. [Solution] The method for regenerating positive electrode material according to the present disclosure includes the step of leaching Ni and Co from battery waste containing Ni and Co into an aqueous ammonia solution containing ammonia and ammonium sulfate. Herein, oxygen is supplied to the aqueous ammonia solution during the leaching.

Description

[Technical Field]

[0001] This disclosure relates to a method for regenerating cathode materials. [Background technology]

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

[0003] Typical examples of positive electrode active materials for lithium-ion secondary batteries used in automotive applications include lithium nickel cobalt manganese composite oxide (NCM) and lithium nickel cobalt aluminum composite oxide (NCA), both of which contain Ni and Co. Therefore, waste from lithium-ion secondary batteries using these positive electrode active materials contains Ni and Co. Non-patent document 1 describes selectively separating Ni and Co from Ni, Co, Mn, and Al contained in the positive electrode waste of used lithium-ion secondary batteries using a leaching solution containing ammonia and ammonium sulfate, and sodium sulfite as a reducing agent. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Waste Management, February 2017, vol.60, p.680-688 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the above prior art, since Ni and Co are separated together, it is advantageous from the viewpoint of production efficiency to reuse them in the production of the positive electrode active material without separating Ni and Co. On the other hand, the conventionally used lithium nickel cobalt manganese composite oxide is one using equimolar amounts of Ni, Co, and Mn (for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.). That is, the molar ratio of Ni / Co (hereinafter, may be simply referred to as "Ni / Co ratio") is 1. However, from the viewpoint of increasing the capacity of the battery, in recent years, compositions with a high nickel content ratio (for example, LiNi 0.6 Co 0.2 Mn 0.2 O2, and LiNi with a Ni / Co ratio of 8 0.8 Co 0.1 Mn 0.1 O2, etc.) of lithium nickel cobalt manganese composite oxide have been developed. Also, in the lithium nickel cobalt aluminum composite oxide, the nickel content ratio is high (for example, the Ni / Co ratio of LiNi 0.8 Co 0.15 Al 0.05 O2 is 5.3).

[0006] Therefore, there is a problem that the Ni / Co ratio in the recovered lithium ion secondary battery is likely to be different from the Ni / Co ratio in the positive electrode active material to be recycled (particularly, there is a problem that the Ni / Co ratio in the positive electrode active material to be recycled is likely to be higher). Thus, it would be useful to have a method capable of recovering Ni and Co from battery waste containing Ni and Co while adjusting the Ni / Co ratio, particularly so that the Ni / Co ratio increases.

[0007] Therefore, an object of the present disclosure is to provide a novel method capable of recovering Ni and Co from battery waste containing Ni and Co while adjusting the Ni / Co ratio.

Means for Solving the Problem

[0008] The method for regenerating positive electrode material according to this disclosure includes the step of leaching Ni and Co from battery waste containing Ni and Co into an aqueous ammonia solution containing ammonia and ammonium sulfate. Herein, oxygen is supplied to the aqueous ammonia solution during the leaching process.

[0009] With this configuration, Ni and Co can be recovered from battery waste containing Ni and Co while adjusting the Ni / Co ratio. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a flowchart showing each step of the method for regenerating cathode material according to this disclosure. [Figure 2] Figure 2 is a schematic longitudinal cross-sectional view showing the internal structure of an example of a lithium-ion secondary battery. [Figure 3] Figure 3 is a schematic exploded view showing the configuration of the electrode body of the lithium-ion secondary battery shown in Figure 2. [Figure 4] Figure 4 is a schematic cross-sectional view of the positive electrode of the lithium-ion secondary battery shown in Figure 2. [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 the steps of the cathode material regeneration method according to the present disclosure. The cathode material regeneration method according to the present disclosure includes, as an essential step, a step (hereinafter also referred to as the "leaching step") S100 in which Ni and Co are leached from battery waste containing Ni and Co into an aqueous ammonia solution containing ammonia and ammonium sulfate. In the leaching step S100, oxygen is supplied to the aqueous ammonia solution during the leaching. The cathode material regeneration method according to the present disclosure may further include, as optional steps, a step (hereinafter also referred to as the "Ni / Co ratio confirmation step") S10 before the leaching step S100, and a step (hereinafter also referred to as the "ammonium sulfate amount selection step") S20 in which the amount of ammonium sulfate is selected according to a desired molar ratio of Ni to Co. In addition, Co compounds precipitate in the leaching step S100. The method for regenerating the cathode material of this disclosure may further include, as an optional step, a step S30 in which the Co compound precipitated in the leaching step S100 is dissolved in water and separated from the solid residue (hereinafter also referred to as the "Co separation step").

[0014] <Lithium-ion rechargeable battery> First, the method for recycling the positive electrode material of 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. 2 and 3. FIG. 2 is a longitudinal sectional view schematically showing the internal structure of an example of a lithium-ion secondary battery. FIG. 3 is an exploded view schematically showing the electrode body of the lithium-ion secondary battery shown in FIG. 2. FIG. 4 is a schematic sectional view along the thickness direction of the positive electrode of the lithium-ion secondary battery shown in FIG. 2. The following description of the lithium-ion secondary battery is for convenience of understanding and does not limit the method for recycling the positive electrode material of the present disclosure in any way.

[0015] As shown in FIG. 2, 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. 2, 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, etc. are used.

[0016] In the illustrated example, the battery case 30 is rectangular. However, the shape of the battery case 30 is not limited to this, 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.

[0017] 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.

[0018] As shown in FIGS. 2 and 3, 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 this 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.

[0019] As shown in FIGS. 2 and 4, 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 non-formed portion 52a of the positive electrode active material layer, 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 non-formed portion 52a of the positive electrode active material layer.

[0020] 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.

[0021] 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.

[0022] As shown in Figure 3, 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.

[0023] An example of a negative electrode current collector 62 constituting the negative electrode sheet 60 is 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.).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The lithium-ion secondary battery 100 is used, for example, in automotive applications (i.e., as a power source for vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs)), and as a power source for electronic devices.

[0028] As described above, in lithium-ion secondary batteries, Li, Ni, and Co are typically used as constituent metal elements of the positive electrode active material. The positive electrode active material may also contain Mn and Al. Al is commonly used as the positive electrode current collector. Cu is commonly used as the negative electrode current collector. In addition, Li is used as the non-aqueous electrolyte in lithium-ion secondary batteries. Al may also be used for the battery case.

[0029] <Leaching process S100> Battery waste containing Ni and Co is used in the leaching process S100. The Ni and Co contained in the battery waste typically originate from the positive electrode active material (particularly lithium transition metal composite oxides containing Ni and Co). However, the Ni and Co contained in the battery waste are not limited to this. In this specification, "battery waste" includes not only used lithium-ion secondary batteries, but also components of used lithium-ion secondary batteries, defective lithium-ion secondary batteries, and components of defective lithium-ion secondary batteries. The waste may have undergone some treatment (e.g., roasting).

[0030] Specific examples of battery waste include black mass from used lithium-ion secondary batteries (especially black mass obtained by crushing and roasting used lithium-ion secondary batteries), positive electrode waste extracted from used lithium-ion secondary batteries, electrode material waste extracted from used lithium-ion secondary batteries, positive electrode waste deemed to be defective, electrode material waste deemed to be defective, and positive electrode active material deemed to be defective.

[0031] It is more preferable that the waste contains Ni and Co as metals. From this viewpoint, it is preferable that the waste is reductively roasted. Preferably, the waste is black mass obtained by crushing and reductively roasting used lithium-ion secondary batteries.

[0032] Specifically, this black mass can be obtained, for example, by crushing lithium-ion secondary batteries according to a known method, sieving them if necessary, and roasting them at 400°C to 1500°C (preferably 700°C to 1000°C) in an atmosphere with an oxygen concentration of 5% by volume or less (preferably 1% by volume or less) (especially in an inert gas atmosphere such as argon gas or nitrogen gas) for 1 to 24 hours (preferably 4 to 12 hours).

[0033] Battery waste may further contain elements other than Ni and Co (especially metallic elements). For example, in addition to Ni and Co, battery waste may further contain Li, Mn, Al, etc. Battery waste may further contain transition metal elements other than Ni and Co.

[0034] In the leaching process S100, an aqueous ammonia solution containing ammonia (NH3) and ammonium sulfate ((NH4)2SO4) is used as the leaching agent.

[0035] 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.

[0036] Normally, when waste containing Ni and Co is leached using an aqueous solution containing ammonia and ammonium sulfate, both Ni and Co readily form ammine complexes and are leached out. Therefore, the molar ratio of Ni to Co in the leachate (i.e., the Ni / Co ratio) is the same as or approximately the same as the Ni / Co ratio in the waste.

[0037] In contrast, the method for regenerating cathode materials according to this disclosure involves supplying oxygen to the ammonia aqueous solution during leaching. This causes oxygen to dissolve in the ammonia aqueous solution. When oxygen is dissolved in the aqueous solution, some of the Co that has leached into the ammonia aqueous solution precipitates as a Co compound due to ammonium sulfate. Consequently, the amount of Co dissolved in the ammonia aqueous solution decreases, and the Ni / Co ratio in the leachate becomes greater than the Ni / Co ratio in the waste. Here, the amount of Co precipitated depends on the amount of ammonium sulfate in the ammonia aqueous solution. Therefore, according to the method for regenerating cathode materials according to this disclosure, the Ni / Co ratio can be adjusted by controlling the amount of ammonium sulfate by supplying oxygen to the ammonia aqueous solution.

[0038] Therefore, in the method for regenerating the cathode material of this disclosure, the amount of ammonium sulfate can be appropriately determined by the ratio of Ni to Co to be leached into the aqueous solution (i.e., the desired Ni / Co ratio). The larger the amount of ammonium sulfate, the greater the amount of Co precipitated, so the Co content in the leached material decreases and the Ni / Co ratio increases.

[0039] From the viewpoint of precipitating the leached Co, the amount of ammonium sulfate is preferably 5 molar times or more, and more preferably 7 molar times or more, relative to the amount of Co in the battery waste. The amount of ammonium sulfate may be 100 molar times or less, 50 molar times or less, or 40 molar times or less, relative to the amount of Co in the battery waste. Furthermore, the concentration of ammonium sulfate in the ammonia aqueous solution is preferably 1.2 mol / L or more, and more preferably 1.4 mol / L or more. The concentration of ammonium sulfate in the ammonia aqueous solution may be 3.0 mol / L or less, or 2.5 mol / L or less.

[0040] The ammonia aqueous solution may contain only water, ammonia, and ammonium sulfate. The ammonia aqueous solution may further contain components other than water, ammonia, and ammonium sulfate, 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).

[0041] The amount of ammonia solution used should preferably be enough to completely immerse the battery waste.

[0042] In the leaching process S100, oxygen is supplied to the ammonia aqueous solution during leaching. Oxygen can be supplied, for example, by introducing an oxygen-containing gas (e.g., oxygen gas, air, etc.) into the 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 the container and pressurizing it while introducing oxygen into it.

[0043] The leaching process S100 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. A bubbling device is also prepared. The bubbling device may be a known device used in leaching. The bubbling device may be attached to the container before the battery waste and ammonia leaching solution are added, or it may be attached to the container after the battery waste and ammonia leaching solution are added.

[0044] Battery waste and an aqueous ammonia solution are placed into a container. The order in which these are placed is not particularly limited; they may be placed in either order or simultaneously. Meanwhile, an oxygen-containing gas is supplied to the aqueous ammonia solution using a bubbling device. Here, it is preferable to supply oxygen gas to the aqueous ammonia solution by bubbling.

[0045] The oxygen supply is preferably equimolar or greater than the amount of potentially oxidizable elements (especially Ni and Co) contained in the battery waste, more preferably 2 molar times or more, and even more preferably 3 molar times or more. The oxygen supply may be 100 molar times or less of the potentially oxidizable elements contained in the battery waste.

[0046] The leaching process S100 may be carried out at room temperature (i.e., 25±10℃) or under heating. The leaching temperature is preferably 15℃ or higher, and more preferably 20℃ or higher. On the other hand, the leaching temperature may be 90℃ or lower, 85℃ or lower, or 80℃ or lower.

[0047] The leaching time can be appropriately determined according to the leaching temperature. The higher the leaching temperature, the shorter the time required to complete leaching. In addition, by dissolving oxygen in the aqueous ammonia solution, the leaching rates of Ni and Co are increased. This is presumably due to the influence of the oxidation of Ni and Co. The leaching time is, for example, 1 hour or more, preferably 2 hours or more, and more preferably 4 hours or more. On the other hand, from the perspective of operation efficiency, the leaching time is, for example, 48 hours or less, preferably 24 hours or less, and more preferably 10 hours or less.

[0048] Stirring is preferably performed during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or more, more preferably 400 rpm or more, and even more preferably 500 rpm or more. The stirring speed may be 2000 rpm or less, 1000 rpm or less, or 800 rpm or less.

[0049] As described above, by performing ammonia leaching, Ni and Co can be leached into the aqueous phase (i.e., the aqueous ammonia solution). That is, the leaching step S100 can be performed. Ammonia leaching can be terminated by performing solid-liquid separation such as filtration. By this solid-liquid separation, a leachate (i.e., an aqueous phase in which Ni and Co have been leached) and a solid residue can be obtained.

[0050] The solid residue contains the precipitated Co compound. This Co compound is a water-soluble salt and is considered to be cobalt sulfate because Co and S elements were detected in the analysis by scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX). The precipitated Co compound can be separated and recovered from the solid residue by dissolving it in water.

[0051] Therefore, as shown in FIG. 1, the method for regenerating the positive electrode material of the present disclosure may further include a Co separation step S30.

[0052] <Co separation step S30> In the Co separation step S30, the Co compound precipitated in the leaching step S100 is dissolved in water and separated from the solid residue. The Co separation step S30 can be carried out according to a known method. Specifically, for example, it can be carried out by immersing the solid residue in water. Alternatively, it can be carried out by washing the solid residue with water. Co can be recovered from the water in which the Co compound is dissolved according to a known method.

[0053] When Mn and Al are contained in the electrode waste, Mn and Al remain in the solid residue obtained in the leaching step S100. Also in the Co separation step S30, Mn and Al remain in the solid residue. Therefore, in this case, in the Co separation step S30, it is possible to separate Mn and Al from Co.

[0054] Also, as described above, according to the method for recycling the positive electrode material of the present disclosure in which oxygen is supplied during leaching, the Ni / Co ratio in the leachate can be adjusted by controlling the concentration of ammonium sulfate. In particular, it can be adjusted so that the Ni / Co ratio in the leachate becomes high.

[0055] Therefore, the method for recycling the positive electrode material of the present disclosure may further include a Ni / Co ratio confirmation step S10 and an ammonium sulfate amount selection step S20 before the leaching step S100, as shown in FIG. 1.

[0056] <Ni / Co ratio confirmation step S10> In the Ni / Co ratio confirmation step S10, the Ni / Co ratio of the battery waste is confirmed. When the material used in the battery waste is known, the Ni / Co ratio can be confirmed accordingly. For example, when the composition of the positive electrode active material is known and Ni and Co are not used other than the positive electrode active material, the Ni / Co ratio in the positive electrode active material can be taken as the Ni / Co ratio in the battery waste.

[0057] If the materials used in battery waste are unknown, the Ni / Co ratio in the battery waste can be determined according to known methods. Specifically, for example, the amount of Ni and Co in the waste can be measured according to known methods using inductively coupled plasma (ICP) emission spectroscopy. The Ni / Co ratio can then be calculated using the obtained Ni and Co amounts.

[0058] <Ammonium sulfate amount selection step S20> In the ammonium sulfate amount selection step S20, the amount of ammonium sulfate is selected according to the desired molar ratio of Ni to Co. Specifically, based on the Ni / Co ratio obtained in the Ni / Co ratio confirmation step S10, the amount of ammonium sulfate is selected so that the amounts of Ni and Co in the leachate satisfy the desired Ni / Co ratio. This desired Ni / Co ratio is typically the Ni / Co ratio when Ni and Co are reused.

[0059] For this selection, it is advantageous to conduct preliminary experiments by taking a sample of battery waste and determining the relationship between the amount of ammonium sulfate and the Ni / Co ratio leached into the ammonia aqueous solution, thereby creating a calibration curve between the amount of ammonium sulfate and the Ni / Co ratio leached into the ammonia aqueous solution. Therefore, the amount of ammonium sulfate can be selected in this process based on this calibration curve.

[0060] Alternatively, for this selection, it is advantageous to conduct preliminary experiments on battery waste with various Ni / Co ratios and to create a database beforehand of the relationship between the Ni / Co ratio in the battery waste, the amount of ammonium sulfate, and the Ni / Co ratio leached into the aqueous solution. Based on this database, the amount of ammonium sulfate can be selected in this process.

[0061] To select the amount of ammonium sulfate, a program utilizing calibration curves or databases may be created and used.

[0062] Based on the selected amount of ammonium sulfate, the leaching process S100 can be performed to obtain a leachate containing Ni and Co in a desired Ni / Co ratio. Ni and Co can be separated from the leachate in a desired Ni / Co ratio according to known methods. Alternatively, the leachate containing Ni and Co in a desired Ni / Co ratio can be used directly in the production of the positive electrode active material.

[0063] The method for recycling positive electrode materials described herein allows for the recovery of Ni and Co from battery waste containing Ni and Co, while adjusting the Ni / Co ratio. In particular, Ni and Co can be recovered while adjusting the Ni / Co ratio to be high. Furthermore, the method for recycling positive electrode materials described herein can be easily implemented. In addition, the leaching rate of Ni and Co is also increased according to the method for recycling positive electrode materials described herein. Therefore, even if the Ni / Co ratio in the battery waste differs from the Ni / Co ratio of the positive electrode active material to be recycled, the positive electrode active material can be efficiently manufactured using Ni and Co recovered from the battery waste. Accordingly, the method for recycling positive electrode materials described herein is extremely useful in the material recycling of lithium-ion secondary batteries.

[0064] The following describes examples relating to this disclosure in detail, but this disclosure is not intended to be limited to those shown in such examples.

[0065] [Comparative Examples 1-5] First, the roasted black mass of the leaching sample 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 750°C for 6 hours in a low-oxygen atmosphere to obtain roasted black mass in which most of the metal was reduced. 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 Ni and Co in the roasted black mass were determined.

[0066] Next, an aqueous ammonia solution was prepared by mixing 28% by mass aqueous ammonia with ammonium sulfate ((NH4)2SO4) as a pH adjuster. The concentration of ammonium sulfate used was as shown in Table 1.

[0067] Here, the theoretical maximum concentrations of Ni and Co in the aqueous ammonia solution were defined as the concentrations when Ni and Co in the roasted black mass were completely dissolved in the aqueous ammonia solution. The amount of roasted black mass corresponding to the theoretical maximum concentrations shown in Table 1 was measured out. The measured roasted black mass was added to the aqueous ammonia solution. Ammonia leaching was performed by stirring at a stirring speed of 500 rpm for 6 hours while maintaining the aqueous ammonia solution at 25°C. After that, solid-liquid separation was performed by filtration to obtain the leachate and solid residue.

[0068] [Examples 1-4] Ammonia leaching was performed in the same manner as described above, except that immediately after adding the measured roasted black muss to the ammonia aqueous solution, oxygen was supplied to the ammonia aqueous solution by bubbling at a supply rate of 0.4 mol / min.

[0069] [Evaluation of leaching rate] ICP emission spectroscopy was performed on the leachate obtained in each example and comparative example, and the concentrations of Ni and Co were determined based on the analysis results. Based on these results, the molar ratio of Ni to Co in the leachate was calculated.

[0070] [Table 1]

[0071] In Comparative Examples 1-4, where oxygen bubbling was not performed during leaching, the Ni / Co ratio in the roasted black mass and the Ni / Co ratio in the leaching solution were almost the same. In Comparative Example 5, where oxygen bubbling was not performed during leaching, the amount of roasted black mass was increased, but the Ni / Co ratio became slightly smaller. This is thought to be due to insufficient leaching time.

[0072] On the other hand, in Examples 1-4, where oxygen bubbling was performed during leaching, the Ni / Co ratio in the leached solution increased in proportion to the amount of ammonium sulfate. Therefore, it can be seen that the positive electrode material regeneration method of this disclosure allows for the recovery of Ni and Co from battery waste containing Ni and Co, while adjusting the Ni / Co ratio to be large. Furthermore, a comparison of Comparative Example 5 with Examples 2-4 shows that oxygen bubbling improves the leaching rate of Ni and Co.

[0073] 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.

[0074] In other words, the method for regenerating the cathode material of this disclosure is as described in the following sections [1] to [7]. [1] A method for regenerating a positive electrode material, comprising the step of leaching Ni and Co from battery waste containing Ni and Co into an aqueous ammonia solution containing ammonia and ammonium sulfate, A regeneration method comprising supplying oxygen to the ammonia aqueous solution during the aforementioned leaching. [2] The method according to item [1], wherein the amount of ammonium sulfate is 5 molar times or more relative to the amount of Co in the battery waste. [3] The method according to item [1] or [2], wherein the concentration of ammonia in the aqueous ammonia solution is 15% by mass or more, and the concentration of ammonium sulfate is 1.2 mol / L or more. [4] The method according to any one of items [1] to [3], wherein oxygen gas is supplied to the aqueous ammonia solution by bubbling during the leaching. [5] The method according to any one of the items [1] to [4], wherein the battery waste contains Ni and Co as metals. [6] The method according to any one of claims [1] to [5], further comprising the steps of: confirming the molar ratio of Ni to Co in the battery waste before the leaching step; and selecting an amount of ammonium sulfate according to a desired molar ratio of Ni to Co. [7] The method according to any one of items [1] to [6], further comprising the step of precipitating a Co compound in the leaching step, dissolving the precipitated Co compound in water, and separating it from the solid residue. [Explanation of symbols]

[0075] 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 method for regenerating a positive electrode material, comprising the step of leaching Ni and Co from battery waste containing Ni and Co into an aqueous ammonia solution containing ammonia and ammonium sulfate, A regeneration method comprising supplying oxygen to the ammonia aqueous solution during the aforementioned leaching.

2. The method according to claim 1, wherein the amount of ammonium sulfate is 5 molar times or more relative to the amount of Co in the battery waste.

3. The method according to claim 1, wherein the concentration of ammonia in the aqueous ammonia solution is 15% by mass or more, and the concentration of ammonium sulfate is 1.2 mol / L or more.

4. The method according to claim 1, wherein oxygen gas is supplied to the ammonia aqueous solution by bubbling during the leaching process.

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

6. The method according to claim 1, further comprising: a step of confirming the molar ratio of Ni to Co in the battery waste before the leaching step; and a step of selecting the amount of ammonium sulfate according to the desired molar ratio of Ni to Co.

7. The method according to claim 1, further comprising the steps of precipitating a Co compound in the leaching step, dissolving the precipitated Co compound in water, and separating it from the solid residue.

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