Method for separating transition metal from Li from compound comprising Li and transition metal

Abstract

The disclosed method for separating a transition metal from Li comprises: a step in which a compound containing Li and a transition metal is dissolved in a carboxylic acid to obtain a first solution containing Li ions, Ni ions, and carboxylate anions; a step for adding an alkali to the first solution to obtain a second solution containing Li ions and a precipitate containing a carboxylic acid transition metal salt; and a step for separating the precipitate from the second solution, wherein the transition metal is at least one type selected from the group consisting of Ni, Co, Mn, Ti, Fe, and Cu.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority to Japanese Patent Application No. 2022 - 174796, filed with the Japan Patent Office on October 31, 2022, and the entire content of the above - mentioned patent application is incorporated herein by reference. Technical field

[0003] This application relates to a method for separating transition metals from Li in a compound containing Li and transition metals. Background art

[0004] From the perspective of protecting the global environment, "manufacturing technologies" that are environmentally friendly in various aspects are desired. In the manufacturing of lithium - ion secondary batteries, legal regulations regarding carbon footprint (CFP) reduction and the proportion of recycled materials used have been achieved in the European region. This trend is considered to also have an impact on the United States and China. In particular, the positive electrode materials of lithium - ion secondary batteries are mainly composed of rare metals such as Ni, Co, and Li, and it is desired to recycle them and reuse them as raw materials for positive electrode materials.

[0005] For example, in the case of recycling black mass (broken electrode materials), from the perspective of CFP, the mainstream method is wet refining rather than dry refining (Patent Documents 1 - 3).

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Laid - Open No. 2016 - 186113

[0009] Patent Document 2: Japanese Patent Application Laid - Open No. 2016 - 186118

[0010] Patent Document 3: Japanese Patent Application Laid - Open No. 2021 - 504885 Summary of the invention

[0011] Problems to be solved by the invention

[0012] In the wet - refining process, lithium is recovered in the form of Li 2 CO 3 and sodium sulfate is generated as a by - product. The economic rationality of such a process is low, and it is not suitable as a recycling process.

[0013] Means for solving the problems

[0014] One aspect of the present application relates to a method for separating a transition metal from Li, the separation method comprising: a step of dissolving a compound containing Li and a transition metal in a carboxylic acid to obtain a first solution containing Li ions, transition metal ions, and carboxylate anions; a step of adding an alkali to the first solution to obtain a second solution containing Li ions and a precipitate containing a transition metal carboxylate salt; and a step of separating the precipitate from the second solution, wherein the transition metal is at least one selected from Ni, Co, Mn, Ti, Fe, and Cu.

[0015] Advantages of the Invention

[0016] According to the present application, it is possible to improve economic rationality in a method for separating a transition metal from Li from a compound containing Li and a transition metal.

[0017] The new features of the present invention are described in the scope of the appended claims. However, the present invention should be more fully understood in both its constitution and content, together with other objects and features of the present invention, from the following detailed description with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flowchart showing the steps of a method for separating a transition metal from Li according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present application will be described by way of example. However, the present application is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be exemplified. However, as long as the effects of the present application can be obtained, other numerical values, materials, etc. may also be applied. It should be noted that components other than the characteristic parts of the present application may be components known in the art. In this specification, when it is described as "a range of numerical value A to numerical value B", numerical value A and numerical value B are included in this range.

[0020] In the following description, when the lower limit and the upper limit of a numerical value regarding a specific physical property, condition, etc. are exemplified, as long as the lower limit is not higher than the upper limit, any one of the exemplified lower limits can be arbitrarily combined with any one of the exemplified upper limits. When multiple materials are exemplified, unless otherwise specified, one of them can be selected and used alone, or two or more of them can be used in combination.

[0021] In addition, the present application includes combinations of matters described in two or more claims arbitrarily selected from the multiple claims described in the scope of the appended claims. That is, as long as there is no technical contradiction, matters described in two or more claims arbitrarily selected from the multiple claims described in the scope of the appended claims can be combined.

[0022] The method for separating a transition metal from Li according to an embodiment of the present application (hereinafter also referred to as "separation method (ML)") has at least the following three steps. It should be noted that in the separation method (ML), a solution containing a transition metal carboxylate and Li ions is obtained. Therefore, the separation method (ML) is both a method for manufacturing a transition metal carboxylate and a method for manufacturing a solution containing Li ions. Hereinafter, the transition metal will sometimes be represented by "M".

[0023] <First Step>

[0024] The first step is a step of dissolving a compound containing Li and a transition metal (hereinafter sometimes also referred to as "compound containing LiM") in a carboxylic acid to obtain a first solution containing Li ions, M ions, and carboxylate anions. By using a carboxylic acid in the dissolution of the compound containing LiM, advantages that cannot be obtained when using inorganic acids such as sulfuric acid and nitric acid are brought about. The first advantage is that since the carboxylic acid is a weak acid, corrosion of equipment is less likely to occur compared to the case of using inorganic acids.

[0025] The carboxylic acid can be used in the form of an aqueous solution of the carboxylic acid. The concentration of the aqueous solution of the carboxylic acid is not particularly limited. For example, it can be 10% by mass to 90% by mass, or it can also be 15% by mass to 50% by mass.

[0026] From the viewpoint of improving the solubility of the compound containing LiM, the pH of the first solution is adjusted to be less than 0.5, for example. The pH of the first solution can also be adjusted to be 0 or less.

[0027] When the compound containing LiM is LiMO 2 , and the carboxylic acid is formic acid, for example, it is presumed that the dissolution reaction proceeds according to the following chemical formula, and usually LiMO 2 dissolves completely. However, the following chemical formula is an example, and a reaction not following the following chemical formula can also occur.

[0028] LiMO 2 +4HCOOH→Li + +M 2+ +2H 2 O+4COOH －

[0029] The compound containing LiM can be an electrode material recovered from a secondary battery. As the compound containing LiM, for example, a broken electrode material called black mass can be used. In this case, the black mass can be mixed with the carboxylic acid to form the first solution.

[0030] Secondary batteries containing a compound containing LiM as an electrode material can be lithium-ion secondary batteries, lithium metal secondary batteries, all-solid-state batteries, etc. For example, after subjecting a secondary battery to a prescribed treatment, it is crushed, and magnetic separation and screening are performed to recover the electrode material.

[0031] The secondary battery can be, for example, an in-vehicle battery, a battery mounted in home appliances or laptops, etc., and is a used secondary battery that is recycled after being discarded due to its lifespan. Alternatively, it can also be a defective secondary battery generated during the manufacturing process. The shape of the secondary battery is not particularly limited. For example, it can be a cylindrical, square, button-type, coin-type, pouch-type, etc. secondary battery.

[0032] Composite metal compounds that can be used as the compound containing LiM can include composite metal oxides, composite metal sulfides, composite metal fluorides, composite metal hydrofluorides, composite metal polyanion compounds, etc. The crystal structure of the composite metal compound is not particularly limited, and examples can include a layered rock salt type, a spinel type, an olivine type, a perovskite type, etc.

[0033] Among them, the method of the present application is useful when the composite metal compound is a composite metal oxide. Therefore, it is desirable that the main component of the compound containing LiM is a composite metal oxide. The so-called main component composite metal oxide is, for example, a composite metal oxide that accounts for 50% by mass or more, further 60% by mass or more, or 70% by mass or more, or 80% by mass or more of the compound containing LiM.

[0034] The transition metal M includes at least one selected from Ni, Co, Mn, Ti, Fe, and Cu. Among them, the method of the present application is useful when the proportion of Ni in the composite metal compound among the metal elements other than Li is high. The proportion of Ni in the composite metal compound among the metal elements other than Li can be 50 atomic% or more, can also be 60 atomic% or more, can also be 70 atomic% or more, or can also be 80 atomic% or more.

[0035] The compound containing LiM can be a composite metal compound containing Ni and a transition metal other than Ni. The composite metal oxide can further contain at least one third metal selected from Fe, Ti, Co, and Mn on the basis of containing Ni. In this case, the third metal can be separated from Li together with Ni.

[0036] The carboxylic acid can be either an aliphatic carboxylic acid or an aromatic carboxylic acid. Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid, acrylic acid, methacrylic acid, oleic acid, benzoic acid, cinnamic acid, naphthoic acid, salicylic acid, mandelic acid, resorcylic acid, maleic acid, phthalic acid, pyromellitic acid, resorcylic acid, succinic acid, glutaric acid, adipic acid, oxalic acid, maleic acid, fumaric acid, tartaric acid, citric acid, etc.

[0037] The carboxylic acid can be used in the form of an aqueous carboxylic acid solution. The concentration of the aqueous carboxylic acid solution is not particularly limited. For example, it can be 5% by mass to 50% by mass, or it can be 10% by mass to 40% by mass. By increasing the carboxylic acid concentration of the aqueous carboxylic acid solution, the dissolution rate of the compound containing LiM can be increased.

[0038] <Second Step>

[0039] The second step is a step of adding a base to the first solution to obtain a second solution containing Li ions and a precipitate containing a nickel carboxylate. The second solution may contain a trace amount of M ions. However, the concentration of M ions contained in the second solution is sufficiently small compared to the concentration of M ions contained in the first solution and can be 0.1 times or less the concentration of M ions contained in the first solution.

[0040] It is speculated that this phenomenon, in which the carboxylic acid transition metal salt is separated and precipitated from the second solution by increasing the pH compared to the first solution, is related to the change in solubility product. The pH of the second solution can be adjusted to, for example, 0.5 or more and 3.5 or less, or it can be adjusted to 1 or more and 3 or less.

[0041] The second advantage of using a carboxylic acid in the dissolution of the compound containing LiM is that a carboxylic acid transition metal salt can be obtained in a state separated from Li ions. If the carboxylic acid transition metal salt is dissolved in an inorganic acid, for example, it can be recovered as a raw material for a new electrode material (positive electrode active material). On the other hand, most of the Li ions are separated in a state dissolved in the second solution that does not contain inorganic acid root anions such as sulfate ions and nitrate ions.

[0042] As the base, NaOH, KOH, LiOH, NH 3 etc. can be used, and there is no particular limitation. The base can also be an aqueous base solution. The base concentration of the aqueous base solution is not particularly limited. For example, it can be 1% by mass to 30% by mass, or it can be 3% by mass to 10% by mass.

[0043] <Third Step>

[0044] The third process is a process of separating the precipitate from the second solution. For example, the precipitate can be separated by filtration to separate the second solution as a filtrate from the precipitate. At this time, most of the transition metals are contained in the precipitate, and most of the Li ions are dissolved in the second solution. The third advantage of using a carboxylic acid in the dissolution of a compound containing LiNi is that almost all of the Li ions can be easily separated as the second solution by filtration. In addition, the fourth advantage is that inorganic acid root anions are not contained in the second solution. That is, by-products such as sulfates and nitrates are not generated.

[0045] In the obtained transition metal carboxylate salts, nickel carboxylate, cobalt carboxylate, manganese carboxylate, titanium carboxylate, etc. are included. If these salts are dissolved in sulfuric acid and the carboxylate anions are removed, sulfates can be obtained. For example, nickel sulfate, cobalt sulfate, manganese sulfate, etc. are useful as raw materials for electrode materials (positive electrode active materials).

[0046] <Fourth Process>

[0047] The separation method (ML) may further include a process of purifying the second solution with an ion exchange resin to obtain a high-concentration Li solution. Since Li ions do not adsorb to the cation exchange resin, the Li ion concentration can be increased as long as the second solution is passed through the cation exchange resin. In addition, since inorganic strong acids such as sulfuric acid and nitric acid are not used, the carboxylate anions can be removed by passing the second solution through the anion exchange resin. By using the cation exchange resin and the anion exchange resin, a concentrated lithium hydroxide solution can be obtained. By drying the concentrated lithium hydroxide solution, LiOH•H 2 O can be obtained. Since the ion exchange resin can be regenerated, LiOH•H 2 O can be obtained at low cost. LiOH•H 2 O is useful as a raw material for electrode materials (positive electrode active materials).

[0048] Figure 1 is a flowchart of the separation method (ML) of the transition metal and Li that summarizes the above first process to fourth process.

[0049] According to the separation method (ML), when the value obtained by dividing the amount of Li in the second solution by the sum of the amount of Li in the second solution and the amount of Li in the precipitate is set as C1, the Li recovery rate expressed as a percentage of C1×100 can be set to 90% or more, and further can be set to 95% or more or 98% or more.

[0050] According to the separation method (ML), when the value obtained by dividing the amount of transition metal in the precipitate by the total of the amount of transition metal in the second solution and the amount of transition metal in the precipitate is set as C2, the transition metal recovery rate expressed as a percentage of C2×100 can be set to 90% or more, and further can be set to 94% or more or 95% or more.

[0051] It should be noted that the amounts of Li and transition metal in the second solution and the precipitate can be measured by inductively coupled plasma (ICP) analysis.

[0052] (Appendix)

[0053] The following technology is disclosed by the above description.

[0054] (Technology 1)

[0055] A method for separating transition metal and Li, the separation method comprising:

[0056] A step of dissolving a compound containing Li and transition metal in a carboxylic acid to obtain a first solution containing Li ions, Ni ions and carboxylate anions;

[0057] A step of adding an alkali to the above first solution to obtain a second solution containing Li ions and a precipitate containing a transition metal carboxylate salt; and

[0058] A step of separating the above precipitate from the above second solution,

[0059] The above transition metal is at least one selected from Ni, Co, Mn, Ti, Fe and Cu.

[0060] (Technology 2)

[0061] According to the method for separating transition metal and Li described in Technology 1, wherein the pH of the above first solution is less than 0.5.

[0062] (Technology 3)

[0063] According to the method for separating transition metal and Li described in Technology 1 or 2, wherein the pH of the above second solution is 0.5 or more and 3.5 or less.

[0064] (Technology 4)

[0065] According to the method for separating transition metal and Li described in any one of Technologies 1 to 3, wherein the above alkali contains NaOH.

[0066] (Technology 5)

[0067] The method for separating a transition metal from Li according to any one of Technologies 1 to 4, wherein the compound containing Li and the transition metal is a composite metal oxide containing Li and the transition metal.

[0068] (Technology 6)

[0069] The method for separating a transition metal from Li according to any one of Technologies 1 to 5, wherein the compound containing Li and the transition metal is an electrode material recovered from a secondary battery.

[0070] (Technology 7)

[0071] The method for separating a transition metal from Li according to any one of Technologies 1 to 6, further comprising a step of purifying the second solution with an ion exchange resin to obtain a high-concentration Li solution.

[0072] (Technology 8)

[0073] The method for separating a transition metal from Li according to any one of Technologies 1 to 7, wherein formic acid is used as the carboxylic acid.

[0074] (Technology 9)

[0075] The method for separating a transition metal from Li according to any one of Technologies 1 to 8, wherein when the value obtained by dividing the amount of Li in the second solution by the sum of the amount of Li in the second solution and the amount of Li in the precipitate is set as C1, the Li recovery rate in terms of the percentage represented by C1×100 is 90% or more.

[0076] (Technology 10)

[0077] The method for separating a transition metal from Li according to any one of Technologies 1 to 9, wherein when the value obtained by dividing the amount of the transition metal in the precipitate by the sum of the amount of the transition metal in the second solution and the amount of the transition metal in the precipitate is set as C2, the transition metal recovery rate in terms of the percentage represented by C2×100 is 90% or more.

[0078] Although the present invention has been described with respect to the presently preferred embodiments, such disclosure should not be construed in a limiting sense. Various modifications and changes will be apparent to those skilled in the art in the technical field to which the present invention pertains upon reading the above disclosure. Accordingly, the scope of the appended claims should be construed to include all modifications and changes without departing from the true spirit and scope of the present invention.

[0079] [Examples]

[0080] Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

[0081] Example 1

[0082] <First Step>

[0083] Prepare LiNi 0.8 Co 0.1 Mn 0.1 O 2 as a compound containing LiM. Dissolve 10 g of LiNi 0.8 Co 0.1 Mn 0.1 O 2 in 100 mL of a 30% by mass aqueous solution of formic acid to prepare a first solution containing Li ions, Ni ions and formate anions. The pH of the first solution is approximately 0.

[0084] <Second Step>

[0085] Add a 5% aqueous sodium hydroxide solution to the first solution to adjust the pH to 1, generating a second solution (pH 1) containing Li ions and a precipitate.

[0086] <Third Step>

[0087] Then, separate the precipitate from the second solution (filtrate) by suction filtration. Analyze the precipitate by X-ray diffraction (XRD). As a result, the formation of nickel formate can be confirmed as the main component.

[0088] >[Evaluation]

[0089] Analyze the Li content, Ni content, Co content and Mn content in the second solution and the precipitate respectively by inductively coupled plasma (ICP) analysis.

[0090] When the value obtained by dividing the Li content in the second solution by the sum of the Li content in the second solution and the Li content in the precipitate is set as C1, calculate the Li recovery rate expressed as C1×100 (%).

[0091] When the value obtained by dividing the Ni content in the precipitate by the sum of the Ni content in the second solution and the Ni content in the precipitate is set as C21, calculate the Ni recovery rate expressed as C21×100 (%).

[0092] When the value obtained by dividing the Co content in the precipitate by the sum of the Co content in the second solution and the Co content in the precipitate is set as C22, calculate the Co recovery rate expressed as C22×100 (%).

[0093] When the value obtained by dividing the Mn content in the precipitate by the sum of the Mn content in the second solution and the Mn content in the precipitate is set as C23, calculate the Mn recovery rate expressed as C23×100 (%).

[0094] The results are shown in Table 1. It should be noted that in Table 1 below, A1 corresponds to Example 1, and A2 and A3 correspond to Examples 2 and 3 described later. In addition, B1 corresponds to Comparative Example 1 described later.

[0095] [Table 1]

[0096]

[0097] 《Example 2》

[0098] Except that in the second step, 5% aqueous sodium hydroxide solution was added until the pH of the second solution reached pH = 3, the same separation operation as in Example 1 was carried out, and the same evaluation was carried out. The results are shown in Table 1.

[0099] 《Comparative Example 1》

[0100] 5% aqueous sodium hydroxide solution was not added to the second solution, and as a result, no precipitate was formed even after 3 days.

[0101] 《Example 3》

[0102] Except that in the second step, 5% aqueous sodium hydroxide solution was added until the pH of the second solution reached pH = 5, the same separation operation as in Example 1 was carried out, and the same evaluation was carried out. The results are shown in Table 1.

[0103] In Examples 1 to 3 and Comparative Example 1, LiNi 0.8 Co 0.1 Mn 0.1 O 2 completely dissolved in the first solution. As shown in Table 1, in Examples 1 and 2, almost all of the transition metal was contained in the precipitate. On the other hand, in Example 3, the precipitate decreased, the recovery rate of the transition metal (M) decreased, and the Li recovery rate also decreased.

[0104] Industrial Applicability

[0105] The method for separating transition metal and Li from a compound containing Li and transition metal of the present application is particularly useful as a process for recycling the electrode material of a secondary battery, has a low treatment cost, a small environmental burden, and excellent economic rationality.

Claims

1. A method for separating a transition metal from Li, the separation method comprising: a step of dissolving a compound containing Li and a transition metal in a carboxylic acid to obtain a first solution containing Li ions, Ni ions, and carboxylate anions; a step of adding an alkali to the first solution to obtain a second solution containing Li ions and a precipitate containing a transition metal carboxylate salt; and a step of separating the precipitate from the second solution, wherein the transition metal is at least one selected from Ni, Co, Mn, Ti, Fe, and Cu.

2. The method for separating a transition metal from Li according to claim 1, wherein the pH of the first solution is less than 0.

5.

3. The method for separating a transition metal from Li according to claim 1, wherein the pH of the second solution is 0.5 or more and 3.5 or less.

4. The method for separating a transition metal from Li according to claim 1, wherein the alkali contains NaOH.

5. The method for separating a transition metal from Li according to claim 1, wherein the compound containing Li and a transition metal is a composite metal oxide containing Li and a transition metal.

6. The method for separating a transition metal from Li according to claim 1, wherein the compound containing Li and a transition metal is an electrode material recovered from a secondary battery.

7. The method for separating a transition metal from Li according to claim 1, further comprising a step of purifying the second solution with an ion exchange resin to obtain a high-concentration Li solution.

8. The method for separating a transition metal from Li according to claim 1, wherein formic acid is used as the carboxylic acid.

9. The method for separating a transition metal from Li according to any one of claims 1 to 8, wherein when the value obtained by dividing the amount of Li in the second solution by the sum of the amount of Li in the second solution and the amount of Li in the precipitate is set as C1, the Li recovery rate in terms of the percentage represented by C1×100 is 90% or more.

10. The method for separating a transition metal from Li according to any one of claims 1 to 8, wherein when the value obtained by dividing the amount of the transition metal in the precipitate by the sum of the amount of the transition metal in the second solution and the amount of the transition metal in the precipitate is set as C2, the transition metal recovery rate in terms of the percentage represented by C2×100 is 90% or more.

Images