WO2024241618A1 - Metal recovery method - Google Patents

Abstract

This method for recovering a metal including cobalt and/or nickel from lithium-ion battery waste comprises: a heat treatment step for performing a heat treatment on the lithium-ion battery waste; a crushing step for crushing the lithium-ion battery waste after the heat treatment step to obtain a crushed product; a sieving step for dividing the crushed product by means of sieving into at least a small-diameter sieved product having a relatively small particle diameter, a large-diameter sieved product having a relatively large particle diameter, and a medium-diameter sieved product having a particle diameter that is between that of the small-diameter sieved product and that of the large-diameter sieved product; and an eddy current sorting step for separating a non-magnetic conductor from the medium-diameter sieved product by means of eddy current sorting, and for removing, as a magnetized product, a magnetic substance including the cobalt and/or the nickel. The method recovers the metal from battery powder that includes the small-diameter sieved product and the magnetized product.

Description

Metal recovery method

This specification relates to a method for recovering metals, including at least one of cobalt and nickel, from lithium-ion battery waste.

Vehicles such as hybrid cars, fuel cell cars, and electric cars are equipped with on-board battery packs that supply power to electric motors as a drive source (see, for example, Patent Documents 1 to 6). In on-board battery packs, battery cells may be housed inside a frame that forms the skeleton of the exterior. Many on-board battery packs are constructed by bundling multiple battery cells into a battery module, and then connecting multiple battery modules together. On-board battery packs may also include a BMS (Battery Management System) that monitors each battery cell, a cooling device that cools the battery, and wires that connect them.

　The battery cells in the above-mentioned vehicle battery packs generally use secondary batteries, particularly nickel-metal hydride batteries, which can be charged to store electricity and used repeatedly, but in recent years, lithium-ion batteries that use lithium transition metal composite oxides for the positive electrode have come to be used. Such vehicle lithium-ion batteries contain valuable metals such as cobalt. Therefore, from the perspective of effective resource utilization, when vehicle lithium-ion batteries are discarded after use, it is desirable to easily recover the valuable metals that may be contained in the lithium-ion battery waste at a relatively low cost in order to reuse them.

Incidentally, when recovering valuable metals from lithium-ion battery waste, not just from in-vehicle batteries, the lithium-ion battery waste may be pre-treated to obtain battery powder that contains as much metal from the positive electrode active material as possible and has removed metal impurities that are not subject to recovery. After that, a wet process may be performed in which the metals in the battery powder are leached with acid or the like, and various metals are recovered from the resulting leaching solution.

JP 2006-179190 A JP 2007-172938 A US Patent Application Publication No. 2007/0141454 JP 2007-172939 A US Patent Application Publication No. 2007/0141455 JP 2011-198713 A

In pre-processing to obtain battery powder from lithium-ion battery waste, a screening process is carried out after a heat treatment process and a crushing process. Small-diameter sieved material with a relatively small particle size selected in the screening process can be used to effectively recover metals as battery powder by wet processing. Large-diameter sieved material with a relatively large particle size selected in the screening process can then be subjected to a specified process so that it can be included in the battery powder and used for wet processing.

On the other hand, the medium-sized sieved material, which is selected in the sieving process as having a particle size intermediate between the small-sized and large-sized sieved material, contains valuable metals such as nickel and cobalt, and it is desirable to recover these metals. However, since the medium-sized sieved material contains relatively large amounts of impurity metals such as aluminum and copper, it is necessary to carry out some appropriate processing before it can be included in the battery powder.

This specification provides a metal recovery method that can effectively separate impurity metals from the medium-sized sieve obtained by sieving and improve the recovery rate of cobalt and/or nickel.

The metal recovery method described in this specification is a method for recovering metals including at least one of cobalt and nickel from lithium ion battery waste, and includes a heat treatment process for performing heat treatment on the lithium ion battery waste, a crushing process for crushing the lithium ion battery waste after the heat treatment process to obtain crushed material, a sieving process for separating the crushed material by sieving at least small-diameter sieved material having a relatively small particle size, large-diameter sieved material having a relatively large particle size, and medium-diameter sieved material having a particle size intermediate between the small-diameter sieved material and the large-diameter sieved material, and an eddy current sorting process for separating non-magnetic conductive material from the medium-diameter sieved material by eddy current sorting, and extracting magnetic material including at least one of cobalt and nickel as magnetic material, thereby recovering the metal from the battery powder including the small-diameter sieved material and the magnetic material.

The above-mentioned metal recovery method can effectively separate impurity metals from the medium-sized sieve fraction obtained by sieving, improving the recovery rate of cobalt and/or nickel.

FIG. 1 is a flow diagram showing a metal recovery method according to one embodiment. FIG. 2 is a flow diagram showing a metal recovery method according to another embodiment. 6 is a photograph showing an example of lithium ion battery waste before and after a heat treatment process. FIG. 2 is a schematic diagram showing an example of an eddy current separator that can be used in the eddy current separation process. 1 is a schematic diagram showing a state where a material is retained above a pulley of an eddy current separator, and a modified example of a belt for preventing this. FIG.

Hereinafter, an embodiment of the above-mentioned metal recovery method will be described in detail.
A metal recovery method in one embodiment is a method for recovering metals including at least one of cobalt and nickel from lithium ion battery waste.

As shown in Figures 1 and 2, this metal recovery method includes a heat treatment process in which lithium ion battery waste is subjected to heat treatment, a crushing process in which the lithium ion battery waste after the heat treatment process is crushed to obtain crushed material, and a sieving process in which the crushed material is separated into at least three types of sieved material having different particle sizes by sieving. The three types of sieved material separated in the sieving process are small diameter sieved material having a relatively small particle size, large diameter sieved material having a relatively large particle size, and medium diameter sieved material having a particle size intermediate between the small diameter sieved material and the large diameter sieved material. Regarding the classification of small-diameter, medium-diameter, and large-diameter sieved materials by particle size, when sieving using a sieve with lattice-shaped sieve holes with a specified side length, the sieved materials that pass through the sieve have a particle size equal to or greater than the specified side length of the sieve holes, and the sieved materials that pass through the sieve have a particle size less than the side length of the sieve holes.

If the medium-sized sieved material is included in the battery powder as is, it will increase the grade of aluminum and copper, which are impurity metals in the battery powder. On the other hand, if the medium-sized sieved material is not included in the battery powder at all, the cobalt and/or nickel contained in the medium-sized sieved material will be lost. Therefore, it is necessary to separate the aluminum and copper from the medium-sized sieved material and recover the cobalt and/or nickel, but it was not possible to sufficiently separate the aluminum and copper using a high-power magnetic separator. This is presumably because the particle size of the medium-sized sieved material is relatively small, and the magnetic cobalt and nickel get caught up in the non-magnetic aluminum and copper, resulting in insufficient separation.

In this embodiment, therefore, an eddy current sorting process is performed on the medium-sized sieved material, non-magnetic conductive materials are separated from the medium-sized sieved material by eddy current sorting, and magnetic materials containing at least one of cobalt and nickel are extracted as magnetic materials. This makes it possible to effectively separate aluminum and copper from cobalt and/or nickel. By including the magnetic materials extracted in the eddy current sorting process in the battery powder, the recovery rate of cobalt and nickel is improved. In some cases, it may also be possible to further improve the recovery rate of lithium.

(Lithium ion battery waste)
Lithium-ion battery waste can be various in-vehicle lithium-ion batteries that can be installed in vehicles such as hybrid cars, fuel cell cars, and electric cars, and that are discarded due to the scrapping of the vehicle, battery replacement, manufacturing defects, or other reasons. However, it is not limited to in-vehicle lithium-ion battery waste, and can include various lithium-ion battery waste for other purposes. Lithium-ion battery waste refers to lithium-ion batteries that are subject to recycling, and it does not matter whether the lithium-ion batteries are traded for a value, or traded free of charge or as industrial waste.

The lithium ion batteries contained in such lithium ion battery waste include a positive electrode material, a negative electrode material, an electrolyte, and an aluminum case around them. Here, the positive electrode material and the negative electrode material can be respectively formed by fixing a positive electrode active material or a negative electrode active material to a positive electrode current collector such as aluminum foil or a negative electrode current collector such as copper foil, for example, with polyvinylidene fluoride (PVDF) or other organic binders. Of these, the positive electrode active material is, for example, a single metal oxide of lithium, nickel, cobalt, and manganese, or a composite metal oxide of two or more of them. Examples of such positive electrode active materials include LiCoO ₂ , LiNiO ₂ , Li-Co-Ni-O ₂ , and Li-Co-Ni-Mn-O. It is desirable to recover the metal contained in the positive electrode active material as a valuable metal in terms of effective utilization of resources. In this embodiment, the metal contained in the positive electrode active material may change its form from the oxide by a heat treatment process or the like described below, but regardless of its form, the metal derived from the positive electrode active material (hereinafter also referred to as "positive electrode-derived metal"), at least cobalt and/or nickel, is the object of recovery. Lithium may also be recovered. In addition, carbon-based materials are often used as the negative electrode active material, and electrolytic solutions such as ethylene carbonate or diethyl carbonate are often used as the electrolyte. In addition, waste lithium-ion batteries for vehicles may include terminals containing copper and/or iron, iron cases, stainless steel cases, etc.

As shown in FIG. 3, lithium-ion battery waste for vehicles has a metal frame containing iron as the exterior skeleton, and the battery cells, which are lithium-ion batteries, are housed inside the frame. The metal constituting the frame may be iron-based. This type of lithium-ion battery waste often contains multiple battery cells, which are bundled together to form a battery module, and are further configured by connecting multiple battery modules together. In addition, lithium-ion battery waste may include a BMS (Battery Management System) that monitors each battery cell, a cooling device that cools the battery, and wires that connect them. The wires are made of metal containing copper, such as copper (Cu wire), and are connected to each battery cell and the BMS to transmit information about the temperature, voltage, etc. of each battery cell to the BMS. In addition, a resin member containing glass fiber may be provided between or around the battery cells. The glass fiber may contain calcium and/or magnesium.

(Heat treatment process)
In the heat treatment process, the lithium-ion battery waste as described above is heated in a heat treatment furnace without being dismantled. Since the lithium-ion battery waste for vehicles has a rigid structure, it is not easy to dismantle it before the heat treatment, and there is a risk of electric shock due to residual voltage if it is dismantled before the heat treatment.

Heat treatment can change the metals contained in the lithium-ion battery waste, such as lithium and cobalt, into a form that is easily dissolved by leaching with water or acid in wet processing. This also removes the electrolyte from the lithium-ion battery waste, and pulverizes the resin components that may be contained inside the frame of the lithium-ion battery waste, turning them into resin powder.

During the heat treatment, it is preferable to heat the lithium-ion battery waste at a temperature of 350°C to 650°C for 1 hour to 8 hours. As a result, the positive electrode active material in the lithium-ion battery waste may be converted to at least one of metallic cobalt (Co) and cobalt oxide (CoO). The positive electrode active material may also be converted to at least one of metallic nickel (Ni) and nickel oxide (NiO, etc.). The positive electrode active material does not exhibit magnetism, but metallic cobalt and metallic nickel do. Therefore, by adjusting the heating temperature, the magnetic material can contain the above-mentioned metallic cobalt and/or metallic nickel in the subsequent magnetic separation process and eddy current separation process, thereby improving the recovery rate of cobalt and nickel. If the heating temperature is too low, there are concerns that the decomposition of lithium metal oxide and the reduction of the nickel oxide and cobalt oxide obtained after the decomposition may be insufficient, and that organic matter such as the electrolyte may not be sufficiently removed. On the other hand, if the heating temperature is too high, the aluminum in the aluminum foil may melt, resulting in a large amount of impurities being mixed in during the wet processing. From this perspective, it is even more preferable to set the heating temperature to 400°C to 600°C.

Furthermore, if the time for which the above-mentioned heating temperature is maintained is short, the heat treatment may not be sufficient, particularly in the case of waste lithium-ion batteries for vehicles, which have a robust structure surrounded by a metal frame, and a large amount of organic matter may remain. However, if the holding time is too long, there is a concern that various components may oxidize and become brittle depending on the atmosphere, and become mixed into the battery powder as impurities. Therefore, it is more preferable to set the holding time to 2 to 9 hours. The holding time may be 6 to 9 hours or 2 to 4 hours.

The heating during roasting can be performed in, for example, an air atmosphere or an inert atmosphere, but is not limited thereto and can be performed in various atmospheres. In particular, heating in an inert atmosphere prevents the combustion of the flammable electrolyte, thereby suppressing the melting of the battery cell housing and the generation of lithium aluminate (LiAlO ₂ ). When lithium aluminate is generated, the aluminum foil becomes brittle and is easily mixed into the battery powder. On the other hand, the aluminum foil that has not reacted to lithium aluminate can be easily separated in the subsequent sieving process. Thus, heating in an inert atmosphere is preferable in that it can suppress the mixing of aluminum into the battery powder. When heating in an air atmosphere, the heating temperature may become relatively high depending on the conditions, which may cause the housing to melt and the aluminum foil to pulverize, and in addition, lithium aluminate may be generated by the reaction of the aluminum foil with the lithium metal derived from the positive electrode due to oxygen in the air, and there is a concern that these may be mixed into the battery powder. If the aluminum grade in the battery powder increases, there is a risk of increasing the loss of cobalt and nickel when removing aluminum in the subsequent wet processing. In addition, when the battery cell housing is prevented from melting by heating in an inert atmosphere, it becomes easier to remove the resin powder containing magnesium and calcium derived from the resin member in the part removal process described later. Therefore, it is preferable to heat in an inert atmosphere.

The heat treatment in an inert atmosphere may be, specifically, an atmosphere containing at least one selected from the group consisting of nitrogen, carbon dioxide, and water vapor. Among these, an atmosphere containing mainly nitrogen is preferable. The heat treatment may be performed while flowing such an inert gas. A certain amount of oxygen may be contained. When the oxygen concentration is sufficiently low, embrittlement of aluminum in the battery waste can be suppressed. If the aluminum becomes embrittled during the heat treatment, there is a concern that the separability of the aluminum may deteriorate during the sieving process described below. When an inert gas is introduced into the heat treatment furnace, the oxygen concentration in the heat treatment furnace is, for example, 0.05% to 4.00% by volume, preferably less than 1% by volume, and more preferably less than 0.1% by volume.

After heating in an inert atmosphere, it is preferable to switch the atmosphere and further heat in an air atmosphere. By heating in an air atmosphere as well, it is possible to suppress the foaming phenomenon that occurs when the battery powder is leached with acid in the subsequent wet processing leaching step. In addition, heating in an air atmosphere can also remove tar caused by resin decomposition in the heat treatment furnace or duct. However, it is important that the aluminum is oxidized to a degree that does not cause it to become embrittled.

The heat treatment furnace used to heat the lithium-ion battery waste is not particularly limited, but for example, an atmospheric electric furnace or atmospheric muffle furnace can be used for a batch type, or a roller hearth kiln or mesh belt kiln can be used for a continuous type. Among these, roller hearth kilns and pusher kilns are preferred because they are suitable for large-volume processing.

(Parts removal process)
After the heat treatment step, a parts removal step can be carried out to remove certain parts from the lithium ion battery waste.

In the parts removal process, metal (typically SUS) frames containing iron can be removed from the lithium-ion battery waste. This allows most of the iron contained in the lithium-ion battery waste to be removed, greatly reducing the amount of iron mixed into the battery powder. As a result, the load required to remove iron in wet processing can be reduced.

In addition, in the part removal process, resin powder obtained by powdering the resin components in the heat treatment process can be removed from the lithium-ion battery waste. Such resin powder may contain calcium and/or magnesium derived from glass fibers, etc. in the resin components. If calcium gets mixed into the battery powder, it can cause problems such as blockages during the solvent extraction in the subsequent wet processing. In addition, magnesium becomes an impurity in the cobalt sulfate and nickel sulfate finally obtained after the wet processing, reducing their quality. For this reason, it is preferable to remove the resin powder in the part removal process.

In addition, in the parts removal process, it is preferable to remove metal wires containing copper from the lithium-ion battery waste. Copper is also an impurity, and if it gets mixed into the battery powder, it will increase the load of the wet processing.

In the part removal process, it is also possible to remove parts other than the frame, and not remove the frame. In this case, the part removal work can be automated using a vibrating feeder, a trommel-type sieve, an air blower, etc., rather than by hand. When automated, it may be possible to remove 99.5% or more by mass of the resin powder and the metal wire containing copper. If the frame is left in the part removal process without being removed, it will be crushed in the crushing process described below, but iron originating from the frame may be mixed into the large-diameter sieved material in the sieving process. In order to remove such iron, it is desirable to perform a preliminary magnetic separation process in which iron is separated from the medium-diameter and large-diameter sieved materials by low-force magnetic separation before the eddy current separation process or the magnetic separation process, as shown in Figure 2.

(Crushing process)
In the crushing process, lithium-ion battery waste that has undergone the part removal process as necessary is crushed. This process destroys the battery cell casings and separates the positive electrode metals such as nickel and cobalt from the aluminum foil to obtain crushed material.

A variety of known crushers can be used here, but specific examples include impact crushers that apply impact while cutting the case and battery, such as a sample mill, hammer mill, pin mill, wing mill, tornado mill, and hammer crusher. A screen can be installed at the outlet of the crusher, so that the batteries are discharged from the crusher through the screen when they have been crushed to a size that can pass through the screen.

In the crushing process, for example, lithium ion battery waste with dimensions of several tens of millimeters (e.g., 120 mm x 80 mm x 10 mm) can be crushed into smaller pieces with dimensions of several tens of millimeters. When lithium ion battery waste is finely crushed in the crushing process, the aluminum foil and copper foil are reduced in size, and impurities such as aluminum and copper are easily contained in the small-diameter sieved material in the sieving process, and thus in the battery powder. The size of the screen of the crusher can be, for example, 10 mm to 30 mm.

(Sieving process)
The crushed material obtained in the above crushing step is subjected to sieving in a sieving step, and is divided into at least three types of particles having different particle sizes, that is, small-diameter particles, medium-diameter particles, and large-diameter particles.

The sieve used in this case may have a mesh size of 9.16 mm, for example. The large-diameter sieve-rejected material may be the undersize material of a sieve with a mesh size of 9.16 mm and the oversize material of a sieve with a medium mesh size, which will be described later, and may further include the oversize material of a sieve with a mesh size of 9.16 mm. The particle size of the large-diameter sieve-rejected material may be, for example, 1 mm or more, or 4.75 mm or more. The large-diameter sieve-rejected material may include a state in which the cobalt or nickel is not separated from the aluminum or copper, such as a sieve with cobalt or nickel still attached to the aluminum foil. The lower limit of the particle size of the sieve-rejected material, such as the large-diameter sieve-rejected material, means that when the sieve-rejected material is sieved using a sieve having a lattice-shaped sieve hole with a side length equal to the lower limit, the sieve-rejected material will be the oversize material of the sieve. On the other hand, the upper limit of the particle size of the sieved material means that when sieved through a sieve with lattice-shaped sieve holes with a side length equal to the upper limit, the sieved material will be under the sieve. The same applies to the particle size of the magnetized material and the re-crushed material described below.

As the sieve with the smallest mesh size, it is preferable to use a sieve with a mesh size of 0.425 mm or less, for example 0.25 mm. If a sieve with mesh sizes that are too large is used, impurities such as aluminum and copper tend to migrate to the small-diameter sieved material, and the amount of impurities mixed into the battery powder tends to increase. On the other hand, if the sieve has mesh sizes that are too small, nickel, cobalt, etc. will not pass through the sieve, and the recovery rate of valuable metals will decrease. Therefore, it is preferable to set the mesh size of the sieve to 0.15 mm or more. By sieving with the sieve with the smallest mesh size, the particle size of the small-diameter sieved material is preferably less than 0.25 mm, and aluminum, copper, etc. are sufficiently removed, and lithium, cobalt, nickel, etc. are contained in large amounts. The small-diameter sieved material is included in the battery powder.

Furthermore, it is preferable that the mesh size of the sieve with an intermediate mesh size is 1 mm to 4.75 mm, and in one example, 1 mm. The intermediate sieve-rejected material can be the material that falls under the medium mesh sieve and the material that remains on the sieve with the smallest mesh size. The particle size of the intermediate sieve-rejected material is, for example, 0.425 mm or more and less than 4.75 mm, and may be 0.25 mm or more and less than 4.75 mm. In intermediate sieve-rejected material of this size, cobalt and nickel are often basically separated from aluminum and copper, and they can be effectively separated in the eddy current sorting process described below. For particles with a particle size of 4.75 mm or more, eddy current sorting may be difficult.

(Eddy current sorting process)
In the eddy current sorting step, non-magnetic conductive materials are separated from the medium-sized sieved materials by eddy current sorting, and magnetic materials containing at least one of cobalt and nickel are extracted as magnetic materials.

As shown in Figure 4, for example, an eddy current separator is equipped with a belt conveyor having a belt that transports the objects (medium-sized objects in this case) and a pulley around which the belt is wound and driven to rotate. Inside the pulley is a rotor that rotates at high speed to generate a high-frequency alternating magnetic field. The rotor has alternating north and south poles arranged in the circumferential direction, and when it rotates at high speed, an alternating magnetic field is generated. When conductive metal (non-magnetic conductive material) in the objects transported by the belt passes through the alternating magnetic field, eddy currents proportional to the alternating magnetic field are generated in the metal, and the magnetic force generated by the current creates a repulsive effect with the magnetic force of the rotor, separating the metal. On the other hand, magnetic metal (magnetic material) in the objects is basically attached to the belt surface by the magnetic force of the rotor and sent to the lower side of the pulley, and when the effect of the magnetic force weakens, it falls off the belt surface.

When performing eddy current sorting, if the target material contains a large amount of iron that is easily attracted to a magnet, the iron will remain on the pulley (on the belt in this case), causing the belt to burn due to induction heating. In the embodiment shown in Figure 1, the metal frame containing iron is removed in the part removal process, and in the embodiment shown in Figure 2, the frame fragments are separated in the preliminary magnetic separation process. Therefore, in both embodiments, the medium-sized sieved material contains almost no iron, making it possible to apply eddy current sorting. Note that the metallic cobalt and metallic nickel that may be contained in the medium-sized sieved material after undergoing the heat treatment process have a smaller magnetic permeability than iron, and CoO and NiO also have a smaller magnetic permeability than iron, and furthermore, both are mixed with non-magnetic carbon, so that retention on the pulley is unlikely to occur.

The copper and aluminum contained in the medium-sized sieved material are non-magnetic conductive materials, and when the magnetic cobalt and nickel are magnetically attached to the belt surface by the magnetic force of the rotor, the repulsive force due to eddy currents is stronger than the effect of being caught in them, and they are pulled away from the belt surface. On the other hand, the cobalt and nickel contained in the medium-sized sieved material are magnetic materials, and they are attached to the belt surface by the magnetic force of the rotor, and do not separate from the belt surface even when the repulsive force due to eddy currents acts. For this reason, eddy current sorting can be used to separate the non-magnetic conductive aluminum and copper from the medium-sized sieved material, and extract the magnetic cobalt and nickel.

It is speculated that some of the copper and aluminum in the medium-sized sieved materials become caught up in the cobalt and nickel particles and adhere to the belt. The copper and aluminum caught up in this way are thought to be weakly magnetically attached to the belt surface by the magnetic force of the rotor due to the cobalt and nickel contained in them.

The particles contained in the medium-sized sieve are thought to be separated around the pulley in the following manner. First, due to the inertial force caused by the movement of the belt, particles made of copper and aluminum are separated above the pulley. Next, although the particles containing copper and aluminum and having weak magnetism do not leave the belt surface due to inertial force, they are repelled from the belt surface by the repulsive action of eddy currents above the pulley, and the copper and aluminum are separated. Next, the effect of the magnetic force weakens at the position where the belt separates from the pulley below the pulley, so of the particles that have adhered up to this point, the particles that are made up of a large proportion of copper and aluminum and have a relatively weak magnetic force fall freely from there and separate. The particles that remain on the belt surface until the end are those made of cobalt and nickel, and those that have little copper or aluminum attached to cobalt or nickel and have almost no repulsive force, and are ultimately collected as magnetic materials.

In this way, eddy current sorting, which utilizes not only the inertial force caused by the movement of the belt but also the repulsive force caused by eddy currents, is effective in separating the impurity metals aluminum and copper from medium-sized sieve-filtered material that contains relatively fine particles such as cobalt, nickel, aluminum, and copper, and in some cases can separate more than 90% by mass of aluminum and copper.

The rotor inside the eddy current separator pulley should preferably rotate at a speed between 1500 rpm and 2500 rpm. If the rotor speed is too fast, nickel and cobalt may also be repelled. On the other hand, if the rotor speed is too slow, there is a concern that copper and aluminum may not be repelled.

As shown in Figure 4, below the pulley of the eddy current separator, a partition plate is provided to guide non-magnetic conductive materials, which are separated from the medium-sized sieved materials transported around the pulley on the belt by the generation of eddy currents and free fall, and magnetic materials, which adhere to the belt surface and then fall, to different discharge outlets.

In eddy current separators, under certain conditions, such as when the belt speed is slow, cobalt and nickel can accumulate above the pulley and remain in one place, causing the amount of accumulation to gradually increase. To prevent this, it is preferable to use a belt with an uneven surface, as shown in the schematic diagram of Figure 5.

When performing eddy current sorting, the surface magnetic flux density on the pulley when the medium-sized sieved objects on the belt conveyor of the eddy current sorter pass through the pulley may be set to, for example, 2000 to 3000 gauss, typically 2500 gauss or less.

The magnetic material extracted by separating the non-magnetic conductive materials using the above-mentioned eddy current sorting has copper and aluminum removed and contains high-quality cobalt and/or nickel. If this magnetic material is included in battery powder and subjected to a wet process, the recovery rate of cobalt and/or nickel can be improved.

(Preliminary magnetic separation process)
If the frame is not removed in the part removal step as in the embodiment shown in Fig. 2, the frame made of a metal such as iron is crushed in the crushing step, and the crushed pieces may be separated into medium-sized and large-sized pieces in the screening step. In this case, it is preferable to perform a preliminary magnetic separation step before the eddy current separation step and the magnetic separation step, and remove crushed pieces such as iron from the medium-sized and large-sized pieces. Various magnetic separators can be used as long as they can recover iron as magnetic material.

In the preliminary magnetic separation process, low magnetic force separation is performed to separate ferromagnetic (high magnetic permeability) iron as magnetic material. Specifically, it is preferable to use a magnetic force with a surface magnetic flux density of, for example, 900 gauss or less, typically 350 to 550 gauss. Here, surface magnetic flux density refers to the magnetic flux density at the surface of the magnetic separator where the medium-sized or large-sized filtered items are subjected to magnetic force. For example, in a pulley-type magnetic separator in which a belt conveyer is wrapped around a magnet pulley, it is the surface magnetic flux density on the magnet pulley when the large-sized filtered items on the belt conveyer pass through the magnet pulley. The same applies to the surface magnetic flux density in the magnetic separation process described below.

(Magnetic separation process)
In the magnetic separation step, the large-diameter sieved matter is subjected to magnetic separation to separate the magnetically attached matter from the large-diameter sieved matter. Any of various known magnetic separators can be used here as long as they can separate the desired magnetically attached matter.

As shown in Figure 1, when the frames are removed from the lithium-ion battery waste in the part removal process described above, the large-diameter sieved material contains almost no iron. Therefore, in the embodiment shown in Figure 1, the above-mentioned preliminary magnetic separation process for separating iron can be omitted, and a magnetic separation process using high magnetic force separation, etc., as described below, can be performed on the large-diameter sieved material. On the other hand, in the embodiment shown in Figure 2, it is preferable to perform this magnetic separation process after the preliminary magnetic separation process.

For magnetic separation, it is preferable to use a magnetic force with a surface magnetic flux density of 5,000 gauss or more. Metallic cobalt (Co), metallic nickel (Ni), and cobalt-nickel alloys exhibit ferromagnetic properties. Therefore, if only these ferromagnetic metals are to be recovered as magnetic materials, the magnetic force used for magnetic separation may be relatively weak. On the other hand, the cobalt and nickel in the large diameter sieve include those that were not separated from the aluminum foil during the crushing process and remain attached to the aluminum foil. Since aluminum is not magnetic, aluminum foil with cobalt or nickel attached to it has weakened magnetism of the cobalt or nickel, making it difficult to magnetically attract the aluminum foil as a whole. For this reason, with a low surface magnetic flux density, it is not possible to magnetically attract the aluminum foil with cobalt or nickel attached, and the cobalt or nickel cannot be recovered. In contrast, if a strong magnetic force of 5,000 gauss or more is used as described above, the cobalt and nickel attached to the aluminum foil can also be magnetically attracted, and much of the nickel, cobalt, etc. in the large-diameter sieve can be contained in the magnetic material.

(Re-crushing process)
The magnetic material obtained in the magnetic separation step is crushed in a re-crushing step to obtain re-crushed material. Here, the magnetic material is crushed to a certain degree of fineness, and the metal derived from the positive electrode that is mainly attached to the aluminum foil is rubbed off, and the aluminum foil to which the metal derived from the positive electrode is not attached is not crushed as much as possible. For example, when the magnetic material has a particle size of about 30 mm or less, the re-crushed material may be obtained in a particle size of several mm in the re-crushing step.

In the re-crushing process, various crushers can be used as in the crushing process, but it is preferable to use a shear-type crusher. As mentioned above, this is to scrape off the metal from the positive electrode attached to the aluminum foil. If a shear-type crusher is used, either a vertical crusher or a horizontal crusher can be used to obtain similar good results. If a crusher that is only intended for fine grinding, such as a single-shaft crusher or a double-shaft crusher, is used, the aluminum foil will also be crushed, and the amount of aluminum impurities mixed in may increase. The screen size of the crusher used in the re-crushing process may be about 5 mm. The smaller the screen size, the better the peelability of cobalt, nickel, and lithium, but if it is too small, the screen may become clogged with fine aluminum pieces from the casing, and chipping (chipping) of the rotating blade may occur. The aluminum pieces are taken into the aluminum foil with the metal from the positive electrode that was rolled up in the crushing process, and are transferred to the magnetically attached side by the high magnetic force separation in the magnetic separation process.

(Re-sieving process)
After the re-crushing step, the re-crushed material obtained thereby is sieved in a re-sieving step to separate it into over-sieve material and under-sieve material.

In the re-sieving process, it is preferable to use a sieve with an opening size of 0.25 mm or less in order to screen out cobalt, nickel, etc. and screen out aluminum. This produces an undersieve material that contains a large amount of valuable metals such as cobalt and nickel. The undersieve material, together with the primary undersieve material mentioned above, is mixed into battery powder and subjected to wet processing.

(Eddy current sorting process)
The residue on the sieve may contain valuable metals such as cobalt, nickel, etc. In order to recover these valuable metals, an eddy current sorting step may be performed in which the residue on the sieve is further subjected to eddy current sorting to separate the re-magnetized material from the residue on the sieve.

This eddy current sorting process can be carried out in much the same way as the eddy current sorting process for the medium-sized sieved material described above, with the conditions adjusted appropriately so that the cobalt and nickel in the sieved material are transferred to the remagnetized material. The remagnetized material obtained can be included in the battery powder together with the small-sized sieved material and the under-sieved material. However, the remagnetized material may contain a certain amount of aluminum, and from the standpoint of suppressing the inclusion of impurities, it may be preferable not to include the remagnetized material in the battery powder. In this case, the eddy current sorting process may be omitted.

(Wet Processing)
The wet treatment can recover valuable metals and other metals from the battery powder by various known methods. For example, the battery powder can be subjected to the same wet treatment as that for consumer lithium-ion battery waste such as electronic devices to recover various metals. Specifically, the battery powder can be subjected to a leaching process for leaching out various metals in the battery powder, and a recovery process for neutralizing and/or solvent extraction of the leached solution to separate and recover the metals dissolved therein.

Next, the metal recovery method described above was experimentally implemented and its effectiveness was confirmed, which will be explained below. However, the explanation here is merely for illustrative purposes and is not intended to be limiting.

(Test Example 1)
The lithium ion battery waste was subjected to a heat treatment, crushed, and then sieved to separate the crushed material into small-diameter, medium-diameter, and large-diameter pieces. The medium-diameter pieces had a particle size of 0.25 mm to 1 mm, and the grades of the main metals (the ratio of the mass of each metal to the mass of the medium-diameter pieces (mass%)) were as shown in Table 1. The medium-diameter pieces were subjected to eddy current sorting using an eddy current sorter as shown in FIG. 4. The results are shown in Table 2.

In condition 2, the magnet (rotor) was not rotated to simulate a high-magnetic separator, and processing was performed in a state where there was no repulsive force due to eddy currents. As a result, as shown in Table 2, the separability of Cu and Al was worse than that under condition 1. This shows that eddy current separation is effective for separating and removing Cu and Al.
Also, as can be seen from Table 2, the recovery rates of Co and Ni were comparable under Condition 1 and Condition 2. Therefore, it was found that the recovery of Co and Ni is the effect of magnetic force, and the repulsive force due to eddy currents assists in the separation of Cu and Al on the upper side of the pulley.

From the above, it was found that the above-mentioned metal recovery method can effectively separate impurity metals from the medium-sized sieved material obtained by sieving, and improve the recovery rate of Co and/or Ni.

Claims (7)

A method for recovering metals including at least one of cobalt and nickel from lithium ion battery waste, comprising the steps of:
a heat treatment step of performing heat treatment on the lithium ion battery waste;
A crushing step of crushing the lithium ion battery waste after the heat treatment step to obtain crushed material;
a sieving step of separating the crushed material into at least small-diameter sieved material having a relatively small particle size, large-diameter sieved material having a relatively large particle size, and medium-diameter sieved material having a particle size intermediate between the small-diameter sieved material and the large-diameter sieved material;
and an eddy current sorting process for separating non-magnetic conductive materials from the medium-sized sieved materials by eddy current sorting and extracting the magnetic materials containing at least one of cobalt and nickel as magnetic materials,
a metal recovery method for recovering the metal from the battery powder containing the small diameter sieved matter and the magnetic matter. The metal recovery method according to claim 1, in which the eddy current sorting process uses an eddy current sorting machine having a belt of a conveyor that transports the medium-diameter sieved material and a belt conveyor pulley around which the belt is wound and driven to rotate, and a rotor that rotates at high speed inside the pulley to generate a high-frequency alternating magnetic field. The metal recovery method according to claim 2, wherein the rotation speed of the rotor inside the pulley is set to 1500 rpm to 2500 rpm during the eddy current sorting process. The metal recovery method according to any one of claims 1 to 3, wherein in the sieving step, a sieve with an opening of 0.425 mm or less and a sieve with an opening of 1 mm to 4.75 mm are used, and the crushed material is separated into at least the small-diameter sieved material, the medium-diameter sieved material, and the large-diameter sieved material. a magnetic separation step of performing magnetic separation on the large diameter sieve and extracting magnetic materials from the large diameter sieve;
A re-crushing step of crushing the magnetic material to obtain a re-crushed material; and
The method further includes a re-sieving step of separating the re-crushed material into oversize material and undersize material by sieving,
The metal recovery method according to any one of claims 1 to 3, wherein the battery powder further contains the undersize matter. The metal recovery method according to claim 5, wherein the magnetic separation step involves magnetic separation using a magnetic force with a surface magnetic flux density of 5,000 gauss or more. The metal recovery method according to claim 5, wherein in the re-sieving step, a sieve with a mesh size of 0.25 mm or less is used to separate the re-crushed material into the oversieved material and the undersieved material.

Images