Method for recovering metal

Abstract

This method for recovering a metal from lithium-ion battery waste comprises: a pretreatment step for subjecting the lithium-ion battery waste to a pretreatment including a heat treatment to obtain an Al-containing intermediate containing aluminum and lithium; a lithium leaching step for bringing the Al-containing intermediate into contact with a liquid to leach lithium in the Al-containing intermediate into the liquid, setting the pH of the liquid at the end of the lithium leaching to 7-13, and obtaining a residue and a lithium-containing solution; and an alkali leaching step for bringing the residue of the lithium leaching step into contact with an alkaline solution and leaching aluminum in the residue into the alkaline solution.

Description

Metal recovery method

[0001] This specification discloses a method for recovering metals from lithium ion battery waste.

[0002] Vehicles such as hybrid vehicles, fuel cell vehicles, and electric vehicles are equipped with an in-vehicle battery pack that supplies power to an electric motor as a drive source (see, for example, Patent Documents 1 to 6). In an in-vehicle battery pack, battery cells may be housed inside a frame that forms the skeleton of the exterior. Note that many in-vehicle battery packs are configured by bundling multiple battery cells into a battery module, and then connecting multiple battery modules together. In addition, an in-vehicle battery pack may further include a battery management system (BMS) that monitors each battery cell, a cooling device that cools the battery, wires that connect them, etc.

[0003] The battery cells of the above-mentioned automotive battery packs generally use secondary batteries, particularly nickel-metal hydride batteries, which can store electricity by charging and be used repeatedly. However, in recent years, lithium-ion batteries using lithium-transition metal composite oxides for the positive electrode have been increasingly used. Furthermore, such automotive lithium-ion batteries contain valuable metals such as cobalt. Therefore, when automotive 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 for reuse, from the perspective of effective resource utilization.

[0004] Incidentally, the process of recovering valuable metals from lithium-ion battery waste, not limited to automotive use, may include, for example, roasting the lithium-ion battery waste or other predetermined pretreatment, and wet processing of the battery powder obtained after the pretreatment.

[0005] Specifically, in the wet treatment, metals such as cobalt, nickel, manganese, lithium, aluminum, and iron in the battery powder are leached with acid to obtain a metal-containing solution containing the dissolved metals. Next, as described in Patent Document 7, for example, aluminum ions, iron ions, and manganese ions are sequentially or simultaneously removed from the metal-containing solution by neutralization or solvent extraction. Thereafter, cobalt ions and nickel ions in the metal-containing solution are separated by solvent extraction. After nickel ions are separated by extraction, a metal-containing solution containing remaining lithium ions is obtained.

[0006] JP 2006-179190 A JP 2007-172938 A U.S. Patent Application Publication No. 2007 / 0141454 JP 2007-172939 A U.S. Patent Application Publication No. 2007 / 0141455 JP 2011-198713 A International Publication No. 2018 / 181816

[0007] It is desirable to remove aluminum from lithium-ion battery waste by pretreatment, but when attempting to recover as much cobalt, nickel, etc. as possible, some of the aluminum may not be removed by pretreatment and may be contained in the battery powder together with cobalt, nickel, etc. In this case, when the metals in the battery powder are leached with acid, the aluminum is leached together with other metals such as cobalt and nickel, and is contained in the metal-containing solution as aluminum ions. When a relatively large amount of aluminum ions is contained in the metal-containing solution, it becomes difficult to sufficiently remove them.

[0008] This specification provides a metal recovery method that can effectively remove aluminum.

[0009] The metal recovery method disclosed in this specification is a method for recovering metals from lithium-ion battery waste, and includes: a pretreatment step of subjecting the lithium-ion battery waste to a pretreatment including a heat treatment to obtain an Al-containing intermediate containing aluminum and lithium; a lithium leaching step of contacting the Al-containing intermediate with a liquid to leach lithium in the Al-containing intermediate into the liquid, adjusting the pH of the liquid at the end of the lithium leaching to 7 to 13, and obtaining a residue and a lithium-containing solution; and an alkaline leaching step of contacting the residue from the lithium leaching step with an alkaline solution to leach aluminum in the residue into the alkaline solution.

[0010] According to the above metal recovery method, aluminum can be effectively removed.

[0011] Fig. 3 is a flow chart showing an example of a process including the metal recovery method of one embodiment. Fig. 4 is a flow chart showing another example of a process including the metal recovery method of one embodiment. Fig. 5 is a flow chart showing an example of a process performed on the battery powder obtained by the process of Fig. 1 or 2. Fig. 6 is a graph showing the change in leaching rate of each metal over time in lithium leaching of Example 1. Fig. 7 is a graph showing the change in leaching rate of each metal and pH over time in alkaline leaching of Example 1.

[0012] An embodiment of the above-described metal recovery method will be described in detail below. One embodiment of the metal recovery method is a method for recovering metals from lithium-ion battery waste. This method includes a pretreatment step in which lithium-ion battery waste is subjected to a pretreatment, including a heat treatment, to obtain an Al-containing intermediate containing aluminum and lithium; a lithium leaching step in which the Al-containing intermediate is brought into contact with a liquid to leach the lithium in the Al-containing intermediate into the liquid, adjusting the pH of the liquid at the end of the lithium leaching to 7 to 13, and obtaining a residue and a lithium-containing solution; and an alkaline leaching step in which the residue from the lithium leaching step is brought into contact with an alkaline solution to leach the aluminum in the residue into the alkaline solution.

[0013] In order to remove aluminum from the Al-containing intermediate, it is effective to leach the aluminum by contacting the Al-containing intermediate with an alkaline solution before the acid leaching step. However, when the Al-containing intermediate is contacted with an alkaline solution, not only the aluminum but also lithium in the Al-containing intermediate is leached into the alkaline solution, resulting in a loss of lithium.

[0014] In contrast, in this embodiment, the lithium leaching step is performed before the alkaline leaching step, and lithium is separated and recovered to a certain extent from the Al-containing intermediate in advance in the lithium leaching step, so that the amount of lithium leached into the alkaline solution in the subsequent alkaline leaching step can be reduced compared to when the alkaline leaching step is performed without the lithium leaching step.

[0015] The metal recovery method of the embodiment described herein can be carried out in the process illustrated in Figures 1 or 2. In Figure 1, lithium-ion battery waste is subjected to a pretreatment process including heat treatment, crushing, and sieving, and the resulting sieved material is treated as an Al-containing intermediate, which is then subjected to the above-mentioned lithium leaching and alkaline leaching processes as wet treatments. In Figure 2, the pretreatment process includes heat treatment, crushing, and sieving, as in Figure 1, but differs from Figure 1 in that the sieved material is separated into small-diameter, medium-diameter, and large-diameter fractions, and the medium-diameter and large-diameter fractions are further treated. The medium-diameter fraction may be subjected to the lithium leaching and alkaline leaching processes as is, or the magnetic fraction obtained by eddy current separation may be subjected to the lithium leaching and alkaline leaching processes. The large-diameter sieved material is subjected to magnetic separation, re-crushing and re-sieving, and the sieved material obtained by re-sieving is subjected to the lithium leaching step and the alkali leaching step, thereby obtaining battery powder.

[0016] To recover metals from battery powder, as shown in Fig. 3, an acid leaching process can be performed in which the battery powder is leached with acid to obtain a metal-containing solution containing various metal ions, and a metal separation process can be performed in which the metal ions are separated from the metal-containing solution. Here, each process will be described with reference to Figs. 1 to 3. However, the flows in Figs. 1 to 3 are merely examples and are not limiting.

[0017] (Lithium-ion battery waste) Lithium-ion battery waste can be various automotive lithium-ion batteries that can be installed in vehicles such as hybrid cars, fuel cell cars, and electric cars, discarded due to vehicle scrapping, battery replacement, manufacturing defects, or other reasons. However, it is not limited to automotive lithium-ion battery waste, and can also include various lithium-ion battery waste for other uses. Lithium-ion battery waste refers to lithium-ion batteries that are eligible for recycling, regardless of whether the lithium-ion batteries are traded for a value, free of charge, or treated as industrial waste.

[0018] The lithium-ion batteries contained in such lithium-ion battery waste include cathode materials, anode materials, and electrolytes, as well as the surrounding aluminum casings. The cathode materials and anode materials may be formed by adhering a cathode active material or an anode active material to a cathode current collector such as aluminum foil or an anode current collector such as copper foil, respectively, using, for example, polyvinylidene fluoride (PVDF) or other organic binders. The cathode active material may be, for example, a single metal oxide of lithium, nickel, cobalt, or manganese, or a composite metal oxide of two or more of these metals. Examples of such cathode active materials include LiCoO2, LiNiO2, Li-Co-Ni-O2, and Li-Co-Ni-Mn-O. It is desirable to recover the metals contained in the cathode active material as valuable metals in order to effectively utilize resources. The metals contained in the positive electrode active material can change form from the oxides described above by heat treatment or the like, as described below. However, regardless of their form, the metals derived from the positive electrode active material, such as cobalt, nickel, and lithium (hereinafter also referred to as "positive electrode-derived metals"), are the targets of recovery here. Carbon-based materials are often used as negative electrode active materials, and electrolytic solutions such as ethylene carbonate or diethyl carbonate are often used as electrolytes. Furthermore, automotive lithium-ion battery waste may also contain terminals containing copper and / or iron, as well as iron and stainless steel housings.

[0019] Automotive lithium-ion battery waste has a metal frame, such as iron, as the exterior framework, with lithium-ion battery cells housed within the frame. This type of lithium-ion battery waste often includes multiple battery cells, bundled together to form a battery module, and then connected to each other. The lithium-ion battery waste may also include a battery management system (BMS) that monitors each battery cell, a cooling device that cools the battery, and wires connecting them. The wires are made of a copper-containing metal, such as copper (Cu wire), and are connected to each battery cell and the BMS to transmit information (such as temperature and voltage) related to the temperature and voltage of each battery cell to the BMS. Resin members may also be provided between or around the battery cells.

[0020] Furthermore, the casing of lithium-ion battery waste typically contains an electrolyte solution, which is made by dissolving an electrolyte such as lithium hexafluorophosphate in an organic solvent, such as ethylene carbonate or diethyl carbonate.

[0021] In some of such lithium-ion battery waste, the positive electrode active material is difficult to separate from the aluminum foil. In contrast, in this embodiment, as described below, by performing an alkaline leaching process, the amount of aluminum ions mixed into the metal-containing solution obtained after the acid leaching process can be reduced. Furthermore, if a pretreatment process as described below is performed, such aluminum can be more effectively removed. In particular, the alkaline leaching process of this embodiment is effective for waste in which the positive electrode active material does not separate from the aluminum foil even after re-crushing as described below in the pretreatment process.

[0022] (Pretreatment Process) In the pretreatment process, at least heat treatment is performed on the lithium-ion battery waste. In many cases, the pretreatment process includes heat treatment, crushing, and sieving, in this order or in any order. In the example shown in FIG. 2 , after heat treatment, crushing, and sieving are performed in order, small-diameter, medium-diameter, and large-diameter particles with different particle sizes are obtained by sieving. The medium-diameter and large-diameter particles are then further processed. Regarding the particle size classification of the small-diameter, medium-diameter, and large-diameter particles, when sieving using a sieve with a lattice-shaped sieve hole with a predetermined side length, the particles that fall over the sieve have a particle size equal to or greater than the predetermined side length of the sieve hole, and the particles that fall under the sieve have a particle size less than the predetermined side length of the sieve hole. After the pretreatment step, battery powder is obtained.

[0023] In the example shown in Figures 1 and 2, the heat treatment, crushing, and sieving are performed in this order. However, for example, although not shown, the order may be crushing, heat treatment, and sieving. In other words, in this embodiment, it is sufficient to perform pretreatment including heat treatment on lithium-ion battery waste, or the heat treatment may be performed after performing treatment other than heat treatment on the lithium-ion battery waste. Furthermore, treatment other than heat treatment, crushing, and sieving may be included in the pretreatment process, such as when heat treatment, crushing, and sieving are performed after dismantling lithium-ion battery waste. For convenience of explanation, the following will be described using an example in which heat treatment, crushing, and sieving are performed in the order shown in Figures 1 and 2.

[0024] The battery powder refers to a powder obtained by subjecting lithium-ion battery waste to some kind of treatment to separate and concentrate the positive electrode material components. The battery powder may be obtained by subjecting lithium-ion battery waste to a heat treatment, and then crushing and sieving the waste as needed, to obtain a powder in which the positive electrode material components are concentrated. In this embodiment, the residue obtained after the alkaline leaching step described below also constitutes the battery powder.

[0025] The heat treatment is performed for the purpose of removing the electrolyte from the lithium-ion battery waste. The temperature at which the lithium-ion battery waste is heated during the heat treatment is not particularly important. During the heat treatment, the lithium-ion battery waste may be heated to a temperature at which the electrolyte can be removed, for example, a relatively low temperature of about 100°C or 200°C (e.g., 100°C or higher, typically 100°C to 185°C or 185°C to 350°C). Low-temperature heating may evaporate the electrolyte, leaving behind lithium hexafluorophosphate and lithium fluoride produced by decomposition of lithium hexafluorophosphate. Because lithium hexafluorophosphate and lithium fluoride are water-soluble and can be leached in an alkaline solution, it is desirable to perform a lithium leaching step before the alkaline leaching step to recover lithium from the lithium hexafluorophosphate and lithium fluoride, as in this embodiment. In addition, lithium-ion battery waste may be heated at a relatively high temperature of 300°C or higher, for example, 350°C to 650°C, particularly 400°C to 600°C, for 1 to 8 hours, either after or without low-temperature heating. High-temperature heating can decompose LiCoO2 and other substances in the positive electrode active material, producing cobalt oxide, metallic cobalt, lithium carbonate, and the like. Such heat treatment can convert cobalt, nickel, and other elements in the positive electrode active material of lithium-ion battery waste into a predetermined form that exhibits magnetism. Although the composition of the positive electrode active material changes due to heat treatment, the term "positive electrode active material" may be used herein even if the material has undergone heat treatment.

[0026] In the heat treatment, heating may be performed in, for example, an air atmosphere or an inert atmosphere, but is not limited thereto and various atmospheres may be used. The heat treatment may be performed in a reduced pressure atmosphere such as a vacuum. Heating in an air atmosphere and heating in an inert atmosphere may both be performed in any order. Preferably, after heating in an inert atmosphere, the atmosphere is switched and further heating is performed in an air atmosphere. The heat treatment furnace is not particularly limited, but for example, an atmospheric and vacuum electric furnace or an atmospheric muffle furnace can be used in the case of a batch type, or a roller hearth kiln or mesh belt kiln can be used in the case of a continuous type.

[0027] After the heat treatment, if necessary, certain parts are removed from the lithium-ion battery waste, and then the lithium-ion battery waste is crushed. This crushing process destroys the battery cell casing and separates the positive electrode metals, such as nickel and cobalt, from the aluminum foil, yielding crushed material.

[0028] Various known crushers can be used here, and specific examples include impact crushers that can crush the case and battery by applying impact while cutting them, such as a sample mill, hammer mill, pin mill, wing mill, tornado mill, hammer crusher, etc. A screen can be installed at the outlet of the crusher, and the batteries are discharged from the crusher through the screen once they have been crushed to a size that can pass through the screen.

[0029] The crushed material obtained by the above-mentioned crushing is subjected to sieving, whereby it is sieved according to its size and separated into multiple types of sieved material with different particle sizes. In the example shown in Figure 1, the over-sieved material obtained by sieving is referred to as an Al-containing intermediate, which is subjected to a lithium leaching process and an alkaline leaching process, and the residue from the alkaline leaching process is referred to as battery powder B. On the other hand, the under-sieved material may contain almost no aluminum but may contain metals derived from the positive electrode. In such cases, the under-sieved material can be referred to as battery powder A. Battery powders A and B are subjected to an acid leaching process, from which metals can be recovered.

[0030] In the example shown in Fig. 2, the crushed material is sieved to obtain at least small-diameter sieved material, medium-diameter sieved material, and large-diameter sieved material, each having a different particle size. While Fig. 2 shows three types of crushed material, it is also possible to divide the crushed material into four or more types of sieved material, including the small-diameter sieved material, medium-diameter sieved material, and large-diameter sieved material. Among these, the small-diameter sieved material, which has a relatively small particle size, may contain positive electrode-derived metals without substantially containing aluminum, and can be subjected to the acid leaching step as battery powder A.

[0031] The medium-sized sieved material may contain not only metals derived from the positive electrode but also aluminum. As described below, eddy current separation may be performed as needed to extract a magnetized material (Al-containing intermediate), followed by the lithium leaching step and the alkaline leaching step. However, this eddy current separation may be omitted, in which case the medium-sized sieved material is subjected to the lithium leaching step and the alkaline leaching step as the Al-containing intermediate. The residue after this alkaline leaching step becomes battery powder B. Alternatively, the lithium leaching step and the alkaline leaching step may be omitted, and the medium-sized sieved material or the magnetized material after eddy current separation may be used as battery powder B.

[0032] For the large-diameter sieved material, which often contains aluminum and positive electrode-derived metals, it is preferable to further perform magnetic separation, re-crushing, and re-sieving to obtain an under-sieved material from which aluminum has been separated as much as possible. The under-sieved material obtained by re-sieving can be input into the acid leaching step as battery powder C. Meanwhile, the over-sieved material obtained by re-sieving is subjected to the lithium leaching step and the alkaline leaching step. The residue after the alkaline leaching step becomes battery powder D. If the lithium-ion battery waste contains a certain amount of copper or aluminum, most of the copper and aluminum will be distributed in the over-sieved material obtained by re-sieving.

[0033] By carrying out the above-mentioned processes (crushing and sieving, eddy current sorting for the medium-sized particles, magnetic sorting for the large-sized particles, re-crushing and re-sieving) to dry-process the Al-containing intermediate to be subjected to the lithium leaching step and the alkaline leaching step described below, thereby reducing the amount of chemicals required for the alkaline solution in the alkaline leaching step, and therefore the cost of those chemicals.

[0034] When sieving the crushed material to obtain small-diameter, medium-diameter, and large-diameter sieved products, the openings of the sieves can be appropriately set taking into consideration the following points.

[0035] Since the small-diameter sieved material is used as is for battery powder A, it is desirable that the amount of impurities other than the metals to be recovered (iron, aluminum, copper, etc.) is small. When the crushed material is classified by particle size, the amount of impurities contained in the small-diameter sieved material is large. Therefore, if the mesh size of the sieve separating the small-diameter sieved material and the medium-diameter sieved material is made small to a certain extent, it is possible to prevent the quality of the impurities contained in battery powder A from increasing.

[0036] On the other hand, if the medium-sized sieved material is subjected to additional treatments or processes (such as eddy current separation, a lithium leaching process, or an alkali leaching process) after sieving, the impurities contained in the medium-sized sieved material can be removed by such treatments or processes. However, from the viewpoint of suppressing increases in processing costs, it is desirable to increase the mesh size of the sieve separating the small-sized sieved material from the medium-sized sieved material and reduce the amount of the medium-sized sieved material while ensuring that the quality of the impurities contained in the small-sized sieved material (battery powder A) is below a predetermined value. In this way, the mesh size separating the small-sized sieved material from the medium-sized sieved material can be set based on the quality of the impurities contained in the small-sized sieved material (battery powder A).

[0037] Next, the mesh size of the sieve separating the medium-sized and large-sized sieved materials can be set based on the iron content of the medium-sized sieved materials. While low-force magnetic separation, which can remove iron, may be performed on the large-sized sieved materials, as described below, low-force magnetic separation is not performed on the medium-sized sieved materials. Furthermore, if the medium-sized sieved materials contain a certain amount of iron, when eddy current separation is performed on the medium-sized sieved materials, the ferromagnetic iron will be included in the magnetic materials to be recovered. Furthermore, as mentioned above, the iron contained in the crushed materials originates from terminals and housings, and is therefore distributed on the larger particle size side. Therefore, it is desirable to appropriately set the mesh size of the sieve separating the medium-sized sieved materials from the large-sized sieved materials so that the medium-sized sieved materials do not contain more iron than the allowable amount.

[0038] In eddy current separation, which is optionally performed on the medium-sized sieved material before the lithium leaching step, non-magnetic conductive materials such as aluminum are removed from the medium-sized sieved material, and a magnetic material containing cobalt, nickel, lithium, etc. is obtained. By removing as much aluminum as possible in this way, the load on the lithium leaching step and the alkaline leaching step can be reduced.

[0039] For eddy current sorting, a known eddy current separator can be used, for example, equipped with a belt conveyor having a belt for transporting the target material (here, medium-sized sieved material) and a pulley around which the belt is wound and driven to rotate. The pulley houses a rotor that rotates at high speed to generate a high-frequency alternating magnetic field. The rotor has alternating north and south poles arranged circumferentially, and when it rotates at high speed, an alternating magnetic field is generated. When non-magnetic conductive materials among the target material being transported by the belt pass through the alternating magnetic field, eddy currents proportional to the alternating magnetic field are generated within the non-magnetic conductive materials. The magnetic force generated by these currents creates a repulsive effect with the magnetic force of the rotor, resulting in the separation of the non-magnetic conductive materials. Meanwhile, magnetic materials among the target material are essentially attracted to the belt surface by the magnetic force of the rotor, sent below the pulley, and then fall off the belt surface when the magnetic influence weakens.

[0040] The magnetized material separated from aluminum and the like by eddy current separation as described above may be subjected to a lithium leaching step. The non-magnetic conductive material separated from the magnetized material by eddy current separation contains a relatively large amount of aluminum, and although not shown in the figure, may be subjected to an alkali leaching step either after or without undergoing the lithium leaching step.

[0041] In magnetic separation of the large-diameter sieved material, for example, low-magnetic separation using a magnetic force with a relatively low surface magnetic flux density to remove iron from the large-diameter sieved material and / or high-magnetic separation using a magnetic force with a relatively high surface magnetic flux density to remove aluminum and the like can be performed. When both low-magnetic separation and high-magnetic separation are performed, high-magnetic separation can be performed after low-magnetic separation. However, if the large-diameter sieved material contains almost no iron, low-magnetic separation may be omitted. Furthermore, if metallic cobalt and the like are not produced by performing the aforementioned heat treatment at a low temperature and are almost absent in the large-diameter sieved material, high-magnetic separation may be omitted. In low-magnetic separation when low-temperature heat treatment is performed, cobalt and the like can be separated into non-magnetic materials. The non-magnetic materials obtained by low-magnetic separation of the large-diameter sieved material and / or the magnetic materials obtained by magnetic separation of the high-magnetic separation are subjected to re-crushing as described below. In the magnetic separation, various magnetic separators can be used as long as they are capable of performing the above-described magnetic separation.

[0042] In low-force magnetic separation, it is preferable to use a magnetic force with a surface magnetic flux density of 350 to 550 gauss. This is to separate ferromagnetic iron as magnetically attached material. In high-force magnetic separation, it is preferable to use a magnetic force with a surface magnetic flux density of 5,000 gauss or more. This is to effectively recover cobalt, nickel, and lithium, some of which are attached to the aluminum foil in the large-diameter sieved material, as magnetically attached material. This also allows aluminum foil to be effectively removed without cobalt or other elements attached. The surface magnetic flux density refers to the magnetic flux density at the surface of the magnetic separator where the medium-diameter or large-diameter sieved material is subjected to magnetic force. For example, in a pulley-type magnetic separator in which a belt conveyor is wrapped around a magnetic pulley, this is the surface magnetic flux density on the magnetic pulley when the large-diameter sieved material on the belt conveyor passes through the magnetic pulley.

[0043] The magnetized material obtained by magnetic separation (high magnetic separation) is crushed in a re-crushing process to produce re-crushed material. Here, the magnetized material is crushed to a certain degree of fineness, and the positive electrode-derived metals that are mainly attached to the aluminum foil are rubbed off, while the aluminum foil to which the positive electrode-derived metals are not attached is minimized in crushing.

[0044] The re-crushed material is then re-sieved to separate it into an oversized material containing aluminum and an undersized material containing cobalt, nickel, lithium, etc. The undersized material obtained by re-sieving has a sufficiently reduced aluminum content and can be subjected to the acid leaching step as battery powder C. On the other hand, the oversized material obtained by re-sieving can be subjected to the lithium leaching step and the alkaline leaching step as an Al-containing intermediate. The residue obtained after the lithium leaching step and the alkaline leaching step for this oversized material or magnetized material becomes battery powder D, which is then subjected to the acid leaching step.

[0045] As shown by the dashed arrow in Figure 2, it is also possible to collectively subject the medium-sized sieved material and the large-sized sieved material to the above-mentioned magnetic separation (low-magnetic separation) without separating them, and then carry out the subsequent steps.

[0046] (Lithium leaching step) In the lithium leaching step, the Al-containing intermediate obtained in the pretreatment step is brought into contact with a liquid by, for example, immersing and stirring the liquid, and lithium in the Al-containing intermediate is selectively leached into the liquid. The liquid used has a pH of 7 to 13 after contact with the Al-containing intermediate.

[0047] By carrying out the lithium leaching step prior to the subsequent alkaline leaching step, the lithium in the Al-containing intermediate can be leached into a liquid and recovered, thereby suppressing the loss of lithium that would otherwise be leached together with aluminum in the alkaline leaching step.

[0048] The liquid to be contacted with the Al-containing intermediate in the lithium leaching step is not particularly limited as long as it has a pH of 7 to 13 at the end of lithium leaching. The pH before contact with the Al-containing intermediate may be less than 7. The pH of the liquid before contact with the Al-containing intermediate may be 2 to 10. The pH here refers to the value measured at room temperature (typically 20°C). If the liquid temperature is higher, the pH is the pH measured when the liquid has cooled to room temperature. The liquid is typically water, and specific examples include tap water, industrial water, distilled water, purified water, ion-exchanged water, pure water, and ultrapure water. The liquid temperature during contact between the Al-containing intermediate and the liquid may be 10 to 80°C. The pulp concentration may be 25 g / L to 450 g / L. This pulp concentration refers to the ratio of the dry weight (g) of the Al-containing intermediate to the amount (L) of the liquid to be contacted with the Al-containing intermediate. The lithium leaching time may be 0.1 to 5 hours. If the lithium leaching time is too short, lithium will not be leached sufficiently, and if the lithium leaching time is too long, a large amount of LiAl2(OH)7 hydrate will be produced, which is difficult to leach in the subsequent alkaline leaching. For this reason, it is particularly preferable to carry out the lithium leaching for a time of 0.5 to 3 hours.

[0049] When water, an example of the liquid, comes into contact with the Al-containing intermediate, the pH may rise to about 11 to 12 due to the leaching of lithium carbonate and the like in the Al-containing intermediate. During lithium leaching, an acid such as sulfuric acid may be added as needed to adjust the pH. The amount of acid added can be adjusted so that the pH is 7 to 13, preferably 7 to 12, at the end of lithium leaching. If the pH is less than 7, there is a risk of cobalt and the like dissolving, and if it exceeds 12, there is a risk of aluminum and the like dissolving.

[0050] After the lithium leaching is completed, solid-liquid separation such as filtration is carried out using a known device and method such as a filter press or a thickener, thereby obtaining a lithium-containing solution containing mainly lithium ions and a residue containing aluminum and other metals such as cobalt and nickel.

[0051] Depending on the conditions (such as the quality of the Al-containing intermediate, the pulp concentration, and the leaching rate), lithium may not be leached to the desired solubility in the liquid. In this case, the liquid (lithium-containing solution) after lithium leaching may be reused for lithium leaching again, thereby reducing costs and the amount of liquid.

[0052] The lithium ion concentration of the lithium-containing solution is preferably 1.0 g / L to 2.5 g / L. The leaching rate of lithium in the lithium leaching step may be, for example, 40% to 60%. The leaching rate of lithium can be calculated by mass from the lithium grade of the Al-containing intermediate before the lithium leaching step and the lithium grade of the residue obtained in the lithium leaching step.

[0053] The lithium-containing solution can be carbonated after concentrating lithium ions by solvent extraction, for example, and then lithium carbonate can be recovered therefrom. When carbonation is performed, for example, the liquid temperature is set to 20°C to 50°C, the pH is set to 10 to 13, and a carbonate such as sodium carbonate can be added to the lithium-containing solution or carbon dioxide gas can be blown into the solution, followed by stirring. This yields lithium carbonate. Furthermore, to improve the quality of the lithium carbonate, purification may be performed. Specifically, the lithium carbonate is purified by subjecting the lithium carbonate to repulp washing and blowing carbon dioxide gas therein to dissolve the carbonic acid in the liquid, removing solid impurities by solid-liquid separation, followed by deoxidation and concentration, and then isolating and recovering high-quality lithium carbonate by solid-liquid separation.

[0054] (Alkali Leaching Step) The residue obtained in the lithium leaching step is subjected to an alkali leaching step in which aluminum is separated and removed from the residue.

[0055] In the alkaline leaching step, the residue after the lithium leaching step is brought into contact with the alkaline solution by, for example, immersing and stirring in the alkaline solution, and aluminum in the residue is leached into the alkaline solution. By leaching lithium in the lithium leaching step described above, the residue after the lithium leaching step has a relatively low lithium content. Therefore, even if a small amount of lithium is leached from the residue together with aluminum in the alkaline leaching step, the amount of leached lithium is reduced. This makes it possible to suppress lithium loss.

[0056] The alkaline solution used in the alkaline leaching step has a pH of 13.0 or more and an OH concentration of 1.0 or more before contacting with the residue. - The concentration can be 8 mol / L or less. The pH of the alkaline solution after contact with the residue is preferably maintained at 12.0 or more, more preferably 13.0 or more. -The concentration may be 8 mol / L or less. By maintaining the pH within the above range during aluminum leaching, aluminum solubility is high, and leaching can be performed in a pH range where aluminum is sufficiently dissolved, and deterioration of filterability due to high alkalinity can be prevented. From this viewpoint, the OH of the alkaline solution after contact with the residue can be reduced. - The concentration is preferably 5 mol / L or less. - By lowering the concentration to a certain extent, components such as sodium derived from the alkaline solution can be easily removed during washing after solid-liquid separation, and there is also the advantage that an increase in acid consumption in the subsequent acid leaching step due to these components can be suppressed. Examples of alkaline solutions that can be used include sodium hydroxide solution and potassium hydroxide solution. The pH mentioned above refers to a value measured at room temperature (typically 20°C). If the temperature of the alkaline solution is higher, the pH is measured when the temperature has cooled to room temperature.

[0057] The temperature of the alkaline solution used to leach aluminum from the residue in the alkaline leaching step is preferably maintained within a range of 10°C to 80°C, and more preferably within a range of 10°C to 50°C. If the liquid temperature is too high, there is a concern that reactivity will increase, resulting in the sudden generation of hydrogen or a sudden rise in the liquid temperature that will become uncontrollable. If the liquid temperature is too low, reactivity will decrease, and the alkaline separation step may take a long time. The pulp consistency can be, for example, 20 g / L to 500 g / L. This pulp consistency refers to the ratio of the dry weight (g) of the residue to the amount (L) of the alkaline solution brought into contact with the residue. The aluminum leaching time may be, for example, 0.5 hours to 3.0 hours.

[0058] Depending on the conditions (residue quality, pulp consistency, leaching rate, etc.), aluminum may not be leached to the desired solubility in the alkaline solution. In this case, the alkaline solution (aluminum leaching solution) after alkaline leaching may be reused for alkaline leaching again, thereby reducing costs and the amount of solution.

[0059] After the aluminum leaching is completed, solid-liquid separation is performed to obtain an aluminum leachate containing aluminum ions and a residue containing cobalt, nickel, etc. The aluminum ion concentration in the aluminum leachate may be, for example, 2 g / L to 60 g / L, or may be 2 g / L to 40 g / L. The residue obtained in the alkali leaching step has a lithium content of 0.5% to 8% by mass, a cobalt content of 1% to 30% by mass, a nickel content of 1% to 30% by mass, a manganese content of 1% to 30% by mass, and an aluminum content of 0.5% to 40% by mass.

[0060] In addition, aluminum may be contained in the Al-containing intermediate before the lithium leaching step in the form of Al (metal) or a trace amount of LiAlO2. LiAlO2 is thought to be generated by the heat treatment described above. When this Al-containing intermediate is subjected to the lithium leaching step, the residue after the lithium leaching step may contain Al (metal) and a trace amount of LiAlO2, LiAl2(OH)7 hydrate, etc. In the alkali leaching step, of these, LiAl2(OH)7 hydrate often does not dissolve. For this reason, a small amount of aluminum may remain in the residue after the alkali leaching step.

[0061] The residue obtained in the alkaline leaching step is battery powder (battery powders B and D in the example of FIG. 2). This battery powder can be subjected to the acid leaching step described below.

[0062] (Acid leaching step) In the acid leaching step, the battery powder is added to an acidic leaching solution such as sulfuric acid, nitric acid, hydrochloric acid, or other inorganic acid to leach metals from the residue with the acid, thereby obtaining a metal-containing solution in which various metals are dissolved.

[0063] The acid leaching step can be carried out by known methods or under known conditions, but the pH is preferably 0.0 to 2.0, and the oxidation-reduction potential (ORP, based on silver / silver chloride potential) may be 0 mV or less.

[0064] The residue remaining after acid leaching can be separated from the metal-containing solution by solid-liquid separation, such as filtration using known devices and methods, such as a filter press or thickener. Much of the copper in the battery powder may be contained in the leaching residue. This solid-liquid separation can be omitted, and the metal separation step, such as neutralization, may be performed without solid-liquid separation after the acid leaching step.

[0065] The metal-containing solution obtained in the acid leaching step may contain at least one ion selected from the group consisting of lithium ions, cobalt ions, nickel ions, manganese ions, aluminum ions, iron ions and copper ions, and typically contains cobalt ions and / or nickel ions.

[0066] The metal-containing solution obtained from the acid leaching step may have a cobalt ion concentration of 10 g / L to 50 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a manganese ion concentration of 0 g / L to 50 g / L, an aluminum ion concentration of 1.0 g / L to 20 g / L, an iron ion concentration of 0.1 g / L to 5.0 g / L, a copper ion concentration of 0.005 g / L to 0.2 g / L, and a fluoride ion concentration of 0.01 g / L to 20 g / L.

[0067] (Metal Separation Step) In the metal separation step, metals such as cobalt and nickel can be separated from the metal-containing solution by various known techniques, and necessary metals can be recovered from the metal-containing solution. Specifically, the metal-containing solution can be neutralized and / or subjected to solvent extraction, etc., to separate and recover each metal in the metal-containing solution.

[0068] The metal recovery method described above was experimentally implemented, and its effectiveness was confirmed. The following description is provided for illustrative purposes only and is not intended to be limiting.

[0069] Example 1 As shown in FIG. 2 , lithium-ion battery waste was subjected to heat treatment, crushing, and sieving. The large-diameter sieved material obtained by the sieving was then further subjected to magnetic separation, re-crushing, and re-sieving. The remaining sieved material was an Al-containing intermediate with a quality (mass %) shown in Table 1. The small-diameter sieved material obtained by the sieving was designated battery powder A. The medium-diameter sieved material obtained by the sieving was subjected to eddy current separation, and the magnetic material separated by the eddy current separation was designated battery powder B. The remaining sieved material obtained by the above re-sieving was designated battery powder C. The quality of the combination of battery powder A, battery powder B, and battery powder C was as shown in Table 2. The distribution rate is the proportion of each metal distributed in the battery powder, based on mass, when the quality of each metal contained in the wound body and electrolyte of the lithium-ion battery waste before treatment is taken as 100%.

[0070]

[0071]

[0072] Table 2 shows that battery powders A to C have relatively high distribution rates of cobalt and nickel, but as shown in Table 1, the Al-containing intermediate also contained a certain amount of cobalt, etc. In order to remove aluminum from the Al-containing intermediate and recover cobalt, etc., the following treatment was carried out.

[0073] The Al-containing intermediate was subjected to lithium leaching for 5 hours at a pulp concentration of 100 g / L and room temperature (20°C). Distilled water with a pH of 5.8 was used for lithium leaching. The changes in the leaching rates of aluminum and lithium over time are shown in Figure 4. In lithium leaching, a high lithium leaching rate is desirable from the viewpoint of suppressing lithium loss during the subsequent alkaline leaching, while a low aluminum leaching rate is desirable from the viewpoint of recovering high-purity lithium. The pH at the end of leaching was 12.7. All of the cobalt and nickel were transferred to the residue and were not leached.

[0074] As can be seen from Figure 4, lithium leaching was almost complete within one hour, and the leaching rate remained constant thereafter. A small amount of aluminum was leached.

[0075] The lithium leaching residue was then immersed in an alkaline solution to perform alkaline aluminum leaching. Here, a 50 g / L aqueous sodium hydroxide solution was used as the alkaline solution. The pulp concentration was 50 g / L, the solution temperature was room temperature (20°C), and the leaching time was 5 hours. The results are shown in the graph in Figure 5. The leaching rate was calculated assuming that the mass of each metal in the Al-containing intermediate before lithium leaching was 100%. Figure 5 also shows the change in pH over time. In alkaline leaching, a higher aluminum leaching rate is desirable because it reduces the amount of aluminum distributed in the alkaline leaching residue (battery powder D) (and the amount of aluminum carried over to the subsequent acid leaching).

[0076] As can be seen from Figure 5, the aluminum leaching rate reached 49% after one hour and gradually decreased after two hours. The lithium leaching rate was suppressed to approximately 8%. Table 3 shows the grades and distribution rates of the battery powders A to C shown in Table 2 combined with the residue (battery powder D) obtained after one hour of alkaline leaching. When this is added to the lithium in the lithium-containing solution obtained by lithium leaching, the grades and distribution rates of the recovered metals are as shown in Table 4.

[0077]

[0078]

[0079] As shown in Table 4, it was possible to recover most of the cobalt, nickel and lithium while removing some of the aluminum.

[0080] Example 2 Aluminum leaching was carried out using an alkali in the same manner as in Example 1, except that the solution temperature was 50° C. for the same residue after lithium leaching as in Example 1. As a result, one hour after the start of the alkali leaching, the aluminum leaching rate was 62%, and the lithium leaching rate was about 13%.

[0081] In the alkaline leaching, at both the liquor temperatures of 20°C in Example 1 and 50°C in Example 2, all of the cobalt and nickel were transferred to the residue and were not leached.

[0082] Table 5 shows the purities and distribution ratios of the sum of battery powders A to C shown in Table 2 and the residue (battery powder D) obtained after one hour of alkaline leaching, and Table 6 shows the purities and distribution ratios of the sum of these and the lithium in the lithium-containing solution obtained by lithium leaching.

[0083]

[0084]

[0085] As shown in Table 6, most of the cobalt, nickel and lithium could be recovered while some of the aluminum was removed.

[0086] Example 3 The same procedure as in Example 1 was repeated, except that the lithium leaching was completed after 1 hour and then the alkaline leaching was carried out. The pH at the end of the lithium leaching was 12.8.

[0087] In alkaline leaching, after 1 hour had passed since the start of leaching, the aluminum leaching rate was 55% and the lithium leaching rate was 9%. The aluminum leaching rate increased by about 5% compared to Example 1. This is thought to be because the lithium leaching time was shortened to the minimum time required for lithium leaching, thereby suppressing the formation of LiAl2(OH)7 hydrate, which is difficult to leach in alkaline leaching, during lithium leaching.

[0088] Table 7 shows the purities and distribution ratios of the sum of battery powders A to C shown in Table 2 and the residue (battery powder D) obtained after one hour of alkaline leaching, and Table 8 shows the purities and distribution ratios of the sum of these and the lithium in the lithium-containing solution obtained by lithium leaching.

[0089]

[0090]

[0091] Example 4 The same procedure as in Example 2 was repeated, except that the lithium leaching was completed in 1 hour, followed by the alkaline leaching, and the alkaline leaching was completed in 3 hours. The pH at the end of the lithium leaching was 12.2.

[0092] In alkaline leaching, after 1 hour from the start of leaching, the leaching rate of aluminum was 89% and the leaching rate of lithium was 16%. When the lithium leaching time was shortened from 5 hours to 1 hour, the leaching rates of both aluminum and lithium in alkaline leaching were higher compared to Example 2.

[0093] Table 9 shows the purities and distribution ratios of the sum of battery powders A to C shown in Table 2 and the residue (battery powder D) obtained after one hour of alkaline leaching, and Table 10 shows the purities and distribution ratios of the sum of these and the lithium in the lithium-containing solution obtained by lithium leaching.

[0094]

[0095]

[0096] Comparative Example 1 was the same as Example 2, except that lithium leaching was not performed. Table 11 shows the grades and distribution ratios of the sum of battery powders A to C shown in Table 2 and the residue (battery powder D) obtained after one hour of alkaline leaching.

[0097]

[0098] Table 11 shows that the distribution ratio of lithium is low, which is due to the loss of lithium during alkaline leaching.

[0099] From the above, it was found that the above-mentioned metal recovery method can effectively remove aluminum while suppressing lithium loss.

Claims

1. A method for recovering metals from lithium ion battery waste, comprising: a pretreatment step of subjecting the lithium ion battery waste to a pretreatment step including a heat treatment to obtain an Al-containing intermediate containing aluminum and lithium; a lithium leaching step of contacting the Al-containing intermediate with a liquid to leach lithium in the Al-containing intermediate into the liquid, adjusting the pH of the liquid at the end of the lithium leaching to 7 to 13, and obtaining a residue and a lithium-containing solution; and an alkaline leaching step of contacting the residue from the lithium leaching step with an alkaline solution to leach aluminum in the residue into the alkaline solution.

2. The metal recovery method according to claim 1, wherein the pH of the alkaline solution before contacting the residue in the alkaline leaching step is set to 13.0 or higher.

3. In the alkaline leaching step, the OH of the alkaline solution contacted with the residue is - 3. The method for recovering metals according to claim 1 or 2, wherein the concentration is 8 mol / L or less.

4. A metal recovery method according to claim 1 or 2, wherein the temperature of the alkaline solution in the alkaline leaching step is set to 10°C to 80°C.

5. A metal recovery method according to claim 1 or 2, wherein the lithium ion battery waste is heated to a temperature of 100°C or higher during the heat treatment in the pretreatment step.

6. A metal recovery method according to claim 1 or 2, wherein the pretreatment step includes crushing the lithium ion battery waste to obtain crushed material, and sieving the crushed material to obtain an undersize material and an oversize material, and the Al-containing intermediate includes the oversize material.

7. The method for recovering metals according to claim 6, further comprising an acid leaching step of leaching battery powder containing the residue obtained in the alkaline leaching step and the undersize material with an acid to obtain a metal-containing solution.

8. The metal recovery method according to claim 7, wherein the lithium ion battery waste contains cobalt and / or nickel, and the metal-containing solution obtained in the acid leaching step contains cobalt ions and / or nickel ions.

9. A metal recovery method as described in claim 6, in which the crushed material is separated by the sieving into sieve products including at least small diameter sieved products having a relatively small particle size, large diameter sieved products having a relatively large particle size, and medium diameter sieved products having a particle size intermediate between the small diameter sieved products and the large diameter sieved products.

10. A metal recovery method according to claim 9, wherein the Al-containing intermediate material comprises the medium-sized sieved material or a magnetic material obtained by subjecting the medium-sized sieved material to eddy current separation.

11. A metal recovery method as described in claim 9, wherein the pretreatment process includes magnetic separation to remove magnetic materials from the large-diameter sieved material, re-crushing to crush the magnetic materials to obtain re-crushed material, and re-sieving to sieve the re-crushed material to obtain under-sieved material and surplus-sieved material, and the Al-containing intermediate includes the surplus-sieved material.

12. A metal recovery method according to claim 1 or 2, further comprising an acid leaching step in which the battery powder containing the residue obtained in the alkaline leaching step is leached with an acid to obtain a metal-containing solution.

13. The metal recovery method according to claim 12, wherein the lithium ion battery waste contains cobalt and / or nickel, and the metal-containing solution obtained in the acid leaching step contains cobalt ions and / or nickel ions.

14. A metal recovery method according to claim 1 or 2, in which lithium is recovered from the lithium-containing solution.

15. A metal recovery method according to claim 1 or 2, wherein the lithium leaching time in the lithium leaching step is 0.5 to 3 hours.