Method for producing a precursor of lithium-ion battery cathode active material, and method for producing lithium-ion battery cathode active material

Abstract

A method for producing a precursor of a lithium ion battery positive electrode active material from lithium ion battery waste, the method comprising: an acid leaching step for leaching metals in a battery powder obtained from lithium ion battery waste with an acid so as to obtain a metal-containing solution that contains cobalt ions and / or nickel ions; a cobalt extraction step for extracting cobalt ions from the metal-containing solution that contains cobalt ions by means of solvent extraction so as to obtain a cobalt-containing solution that contains sodium ions, and / or a nickel extraction step for extracting nickel ions from the metal-containing solution that contains nickel ions by means of solvent extraction so as to obtain a nickel-containing solution that contains sodium ions; a mixing step for preparing a mixed solution that contains cobalt ions and / or nickel ions, and sodium ions with use of the cobalt-containing solution and / or the nickel-containing solution; a coprecipitation step for obtaining a composite salt that contains cobalt and / or nickel by a coprecipitation reaction by adding a complexing agent to the mixed solution and using sodium hydroxide and / or sodium carbonate as a pH adjuster; and a cleaning step for cleaning the composite salt so as to obtain a precursor.

Description

[Technical Field]

[0001] This specification describes a method for producing a precursor for lithium-ion battery cathode active material from lithium-ion battery waste, and a method for producing lithium-ion battery cathode active material using the precursor obtained thereby. [Background technology]

[0002] To recover valuable metals from lithium-ion battery waste, for example, battery powder obtained through roasting or other predetermined dry pretreatments of lithium-ion battery waste may be subjected to wet treatment (see, for example, Patent Document 1).

[0003] In the wet process, metals such as cobalt, nickel, manganese, lithium, aluminum, and iron in the battery powder are leached with acid to obtain a metal-containing solution in which these metals have dissolved. Next, if necessary, aluminum and iron are removed from the metal-containing solution by neutralization, and then the aluminum, manganese, cobalt, nickel, etc. dissolved in the metal-containing solution are separated from the metal-containing solution by solvent extraction. The cobalt-containing solution and nickel-containing solution obtained by separating cobalt and nickel from the metal-containing solution, respectively, may be subjected to crystallization treatment to recover them as cobalt salts and nickel salts. After that, lithium is recovered from the lithium-containing solution in which lithium has dissolved and remained. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2018 / 181816 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, when using cobalt and / or nickel recovered from lithium-ion battery waste as described above in the production of a precursor for lithium-ion battery cathode active material, it is conceivable to dissolve the above-mentioned cobalt salt and / or nickel salt in a liquid, mix in manganese or the like, and then apply the so-called coprecipitation method to the mixed solution. However, this method cannot be said to be simple in terms of process, as it involves redissolving the cobalt salt or nickel salt that has been precipitated by crystallization treatment after solvent extraction.

[0006] To address this, omitting the crystallization process and using the cobalt-containing solution and / or nickel-containing solution obtained by solvent extraction directly to prepare the mixed solution simplifies the process, but sodium that was removed during the crystallization process is introduced into the mixed solution. Furthermore, when a pH adjuster is used during coprecipitation, the resulting precursor contains impurities derived from both the pH adjuster and sodium introduced from the cobalt-containing solution and / or nickel-containing solution.

[0007] This specification provides a method for producing a precursor for lithium-ion battery cathode active material, which allows for the production of a precursor from lithium-ion battery waste with suppressed contamination of impurities other than sodium, while using a somewhat simplified process, and also provides a method for producing lithium-ion battery cathode active material. [Means for solving the problem]

[0008] The method for producing a precursor of lithium-ion battery positive electrode active material described in this specification is a method for producing a precursor of lithium-ion battery positive electrode active material from lithium-ion battery waste, comprising: an acid leaching step of leaching metal in battery powder obtained from lithium-ion battery waste with acid to obtain a metal-containing solution containing cobalt ions and / or nickel ions; a cobalt extraction step of extracting cobalt ions from the metal-containing solution containing cobalt ions by solvent extraction to obtain a cobalt-containing solution containing sodium ions, and / or a nickel extraction step of extracting nickel ions from the metal-containing solution containing nickel ions by solvent extraction to obtain a nickel-containing solution containing sodium ions; a mixing step of preparing a mixed solution containing cobalt ions and / or nickel ions and sodium ions using the cobalt-containing solution and / or nickel-containing solution; a coprecipitation step of using sodium hydroxide and / or sodium carbonate as pH adjusters and adding a complexing agent to the mixed solution to obtain a complex salt containing cobalt and / or nickel by a coprecipitation reaction; and a washing step of washing the complex salt to obtain a precursor.

[0009] A method for producing a lithium-ion battery positive electrode active material described in this specification is a method for producing a lithium-ion battery positive electrode active material using a precursor produced by the method for producing a lithium-ion battery positive electrode active material described above, comprising: a lithium salt production step of obtaining a lithium salt from at least a portion of the lithium-containing solution obtained after the cobalt extraction step and / or nickel extraction step; and a calcination step of mixing the precursor obtained in the coprecipitation step with the lithium salt obtained in the lithium salt production step, and heating and calcining the resulting mixture. [Effects of the Invention]

[0010] According to the above-described method for producing the precursor of lithium-ion battery positive electrode active material, the process is somewhat simplified, and compared to cases where pH adjusters other than sodium hydroxide and sodium carbonate are used, it is possible to produce a precursor from lithium-ion battery waste with suppressed contamination of impurities other than sodium. [Brief explanation of the drawing]

[0011] [Figure 1] This is a flowchart showing the preceding steps in a method for producing a precursor of a lithium-ion battery positive electrode active material according to one embodiment of this invention. [Figure 2] This is a flowchart showing the subsequent steps following Figure 1. [Figure 3] This is a flowchart illustrating an example of a pretreatment process for obtaining battery powder from lithium-ion battery waste. [Figure 4] This flowchart shows an example of a treatment that can be performed on a cobalt-containing solution. [Figure 5] This is a flowchart showing an example of a treatment that can be performed on nickel-containing solutions. [Figure 6] This is a flowchart illustrating a method for producing lithium-ion battery cathode active material from a precursor. [Modes for carrying out the invention]

[0012] Embodiments of this invention will be described in detail below. A method for producing a precursor of lithium-ion battery positive electrode active material (hereinafter simply referred to as "positive electrode active material") according to one embodiment is a method for producing a precursor of positive electrode active material from lithium-ion battery waste, and as shown in Figures 1 and 2, includes an acid leaching step, a neutralization step, a manganese extraction step, a cobalt extraction step, a nickel extraction step, a mixing step, a coprecipitation step, and a washing step.

[0013] In the acid leaching process, a metal-containing solution containing cobalt ions and / or nickel ions is obtained by leaching metals from battery powder obtained from lithium-ion battery waste with acid. In the cobalt extraction process, a cobalt-containing solution is obtained by extracting cobalt ions from the metal-containing solution containing cobalt ions by solvent extraction. In the nickel extraction process, a nickel-containing solution is obtained by extracting nickel ions from the metal-containing solution containing nickel ions by solvent extraction. After the acid leaching process and before the cobalt extraction or nickel extraction process, a neutralization process or manganese extraction process, as described later, may be performed as needed, but the neutralization process and / or manganese extraction process may be omitted. When both the cobalt extraction process and the nickel extraction process are performed, the cobalt-containing solution and the nickel-containing solution can be used in the mixing process, as shown in Figure 2. When at least one of the cobalt extraction process or the nickel extraction process is performed, only one of the resulting cobalt-containing solution or nickel-containing solution can be used in the mixing process.

[0014] In the mixing step, a mixed solution containing cobalt ions and / or nickel ions is prepared using a cobalt-containing solution and / or a nickel-containing solution. Subsequently, in the coprecipitation step, a pH adjuster and a complexing agent are added to the mixed solution, and a complex salt containing cobalt and / or nickel is produced by a coprecipitation reaction. The mixed solution may further contain manganese ions, in which case the complex salt will also contain manganese. Here, since the cobalt-containing solution and / or nickel-containing solution are used directly in the mixing step to prepare the mixed solution without performing crystallization treatment to precipitate cobalt salt from the cobalt-containing solution or crystallization treatment to precipitate nickel salt from the nickel-containing solution, the process is expected to be simplified. However, it is possible to perform a cobalt crystallization step or a nickel crystallization step on at least a portion of the remainder of the cobalt-containing solution or nickel-containing solution (see Figures 4 and 5), and use or sell the resulting cobalt salt or nickel salt for purposes other than the manufacture of the precursor.

[0015] Incidentally, the battery powder may contain sodium. This sodium is leached in the acid leaching step and contained in the metal-containing solution, and is not completely separated even after passing through the neutralization step and / or the manganese extraction step, and may be extracted together with cobalt or nickel in the cobalt extraction step or the nickel extraction step. In addition, sodium may be mixed in due to sodium hydroxide added as a pH adjuster in the neutralization step and each extraction step. At this time, the cobalt-containing solution and / or the nickel-containing solution contain sodium ions. When the mixing step is performed using such a cobalt-containing solution and / or nickel-containing solution, the mixed solution obtained in the mixing step will contain the above-mentioned sodium ions brought in. On the other hand, in this embodiment, sodium hydroxide and / or sodium carbonate is used as a pH adjuster in the coprecipitation step. In this case, the main impurity in the double salt obtained in the coprecipitation step is sodium, and no other impurity mixing of other substances occurs when other pH adjusters are used. Also here, since sodium mainly adheres to the particle surface of the double salt, etc., it can be effectively removed by performing a washing step thereafter. As a result, a precursor with a relatively low impurity content can be produced.

[0016] The battery powder used in the flow of FIG. 1 is obtained from lithium-ion battery waste. More specifically, the battery powder may be obtained by performing pretreatment steps such as roasting, crushing, and sieving on the lithium-ion battery waste as illustrated in FIG. 3. Here, the details of each step will be described according to FIGS. 1 to 3, but FIGS. 1 to 3 are illustrative and are not limited to such a specific flow.

[0017] (Lithium-ion battery waste) The lithium-ion battery waste to be targeted is a lithium-ion secondary battery that can be used in mobile phones and various other electronic devices, etc., and is discarded due to the battery product's lifespan, manufacturing defects, or other reasons. Recovering valuable metals from such lithium-ion battery waste is preferable from the perspective of effective utilization of resources. Lithium-ion battery waste refers to lithium-ion batteries that are targets for recycling, regardless of whether the lithium-ion batteries are traded at a valuable price or are traded free of charge or as industrial waste.

[0018] Lithium-ion battery waste has a casing containing aluminum as an outer packaging that wraps around it. Examples of such a casing include those made only of aluminum, those containing aluminum and iron, aluminum laminates, etc. Also, lithium-ion battery waste contains, within the above casing, a positive electrode active material composed of a single metal oxide containing lithium and one selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more of them, etc., and the positive electrode active material may include an aluminum foil (positive electrode substrate) coated and fixed with, for example, polyvinylidene fluoride (PVDF) or other organic binders. Additionally, lithium-ion battery waste may contain copper, iron, etc. Further, inside the casing of lithium-ion battery waste, there is usually an electrolyte solution in which an electrolyte such as lithium hexafluorophosphate is dissolved in an organic solvent. Examples of the organic solvent that may be used include ethylene carbonate, diethyl carbonate, etc.

[0019] (Pretreatment process) Lithium-ion battery waste is often subjected to a dry pretreatment process, although some wet treatments may be included. The pretreatment process can involve at least one of the following: roasting, crushing, and sieving. Through this pretreatment, lithium-ion battery waste becomes battery powder. The roasting, crushing, and sieving steps in the pretreatment process may be performed individually as needed, and in any order. Battery powder refers to the powder obtained by separating and concentrating the positive electrode material components from lithium-ion battery waste through some form of pretreatment. Battery powder can also be obtained by crushing and sieving lithium-ion battery waste, with or without heat treatment, to concentrate the positive electrode material components into a powder.

[0020] In roasting, the lithium-ion battery waste described above is heated. Roasting can change metals such as lithium and cobalt contained in the lithium-ion battery waste into a form that is easily soluble. During roasting, it is preferable to heat the lithium-ion battery waste and maintain it at a temperature range of, for example, 450°C to 1000°C, preferably 600°C to 800°C, for 0.5 to 4 hours. Roasting can be performed either under an atmospheric atmosphere or under an inert atmosphere such as nitrogen, or both under an atmospheric atmosphere and under an inert atmosphere may be performed in that order or in the reverse order. The roasting furnace may be batch type or continuous type; for example, a stationary furnace can be used for batch type, a rotary kiln furnace for continuous type, and various other types of furnaces can also be used.

[0021] During roasting, at least a portion of the electrolyte is removed from lithium-ion battery waste due to evaporation. In most cases, when lithium-ion battery waste is heated during roasting, the components of the electrolyte inside evaporate sequentially, starting with those with lower boiling points. When roasting is performed, the electrolyte is removed and rendered harmless, and the organic binder is decomposed, which promotes the separation of aluminum foil and positive electrode active material during the crushing and sieving processes described later. Although the composition of the positive electrode active material changes due to roasting, for convenience, it will be referred to as positive electrode active material even after roasting.

[0022] After roasting, crushing can be performed to extract positive electrode active material and other components from the lithium-ion battery waste casing. Crushing destroys the lithium-ion battery waste casing and selectively separates the positive electrode active material from the aluminum foil coated with it.

[0023] Various known devices or equipment can be used for crushing, but it is particularly preferable to use an impact-type crusher that can crush lithium-ion battery waste by applying impact while cutting it. Examples of such impact-type crushers include sample mills, hammer mills, pin mills, wing mills, tornado mills, and hammer crushers. A screen can be installed at the outlet of the crusher, so that the lithium-ion battery waste is crushed to a size that can pass through the screen and then discharged from the crusher through the screen.

[0024] After crushing the lithium-ion battery waste, sieving is performed using a sieve with an appropriate mesh size. This allows for obtaining battery powder with aluminum and copper remaining on the sieve surface, and with a certain amount of aluminum and copper removed from the bottom of the sieve.

[0025] The battery powder obtained in the pretreatment process contains nickel, cobalt, lithium, manganese, etc. For example, the cobalt content of the battery powder is 1% to 30% by mass, the nickel content is 1% to 30% by mass, the lithium content is 2% to 8% by mass, and the manganese content is 1% to 30% by mass, but this is not limited to these. The battery powder may also contain aluminum at 1% to 10% by mass, iron at 1% to 5% by mass, copper at 1% to 10% by mass, and sodium at 0.001% to 0.1% by mass.

[0026] (Acid leaching process) In the acid leaching process, an acidic leaching solution such as sulfuric acid is used to leach the metal from the battery powder. This yields a solution in which the metal from the battery powder has dissolved, as well as any remaining leaching residue. Here, the solution in which the metal from the battery powder has dissolved in it, from the end of the acid leaching process to the nickel extraction process described later, is also referred to as the metal-containing solution.

[0027] In the acid leaching process, the pH of the acidic leaching solution and the post-leaching solution may be set to less than 3.5. The oxidation-reduction potential (ORP value, based on silver / silver chloride potential) may also be 100 mV or less. After leaching is complete, solid-liquid separation may be performed to separate the leaching residue from the metal-containing solution; however, solid-liquid separation may be omitted, and the metal-containing solution containing the leaching residue may be used in the subsequent neutralization process. As a diluent to adjust the pH of the acidic leaching solution, the post-extraction solution from the nickel extraction process (a lithium-containing solution such as lithium sulfate solution) or water can be used, as described later. This allows lithium ions to circulate within the series of steps in the wet treatment process, concentrating the lithium ions in the solution within that process.

[0028] The metal-containing solution obtained in the acid leaching process may have, for example, a cobalt ion concentration of 5 g / L to 50 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a lithium ion concentration of 2 g / L to 10 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 sodium ion concentration of 0.001 g / L to 0.1 g / L.

[0029] (neutralization process) If the metal-containing solution obtained in the acid leaching process contains aluminum ions and / or iron ions, a neutralization process can be performed after the acid leaching process. In the neutralization process, the pH of the metal-containing solution is increased, thereby causing the aluminum ions and / or iron ions to precipitate as solids, and these precipitates are separated. When the metal-containing solution contains aluminum ions and iron ions, the neutralization process preferably includes a dealuminizing step and a deiraging step. However, if the metal-containing solution does not contain aluminum ions and / or iron ions, the dealuminizing step and / or deiraging step may be omitted.

[0030] In the dealuminization stage, at least some of the aluminum ions are precipitated by increasing the pH of the metal-containing solution and then removed by solid-liquid separation. At this time, for example, if the pH is raised to the range of 4.0 to 5.0 using a pH adjusting agent at a liquid temperature of 50°C to 90°C, aluminum ions can be effectively separated while suppressing the precipitation of nickel ions and / or cobalt ions.

[0031] In the iron removal stage, an oxidizing agent is added, and then a pH adjuster is added to raise the pH to within the range of 4.0 to 5.0. This oxidizes the iron ions from divalent to trivalent, causing them to precipitate as a solid such as an oxide or iron hydroxide (Fe(OH)3), which can then be removed by solid-liquid separation. The oxidation-reduction potential (ORP value, based on silver / silver chloride potential) during oxidation is preferably 300mV to 900mV. The oxidizing agent is not particularly limited as long as it can oxidize iron ions, but manganese dioxide, positive electrode active material, and / or manganese-containing leaching residue obtained by leaching the positive electrode active material are preferred. Manganese-containing leaching residue obtained by leaching the positive electrode active material with acid may contain manganese dioxide. When the above-mentioned positive electrode active material is used as the oxidizing agent, a precipitation reaction occurs in which manganese ions in the liquid become manganese dioxide, and the precipitated manganese can be removed together with the iron.

[0032] Examples of pH adjusting agents used in neutralization steps such as the aluminum removal and iron removal steps described above include solid or liquid lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia. Among these, lithium hydroxide is preferred because it can prevent contamination of the lithium hydroxide recovered in the crystallization step described later with sodium and other substances. A lithium hydroxide solution obtained by hydroxylating the lithium-containing solution after the nickel extraction step described later can be used as the pH adjusting agent, thereby circulating lithium ions throughout the series of steps.

[0033] (Manganese extraction process) After the neutralization step described above, the metal-containing solution can be removed by solvent extraction in the manganese extraction step, if necessary, to extract the manganese ions. In this step, if aluminum ions remain in the metal-containing solution, not only the manganese ions but also the aluminum ions will be extracted and removed. However, the manganese extraction step may be omitted.

[0034] For the extraction of manganese ions, it is preferable to use an extractant containing a phosphate ester extractant. A specific example of a phosphate ester extractant is di-2-ethylhexyl phosphate (abbreviation: D2EHPA, for example, trade name: DP8R). Alternatively, the extractant may be a mixture of a phosphate ester extractant and an oxime extractant. In this case, the oxime extractant is preferably an aldoxime or one whose main component is an aldoxime. Specifically, examples include 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecylsalicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), and 5-nonylsalicylaldoxime (trade name: ACORGAM5640).

[0035] The extractant may be diluted with a hydrocarbon-based organic solvent such as aromatic, paraffinic, or naphthenic solvent to a concentration of 10% to 30% by volume, and this diluted solvent may be used as the solvent.

[0036] During extraction, the equilibrium pH is preferably set to 2.3 to 3.5, more preferably 2.5 to 3.0. A lithium hydroxide solution is preferred as the pH adjusting agent used at this time; for example, a lithium hydroxide solution obtained by hydroxylation treatment of the lithium-containing solution after the nickel extraction step described later can be used.

[0037] A mixer-settler may be used for extraction. In this case, first, the pH is adjusted, for example by adding a pH adjuster to the solvent. Then, the metal-containing solution (aqueous phase) and the solvent (organic phase) are mixed in the mixer to form a mixture, which is then stirred for, for example, 5 to 60 minutes. During this time, the target metal ions, such as manganese ions, in the metal-containing solution migrate to the solvent. The extraction temperature should be room temperature (around 15 to 25°C) to 60°C or lower, and is preferably 35 to 45°C due to the extraction rate, phase separation, and evaporation of the organic solvent. After that, the mixture is allowed to stand in the settler, and the aqueous phase and organic phase are separated based on their specific gravity difference. This yields the extracted solution from which the solvent has been separated. Extractions in processes other than manganese extraction can be carried out in substantially the same manner.

[0038] For extraction, it is desirable to use a counter-flow multi-stage extraction method in which the flow directions of the aqueous phase and solvent used in each extraction are reversed. This method suppresses the extraction of cobalt ions, nickel ions, and lithium ions while increasing the extraction rate of manganese ions. When using a counter-flow multi-stage extraction method, it is effective to set the equilibrium pH during the first extraction stage to a value within the range mentioned above, and then lower the equilibrium pH during each subsequent extraction stage.

[0039] In the metal-containing solution after the manganese extraction process, for example, the cobalt ion concentration may be 0 g / L to 50 g / L, the nickel ion concentration 0 g / L to 50 g / L, the lithium ion concentration 1 g / L to 30 g / L, and the sodium ion concentration 0.001 g / L to 0.1 g / L.

[0040] (Cobalt extraction process) For example, if cobalt ions are present in the metal-containing solution after the manganese extraction process, a cobalt extraction process can be performed to extract and separate the cobalt ions from the metal-containing solution using solvent extraction.

[0041] For the extraction of cobalt ions, it is preferable to use a solvent containing a phosphate-based extractant, particularly a phosphonic acid ester extractant. In particular, 2-ethylhexyl 2-ethylhexylphosphonate (trade names: PC-88A, Ionquest801) is preferred from the viewpoint of separation efficiency between nickel ions and cobalt ions. The extractant can be diluted with a hydrocarbon-based organic solvent to a concentration of 10% to 30% by volume and used as the solvent.

[0042] When extracting cobalt ions, the equilibrium pH during extraction should preferably be 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is lower than 5.0, there is a risk that the cobalt ions may not be sufficiently extracted into the solvent. In this case, it is preferable to use a lithium hydroxide solution as the pH adjusting agent, for example, a lithium hydroxide solution obtained by hydroxylation treatment of the lithium-containing solution after the nickel extraction step described later can be used.

[0043] When extracting cobalt ions, it is desirable to use a counter-flow multi-stage extraction method in which the flow directions of the aqueous phase and solvent used in each extraction are reversed. This method suppresses the extraction of nickel ions and lithium ions while increasing the extraction rate of cobalt ions.

[0044] During the extraction process described above, not only cobalt ions but also small amounts of nickel and lithium ions may be extracted into the solvent. In this case, if necessary, the solvent from which the cobalt ions were extracted may be scrubbed once or more times using a scrubbing solution to remove any nickel and lithium ions that may be present in the solvent. The scrubbing solution can be, for example, a sulfuric acid solution with a pH of 3.5 to 5.5. The post-scrubbing solution may contain nickel and lithium ions. Therefore, it is desirable to mix part or all of the post-scrubbing solution with the metal-containing solution after the manganese extraction process and use this as the pre-extraction solution for the cobalt extraction process. This allows for the circulation or retention of nickel and lithium ions within the series of processes and concentration without loss. However, if the solvent from which the cobalt ions were extracted does not contain nickel or lithium ions, scrubbing may not be necessary.

[0045] Subsequently, back-extraction is performed using a solvent containing cobalt ions. The back-extract solution used can be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, and can be appropriately determined depending on the subsequent mixing and crystallization steps. In many cases, sulfuric acid can be used as the back-extract solution. Back-extraction is carried out under pH conditions that allow as many cobalt ions as possible to transfer from the solvent to the back-extract solution. Specifically, the pH is preferably in the range of 2.0 to 4.0, and more preferably in the range of 2.5 to 3.5.

[0046] (Nickel extraction process) If nickel ions are present in the metal-containing solution after the cobalt extraction process has extracted cobalt ions, a nickel extraction process can be performed to extract the nickel ions from the metal-containing solution using a solvent extraction method.

[0047] The solvent used in the nickel extraction process preferably contains a carboxylic acid-based extractant. Examples of carboxylic acid-based extractants include neodecanoic acid and naphthenic acid, but neodecanoic acid (such as Versatic Acid 10 (VA-10) manufactured by Shell Chemical Corporation) is preferred due to its ability to extract nickel ions. The extractant may be diluted using a hydrocarbon-based organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% to 30% by volume, and this may be used as the solvent.

[0048] The equilibrium pH during extraction is preferably 6.0 to 8.0, more preferably 6.8 to 7.2. A lithium hydroxide solution is preferred as the pH adjusting agent used at this time. For example, a lithium hydroxide solution obtained by hydroxylation treatment of the lithium-containing solution after the nickel extraction step described later can be used.

[0049] Extraction should preferably be carried out in multiple stages using a counter-flow method, where the flow directions of the metal-containing solution and the solvent are opposite. This suppresses the extraction of lithium ions into the solvent and increases the extraction rate of nickel ions. When using a multi-stage counter-flow extraction method, it is effective to set the equilibrium pH during the first extraction stage to a value within the aforementioned range, and then lower the equilibrium pH during extraction with each subsequent stage.

[0050] For solvents that have become nickel-containing after extraction, scrubbing may be performed one or more times using a scrubbing solution to remove any lithium ions that may be present in the solvent, if necessary. The scrubbing solution can be, for example, a sulfuric acid solution with a pH of 5.0 to 6.0. Here, the post-scrubbing solution may contain lithium ions. Therefore, it is desirable to mix part or all of the post-scrubbing solution with the metal-containing solution after the cobalt extraction step and use this as the pre-extraction solution for the nickel extraction step. This allows for the circulation or retention of lithium ions within the series of steps and concentration without loss. However, if the nickel-containing solvent does not contain lithium ions, scrubbing may not be necessary.

[0051] Subsequently, back-extraction is performed using a solvent containing nickel ions. The back-extract solution used can be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, and can be appropriately determined depending on the subsequent mixing and crystallization steps. In many cases, sulfuric acid can be used as the back-extract solution. In back-extraction, the pH is preferably in the range of 1.0 to 3.0, and more preferably 1.5 to 2.5. The O / A ratio and the number of times can be appropriately determined, but the O / A ratio is 5 to 1, more preferably 4 to 2.

[0052] The post-extraction solution (such as lithium sulfate solution) after nickel ions have migrated to the solvent mainly contains lithium ions and may be added to the acidic leaching solution in the acid leaching step. This allows the lithium ions contained in the post-extraction solution to be circulated throughout the series of processes.

[0053] (Mixing process) In the mixing process, a mixed solution such as a sulfuric acid solution containing cobalt ions, nickel ions, manganese ions, and sodium ions is prepared using the above-mentioned cobalt-containing solution and / or nickel-containing solution. Specifically, cobalt ions, nickel ions, and manganese ions can be mixed and prepared in a solution containing the cobalt-containing solution and / or nickel-containing solution, while adding manganese sources, cobalt sources, nickel sources, etc., as needed.

[0054] As shown in Figure 2, when using cobalt-containing solutions and nickel-containing solutions, a manganese source may be added, but a cobalt source and / or nickel source may also be added separately. When using either a cobalt-containing solution or a nickel-containing solution, a cobalt source and / or nickel source may be added in addition to the manganese source. When preparing the mixed solution, it is sufficient to use a cobalt-containing solution and / or nickel-containing solution obtained from lithium-ion battery waste as described above.

[0055] The amount of cobalt-containing solution and / or nickel-containing solution, manganese source, etc. added can be determined according to the desired composition of the precursor or cathode active material to be manufactured. For example, the amount of each solution added may be adjusted so that the molar ratio of cobalt ions, nickel ions, and manganese ions in the mixed solution is, for example, 50:20:30.

[0056] The cobalt-containing solution and / or nickel-containing solution contain sodium ions, for example, from sodium contained in lithium-ion waste or sodium hydroxide, a pH adjuster added in the previous step. In this embodiment, since the cobalt-containing solution and nickel-containing solution are used in the mixing step without crystallization of cobalt salts or nickel salts, the mixed solution contains sodium ions introduced from the cobalt-containing solution and nickel-containing solution. The sodium ion concentration of the mixed solution may be, for example, 1 mg / L to 500 mg / L.

[0057] As a manganese source, it is also possible to use a manganese-containing solution or manganese compound (i.e., a manganese source derived from lithium-ion battery waste) that can be recovered by extracting manganese ions in the manganese extraction process described above. However, the manganese-containing solution or manganese compound obtained after the manganese extraction process may contain a certain amount of aluminum. Therefore, from the viewpoint of further reducing impurities such as aluminum in the precursor, it is desirable to prepare the mixed solution using a manganese source that is not derived from lithium-ion battery waste in the mixing process.

[0058] (Co-precipitation process) In the coprecipitation step, a pH adjuster is added to the mixed solution obtained in the mixing step to adjust the pH, and a complexing agent is also added. This causes a coprecipitation reaction, in which cobalt ions, nickel ions, and manganese ions in the mixed solution precipitate to obtain a complex salt containing cobalt, nickel, and manganese. Typically, this complex salt may be a complex hydroxide containing cobalt, nickel, and manganese.

[0059] The coprecipitation reaction can be carried out under conditions commonly used in the production of cathode active material precursors. More specifically, for example, the temperature of the mixed solution can be set to 50°C to 70°C, and the pH of the mixed solution can be adjusted to 10.0 to 11.0 by adding a pH adjusting agent. In this case, the mixed solution may be stirred at a speed of 500 rpm to 1000 rpm. As complexing agents, aqueous ammonia, aqueous ammonium sulfate, aqueous ammonium chloride, etc., can be used.

[0060] Here, sodium hydroxide and / or sodium carbonate are used as pH adjusters. As a result, the impurities introduced due to the use of the pH adjuster are the same sodium as the impurities introduced from the cobalt-containing solution and / or nickel-containing solution and present in the mixed solution, as described above. This sodium then mixes into the complex salt produced by the coprecipitation reaction, but can be effectively removed in the washing step described below. If pH adjusters other than sodium hydroxide and sodium carbonate are used, the addition of such pH adjusters will introduce other impurities other than sodium into the complex salt, and even if the sodium can be removed, these other impurities may remain in the precursor.

[0061] (Washing process) The complex salt obtained in the mixing step is subjected to washing in the washing step. This washing is primarily performed to remove impurities such as sodium contained in the complex salt. Through the washing step, a precursor can be produced.

[0062] The complex salt produced in the mixing process tends to have sodium mainly attached to its particle surface. Therefore, washing the complex salt in the washing process washes away the sodium attached to its particle surface, resulting in a precursor with a sufficiently low sodium content.

[0063] For washing, for example, the complex salt can be added to a washing solution such as pure water to form a slurry, and after stirring or other operations as necessary, the complex salt can be extracted by solid-liquid separation. Such washing is not limited to a single process, but can be repeated multiple times.

[0064] The precursor obtained after the washing process may have a sodium content of, for example, 100 ppm by mass or less, and even 30 ppm by mass or less. As mentioned earlier, the use of sodium hydroxide as a pH adjuster in the coprecipitation process results in a precursor with a sufficiently reduced content of other impurities.

[0065] (Cobalt crystallization process and nickel crystallization process) The cobalt-containing solution obtained in the cobalt extraction process and the nickel-containing solution obtained in the nickel extraction process are basically used in the mixing process to produce precursors, as described above. On the other hand, it is not necessary to use all of the cobalt-containing solution or nickel-containing solution in the production of precursors. A portion of the cobalt-containing solution and / or nickel-containing solution can be used in the mixing process, and at least a portion of the remainder can be subjected to crystallization treatment by a cobalt crystallization process and / or nickel crystallization process. The resulting cobalt salt and / or nickel salt can be used for various purposes, including sale.

[0066] In the cobalt crystallization process, the cobalt-containing solution (post-extraction solution) obtained by back-extraction in the aforementioned cobalt extraction process is concentrated by heating it to, for example, 40°C to 120°C. This causes the cobalt ions to crystallize, yielding cobalt salts such as cobalt sulfate. The cobalt salts obtained in this way may have a nickel content of 5 ppm by mass or less.

[0067] The post-crystallization solution from the cobalt crystallization process may contain uncrystallized cobalt and lithium ions. It is desirable to mix such post-crystallization solution with the cobalt-containing solution used before the crystallization process and use it for a second crystallization process, to use it to adjust the cobalt ion concentration of the scrubbing solution used as the solvent for extracting cobalt ions in the cobalt extraction process, or to mix it with the metal-containing solution after the manganese extraction process and use it in the cobalt extraction process. In this way, cobalt and lithium ions can be circulated or retained and concentrated within the series of processes without loss.

[0068] Furthermore, in the nickel crystallization process, if a back-extracted solution such as nickel sulfate solution is obtained by back-extraction, the nickel-containing solution obtained as the back-extracted solution in the nickel extraction process described above, or a nickel-containing solution obtained by electrolysis and dissolution of the back-extracted solution as needed, is heated to 40°C to 120°C and concentrated. As a result, nickel ions crystallize, and nickel salts such as nickel sulfate are obtained.

[0069] The post-crystallization solution from the nickel crystallization process may contain uncrystallized nickel and lithium ions. Such post-crystallization solution is preferably mixed with the nickel-containing solution from the pre-crystallization process for further crystallization, used to adjust the nickel ion concentration in the scrubbing solution for the nickel-containing solvent, or mixed with the metal-containing solution from the cobalt extraction process for use in the nickel extraction process. In this way, nickel and lithium ions can be circulated or retained and concentrated within the series of processes without loss.

[0070] As described above, by returning the solution to the previous step and circulating lithium ions throughout the series of steps, sodium ions can also be concentrated as a result. The embodiment described here is particularly effective when sodium ions are circulated along with lithium ions throughout the series of steps, as it allows for the production of a precursor while effectively removing sodium ions in the washing step.

[0071] (Lithium salt production process) In an embodiment of the method for producing a positive electrode active material, to produce a positive electrode active material using the above-mentioned precursor, a lithium salt preparation step can be performed to obtain a lithium salt from at least a portion of the lithium-containing solution obtained after the cobalt extraction step and / or nickel extraction step (see Figure 1). Examples of lithium salts include lithium carbonate and lithium hydroxide.

[0072] When producing lithium carbonate, a carbonate such as sodium carbonate or carbon dioxide gas can be added to a lithium-containing solution, or carbon dioxide gas can be blown in to perform a carbonation treatment, thereby precipitating lithium carbonate. From the viewpoint of preventing an increase in impurities, blowing in carbon dioxide gas is preferable. After adding the carbonate or blowing in carbon dioxide gas, for example, the liquid temperature can be kept within the range of 50°C to 90°C and stirred as needed, and this temperature can be maintained for 0.5 to 2 hours.

[0073] The lithium carbonate obtained in this way may be purified by washing, dissolving, decarboxylation, etc., as needed, to increase its purity.

[0074] When producing lithium hydroxide, a lithium-containing solution can be subjected to a hydroxide treatment to obtain a lithium hydroxide solution, after which lithium hydroxide can be precipitated by crystallization. Examples of hydroxide treatments include carbonation and chemical conversion using calcium hydroxide after producing lithium carbonate, chemical conversion using barium hydroxide, and electrodialysis.

[0075] In the case of carbonation and chemical conversion methods, a lithium carbonate solution is first obtained by adding a carbonate to a lithium-containing solution or by blowing in carbon dioxide. Then, in the so-called chemical conversion method, calcium hydroxide is added to the lithium carbonate solution, and a lithium hydroxide solution can be produced according to the reaction equation Li2CO3 + Ca(OH)2 → 2LiOH + CaCO3. Calcium that may remain in the solution can be removed using cation exchange resins or chelating resins.

[0076] When using barium hydroxide, a lithium hydroxide solution can be obtained by adding barium hydroxide to a lithium-containing solution and following the reaction Li2SO4 + Ba(OH)2 → 2LiOH + BaSO4. Barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin or chelating resin.

[0077] In electrodialysis, a lithium-containing solution is placed in the desalination chamber between the anion exchange membrane and the cation exchange membrane in a bipolar membrane electrodialysis machine. Pure water is then placed in the acid chamber between the bipolar membrane and the anion exchange membrane, and in the alkaline chamber between the cation exchange membrane and the bipolar membrane, and a voltage is applied between the electrodes. As a result, lithium in the metal-containing solution in the desalination chamber moves to the alkaline chamber, where the pure water is decomposed into hydroxide ions by the bipolar membrane, yielding a lithium hydroxide solution. Anions of inorganic acids such as sulfuric acid in the metal-containing solution in the desalination chamber pass through the anion exchange membrane and move to the acid chamber.

[0078] The crystallization of lithium hydroxide can be performed by heating and concentrating the lithium hydroxide solution or by vacuum distillation. In the case of heating and concentrating, a higher temperature during crystallization is preferable as it speeds up the process. However, after crystallization, the temperature at which the crystallized material is dried should preferably be below 60°C to prevent the desorption of water of crystallization. This is because anhydrous lithium hydroxide from which water of crystallization has been desorbed is hygroscopic and difficult to handle. Subsequently, the lithium hydroxide can be subjected to grinding or other treatments to adjust it to the desired physical properties.

[0079] (Firing process) In the calcination process, the precursor obtained in the aforementioned coprecipitation process and a lithium salt such as lithium carbonate or lithium hydroxide obtained in the lithium salt production process above are mixed by kneading or other means, and the mixture is heated and calcined.

[0080] Here, for example, the mixture can be heated in an atmospheric environment at a temperature of 450°C to 900°C for 8 to 12 hours. When lithium carbonate is used as the lithium salt, it may be heated at 720°C to 780°C for 2 hours, followed by heating at 860°C to 900°C for 8 hours, totaling approximately 24 hours including the heating and cooling times. When lithium hydroxide is used as the lithium salt, it may be heated at 450°C to 550°C for 8 hours, followed by heating at 860°C to 900°C for 4 hours, totaling approximately 24 hours including the heating and cooling times.

[0081] After the firing process, crushing and other processes are performed as necessary. For example, Li[Ni a Co b Mn (1-a-b) O2 (NCM) or Li[Ni a Co b Al (1-a-b) (NCA) ternary system, or Li[Ni a Co b Mn c Al (1-a-b-c) (NCMA) quaternary system and other cathode active materials can be produced.

Example

[0082] Next, the above-described methods for manufacturing the precursor and the cathode active material were experimentally implemented to produce the precursor and the cathode active material, which will be described below. However, the description here is for the purpose of mere exemplification and is not intended to be limited thereto.

[0083] (Manufacturing Method) In the example, as shown in FIG. 1, neutralization, manganese extraction, cobalt extraction, and nickel extraction were sequentially performed on the metal-containing solution obtained by leaching the battery powder of lithium-ion battery waste with an acid, to obtain cobalt sulfate solution as a cobalt-containing solution and nickel sulfate solution as a nickel-containing solution, respectively.

[0084] Then, as shown in FIG. 2, a cobalt sulfate solution and a nickel sulfate solution (recycled solution) were mixed while adding a manganese source to prepare a mixed solution (sulfuric acid-based raw material), and sodium hydroxide as a pH adjuster and aqueous ammonia as a complexing agent were added thereto to cause a coprecipitation reaction, and the composite hydroxide containing cobalt, nickel, and manganese was purified. In the coprecipitation reaction, the liquid temperature was 60 °C, the pH was 10.2, and stirring was performed at 1000 rpm. Thereafter, the composite hydroxide was washed with pure water to produce the precursor.

[0085] Subsequently, the precursor was mixed with lithium carbonate obtained in the lithium salt preparation shown in Figure 1, and the mixture was heated in an air atmosphere at a temperature of 720°C to 900°C for 10 hours. This produced the cathode active material.

[0086] In the comparative example, the cobalt sulfate solution and nickel sulfate solution obtained by cobalt extraction and nickel extraction, respectively, as shown in Figures 4 and 5, were crystallized to obtain cobalt sulfate and nickel sulfate (recycled sulfate). These cobalt sulfate and nickel sulfate solutions were dissolved in pure water, and a manganese source was added to prepare a mixed solution (sulfuric acid-based raw material). From there, the precursor and cathode active material were produced in the same manner as in the example.

[0087] (evaluation) In this example, crystallization and redissolution of cobalt and nickel after extraction were not performed as in the comparative example, so the process can be said to be simpler compared to the comparative example.

[0088] Table 1 shows the content of impurities in the mixed solution (sulfuric acid-based raw material) prepared from the recycled liquid in the example, the mixed solution (sulfuric acid-based raw material) prepared from the recycled sulfate in the comparative example, and the precursor and cathode active material obtained in the example and comparative example. The impurity components of the mixed solution were measured by ICP-MS. For the precursor and cathode active material, the impurity components (except K) were measured by ICP-MS, and K was measured by atomic absorption spectrometry. Here, the samples were dissolved in aqua regia as a pretreatment.

[0089] [Table 1]

[0090] Table 1 shows that the sodium content of the precursor and cathode active material in the examples was similar to or lower than that of the comparative examples. This is presumed to be due to the effective removal of sodium during washing after coprecipitation.

[0091] Furthermore, the average particle size (D50), tap density (TAP), and BET specific surface area (BET) of each precursor obtained in the examples and comparative examples were confirmed. The average particle size was measured by laser diffraction / scattering. The tap density was measured according to JIS Z2512:2012. The BET specific surface area was measured by the BET method. These results are shown in Table 2. Table 2 also includes SEM images of each precursor.

[0092] [Table 2]

[0093] As shown in Table 2, the precursors of the examples had sufficiently small particle sizes and were comparable to the precursors of the comparative examples in terms of tap density and BET specific surface area.

[0094] From the above, it was found that, according to the manufacturing method described above, a precursor with a suppressed increase in impurity content can be produced from lithium-ion battery waste, even with a simplified process.

Claims

1. A method for producing a precursor for lithium-ion battery cathode active material from lithium-ion battery waste, An acid leaching step involves leaching metals from battery powder obtained from lithium-ion battery waste with acid to obtain a metal-containing solution containing cobalt ions and / or nickel ions, A cobalt extraction step of extracting cobalt ions from the metal-containing solution containing cobalt ions by solvent extraction to obtain a cobalt-containing solution containing sodium ions, and / or a nickel extraction step of extracting nickel ions from the metal-containing solution containing nickel ions by solvent extraction to obtain a nickel-containing solution containing sodium ions. A mixing step of preparing a mixed solution containing cobalt ions and / or nickel ions and sodium ions using the aforementioned cobalt-containing solution and / or nickel-containing solution, A coprecipitation step is performed in which sodium hydroxide and / or sodium carbonate are used as pH adjusters in the mixed solution, and a complexing agent is added, and a complex salt containing cobalt and / or nickel is obtained by a coprecipitation reaction. A washing step to wash the aforementioned complex salt to obtain a precursor, A method for producing a precursor of lithium-ion battery cathode active material, including [the specified element].

2. The mixed solution contains manganese ions, and the complex salt contains manganese. A method for producing a precursor of lithium-ion battery cathode active material according to claim 1, wherein in the mixing step, a manganese source not derived from lithium-ion battery waste is added to produce the mixed solution.

3. A portion of the cobalt-containing solution and / or nickel-containing solution is subjected to the mixing step. A method for producing a precursor of a lithium-ion battery cathode active material according to claim 1, comprising a cobalt crystallization step of subjecting at least a portion of the remainder of the cobalt-containing solution to a crystallization treatment to obtain a cobalt salt, and / or a nickel crystallization step of subjecting at least a portion of the remainder of the nickel-containing solution to a crystallization treatment to obtain a nickel salt.

4. A method for producing a lithium-ion battery cathode active material using a precursor produced by the method for producing a lithium-ion battery cathode active material precursor described in claim 1 or 2, A lithium salt preparation step, comprising obtaining a lithium salt from at least a portion of the lithium-containing solution obtained after the cobalt extraction step and / or nickel extraction step, A calcination step is performed in which the precursor obtained in the coprecipitation step is mixed with the lithium salt obtained in the lithium salt production step, and the resulting mixture is heated and calcined. A method for producing a lithium-ion battery cathode active material, including [the specified element].

5. The method for producing a lithium-ion battery cathode active material according to claim 4, wherein the lithium salt is lithium carbonate or lithium hydroxide.

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