Method for producing precursor of lithium ion battery positive electrode active material, and method for producing lithium ion battery positive electrode 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

Method for producing a precursor of a positive electrode active material for a lithium ion battery and method for producing a positive electrode active material for a lithium ion battery

[0001] This specification describes a method for producing a precursor of a lithium ion battery positive electrode active material from lithium ion battery waste, and a method for producing a lithium ion battery positive electrode active material using the precursor obtained thereby.

[0002] To recover valuable metals from lithium-ion battery waste, for example, the lithium-ion battery waste may be roasted or subjected to other predetermined dry pretreatments to obtain battery powder, which may then 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 the metals are dissolved. Next, if necessary, aluminum and iron are removed from the metal-containing solution by neutralization, and then the aluminum, manganese, cobalt, nickel, and other metals 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 are sometimes subjected to crystallization treatment to recover cobalt salts and nickel salts, respectively. Lithium is then recovered from the lithium-containing solution in which lithium has dissolved and remained.

[0004] International Publication No. 2018 / 181816

[0005] When cobalt and / or nickel recovered from lithium-ion battery waste as described above are used to produce a precursor of a lithium-ion battery positive electrode active material, it is conceivable to dissolve the cobalt salt and / or nickel salt in a liquid, mix manganese, etc., thereto, and then apply a so-called coprecipitation method to the resulting mixed solution. However, this method is not particularly simple because the cobalt salt and / or nickel salt that were once precipitated by crystallization treatment after solvent extraction must be re-dissolved.

[0006] To address this issue, the crystallization process can be omitted and the cobalt-containing solution and / or nickel-containing solution obtained by solvent extraction can be used directly to prepare the mixed solution. This simplifies the process, but the sodium removed by the crystallization process is carried over to the mixed solution. Furthermore, a pH adjuster is used during coprecipitation by the coprecipitation method, and the precursor obtained thereby contains both substances derived from the pH adjuster and sodium carried over from the cobalt-containing solution and / or nickel-containing solution as impurities.

[0007] This specification provides a method for producing a precursor of a positive electrode active material for a lithium ion battery, which can produce a precursor from lithium ion battery waste with reduced contamination of impurities other than sodium while using somewhat simplified steps, and a method for producing a positive electrode active material for a lithium ion battery.

[0008] The method for producing a precursor of a lithium-ion battery positive electrode active material described in this specification is a method for producing a precursor of a lithium-ion battery positive electrode active material from lithium-ion battery waste, and includes the following steps: an acid leaching step of leaching metals in battery powder obtained from the 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 using the cobalt-containing solution and / or the nickel-containing solution to prepare a mixed solution containing cobalt ions and / or nickel ions and sodium ions; a coprecipitation step of using sodium hydroxide and / or sodium carbonate as a pH adjuster and adding a complexing agent to the mixed solution to obtain a composite salt containing cobalt and / or nickel by a coprecipitation reaction; and a washing step of washing the composite salt to obtain a precursor.

[0009] One 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 above-mentioned method for producing a precursor of a lithium ion battery positive electrode active material, and includes a lithium salt production step of obtaining a lithium salt from at least a part of the lithium-containing solution obtained after the cobalt extraction step and / or the 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 obtained mixture.

[0010] According to the above-described method for producing a precursor of a lithium-ion battery positive electrode active material, it is possible to produce a precursor from lithium-ion battery waste with reduced contamination of impurities other than sodium, while using a somewhat simplified process, as compared to the case where a pH adjuster other than sodium hydroxide and sodium carbonate is used.

[0011] Fig. 1 is a flow chart showing the first step in a method for producing a precursor of a lithium ion battery positive electrode active material according to one embodiment of the present invention. Fig. 2 is a flow chart showing the second step following Fig. 1. Fig. 3 is a flow chart showing an example of a pretreatment step for obtaining battery powder from lithium ion battery waste. Fig. 4 is a flow chart showing an example of a treatment that can be performed on a cobalt-containing solution. Fig. 5 is a flow chart showing an example of a treatment that can be performed on a nickel-containing solution. Fig. 6 is a flow chart showing a method for producing a lithium ion battery positive electrode active material from a precursor.

[0012] An embodiment of the present invention will be described in detail below. A method for producing a precursor of a 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 a positive electrode active material from lithium ion battery waste, and 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, as shown in Figures 1 and 2.

[0013] In the acid leaching process, metals in battery powder obtained from lithium-ion battery waste are leached with acid to obtain a metal-containing solution containing cobalt ions and / or nickel ions. In the cobalt extraction process, cobalt ions are extracted from the metal-containing solution containing cobalt ions by solvent extraction to obtain a cobalt-containing solution. In the nickel extraction process, nickel ions are extracted from the metal-containing solution containing nickel ions by solvent extraction to obtain a nickel-containing solution. After the acid leaching process, a neutralization process or manganese extraction process (described below) may be performed as needed before the cobalt extraction process or nickel extraction process, 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 each be used in the mixing process, as shown in FIG. 2 . When at least one of the cobalt extraction process or the nickel extraction process is performed, only one of the cobalt-containing solution or the nickel-containing solution obtained thereby 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. Then, in the coprecipitation step, a pH adjuster and a complexing agent are added to the mixed solution, and a composite salt containing cobalt and / or nickel is generated by a coprecipitation reaction. The mixed solution may further contain manganese ions, in which case the composite salt further contains manganese. Here, the mixed solution is prepared using the cobalt-containing solution and / or the nickel-containing solution directly in the mixing step without performing a crystallization treatment to precipitate a cobalt salt from the cobalt-containing solution or a crystallization treatment to precipitate a nickel salt from the nickel-containing solution, which is expected to simplify the process. However, it is possible to perform a cobalt crystallization step or a nickel crystallization step on at least a portion of the remaining cobalt-containing solution or nickel-containing solution (see FIGS. 4 and 5 ), and the resulting cobalt salt or nickel salt may be used or sold for purposes other than precursor production.

[0015] Incidentally, battery powders may contain sodium. This sodium is leached in the acid leaching process and included in the metal-containing solution. Even after the neutralization process and / or manganese extraction process, it is not completely separated and may be extracted along with cobalt and nickel in the cobalt extraction process or nickel extraction process. Furthermore, sodium may be contaminated due to sodium hydroxide added as a pH adjuster in the neutralization process or each extraction process. In this case, the cobalt-containing solution or nickel-containing solution contains sodium ions. If such a cobalt-containing solution and / or nickel-containing solution is used in the mixing process, the resulting mixed solution will contain the sodium ions. In contrast, in this embodiment, sodium hydroxide and / or sodium carbonate are used as pH adjusters in the coprecipitation process. In this case, the primary impurity in the composite salt obtained in the coprecipitation process is sodium, preventing the contamination of other impurities that occurs when other pH adjusters are used. Furthermore, since sodium primarily adheres to the particle surfaces of the composite salt, it can be effectively removed by a subsequent washing process. As a result, a precursor with a relatively low impurity content can be produced.

[0016] The battery powder used in the flow chart of Fig. 1 is obtained from lithium-ion battery waste. More specifically, the battery powder may be obtained by subjecting lithium-ion battery waste to pretreatment processes such as roasting, crushing, and sieving, as illustrated in Fig. 3. Here, the details of each process will be described according to Figs. 1 to 3, but Figs. 1 to 3 are merely examples and are not limited to such specific flows.

[0017] (Lithium-ion battery waste) The lithium-ion battery waste in question is lithium-ion secondary batteries that can be used in mobile phones and various other electronic devices, and which have been discarded due to the end of the battery product's life, manufacturing defects, or other reasons. Recovering valuable metals from such lithium-ion battery waste is desirable from the perspective of effective resource utilization. Lithium-ion battery waste refers to lithium-ion batteries that are eligible for recycling, regardless of whether they are traded for a value, free of charge, or treated as industrial waste.

[0018] Lithium-ion battery waste has an aluminum-containing casing as an exterior that encases the battery. This casing can be made of aluminum alone, aluminum and iron, or aluminum laminate. Lithium-ion battery waste may also contain a cathode active material, such as a single metal oxide containing lithium and one or more selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more selected metals. The cathode active material may also be coated and fixed to an aluminum foil (cathode substrate) with an organic binder, such as polyvinylidene fluoride (PVDF). Lithium-ion battery waste may also contain copper, iron, etc. Furthermore, the casing of lithium-ion battery waste typically contains an electrolyte solution, such as lithium hexafluorophosphate, dissolved in an organic solvent. Examples of organic solvents that may be used include ethylene carbonate and diethyl carbonate.

[0019] (Pretreatment Process) In many cases, lithium-ion battery waste undergoes a pretreatment process as a dry process, but wet processing may also be included as part of the process. In the pretreatment process, at least one of roasting, crushing, and sieving may be performed. Lithium-ion battery waste undergoes the pretreatment process to become battery powder. The roasting, crushing, and sieving processes of the pretreatment process may be performed individually as needed, or may be performed in any order. Battery powder refers to powder obtained by separating and concentrating positive electrode material components from lithium-ion battery waste through some kind of pretreatment. Battery powder may also be obtained as a powder by concentrating positive electrode material components by crushing and sieving lithium-ion battery waste with or without heat treatment.

[0020] In the roasting process, the lithium-ion battery waste is heated. The roasting process can convert metals such as lithium and cobalt contained in the lithium-ion battery waste into a soluble form. The roasting process is preferably carried out by heating the lithium-ion battery waste, for example, at a temperature of 450°C to 1000°C, preferably 600°C to 800°C, for 0.5 to 4 hours. The roasting process can be carried out either in an air atmosphere or in an inert atmosphere such as nitrogen. Alternatively, both the air atmosphere and the inert atmosphere may be carried out in this order or in the reverse order. The roasting furnace may be either a batch furnace or a continuous furnace. For example, a stationary furnace may be used in the batch furnace, and a rotary kiln may be used in the continuous furnace. Various other furnaces may also be used.

[0021] During roasting, at least a portion of the electrolyte is removed from the lithium-ion battery waste by evaporation, etc. In many cases, when lithium-ion battery waste is heated during roasting, the components of the internal electrolyte evaporate sequentially, starting with those with low boiling points. When roasting is performed, the electrolyte is removed and rendered harmless, and the organic binder is decomposed, facilitating separation of the aluminum foil and the positive electrode active material during crushing and sieving, as described below. Note that although the composition of the positive electrode active material changes upon roasting, for convenience, the term "positive electrode active material" will be used herein even if the material has undergone roasting.

[0022] After roasting, the lithium-ion battery waste can be crushed to remove the positive electrode active material and other materials from the casings. In the crushing, the casings of the lithium-ion battery waste are destroyed and the positive electrode active material is selectively separated from the aluminum foil on which the positive electrode active material is applied.

[0023] For crushing, various known devices or equipment can be used, but it is particularly preferable to use an impact crusher that can crush lithium-ion battery waste by applying impact while cutting the waste. Examples of this impact crusher include a sample mill, hammer mill, pin mill, wing mill, tornado mill, and hammer crusher. A screen can be installed at the outlet of the crusher, and the lithium-ion battery waste is discharged from the crusher through the screen once it has been crushed to a size that can pass through the screen.

[0024] After crushing the lithium-ion battery waste, it is sieved using a sieve with appropriate openings, whereby aluminum and copper remain on the sieve and battery powder from which aluminum and copper have been removed to some extent is obtained below the sieve.

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

[0026] (Acid Leaching Step) In the acid leaching step, an acidic leaching solution such as sulfuric acid is used to leach the metals in the battery powder. This results in a solution in which the metals in the battery powder are dissolved and a leaching residue that remains undissolved. Here, the solution in which the metals in the battery powder are dissolved is also referred to as a metal-containing solution in each step from the end of the acid leaching step to the nickel extraction step described below.

[0027] In the acid leaching step, the pH of the acidic leachate or post-leaching solution may be adjusted to less than 3.5. The oxidation-reduction potential (ORP value, based on silver / silver chloride potential) may be 100 mV or less. After leaching is completed, solid-liquid separation may be performed to separate the leaching residue from the metal-containing solution. However, the metal-containing solution containing the leaching residue may be subjected to the subsequent neutralization step without solid-liquid separation. As described below, the post-extraction solution from the nickel extraction step (a lithium-containing solution such as a lithium sulfate solution) or water may be used as a diluent for adjusting the pH of the acidic leachate. This allows lithium ions to circulate throughout the series of steps in the wet treatment, allowing the lithium ions in the solution to be concentrated during the process.

[0028] The metal-containing solution obtained in the acid leaching step 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 Step) When the metal-containing solution obtained in the acid leaching step contains aluminum ions and / or iron ions, a neutralization step can be carried out after the acid leaching step. In the neutralization step, the pH of the metal-containing solution is increased, thereby precipitating aluminum ions and / or iron ions as solids, and the precipitate is separated. When the metal-containing solution contains aluminum ions and iron ions, the neutralization step preferably includes a dealumination step and a de-ironization step. However, when the metal-containing solution does not contain aluminum ions and / or iron ions, the dealumination step and / or the de-ironization step may be omitted.

[0030] In the dealumination step, the pH of the metal-containing solution is increased to precipitate at least a portion of the aluminum ions, which are then removed by solid-liquid separation. At this time, for example, by increasing the pH to within a range of 4.0 to 5.0 using a pH adjuster at a liquid temperature of 50 to 90° C., the aluminum ions can be effectively separated while suppressing the precipitation of nickel ions and / or cobalt ions.

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

[0032] Examples of pH adjusters used for neutralization in the above-mentioned dealumination step, iron removal step, etc. include solid or liquid lithium hydroxide, sodium hydroxide, sodium carbonate, ammonia, etc., of which lithium hydroxide is preferred because it can prevent sodium and the like from being mixed into the lithium hydroxide recovered in the crystallization step described below. As the pH adjuster, a lithium hydroxide solution obtained by subjecting the lithium-containing solution after the nickel extraction step described below to a hydroxide treatment can be used, thereby circulating lithium ions within the series of steps.

[0033] (Manganese Extraction Step) After the metal-containing solution has been subjected to the neutralization step as necessary, manganese ions can be extracted and removed by solvent extraction in the manganese extraction step. Here, if aluminum ions remain in the metal-containing solution, not only the manganese ions but also the aluminum ions are 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 phosphoric acid (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 containing aldoxime as the main component. Specific examples include 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecylsalicyldoxime (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 organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% by volume to 30% by volume, and this may be used as the solvent.

[0036] During extraction, the equilibrium pH is preferably adjusted to 2.3 to 3.5, more preferably 2.5 to 3.0. The pH adjuster used at this time is preferably a lithium hydroxide solution, and for example, a lithium hydroxide solution obtained by hydroxide treatment of the lithium-containing solution after the nickel extraction step described below can be used.

[0037] A mixer-settler may be used for extraction. In this case, the pH is first adjusted, for example, by adding a pH adjuster to the solvent. The metal-containing solution (aqueous phase) and the solvent (organic phase) are then mixed in the mixer to form a mixed solution, which is then stirred for, for example, 5 to 60 minutes. During this process, the target metal ions, such as manganese ions, in the metal-containing solution are transferred to the solvent. The temperature during extraction is set to room temperature (approximately 15 to 25°C) to 60°C or less, with 35 to 45°C being preferred for reasons of extraction speed, phase separation, and evaporation of the organic solvent. The mixed solution is then allowed to stand in the settler, and the aqueous and organic phases are separated based on the difference in their specific gravities. This results in a post-extraction solution from which the solvent has been separated. Extractions in processes other than the manganese extraction process can also be performed in a substantially similar manner.

[0038] During extraction, it is desirable to perform extraction by countercurrent multistage extraction, in which the aqueous phase and the solvent used in each extraction flow in opposite directions. This makes it possible to increase the extraction rate of manganese ions while suppressing the extraction of cobalt ions, nickel ions, and lithium ions. When using countercurrent multistage extraction, it is effective to set the equilibrium pH during the first extraction stage within the above-mentioned range and to lower the equilibrium pH during each subsequent extraction stage.

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

[0040] (Cobalt Extraction Step) For example, if cobalt ions are contained in the metal-containing solution after the manganese extraction step, a cobalt extraction step can be carried out to extract and separate the cobalt ions from the metal-containing solution by solvent extraction.

[0041] For the extraction of cobalt ions, it is preferable to use a solvent containing a phosphoric acid extractant, especially a phosphonate extractant. 2-Ethylhexyl 2-ethylhexyl phosphonate (trade names: PC-88A, Ionquest 801) is particularly suitable from the viewpoint of the separation efficiency of nickel ions and cobalt ions. The extractant can be used as a solvent by diluting it with a hydrocarbon organic solvent to a concentration of 10% to 30% by volume.

[0042] When extracting cobalt ions, the equilibrium pH during extraction is preferably 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is lower than 5.0, the cobalt ions may not be sufficiently extracted into the solvent. In this case, a lithium hydroxide solution is preferably used as the pH adjuster, and for example, a lithium hydroxide solution obtained by hydroxide treatment of the lithium-containing solution after the nickel extraction step described below can be used.

[0043] Cobalt ion extraction is also preferably performed by countercurrent multistage extraction, in which the aqueous phase and the solvent flow in opposite directions in each extraction, which can increase the extraction rate of cobalt ions while suppressing the extraction of nickel ions and lithium ions.

[0044] During the extraction, not only cobalt ions but also small amounts of nickel ions and lithium ions may be extracted into the solvent. In this case, if necessary, the solvent from which the cobalt ions have been extracted may be subjected to one or more scrubbing steps using a scrubbing solution to remove nickel ions and lithium ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid solution with a pH of 3.5 to 5.5. The post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to mix some or all of the post-scrubbing solution with the metal-containing solution from the manganese extraction step and use this as the pre-extraction solution for the cobalt extraction step. This allows nickel ions and lithium ions to be circulated or retained within the series of steps and concentrated without loss. However, if the solvent from which the cobalt ions have been extracted does not contain nickel ions or lithium ions, scrubbing may not be necessary.

[0045] Thereafter, stripping is performed on a solvent containing cobalt ions. The stripping solution used for stripping may be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, and can be appropriately selected depending on the subsequent mixing step and crystallization step. In many cases, sulfuric acid can be used as the stripping solution. Stripping is performed under pH conditions such that as much of the cobalt ions as possible are transferred from the solvent to the stripping solution. Specifically, the pH is preferably in the range of 2.0 to 4.0, and even more preferably in the range of 2.5 to 3.5.

[0046] (Nickel Extraction Step) When nickel ions are contained in the metal-containing solution after the cobalt ions have been extracted in the cobalt extraction step, a nickel extraction step can be carried out to extract nickel ions from the metal-containing solution by a solvent extraction method.

[0047] The solvent used in the nickel extraction step preferably contains a carboxylic acid extractant. Examples of carboxylic acid extractants include neodecanoic acid and naphthenic acid. Of these, neodecanoic acid (such as Versatic Acid 10 (VA-10) manufactured by Shell Chemical Industries, Ltd.) is preferred due to its ability to extract nickel ions. The extractant may be diluted with a hydrocarbon organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% by volume 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 preferably used as a pH adjuster for adjusting the pH at this time, and for example, a lithium hydroxide solution obtained by hydroxide treatment of the lithium-containing solution after the nickel extraction step described below can be used.

[0049] The extraction is preferably performed in multiple stages using a countercurrent method, in which the metal-containing solution and the solvent flow in opposite directions. This suppresses the extraction of lithium ions into the solvent, thereby increasing the extraction rate of nickel ions. When performing multiple countercurrent extraction stages, it is effective to set the equilibrium pH during the first extraction stage within the above-mentioned range and then gradually lower the equilibrium pH during each stage.

[0050] If necessary, the solvent that has become nickel ion-containing after extraction may be subjected to one or more scrubbing steps using a scrubbing solution to remove lithium ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid acidic solution having a pH of 5.0 to 6.0. The post-scrubbing solution may contain lithium ions. Therefore, it is desirable to mix a portion or all of the post-scrubbing solution with the metal-containing solution obtained after the cobalt extraction step, and use this as the pre-extraction solution for the nickel extraction step. This allows the lithium ions to be circulated or retained within the series of steps and concentrated without loss. However, if the nickel ion-containing solvent does not contain lithium ions, scrubbing may not be necessary.

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

[0052] The post-extraction solution (lithium sulfate solution, etc.) after the nickel ions have been transferred to the solvent mainly contains lithium ions, and may be added to the acid leaching solution in the acid leaching step, thereby circulating the lithium ions contained in the post-extraction solution within the series of steps.

[0053] (Mixing Step) In the mixing step, the cobalt-containing solution and / or nickel-containing solution is used to prepare a mixed solution such as a sulfuric acid solution containing cobalt ions, nickel ions, manganese ions, and sodium ions. Specifically, the mixed solution can be prepared by mixing cobalt ions, nickel ions, and manganese ions in a solution containing the cobalt-containing solution and / or nickel-containing solution while adding a manganese source, a cobalt source, a nickel source, or the like, as necessary.

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

[0055] The amounts of the cobalt-containing solution and / or nickel-containing solution, manganese source, etc. added can be determined depending on the intended composition of the precursor or positive electrode active material to be produced, etc. For example, the amounts of the solutions added may be adjusted so that the molar ratio of cobalt ions, nickel ions, and manganese ions in the mixed solution becomes, for example, 50:20:30.

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

[0057] As the manganese source, a manganese-containing solution or manganese compound that can be recovered by extracting manganese ions in the manganese extraction step (i.e., a manganese source derived from lithium-ion battery waste) can also be used. However, the manganese-containing solution or manganese compound obtained after the manganese extraction step 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 a mixed solution in the mixing step using a manganese source that is not derived from lithium-ion battery waste.

[0058] (Coprecipitation Step) 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, and cobalt ions, nickel ions, and manganese ions in the mixed solution are precipitated to obtain a composite salt containing cobalt, nickel, and manganese. Typically, this composite salt may be a composite 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 adjuster. In this case, the mixed solution may be stirred at a speed of 500 rpm to 1000 rpm. Examples of the complexing agent that can be used include ammonia water, an ammonium sulfate aqueous solution, and an ammonium chloride aqueous solution.

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

[0061] (Washing Step) The composite salt obtained in the mixing step is subjected to washing in the washing step. This washing is performed mainly for the purpose of removing impurities such as sodium contained in the composite salt. By passing through the washing step, a precursor can be produced.

[0062] The composite salt produced in the mixing step tends to have sodium attached mainly to the particle surface, so by washing the composite salt in the washing step, the sodium attached to the particle surface is washed away, resulting in a precursor with a sufficiently low sodium content.

[0063] In the washing, for example, the composite salt is put into a washing liquid such as pure water to form a slurry, and after performing an operation such as stirring as necessary, the composite salt can be extracted by solid-liquid separation. Such washing is not limited to one time, and may be repeated multiple times.

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

[0065] (Cobalt Crystallization Step and Nickel Crystallization Step) The cobalt-containing solution obtained in the cobalt extraction step and the nickel-containing solution obtained in the nickel extraction step are basically subjected to the mixing step as described above and used to produce a precursor. On the other hand, it is not necessary to use the entire cobalt-containing solution or nickel-containing solution to produce a precursor. A portion of the cobalt-containing solution and / or the nickel-containing solution is subjected to the mixing step, and at least a portion of the remaining solution can be subjected to a crystallization treatment by a cobalt crystallization step and / or a nickel crystallization step. The cobalt salt and / or nickel salt obtained thereby can be used for various purposes, including sales.

[0066] In the cobalt crystallization step, the cobalt-containing solution (post-stripping solution) obtained by stripping in the cobalt extraction step described above is concentrated by heating, for example, to 40°C to 120°C. This causes cobalt ions to crystallize, yielding a cobalt salt such as cobalt sulfate. The cobalt salt thus obtained may have a nickel content of 5 ppm by mass or less.

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

[0068] In the nickel crystallization step, when a stripped solution such as a nickel sulfate solution is obtained by stripping, the nickel-containing solution obtained as the stripped solution obtained by stripping in the nickel extraction step described above, or the nickel-containing solution obtained by electrolyzing and dissolving the stripped solution as needed, is concentrated by heating to 40° C. to 120° C. This causes nickel ions to crystallize, and a nickel salt such as nickel sulfate is obtained.

[0069] The solution after the crystallization of the nickel crystallization step may contain nickel ions and lithium ions that have not crystallized. It is desirable to mix such a solution after the crystallization step with the nickel-containing solution before the crystallization step and subject it to another crystallization step, to use it to adjust the nickel ion concentration of the scrubbing solution for the solvent containing nickel ions, or to mix it with the metal-containing solution after the cobalt extraction step and subject it to the nickel extraction step. In this way, nickel ions and lithium ions can be concentrated by circulating or retaining them within a series of steps without loss.

[0070] When the solution is returned to the previous step as described above and lithium ions are circulated within the series of steps, sodium ions can also be concentrated concomitantly. The embodiment described here is particularly effective when sodium ions are circulated within the series of steps together with lithium ions as described above, because the precursor can be produced while effectively removing sodium ions in the washing step.

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

[0072] When producing lithium carbonate, lithium carbonate can be precipitated by adding a carbonate such as sodium carbonate to a lithium-containing solution or by blowing carbon dioxide gas into the solution to perform a carbonation treatment. From the viewpoint of preventing an increase in impurities, blowing in carbon dioxide gas is preferred. After adding the carbonate or blowing in the carbon dioxide gas, the liquid temperature can be set to a range of 50°C to 90°C, and the solution can be stirred as necessary and maintained at this temperature for 0.5 to 2 hours.

[0073] The lithium carbonate thus obtained may be purified, as needed, by washing, dissolution, decarbonation, or the like, in order to increase its purity.

[0074] In producing lithium hydroxide, a lithium-containing solution is subjected to a hydroxide treatment to obtain a lithium hydroxide solution, and then lithium hydroxide can be precipitated by crystallization. Examples of the hydroxide treatment include a carbonation and chemical conversion method in which lithium carbonate is produced and then calcium hydroxide is used, a chemical conversion method in which barium hydroxide is used, and a technique using electrodialysis.

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

[0076] When barium hydroxide is used, it is added to a lithium-containing solution, and a lithium hydroxide solution is obtained based on the reaction LiSO + Ba(OH) → 2LiOH + BaSO. Note that barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin, chelating resin, or the like.

[0077] In electrodialysis, a bipolar membrane electrodialysis device is used. A lithium-containing solution is placed in the deionization compartment between the anion exchange membrane and the cation exchange membrane. Pure water is placed in the acid compartment between the bipolar membrane and the anion exchange membrane, and in the alkaline compartment between the cation exchange membrane and the bipolar membrane. A voltage is then applied between the electrodes. Lithium in the metal-containing solution in the deionization compartment moves to the alkaline compartment, where the bipolar membrane decomposes the pure water into hydroxide ions, producing a lithium hydroxide solution. Anions of inorganic acids, such as sulfuric acid, in the metal-containing solution in the deionization compartment pass through the anion exchange membrane and move to the acid compartment.

[0078] Crystallization of lithium hydroxide can be performed by subjecting the lithium hydroxide solution to a crystallization procedure such as heat concentration or vacuum distillation. In the case of heat concentration, the higher the temperature during crystallization, the faster the process progresses, which is preferable. However, after crystallization, the temperature during drying of the crystallized product is preferably less than 60°C, at which water of crystallization does not detach. This is because anhydrous lithium hydroxide from which water of crystallization has been detached is deliquescent and therefore difficult to handle. Thereafter, a pulverization process or the like can be performed to adjust the lithium hydroxide to the required physical properties.

[0079] (Firing Step) In the firing step, the precursor obtained in the coprecipitation step described above and a lithium salt such as lithium carbonate or lithium hydroxide obtained in the lithium salt preparation step as a lithium source are mixed by kneading or the like, and the mixture is heated and fired.

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

[0081] After the firing step, crushing or other treatments are carried out 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) or other positive electrode active materials can be produced.

[0082] Next, the above-described methods for producing a precursor and a cathode active material were experimentally carried out to produce a precursor and a cathode active material, which will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

[0083] (Production Method) In the examples, as shown in FIG. 1 , a metal-containing solution was obtained by leaching battery powder from lithium-ion battery waste with acid, and neutralization, manganese extraction, cobalt extraction, and nickel extraction were sequentially performed on the metal-containing solution, thereby obtaining a cobalt sulfate solution as a cobalt-containing solution and a nickel sulfate solution as a nickel-containing solution.

[0084] 2, a cobalt sulfate solution and a nickel sulfate solution (recycled liquid) were mixed while adding a manganese source to prepare a mixed solution (sulfuric acid-based raw material), to which aqueous ammonia was added as a pH adjuster for sodium hydroxide and a complexing agent to cause a coprecipitation reaction, thereby purifying a composite hydroxide containing cobalt, nickel, and manganese. In the coprecipitation reaction, the liquid temperature was 60°C, the pH was 10.2, and the mixture was stirred at 1000 rpm. The composite hydroxide was then washed with pure water to produce a precursor.

[0085] Thereafter, the precursor was mixed with the lithium carbonate obtained in the lithium salt preparation process shown in Fig. 1, and the mixture was heated in an air atmosphere at a temperature of 720°C to 900°C for 10 hours, thereby producing a positive electrode active material.

[0086] In the comparative example, the cobalt sulfate solution and nickel sulfate solution obtained in the cobalt extraction and nickel extraction steps shown in Figure 1 were crystallized to obtain cobalt sulfate and nickel sulfate (recycled sulfates), as shown in Figures 4 and 5. The cobalt sulfate and nickel sulfate were dissolved in pure water, and a manganese source was added to prepare a mixed solution (sulfuric acid-based raw material). Thereafter, a precursor and a positive electrode active material were produced in the same manner as in the examples.

[0087] (Evaluation) In the examples, crystallization and re-dissolution after extraction of cobalt and nickel, as in the comparative examples, were not carried out, and therefore it can be said that the process was simplified compared to the comparative examples.

[0088] Table 1 shows the impurity contents in the mixed solution (sulfuric acid-based raw material) prepared from the recycled solution in the Examples, the mixed solution (sulfuric acid-based raw material) prepared from the recycled sulfate in the Comparative Examples, and the precursors and positive electrode active materials obtained in the Examples and Comparative Examples. The impurity components in the mixed solution were measured by ICP-MS. In the precursor and the positive electrode active material, the impurity components (other than K) were measured by ICP-MS, and K was measured by atomic absorption spectrometry. Here, the samples were dissolved in an aqua regia system as a pretreatment.

[0089]

[0090] As can be seen from Table 1, the sodium contents of the precursors and positive electrode active materials of the examples were comparable to or less than those of the comparative examples. This is presumably because sodium was effectively removed by washing after coprecipitation.

[0091] 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 also determined. The average particle size was measured by a laser diffraction / scattering method. The tap density was measured according to JIS Z2512:2012. The BET specific surface area was measured by the BET method. The results are shown in Table 2. Table 2 also includes SEM images of each precursor.

[0092]

[0093] As can be seen from 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 the above-mentioned production method can produce a precursor from lithium ion battery waste with a suppressed increase in impurity content, even though the process is simplified.

Claims

1. A method for producing a precursor of a positive electrode active material for lithium ion batteries from lithium ion battery waste, comprising: an acid leaching step of leaching metals in battery powder obtained from the 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 using the cobalt-containing solution and / or the nickel-containing solution to prepare a mixed solution containing cobalt ions and / or nickel ions, and sodium ions; a coprecipitation step of using sodium hydroxide and / or sodium carbonate as a pH adjuster and adding a complexing agent to the mixed solution to obtain a composite salt containing cobalt and / or nickel by a coprecipitation reaction; and a washing step of washing the composite salt to obtain a precursor.

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

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

4. A method for producing a lithium ion battery positive electrode active material using a precursor produced by the method for producing a precursor of a lithium ion battery positive electrode active material described in claim 1 or 2, comprising: a lithium salt preparation step of obtaining a lithium salt from at least a part of the lithium-containing solution obtained after the cobalt extraction step and / or the 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 preparation step, and heating and calcining the resulting mixture.

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

Images