Method for recovering lithium compounds from the cathode material of lithium-ion batteries

Abstract

The present invention relates to a method for recovering lithium compounds, and more particularly to a method for recovering lithium compounds characterized by comprising: (a) extracting a reductive roasted product of a lithium-ion battery cathode material with an organic solvent containing a cation exchange extractant to obtain an organic solvent from which lithium has been extracted and an extraction residue; (b) separating the organic solvent from which lithium has been extracted from the extraction residue; (c) stripping the separated organic solvent from which lithium has been extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent; (d) separating the lithium-containing aqueous solution from the organic solvent; and (e) carbonating lithium in the separated lithium-containing aqueous solution to obtain lithium carbonate. The present invention relates to a method for recovering lithium compounds from lithium-ion battery cathode materials, which involves directly extracting lithium from the reductively roasted product of the cathode material of a lithium-ion battery using an organic solvent containing a cation exchange extractant, and then removing it using an acidic solution. This method achieves a high lithium recovery rate and improves economic efficiency and economy by reducing the energy, time, and cost associated with lithium recovery.

Description

Technical Field

[0001] [Cross-reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0088106 filed on July 4, 2024, and all contents disclosed in the document of said Korean patent application are incorporated as a part of the present specification.

[0002] The present invention relates to a method for recovering a lithium compound from a positive electrode material of a lithium ion battery. More specifically, the present invention relates to a method for recovering a lithium compound from a positive electrode material of a lithium ion battery, wherein lithium is directly extracted from a reduced roasted product of the positive electrode material of the lithium ion battery with an organic solvent containing a cation exchange extractant, and then stripped using an acidic solution, thereby achieving a high lithium recovery rate, reducing the energy, time and cost required for concentration to recover lithium, and improving economic efficiency and efficiency.

Background Art

[0003] Demand for lithium ion batteries has continuously increased along with the market for portable electronic devices since the 1990s. With the recent rapid expansion of the electric vehicle market, the global demand for lithium ion batteries has also increased sharply. This may cause instability in the supply and demand of lithium resources in the near future, and continuously accumulated end-of-life waste batteries may also cause major environmental problems. To solve such problems, recycling of used lithium ion batteries is a very important technical issue.

[0004] Lithium ion batteries are broadly composed of: a positive electrode in which a positive electrode active material layer is coated on a metal foil such as aluminum, a negative electrode in which a negative electrode active material layer is coated on a metal foil such as copper, a separator that prevents the positive electrode and the negative electrode from mixing, and an electrolyte that allows lithium ions to move between the positive electrode and the negative electrode.

[0005] The positive electrode accounts for more than 60% of the cost of a lithium-ion battery. For such positive electrodes, lithium cobalt oxide (LiCoO2) is used because it has excellent reversibility, low self-discharge rate, high capacity, high energy density, and is easy to synthesize. In addition, to reduce the amount of expensive cobalt used, composite oxides such as lithium nickel cobalt manganese oxide (Li(Ni,Co,Mn)O2), lithium manganese oxide (LiMnO2), and lithium iron phosphorus oxide (LiFePO4), which contain Ni and Mn, are used. Since the above-mentioned positive electrode materials contain about 5-7% by weight of lithium, methods for recovering lithium compounds from the positive electrode material of waste lithium-ion batteries are attracting considerable attention.

[0006] Conventional methods for recovering lithium compounds from the cathode material of waste lithium-ion batteries involve converting lithium to lithium carbonate through a reduction heat treatment using carbon, followed by water leaching. While this method allows for selective recovery of lithium, it suffers from low lithium recovery rates and the significant energy, cost, and time required for processes such as evaporation, vacuum concentration, or electrochemical concentration to concentrate the lithium carbonate.

[0007] Therefore, there is a need to develop a method for recovering lithium compounds from the cathode material of waste lithium-ion batteries that can increase the recovery rate of lithium compounds recovered from the cathode material of waste lithium-ion batteries and reduce the energy, cost, and time required for lithium concentration. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent No. 10-2015-0094412 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] To solve the problems of the conventional technology described above, the present invention aims to provide a method for recovering lithium compounds from lithium-ion battery cathode materials, which achieves a high lithium recovery rate and improves economic efficiency and economy by reducing the energy, time, and cost required for lithium concentration. This is achieved by directly extracting lithium from the reductively roasted product of the cathode material of a lithium-ion battery with an organic solvent containing a cation exchange extractant, and then removing it using an acidic solution.

[0010] Furthermore, the present invention aims to provide a high-purity lithium compound.

[0011] The above-mentioned and other objectives of the present invention can all be achieved by the present invention as described below. [Means for solving the problem]

[0012] To achieve the above objectives, I) the present invention provides a method for recovering lithium compounds, comprising the steps of: (a) extracting a reductive roasted product of a lithium-ion battery cathode material with an organic solvent containing a cation exchange extractant to obtain an organic solvent from which lithium has been extracted and an extraction residue; (b) separating the organic solvent from which lithium has been extracted from the extraction residue; (c) stripping the separated organic solvent from which lithium has been extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent; (d) separating the lithium-containing aqueous solution from the organic solvent; and (e) carbonating lithium in the separated lithium-containing aqueous solution to obtain lithium carbonate.

[0013] II) In I) above, the reductive roasted product of the positive electrode material may preferably be obtained by mixing the positive electrode material of a lithium-ion battery and a carbon-containing reducing agent, roasting them at 550 to 750°C, and then crushing them.

[0014] III) In I) or II) above, the carbon-containing reducing agent may preferably be used in amounts of 0 to 3 moles per mole of positive electrode active material in the positive electrode material of the lithium-ion battery.

[0015] IV) In I) to III) above, the carbon-containing reducing agent may preferably be an organic substance containing carbon, an inorganic substance containing carbon, a negative electrode material, or a mixture thereof.

[0016] V) In I) to IV) above, the roasting may preferably be carried out under a reducing gas or an inert gas.

[0017] VI) In I) to V) above, the positive electrode material of the lithium-ion battery may preferably be one or more selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide; lithium nickel oxide; nickel-manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co).

[0018] VII) In I) to VI) above, the positive electrode material of the lithium-ion battery may preferably be the positive electrode material of a discarded lithium-ion battery.

[0019] VIII) In the above I) to VII), a milling machine may preferably be used for the grinding.

[0020] IX) In steps I) to VIII) above, the cation exchange extractant in step (a) may preferably include an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof.

[0021] X) In any one of I) to IX) above, the alkyl phosphate-based extractant preferably may comprise one or more selected from the group consisting of Di-(2-ethylhexyl)phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and Bis(2,4,4-trimethylpentyl)phosphinic acid.

[0022] XI) In any one of I) to X) above, the alkyl monocarboxylic acid preferably may comprise a compound represented by the following Chemical Formula 1.

[0023]

Chemical Formula

[0024] In Chemical Formula 1 above, R1 and R2 are each independently an alkyl group, and the total number of carbon atoms in R1 and R2 is 5 to 9.

[0025] XII) In any one of I) to XI) above, in the step (a), the organic solvent preferably may comprise one or more selected from the group consisting of kerosene, hexane, benzene and toluene.

[0026] XIII) In any one of I) to XII) above, the content of the cation exchange extractant in the step (a) is preferably 0.9 to 2.5 moles per 1 mole of lithium in the reduced and roasted product of the positive electrode material of a lithium ion battery.

[0027] XIV) In any one of I) to XIII) above, in the step (a), the solid-liquid ratio of the reduced and roasted product of the positive electrode material of a lithium ion battery to the organic solvent containing the cation exchange extractant may preferably be 1 g / 8 mL to 1 g / 44 mL.

[0028] XV) In steps I) to XIV) above, in step (b), vacuum filtration may preferably be used to separate the organic solvent from which lithium has been extracted from the extraction residue.

[0029] XVI) In steps I) to XV) above, in step (c), the volume ratio of the organic solvent from which lithium was extracted to the acidic solution (organic / aqueous volume ratio) may preferably be 0.5 to 10.

[0030] XVII) In steps I) to XVI), the acidic solution in step (c) may preferably be an aqueous sulfuric acid solution, an aqueous hydrochloric acid solution, or an aqueous nitric acid solution.

[0031] XVIII) In steps I) to XVII) above, carbonation in step (e) may preferably be carried out by adding a carbonate or carbon dioxide.

[0032] XIX) In steps I) to XVIII), the organic solvent separated in step (d) may preferably be reused for extraction in step (a).

[0033] XX) In I) to XIX) above, the method for recovering lithium compounds from the positive electrode material of the lithium-ion battery preferably further includes the step of leaching the extraction residue obtained in step (b) with an acid to obtain a leachate in which residual metal compounds are dissolved. [Effects of the Invention]

[0034] According to the present invention, lithium is extracted directly from the reductively roasted product of the positive electrode material of a lithium-ion battery using an organic solvent containing a cation exchange extractant, and then removed using an acidic solution. This greatly improves the lithium recovery rate, reduces the loss of organometallic compounds, and significantly reduces the energy, time, and cost required in the concentration process for lithium recovery, thereby improving economic efficiency and overall economy.

[0035] Furthermore, the organic solvent containing the cation exchange extractant, which is separated after desorption, can be reused for extraction, thereby reducing wastewater generation and lowering production costs. [Brief explanation of the drawing]

[0036] The following drawings accompanying this specification illustrate embodiments of the present invention and, together with the detailed description below, serve to further illustrate the technical concept of the present invention. Therefore, the present invention should not be construed as being limited to the matters depicted in these drawings. [Figure 1] This is Example 1 of the present invention, showing kerosene containing a cation exchange extractant (di-2-ethylhexyl phosphate) before and after lithium extraction. The left side shows the state before extraction, and the right side shows the state after extraction. [Figure 2] This is a process diagram for a method of recovering a lithium compound from the cathode material of a lithium-ion battery, according to one embodiment of the present invention. [Figure 3] This graph shows the extraction rates of Li, Ni, Co, Mn, and Al in Examples 1 to 4 according to the present invention. [Figure 4] This graph shows the extraction rates of Li, Ni, Co, Mn, and Al in Examples 1, 5, and 6 according to the present invention. [Figure 5] This graph shows the extraction rates of Li, Ni, Co, Mn, and Al in Examples 1, 7, and 8 according to the present invention. [Figure 6] This shows the lithium carbonate recovered from Example 8 according to the present invention. [Modes for carrying out the invention]

[0037] The inventors of the present invention were researching a method for recovering lithium compounds from the positive electrode material of lithium-ion batteries. They found that when lithium is directly extracted from the reductively roasted product of the positive electrode material of lithium-ion batteries using an organic solvent containing a cation exchange extractant, and then removed with an acidic solution, the lithium recovery rate is high. This method also reduces the energy, cost, and time required in the concentration process for lithium recovery, while allowing for easy concentration. Based on this, they continued their research and completed the present invention.

[0038] Method for recovering lithium compounds from the cathode material of lithium-ion batteries The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, comprising the steps of: (a) extracting the reductive roasted product of the positive electrode material of the lithium-ion battery with an organic solvent containing a cation exchange extractant to obtain the organic solvent from which lithium has been extracted and the extraction residue; (b) separating the organic solvent from which lithium has been extracted from the extraction residue; (c) stripping the separated organic solvent from which lithium has been extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent; (d) separating the lithium-containing aqueous solution from the organic solvent; and (e) carbonating lithium in the separated lithium-containing aqueous solution to obtain lithium carbonate. In this case, the lithium recovery rate is high, and the energy, time, and cost required for concentration to recover lithium are reduced, resulting in excellent economy and efficiency.

[0039] The following describes in detail, step by step, the method for recovering lithium compounds from the cathode material of the lithium-ion battery described in this document.

[0040] However, the terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their invention. Therefore, it should be understood that the embodiments and configurations shown in the drawings described herein are merely embodiments of the present invention and do not represent the entirety of the technical idea of ​​the present invention, and that there may be various equivalents and modifications that can substitute for them, and that they may be arranged, substituted, combined, separated or designed in various other configurations.

[0041] All technical and scientific terms used herein have the same meaning as those commonly understood by those with ordinary skill in the art to which this invention pertains, unless otherwise defined.

[0042] (a) A step of extracting the reductively roasted product of the positive electrode material of a lithium-ion battery with an organic solvent containing a cation exchange extractant, and obtaining the organic solvent from which lithium has been extracted and the extraction residue. The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, which may include the steps of (a) extracting the reductive roasted product of the positive electrode material of the lithium-ion battery with an organic solvent containing a cation exchange extractant, and obtaining the organic solvent from which lithium has been extracted and the extraction residue. In this case, by directly extracting lithium from the reductive roasted product of the positive electrode material of the lithium-ion battery, the lithium recovery rate is greatly improved, and there is an economic advantage in that the organic solvent contains few impurities such as Ni, Co, and Mn, and the extraction residue contains a large amount of Ni, Co, Mn, etc., making it easy to manufacture as a precursor raw material.

[0043] The term "cathode material" as used herein means that it contains or is a cathode active material.

[0044] In step (a) above, the cation exchange extractant may include, for example, an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof. In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reductive roasted product of the positive electrode material of the lithium-ion battery.

[0045] The alkyl phosphate extractant may, for example, include one or more selected from the group consisting of di-(2-ethylhexyl)phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and bis(2,4,4-trimethylpentyl)phosphinic acid. Preferably, it may include di-2-ethylhexyl phosphate, which has the advantage of greatly improving the lithium recovery rate by directly extracting lithium from the reductive roasted product of the positive electrode material of the lithium-ion battery.

[0046] The alkyl monocarboxylic acid mentioned above may include, for example, a compound represented by the following chemical formula 1. In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reductive roasted product of the positive electrode material of the lithium-ion battery.

[0047] [ka]

[0048] In the above chemical formula 1, R1 and R2 are each independently alkyl groups, and the total number of carbon atoms in R1 and R2 is 5 to 9, preferably 6 to 8, and more preferably 7.

[0049] The aforementioned cationic extractant can exist, for example, in the form of a monomer, dimer, or polymer. In the case of a monomer, it reacts with lithium as shown in reaction equation 1 below, and in the case of a dimer, it reacts with lithium as shown in reaction equation 2 below.

[0050] [Reaction Equation 1] Li+(aq)+HA(org)=LiA(orq)+H+(aq) [Reaction Equation 2] Li+(aq)+(HA)2(org)=Li(A·HA)n(orq)+H+(aq) In reaction equations 1 and 2, A is a cation exchange extractant.

[0051] In step (a) above, the organic solvent is used to dilute the cation exchange extractant and may include, for example, one or more selected from the group consisting of kerosene, hexane, benzene, and toluene. Preferably, it may be kerosene, in which case there is an economic advantage in that the viscosity of the cation exchange extractant is reduced, thereby facilitating its bonding with the reductive roasted product of the positive electrode material of the lithium-ion battery and reducing the amount of cation exchange extractant used.

[0052] As the kerosene mentioned above, it can be obtained by heating crude oil, collecting the gas that vaporizes at 180-250°C, and then liquefying it.

[0053] As the hexane mentioned above, it can be obtained by heating crude oil, collecting the gas that vaporizes at 65-70°C, and then liquefying it.

[0054] As the benzene, an aromatic compound produced by a hydrodealkylation process of toluene at 500-650°C can be used.

[0055] As the toluene mentioned above, aromatic compounds obtained by separating and refining by-products generated during the production of gasoline from crude oil can be used.

[0056] In step (a) above, the organic solvent may, for example, contain a cation exchange extractant at a concentration of 0.7 to 1.3 molars (mol / L), preferably 0.8 to 1.2 molars (mol / L), and more preferably 0.9 to 1.1 molars (mol / L). Within this range, there is the advantage that lithium in the reductively roasted product of the positive electrode material of the lithium-ion battery can be easily leached out.

[0057] In step (a) above, the cation exchange extractant can, for example, be present in an amount of 0.9 to 2.5 moles, preferably 1.0 to 2.4 moles, more preferably 1.2 to 2.3 moles, even more preferably 1.3 to 2.2 moles, and even more preferably 1.4 to 2.1 moles per mole of lithium in the reduced roasted product of the positive electrode material of the lithium-ion battery. Within this range, the lithium in the reduced roasted product of the positive electrode material of the lithium-ion battery binds sufficiently with the cation exchange extractant, which has the advantage of being easily extracted into an organic solvent.

[0058] In step (a) above, the solid-liquid ratio of the reductive roasted product of the lithium-ion battery positive electrode material to the organic solvent containing the cation exchange extractant may be, for example, 1g / 8mL to 1g / 44mL, preferably 1g / 15mL to 1g / 42mL, more preferably 1g / 18mL to 1g / 42mL, even more preferably 1g / 18mL to 1g / 35mL, and even more preferably 1g / 18mL to 1g / 25mL. Within this range, the lithium in the reductive roasted product of the lithium-ion battery positive electrode material binds smoothly with the cation exchange extractant, which has the advantage of being easily extracted into the organic solvent.

[0059] In this description, the solid-liquid ratio refers to the volume of liquid relative to the weight of the solid, that is, the volume (mL) of the organic solvent containing the cation exchange extractant relative to the content (g) of the reductively roasted product of the positive electrode material of the lithium-ion battery.

[0060] In the extraction in step (a) above, the lithium in the reductive roasted product of the positive electrode material of the lithium-ion battery combines with the cation exchange extractant to form a complex, which is then extracted into an organic solvent.

[0061] In step (a) above, the extraction can be carried out, for example, by adding the reductive roasted product of the lithium-ion battery cathode material to an organic solvent containing a cation exchange extractant, and then stirring with a stirrer at room temperature. In this case, the lithium in the reductive roasted product of the lithium-ion battery cathode material is easily extracted into the organic solvent, which has the advantage of shortening the extraction time.

[0062] In this description, "room temperature" can refer to any single location within the range of 20±5℃.

[0063] The stirring speed may be, for example, 100 to 500 rpm, preferably 200 to 400 rpm, and more preferably 250 to 350 rpm. Within this range, there is the advantage that lithium can be easily extracted from the reductive roasted product of the positive electrode material of the lithium-ion battery.

[0064] The stirring time may be, for example, 0.5 hours or more, preferably 0.5 to 2 hours, more preferably 0.5 to 1.5 hours, and even more preferably 0.7 to 1.2 hours. Within this range, lithium in the reductive roasted product of the positive electrode material of the lithium-ion battery is sufficiently extracted, and lithium compounds are recovered in high yield.

[0065] In step (a) above, the reductive roasted product of the lithium-ion battery cathode material may, for example, be obtained by roasting the lithium-ion battery cathode material, or a mixture of lithium-ion battery cathode material and a carbon-containing reducing agent, at 550 to 750°C and then grinding it. In this case, there is an advantage that the lithium recovery rate is improved because lithium is easily extracted into an organic solvent containing a cation exchange extractant.

[0066] As an example, the aforementioned roasting process can be used to obtain a reduced roasted product of lithium-ion battery cathode material by heat-treating the cathode material of lithium-ion battery, or lithium-ion battery cathode material and a carbon-containing reducing agent, at 550-750°C. In this case, the binder added during the manufacturing of the cathode material is removed, and metallic substances bonded to oxygen are reduced, resulting in the recovery of high-purity lithium compounds in high yield.

[0067] As a specific example, the reductive roasted lithium-ion battery positive electrode material can be obtained by crushing the lithium-ion battery positive electrode to separate the current collector, and then heat-treating the resulting powdered lithium-ion battery positive electrode material at 550-750°C. In this case, the conductive material and binder within the lithium-ion battery positive electrode material act as reducing agents, and through roasting, the binder added during the manufacturing of the positive electrode material is removed, and metallic substances bound to oxygen are reduced, resulting in the advantage of recovering high-purity lithium compounds in high yield.

[0068] As another specific example, the reduced roasted lithium-ion battery cathode material can be obtained by crushing the lithium-ion battery cathode to separate the current collector, then mixing the resulting powdered lithium-ion battery cathode material with a carbon-containing reducing agent and heat-treating it at 550-750°C. In this case, the advantage is that the binder added during the manufacturing of the cathode material is removed through roasting, and metallic substances bound to oxygen are reduced, thereby recovering high-purity lithium compounds in high yield.

[0069] The positive electrode material and carbon-containing reducing agent of the lithium-ion battery can preferably be mixed dry, which has the advantage of maximizing the carbon reduction effect.

[0070] The carbon-containing reducing agent may be used in amounts of 0 to 3 moles, or more than 0 moles but less than or equal to 3 moles, preferably 0.3 to 3 moles, more preferably 0.3 to 2 moles, even more preferably 0.7 to 1.5 moles, and even more preferably 0.9 to 1.2 moles, per mole of positive electrode active material in the positive electrode material of a lithium-ion battery. Within this range, it is possible to reduce the amount of carbon-containing compound used as a reducing agent while maintaining high heat treatment efficiency and shortening the reaction time. Furthermore, even if the amount of carbon-containing reducing agent exceeds 3 moles per mole of positive electrode material in a lithium-ion battery, the recovery rate of lithium compounds does not increase, and production costs increase.

[0071] In this description, the content (moles) of the positive electrode active material in the positive electrode material can be measured by a method commonly used for measuring the content of positive electrode active material in the art to which this invention belongs. For example, it can be calculated using the content and molecular weight of the metal component measured by ICP analysis. Specifically, in ICP analysis, 0.01 g of positive electrode material, 3 mL of HCl, and 0.5 mL of H2O2 are placed in a conical tube and mixed, then heated to dissolve. Once the positive electrode material has dissolved, it is placed in a 50 mL tube for dilution, and the content (moles) of the metal component can be measured by ICP analysis.

[0072] As another example, the weight ratio of the positive electrode material to the carbon-containing reducing agent in the lithium-ion battery may be 1:0.06 to 1:0.19, preferably 1:0.08 to 1:0.17, more preferably 1:0.10 to 1:0.15, and even more preferably 1:0.11 to 1:0.13. Within this range, there is an effect of high heat treatment efficiency and shortened reaction time.

[0073] The carbon-containing reducing agent may, for example, be an organic substance containing carbon, an inorganic substance containing carbon, a negative electrode material, or a mixture thereof, and preferably graphite, in which case it has the advantage of reacting easily with lithium in the positive electrode material of the lithium-ion battery.

[0074] The graphite may preferably have a fixed carbon content of 90% by weight or more, more preferably 95% by weight or more, and even more preferably 98% by weight or more. Within this range, there is the advantage that it reacts easily with lithium in the cathode material.

[0075] In this document, fixed carbon content (by weight) refers to the content of the combustible residue remaining after volatile components have evaporated from carbon, excluding volatile components, moisture, and ash.

[0076] The aforementioned graphite may preferably be graphite derived from the negative electrode material, in which case there are advantages in reducing production costs and reusing resources.

[0077] In this description, roasting can be defined according to the definition used in the technical field to which this invention belongs, and specifically, it can be defined as a process that induces a gas-solid reaction at a high temperature to impart advantageous chemical properties for subsequent processes.

[0078] The roasting step may, for example, not include any reducing agent other than a carbon-containing reducing agent. In this case, there is an advantage in that the purity and recovery rate of the recovered lithium compound can be increased by reducing impurities.

[0079] The roasting may, for example, be carried out under a reducing gas or inert gas atmosphere, preferably under a nitrogen (N2) gas or argon gas atmosphere, more preferably under a nitrogen (N2) gas atmosphere. In this case, there is the advantage that the cathode material is easily reduced and lithium compounds can be recovered in high yield.

[0080] As an example, the positive electrode material of the lithium ion battery may be one or more selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compounds; lithium nickel cobalt aluminum oxide; lithium nickel oxide; nickel-manganese-based lithium composite metal oxides obtained by substituting a part of nickel (Ni) with manganese (Mn) in said lithium nickel oxide; and NCM-based lithium composite transition metal oxides obtained by substituting a part of nickel (Ni) with manganese (Mn) and cobalt (Co) in said lithium nickel oxide, and in this case, there is an effect of being excellent in reversible capacity and thermal stability.

[0081] As another specific example, the positive electrode material of the lithium ion battery is a compound represented by the following Chemical Formula 2 (Chemical Formula 2) LiaNixMnyCozMwO2+δ (In Chemical Formula 2, M comprises one or more selected from the group consisting of B, W, Al, Ti and Mg, wherein 1<a≦1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≦w≦0.1, -0.02≦δ≦0.02, and x+y+z+w=1.).

[0082] As an example, the positive electrode material of the lithium ion battery may be a positive electrode material from a spent lithium ion battery. In this case, valuable lithium as well as Ni, Co, Mn and the like can be recovered, which has the economic advantage of reusing resources.

[0083] As an example, the flow rate of the reducing gas or inert gas may be 1 to 30 L / min, preferably 3 to 25 L / min, more preferably 5 to 20 L / min, and still more preferably 7 to 12 L / min. Within this range, there is an advantage of excellent reaction efficiency.

[0084] The roasting process can be carried out, for example, at 550-750°C, preferably at 570-730°C, more preferably at 600-720°C, and even more preferably at 620-700°C. Within this range, lithium in the cathode material is converted to lithium carbonate at a high level, which has the advantage of reducing manufacturing costs.

[0085] After roasting, the material can be cooled in a furnace.

[0086] In this description, furnace cooling refers to the operation of cooling a heat-treated material in a heating furnace, specifically a method of gradually cooling it from a high temperature inside the furnace.

[0087] The rate at which the temperature rises to reach the roasting temperature is, for example, 1 to 20°C / min, preferably 3 to 10°C / min, and more preferably 3 to 7°C / min. Within this range, the burden on the roasting equipment is suppressed, and there is the advantage that thermal shock and other problems do not occur in the positive electrode material.

[0088] The roasting can be carried out for, for example, 0.5 to 7 hours, preferably 2 to 6.5 hours, more preferably 3 to 6 hours, and even more preferably 4 to 6 hours. Within this range, the binder in the cathode material is removed, and lithium is converted to lithium carbonate by carbon at a high level, which has the advantage.

[0089] In this description, roasting time refers to the time spent processing at the roasting temperature, and does not include the time it takes to reach that roasting temperature.

[0090] The aforementioned roasting can, for example, be carried out under atmospheric pressure, which has the advantages of reducing labor costs and ensuring a safer process.

[0091] In this text, atmospheric pressure can be normal pressure and refers to 1 atm as the pressure of air (atmosphere).

[0092] The roasting process can be carried out using various types of furnaces, for example, preferably in a box-type furnace, and more preferably in a closed-type firing furnace. In this case, continuous processing is possible, productivity is excellent, and the reduction reaction can be promoted, which has the advantage of a superior conversion rate to lithium compounds.

[0093] The reaction mechanism that occurs in the roasting step is, as an example, as shown in the following reaction equations 3 to 5.

[0094] [Reaction Equation 3] 4LiMeO2 + C- → 2Li2O + 4MeO + CO2 [Reaction Equation 4] Li2O + CO2- → Li2CO3 [Reaction Equation 5] 2MeO + C- → 2Me + CO2 In reaction equations 3 to 5, Me is one or more of Ni, Co, and Mn.

[0095] Specifically, the reaction mechanism that occurs in the roasting step involves a phase decomposition as shown in reaction equation 3 when 0.3 moles or more of carbon-containing reducing agent are added per mole of positive electrode active material in the positive electrode material. Simultaneously with reaction equation 3, a phase change to Li2CO3 occurs as shown in reaction equation 4. At this time, the reaction shown in reaction equation 5 occurs due to the addition of 0.3 moles or more of carbon-containing reducing agent, and the CO2 generated at this time causes the excess Li2O generated in reaction equation 3 to undergo a phase change to Li2CO3.

[0096] The aforementioned crushing refers to crushing, grinding, or both.

[0097] The aforementioned grinding step can, for example, be performed using a milling machine, preferably a roll press, a ball mill, or a pin mill, and more preferably a roll mill and a pin mill can be used sequentially. In this case, the specific surface area of ​​the reductively roasted material of the positive electrode material of the lithium-ion battery increases, making lithium extraction easier, which has the advantage of increasing the lithium recovery rate.

[0098] The reductive roasted product of the lithium-ion battery cathode material obtained after the grinding step may, for example, have an average particle size (D50) of 0.5 to 50 μm, preferably 1 to 40 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm. Within this range, lithium can be easily extracted from the reductive roasted product of the lithium-ion battery cathode material, which has the advantage of increasing the lithium recovery rate.

[0099] In this description, the average particle size (D50) of the reductively roasted material can be measured by a measurement method commonly used in the art to which the present invention pertains. For example, it can be measured using the laser diffraction method. Specifically, the particles of the reductively roasted material are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer such as Microtrac S3500, and ultrasonic waves of approximately 28 kHz are irradiated at an output of 60 W. The average particle size (D50) based on the 50% standard of the particle size distribution in the measuring device can then be calculated.

[0100] The aforementioned grinding can, for example, be carried out under dry conditions. In this case, the reductive roasted material of the positive electrode of the lithium-ion battery is uniformly ground, which has the advantage of facilitating lithium extraction.

[0101] In this description, dry conditions are the opposite concept to wet conditions, which use solvents or additives, and can mean methods that do not use solvents or additives.

[0102] (b) Step of separating the organic solvent from which the lithium was extracted from the extraction residue. The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, which may include the step of (b) separating the organic solvent from which the lithium was extracted from the extraction residue. In this case, the separated organic solvent from which the lithium was extracted contains few impurities such as Ni, Co, and Mn, resulting in a high lithium recovery rate. Furthermore, the extraction residue contains a large amount of Ni, Co, Mn, etc., which has the economic advantage of being easily manufactured as a precursor raw material.

[0103] In step (b) above, the separation can be carried out, for example, by vacuum filtration. In this case, the organic solvent from which lithium has been extracted and the extraction residue can be easily separated by only a simple process, which has the advantage of reducing labor costs.

[0104] The aforementioned reduced-pressure filtration may preferably be vacuum reduced-pressure filtration, specifically vacuum reduced-pressure filtration using a filtration flask, which has the advantage that the organic solvent from which lithium has been extracted and the extraction residue can be easily separated.

[0105] In the present invention, vacuum vacuum filtration is not particularly limited as long as it is a normal vacuum vacuum filtration in the art to which the present invention belongs, and as an example, it may include filtration in a partial vacuum or low pressure state.

[0106] The organic solvent from which the lithium was extracted contains a cation exchange extractant.

[0107] (c) Steps to remove (stripping) the organic solvent from which the separated lithium was extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent. The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, which may include the step of (c) stripping the organic solvent from which the separated lithium has been extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent. In this case, there is an advantage that lithium can be easily recovered by back-extracting the lithium that has been combined with a cation exchange extractant and extracted into the organic solvent with an acidic solution.

[0108] In step (c) above, the volume ratio of the organic / aqueous solution from which lithium has been extracted to the acidic solution may be, for example, 0.5 to 10, preferably 1 to 8, more preferably 1 to 7, even more preferably 1 to 6, even more preferably 1.5 to 6, particularly preferably 2.5 to 6, particularly even more preferably 3.5 to 6.0, and in the most preferred example, 4 to 5.5. Within this range, lithium is easily back-extracted into the acidic solution, which has the advantage of easily recovering lithium in subsequent steps, reducing the energy, cost, and time required to concentrate lithium, and improving economy and efficiency.

[0109] In step (c) above, the acidic solution may be, for example, an aqueous sulfuric acid solution, an aqueous hydrochloric acid solution, or an aqueous nitric acid solution, preferably an aqueous sulfuric acid solution. In this case, the lithium in the organic solvent is easily removed into the acidic solution, which has the advantage of increasing the lithium recovery rate and allowing lithium to be easily concentrated and recovered.

[0110] The acidic solution may, for example, contain an acid at a concentration of 0.5 to 1.5 molars (mol / L), preferably 0.7 to 1.3 molars, and more preferably 0.9 to 1.1 molars. Within this range, lithium in the organic solvent is easily removed into the acidic solution, which increases the lithium recovery rate and has the advantage of allowing lithium to be easily concentrated and recovered.

[0111] The acidic solution may, for example, have a pH of 1 or less, preferably pH 0 to 1, and more preferably pH 0 to 0.5. Within this range, lithium in the organic solvent is easily removed into the acidic solution, which has the advantage of increasing the lithium recovery rate and allowing lithium to be easily concentrated.

[0112] In step (c) above, the removal can be carried out, for example, by adding an acidic solution to the organic solvent from which the separated lithium was extracted, and then stirring it with a stirrer at room temperature.

[0113] The stirring can be performed, for example, at 300 to 800 rpm, preferably 400 to 700 rpm, and more preferably 500 to 700 rpm. Within this range, there is the advantage that the back extraction of lithium from the organic solvent into an acidic solution is promoted.

[0114] The stirring can be carried out for, for example, 20 minutes or more, preferably 20 to 60 minutes, and more preferably 20 to 40 minutes, and within this range, lithium has the advantage of being sufficiently back-extracted from the organic solvent into the acidic solution.

[0115] (d) Step of separating the lithium-containing aqueous solution from the organic solvent. The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, which may include the step of separating the lithium-containing aqueous solution from the organic solvent. In this case, there is an advantage that the subsequent carbonation step of carbonizing lithium can be carried out smoothly.

[0116] The organic solvent obtained after separation in step (d) above can be reused in the extraction in step (a) above, for example, which reduces wastewater generation, lowers production costs, and has the advantage of being environmentally friendly.

[0117] (e) A step of obtaining lithium carbonate by carbonating lithium in the separated lithium-containing aqueous solution. The present invention provides a method for recovering lithium compounds from the positive electrode material of a lithium-ion battery, which may include the step of (e) carbonating lithium in a separated lithium-containing aqueous solution to obtain lithium carbonate, in which case there is an advantage that the energy, cost, and time required for concentration to recover lithium are greatly reduced.

[0118] In step (e) above, carbonation may be carried out by adding a carbonate or carbon dioxide, for example, which has the advantage of recovering lithium as lithium carbonate in high yield and reducing the energy, cost, and time required for concentration to recover lithium.

[0119] The carbonate may, for example, be one or more selected from the group consisting of sodium carbonate, ammonium carbonate, and potassium carbonate. In this case, lithium can be recovered in high yield as lithium carbonate, and the energy, cost, and time required for concentration to recover lithium are reduced.

[0120] The carbon dioxide gas may, for example, be carbon dioxide, in which case lithium can be recovered in high yield as lithium carbonate, and the energy, cost, and time required for concentration to recover lithium are reduced.

[0121] As an example, the carbonate can be added in an amount of 0.5 to 2.5 moles, preferably 0.7 to 2 moles, more preferably 1 to 1.7 moles, and even more preferably 1 to 1.5 moles per mole of lithium in a lithium-containing aqueous solution. Within this range, there is the advantage of reducing the energy, cost, and time required for concentration to recover lithium.

[0122] Preferably, the process may further include a step of removing impurities from the separated lithium-containing aqueous solution before the carbonation in step (e), which has the advantage of removing impurities such as Ni, Co, and Mn contained in the lithium-containing aqueous solution, thereby improving the purity of the lithium carbonate.

[0123] The aforementioned impurity removal step can, for example, be adjusted to pH 10-12 by adding a basic compound. In this case, impurities such as Ni, Co, and Mn are removed from the separated lithium-containing aqueous solution, which has the advantage of improving the purity of lithium carbonate.

[0124] In this description, pH can be measured by a measurement method commonly used in the art to which the present invention pertains, and unless otherwise specified, it can be measured at room temperature using a general pH measuring device, specifically using a METTLER TOLEDO SevenDirect SD30.

[0125] The basic compound may, for example, be a metal hydroxide, a metal carbon oxide, or a mixture thereof. In this case, there is the advantage that impurities such as Ni, Co, and Mn are removed from the separated lithium-containing aqueous solution, thereby improving the purity of the lithium carbonate.

[0126] The metal hydroxide may preferably be sodium hydroxide, potassium hydroxide, or a mixture thereof. In this case, there is an advantage in that impurities such as Ni, Co, and Mn are removed from the separated lithium-containing aqueous solution, thereby improving the purity of lithium carbonate.

[0127] The metal carbon oxide may preferably be sodium carbonate, potassium carbonate, or a mixture thereof. In this case, there is an advantage in that impurities such as Ni, Co, and Mn are removed from the separated lithium-containing aqueous solution, thereby improving the purity of the lithium carbonate.

[0128] For example, the lithium carbonate obtained after carbonation in step (e) above can be washed with water and then dried to obtain the final lithium carbonate.

[0129] Furthermore, the method for recovering lithium compounds from the positive electrode material of a lithium-ion battery according to the present invention may include a step of leaching the extraction residue separated in step (b) above with an acid, for example, to obtain a leachate in which residual metal compounds are dissolved. In this case, Ni, Co, Mn, etc., can be recovered and easily manufactured as precursor raw materials, thereby reusing resources and offering excellent economic advantages.

[0130] The acid may, for example, be sulfuric acid, nitric acid, or hydrochloric acid, and preferably sulfuric acid, in which case there is the effect of being able to recover residual metal compounds in high purity.

[0131] Figure 2 below is a flowchart illustrating one embodiment of the present invention, showing a method for recovering lithium carbonate from the cathode material of a lithium-ion battery.

[0132] Referring to Figure 2, first, the lithium-ion battery cathode material and a carbon-containing reducing agent are mixed and then roasted to produce a reduced roasted product of the lithium-ion battery cathode material (step S10).

[0133] The positive electrode material of the lithium-ion battery may preferably be positive electrode material from a discarded lithium-ion battery, defective products generated during the coating process of the positive electrode, or positive electrode scrap discarded after cutting the electrode plate. Preferably, it may be positive electrode material from a discarded lithium-ion battery, and more specifically, it may be positive electrode material powder obtained by crushing the positive electrode.

[0134] The positive electrode material of the lithium-ion battery is preferably one or more selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide; lithium nickel oxide; nickel-manganese-based lithium composite metal oxide in which a portion of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a portion of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co). In this case, there is an effect of excellent reversible capacity and thermal stability.

[0135] The carbon-containing reducing agent may preferably be an organic substance containing carbon, an inorganic substance containing carbon, a negative electrode material, or a mixture thereof, and more specifically, it may be a negative electrode material, in which case lithium can be easily extracted in the extraction step.

[0136] The carbon-containing reducing agent may be used, for example, at a rate of 0 to 3 moles per mole of positive electrode active material in the positive electrode material of a lithium-ion battery, or more than 0 moles but less than or equal to 3 moles. Specifically, 1 mole can be used, and within this range, the roasting efficiency is high and the roasting time is shortened. Furthermore, even if more than 3 moles of the carbon-containing reducing agent are added per mole of positive electrode active material in the positive electrode material of a lithium-ion battery, the lithium recovery rate will not increase further, and production costs will increase.

[0137] As another example, the weight ratio of the positive electrode material to the carbon-containing reducing agent in the lithium-ion battery may be 1:0.06 to 1:0.19, and specifically, it may be 1:0.11 to 0.13. Within this range, there is an effect of high heat treatment efficiency and shortened reaction time.

[0138] The positive electrode material and carbon of the lithium-ion battery can preferably be dry-mixed, which has the advantage of maximizing the reducing effect of the carbon-containing reducing agent.

[0139] Generally, lithium-ion battery cathode materials undergo complex processes during manufacturing to maintain or improve battery properties, including firing, addition of carbon and other metal oxides, and heat fusion after binder addition. For these reasons, discarded lithium-ion battery cathode materials come to contain various oxide forms of valuable metals and impurities, which can act as an obstacle when recovering lithium and valuable metals. Here, to eliminate such obstacles, the binder added during the manufacturing of the cathode material is removed and metallic substances bound to oxygen are reduced by roasting at high temperatures with a carbon-containing reducing agent. This process is called the roasting step.

[0140] The roasting process can be carried out, for example, under a reducing gas or inert gas atmosphere, specifically under a nitrogen gas atmosphere, which has the advantage of easily reducing the cathode material. In this case, the flow rate of the reducing gas or inert gas may be 1 to 20 L / min, specifically 10 L / min, and within this range, there is the advantage of easily removing the binder added during the manufacture of the cathode material and reducing metallic substances that are bound to oxygen.

[0141] The aforementioned roasting can be carried out at temperatures of 550-750°C, for example, and specifically at 650°C, and within this range, the positive electrode material is sufficiently reduced.

[0142] The rate at which the temperature rises to reach the aforementioned roasting temperature may be, for example, 1 to 20°C / min, specifically 3°C / min. Within this range, the burden on the roasting equipment is suppressed, and there is the advantage that thermal shock and other problems do not occur to the positive electrode material.

[0143] The aforementioned roasting can be carried out for 0.5 to 7 hours as an example, and specifically for 5 hours, and within this range, the positive electrode material is sufficiently reduced.

[0144] The aforementioned roasting can, for example, be carried out under atmospheric pressure, which has the advantages of being a safe process and reducing production costs.

[0145] Preferably, the roasting can be carried out using a closed-type firing furnace. In this case, continuous processing is possible, productivity is excellent, and the reduction reaction can be promoted, which has the advantage of allowing the recovery of high-purity lithium in high yield.

[0146] After roasting, the material can be slowly or rapidly cooled in the air.

[0147] Next, the reduced roasted product of the lithium-ion battery cathode material is crushed to obtain a powdered reduced roasted product of the lithium-ion battery cathode material (step S20).

[0148] By crushing the reductively roasted material of the positive electrode of the lithium-ion battery, the specific surface area is increased, making lithium extraction easier, which has the advantage of increasing the lithium recovery rate.

[0149] The reduced roasted product of the crushed lithium-ion battery cathode material may have an average particle size of, for example, 0.5 to 50 μm, and more specifically, 10 to 15 μm. Within this range, there is the advantage that the lithium recovery rate is maximized.

[0150] The aforementioned crushing can be carried out using, for example, a milling machine, specifically by sequentially using a roll mill and a pin mill. In this case, there is the advantage that the material can be uniformly crushed or crushed.

[0151] The aforementioned grinding may be dry grinding, which has the advantage of uniformly crushing or grinding the material and increasing the specific surface area of ​​the material.

[0152] Next, the reduced roasted product of the crushed lithium-ion battery cathode material is extracted with an organic solvent containing a cation exchange extractant to obtain the organic solvent from which lithium has been extracted and the extraction residue (step S30).

[0153] The cation exchange extractant may include, as an example, an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof.

[0154] The alkyl phosphate extractant may, for example, include one or more selected from the group consisting of di-(2-ethylhexyl)phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and bis(2,4,4-trimethylpentyl)phosphinic acid. Specifically, it may include di-(2-ethylhexyl)phosphate (D2EHPA), which has the advantage of greatly improving the lithium recovery rate by directly extracting lithium from the reductive roasted product of the positive electrode material of a lithium-ion battery.

[0155] The alkyl monocarboxylic acid mentioned above can include, for example, a compound represented by the following chemical formula 1, and specifically, neodecanoic acid. In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reductive roasted product of the positive electrode material of a lithium-ion battery.

[0156] [ka]

[0157] (In the above chemical formula 1, R1 and R2 are each independently alkyl groups, and the total number of carbon atoms in R1 and R2 is 5 to 9, preferably 6 to 8, and more preferably 7.)

[0158] The aforementioned organic solvent may, for example, include one or more selected from the group consisting of kerosene, hexane, benzene, and toluene. A specific example is kerosene, in which case there is an economic advantage in that the viscosity of the cation exchange extractant is reduced, thereby facilitating its bonding with the reductively roasted product of the positive electrode material of the lithium-ion battery, and reducing the amount of cation exchange extractant used.

[0159] The cation exchange extractant can, for example, contain 0.9 to 2.5 moles per mole of lithium in the reductive roasted product of the positive electrode material of a lithium-ion battery, and more specifically, 1 to 2 moles. Within this range, lithium can be easily and directly extracted from the reductive roasted product of the positive electrode material of a lithium-ion battery using an organic solvent containing the cation exchange extractant, which is an advantage.

[0160] The solid-liquid ratio of the reductive roasted product of the lithium-ion battery's positive electrode material to the organic solvent containing the cation exchange extractant may be, for example, 1 g / 8 mL to 1 g / 44 mL, and more specifically, 1 g / 10 mL to 1 g / 40 mL. Within this range, lithium can be sufficiently and directly extracted from the reductive roasted product of the lithium-ion battery's positive electrode material using the organic solvent containing the cation exchange extractant.

[0161] In step S30, the extraction can be carried out, for example, by adding an organic solvent containing a cation exchange extractant to the reductively roasted product of the lithium-ion battery cathode material, and then stirring it with a stirrer at room temperature. In this case, lithium in the reductively roasted product of the lithium-ion battery cathode material can be easily extracted, and the extraction time can be shortened.

[0162] The aforementioned stirring can be performed at, for example, 100 to 500 rpm, and more specifically, at 300 rpm. Within this range, there is the advantage of promoting the extraction of lithium compounds from the crushed material.

[0163] The aforementioned stirring can be carried out for 30 minutes or more, and more specifically for 60 minutes. Within this range, lithium compounds are sufficiently extracted from the reductively roasted material of the lithium-ion battery's cathode, which has the advantage of allowing lithium to be recovered with a high recovery rate.

[0164] The organic solvent from which lithium has been extracted, obtained after the extraction step (step S30), has a low content of impurities such as Ni, Co, and Mn, allowing for the easy recovery of high-purity lithium. Furthermore, the extraction residue contains Ni, Co, Mn, etc., and can therefore be used as a precursor raw material, offering economic advantages.

[0165] Next, the organic solvent from which lithium was extracted and the extraction residue are separated (step S40).

[0166] The separation of the organic solvent from which lithium was extracted from the extraction residue can preferably be performed using vacuum filtration. In this case, the organic solvent from which lithium was extracted and the extraction residue can be easily separated in a simple process, which has the advantage of reducing labor costs.

[0167] Through the separation described above, an organic solvent containing a dissolved lithium compound and an extraction residue are obtained.

[0168] Next, the organic solvent from which the separated lithium was extracted is stripped with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent (step S50).

[0169] In step S50, the removal process has the advantage of easily recovering lithium in subsequent steps by removing the lithium that has been extracted by binding with the cation exchange extractant in the organic solvent and back-extracting it into an acidic solution, and also by reducing the energy, cost, and time required for recovery.

[0170] The volume ratio of the organic solvent from which the separated lithium was extracted to the acidic solution (organic / aqueous volume ratio) may be 0.5 to 10, for example, and more specifically, 1 to 5. Within this range, lithium is easily removed, increasing the lithium recovery rate, and lithium is easily concentrated, which reduces the energy, cost, and time required, thus improving economic efficiency and productivity.

[0171] The acidic solution may be, for example, an aqueous solution of sulfuric acid, an aqueous solution of hydrochloric acid, or an aqueous solution of nitric acid, and a specific example may be an aqueous solution of sulfuric acid. In this case, lithium in the organic solvent is easily removed into the acidic solution, which increases the recovery rate of lithium. Furthermore, lithium can be easily concentrated, which reduces the energy, cost, and time required, thus improving economic efficiency and productivity.

[0172] The aforementioned acidic solution can, for example, contain an acid at a concentration of 0.5 to 1.5 molars (mol / L), and more specifically, at a concentration of 1 molar. Within this range, lithium in the organic solvent is easily removed into the acidic solution, which increases the lithium recovery rate and has the advantage of allowing lithium to be easily concentrated and recovered.

[0173] The aforementioned acidic solution may have a pH of 1 or less, for example, and could be pH 0. Within this range, lithium in the organic solvent is easily removed into the acidic solution, which increases the lithium recovery rate and has the advantage of allowing lithium to be easily recovered.

[0174] The removal in step S50 can be carried out by adding an acidic solution to the organic solvent from which the separated lithium was extracted, and then stirring it with a stirrer at room temperature.

[0175] The aforementioned stirring can be performed at, for example, 300 to 800 rpm, and more specifically, at 600 rpm. Within this range, there is the advantage that the back extraction of lithium from the organic solvent to the acidic solution is promoted.

[0176] The aforementioned stirring can be carried out for 20 minutes or more, for example, and specifically for 30 minutes, and within this range, there is the advantage that sufficient back-extraction of lithium from the organic solvent to the acidic solution is achieved.

[0177] Next, the lithium-containing aqueous solution and the organic solvent are separated (step S60).

[0178] In step S60, the separation involves separating the lithium-containing aqueous solution from the organic solvent to obtain the lithium-containing aqueous solution and the organic solvent, and recovering the lithium compound from the lithium-containing aqueous solution.

[0179] Furthermore, the separated organic solvent can be transferred to the extraction step (step S30) and reused. In this case, the generation of wastewater is reduced, production costs are lowered, and it has the advantage of being environmentally friendly.

[0180] Next, lithium is carbonated in the separated lithium-containing aqueous solution to obtain lithium carbonate (step S70).

[0181] The aforementioned carbonation can be carried out by adding a carbonate or carbon dioxide, and specifically by adding sodium carbonate, which has the advantage of rapidly converting lithium into lithium carbonate.

[0182] For example, the carbonate can be added at a rate of 0.5 to 2.5 moles per mole of lithium in a lithium-containing aqueous solution, and specifically, 1.2 moles can be added. In this case, there is the advantage of rapidly converting lithium into lithium carbonate.

[0183] The separated lithium-containing aqueous solution can be adjusted to a pH of 10-12 by adding a basic compound before carbonation. Specifically, sodium hydroxide can be added to adjust the pH to 10-12 and remove impurities. In this case, there is the advantage of improving the purity and recovery rate of lithium carbonate.

[0184] The lithium carbonate obtained after carbonation in step S70 can be washed with water and then dried to obtain the final lithium carbonate.

[0185] On the other hand, the extraction residue obtained after separation in step S40 is leached with acid (step S80).

[0186] After the acid leaching, a leachate containing dissolved residual metal compounds is obtained, and the acid may specifically be sulfuric acid.

[0187] The leachate (step S90) in which the residual metal compounds are dissolved contains residual metal compounds, specifically Ni, Co, and Mn, and can be used as a precursor raw material, thus offering economic advantages.

[0188] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications fall within the scope of the appended claims.

[0189] [Example I: Extraction rates of Li, Ni, Co, Mn, and Al based on solid-liquid ratio in the extraction step] Example 1 300g of powdered positive electrode material and 37.04g of negative electrode material (equivalent to 1 mole for every 1 mole of positive electrode active material in the positive electrode material) obtained from waste lithium-ion batteries were dry-mixed, then placed in a sealed firing furnace, heated to 650°C under a nitrogen atmosphere, held for 5 hours for heat treatment (roasting), and then cooled in the furnace for more than 10 hours to obtain reduced-roasted lithium-ion battery positive electrode material. Here, the temperature rise rate to reach the roasting temperature was 3°C / min, and nitrogen was supplied at 10 L / min.

[0190] The powdered cathode material obtained from the aforementioned waste lithium-ion battery was analyzed for its components by ICP analysis, as shown in Table 1 below. For the ICP analysis, 0.01 g of cathode material, 3 mL of HCl, and 0.5 mL of H2O2 were placed in a conical tube, mixed, and then heated to dissolve. Once the cathode material was dissolved, it was diluted in a 50 mL tube and measured by ICP analysis.

[0191] [Table 1]

[0192] The reduced-roasted lithium-ion battery cathode material was sequentially ground using a roll mill and a pin mill to obtain a powdered reduced-roasted lithium-ion battery cathode material with an average particle size (D50) of 11.5 μm.

[0193] The average particle size (D50) was measured using the laser diffraction method. Specifically, particles of the reductively roasted material were dispersed in a dispersion medium, then introduced into a Microtrac S3500 laser diffraction particle size analyzer. Ultrasound at approximately 28 kHz was irradiated at an output of 60 W, and the average particle size (D50) based on the 50% standard of the particle size distribution in the analyzer was calculated.

[0194] The reductive roasted product of the positive electrode material of the aforementioned lithium-ion battery was analyzed for its components by ICP analysis, and the results are shown in Table 2 below.

[0195] [Table 2]

[0196] Kerosene containing di-2-ethylhexyl phosphate (D2EHPA) at a concentration of 1 molar (mol / L) was prepared as a cation exchange extractant (hereinafter referred to as "D2EHPA-containing kerosene"). 20 mL of D2EHPA-containing kerosene was added to 1 g of the aforementioned powdered reductive roasted material, and extraction was carried out at room temperature for 1 hour to obtain the organic solvent from which lithium had been extracted and the extraction residue. During the extraction, the mixture was stirred at 300 rpm. At this time, the solid-liquid ratio was 1 g / 20 mL, and the amount of D2EHPA was equal to 2 moles, based on 1 mole of lithium in the reductive roasted material of the positive electrode material of a lithium-ion battery.

[0197] The lithium extracted from the D2EHPA-containing kerosene and the extraction residue were separated by vacuum filtration.

[0198] The D2EHPA-containing kerosene from which the separated lithium had been extracted was stripped with a 1 molar (mol / L) sulfuric acid aqueous solution, and lithium was back-extracted into the sulfuric acid aqueous solution to obtain a lithium-containing aqueous solution and D2EHPA-containing kerosene. At this time, the volume ratio (organic / aqueous volume ratio, O / A ratio) of the D2EHPA-containing kerosene from which the lithium had been extracted to the sulfuric acid aqueous solution was 1, and the stripping was carried out at room temperature with stirring at 600 rpm for 30 minutes.

[0199] The lithium-containing aqueous solution and the D2EHPA-containing kerosene were separated using a separation funnel.

[0200] Since the separated lithium-containing aqueous solution contained impurities including Ni, Co, and Mn, a 4-mol / L sodium hydroxide solution was added to raise the pH to 12, obtaining a precipitate containing Ni, Co, and Mn, as well as the lithium-containing aqueous solution. An impurity separation step was then performed to separate these two components. This impurity separation step was carried out at room temperature with stirring. The separation of the precipitate containing Ni, Co, and Mn from the lithium-containing aqueous solution was performed using vacuum filtration.

[0201] After separating the impurities, sodium carbonate was added to the purified lithium-containing aqueous solution to carbonate it, and lithium was recovered as lithium carbonate. The amount of sodium carbonate added was 1.2 moles per mole of lithium in the lithium-containing aqueous solution. At this time, the sodium carbonate was added at 80°C while stirring.

[0202] After the carbonation was completed, lithium carbonate was separated from the aqueous solution in the form of a wet cake.

[0203] To remove the large amount of sodium contained in the synthesized lithium carbonate in the wet cake state, the synthesized lithium carbonate was washed with water at 80°C. At this time, the mineral-to-liquid ratio (mineral-to-liquid ratio) of water to lithium carbonate powder was 1 g / 3 mL, and the washing process was carried out while stirring.

[0204] The washed lithium carbonate was dried at 130°C using a hot air dryer to obtain the final lithium carbonate.

[0205] Example 2 The procedure was carried out in the same manner as in Example 1, except that the solid-liquid ratio of the powdered reductive roasted material to the D2EHPA-containing kerosene was changed to 1 g / 10 ml.

[0206] Example 3 The procedure was carried out in the same manner as in Example 1, except that the solid-liquid ratio of the powdered reductive roasted material to the D2EHPA-containing kerosene was changed to 1 g / 30 ml.

[0207] Example 4 The procedure was carried out in the same manner as in Example 1, except that the solid-liquid ratio of the powdered reductive roasted material to the D2EHPA-containing kerosene was changed to 1 g / 40 ml.

[0208] [Test Example I: Extraction amounts and extraction rates of Li, Ni, Co, Mn, and Al] The lithium-containing aqueous solutions obtained in Examples 1-4, separated after desorption, were used to measure the content of Li, Ni, Co, Mn, and Al through ICP analysis. The results are shown in Table 3 and Figure 3 below.

[0209] *ICP analysis: 0.2 g of lithium-containing aqueous solution was taken and placed in a conical tube. After accurately weighing it, 0.1 ml of 70% by weight nitric acid was added, followed by 500 μl of 1000 mg / kg internal STD(Sc). The solution was then diluted with ultrapure water to a volume of 50 ml, and the contents of Li, Ni, Co, Mn, and Al were measured by ICP analysis.

[0210] *Extraction rate (weight %): The content of Li, Ni, Co, Mn, and Al in the reduced roasted product of the cathode material of lithium-ion batteries was measured by ICP analysis, and the extraction rate was calculated using the following formula 1.

[0211] [Formula 1] Extraction rate of component M (weight %) = [Content of component M in lithium-containing aqueous solution (g) / Content of component M in the reduced roasted material of the positive electrode material of lithium-ion batteries (g)] × 100 In the above formula 1, M is Li, Ni, Co, Mn, or Al.

[0212] [Table 3]

[0213] As shown in Table 3 and Figure 3 above, the extraction rate of Li was high within the solid-liquid ratio range of 1 g / 10 ml to 1 g / 40 ml, while the extraction rates of Ni, Co, Mn, and Al were low. In particular, the extraction rate of Li exceeded 99% by weight at solid-liquid ratios of 1 g / 20 ml or higher, and the extraction rates of Co and Mn were even lower at a solid-liquid ratio of 1 g / 10 ml.

[0214] [Example II: Extraction rate based on the molar ratio of lithium to D2EHPA in the reductive roasted product of the positive electrode material of a lithium-ion battery during the extraction step] Example 5 The procedure was carried out in the same manner as in Example 1, except that D2EHPA was added in an amount equal to 1.41 moles based on 1 mole of lithium in the reduced roasted product of the positive electrode material of the lithium-ion battery.

[0215] Example 6 The procedure was carried out in the same manner as in Example 1, except that D2EHPA was added in an amount equal to 1 mole based on 1 mole of lithium in the reduced roasted product of the positive electrode material of the lithium-ion battery.

[0216] [Test Example II: Content and Extraction Rate of Li, Ni, Co, Mn, and Al] The content of Li, Ni, Co, Mn, and Al was measured by ICP analysis using the same method as in Test Example I, and is shown in Table 4 below. The extraction rates calculated from the measured content are shown in Table 5 and Figure 4 below.

[0217] [Table 4]

[0218] As shown in Table 4 above, it was confirmed that when the molar ratio of D2EHPA to 1 mole of Li in the powdered reductive roasted material was 1 to 2, the amount of Li extracted was large, while the amounts of Ni, Co, Mn, and Al extracted were small.

[0219] [Table 5]

[0220] As shown in Table 5 above and Figure 4 below, it was confirmed that when the molar ratio of D2EHPA to 1 mole of Li in the powdered reductive roasted material was 1 to 2, the extraction rate of Li was high, while the extraction rates of Ni, Co, Mn, and Al were low.

[0221] [Example III: Extraction amount based on O / A ratio in the decontamination step] Example 7 The procedure was carried out in the same manner as in Example 1, except that the O / A ratio was changed to 3. At this time, the pH of the Li-containing aqueous solution was measured after removal.

[0222] Example 8 The procedure was carried out in the same manner as in Example 1, except that the O / A ratio was changed to 5. At this time, the pH of the Li-containing aqueous solution was measured after removal.

[0223] [Test Example III: Extraction amounts of Li, Ni, Co, Mn, and Al, and pH of Li-containing aqueous solution] The content of Li, Ni, Co, Mn, and Al was measured by ICP analysis using the same method as in Test Example I, and the results are shown in Table 6 and Figure 5 below.

[0224] pH was measured at room temperature using a METTLER TOLEDO SevenDirect SD30.

[0225] [Table 6]

[0226] As shown in Table 6 above and Figure 5 below, it was confirmed that when the O / A ratio was 1 to 5, the amount of Li extracted was large, while the amounts of Ni, Co, Mn, and Al extracted were small. Specifically, it was confirmed that the amount of Li extracted was largest in Example 8, where the O / A ratio was 5.

[0227] [Example IV: Recovery of lithium carbonate from lithium-containing aqueous solution separated after desorption] The Li, Ni, Co, Mn, and Al content of the lithium-containing aqueous solution obtained in Example 8, the lithium-containing aqueous solution after pH adjustment, and the filtrate remaining after carbonation were measured by ICP analysis and are shown in Table 7.

[0228] [Table 7]

[0229] As shown in Table 7 above, the lithium-containing aqueous solution from which impurities were removed by pH adjustment was found to be free of Ni, Co, and Mn, confirming that it was recovered as high-purity lithium carbonate.

[0230] [Example V: Impurity content of recovered lithium carbonate] The impurity content of the lithium carbonate recovered by carbonation in Example 8 was measured by ICP analysis and is shown in Table 8 below.

[0231] [Table 8]

[0232] *ND: Not Detected As shown in Table 8 above, since no components other than Na, Ca, Ni, Co, Mn, etc. were detected in the recovered lithium carbonate, it was confirmed that it was recovered as high-purity lithium carbonate.

Claims

1. (a) A step of extracting the reductively roasted product of the positive electrode material of a lithium-ion battery with an organic solvent containing a cation exchange extractant, and obtaining the organic solvent from which lithium has been extracted and the extraction residue, (b) A step of separating the organic solvent from which the lithium was extracted from the extraction residue, (c) The step of stripping the organic solvent from which the separated lithium was extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent, (d) A step of separating the lithium-containing aqueous solution from the organic solvent, (e) A step of obtaining lithium carbonate by carbonating lithium in a separated lithium-containing aqueous solution, A method for recovering lithium compounds, characterized by including [a specific component].

2. The method for recovering a lithium compound according to claim 1, characterized in that in step (a) above, the reductive roasted product of the positive electrode material of a lithium-ion battery is obtained by mixing the positive electrode material of a lithium-ion battery and a carbon-containing reducing agent, roasting them at 550 to 750°C, and then crushing them.

3. The method for recovering lithium compounds according to claim 2, characterized in that the carbon-containing reducing agent is used at a rate of 0 to 3 moles per mole of positive electrode active material in the positive electrode material of a lithium-ion battery.

4. The method for recovering a lithium compound according to claim 2, characterized in that the carbon-containing reducing agent is an organic substance containing carbon, an inorganic substance containing carbon, a negative electrode material, or a mixture thereof.

5. The method for recovering a lithium compound according to claim 2, characterized in that the roasting is carried out under a reducing gas or an inert gas.

6. The method for recovering a lithium compound according to claim 2, characterized in that the positive electrode material of the lithium-ion battery is one or more selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate compound, lithium nickel cobalt aluminum oxide, lithium nickel oxide, nickel-manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn), and NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co).

7. The method for recovering a lithium compound according to claim 2, characterized in that the positive electrode material of the lithium-ion battery is the positive electrode material of a discarded lithium-ion battery.

8. The method for recovering a lithium compound according to claim 2, characterized in that a milling machine is used in the grinding process.

9. The method for recovering a lithium compound according to claim 1, characterized in that in step (a) above, the cation exchange extractant comprises an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof.

10. The method for recovering a lithium compound according to claim 9, characterized in that the alkyl phosphate extractant comprises one or more selected from the group consisting of di-2-ethylhexyl phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and bis(2,4,4-trimethylpentyl)phosphinic acid.

11. The method for recovering lithium compounds according to claim 9, characterized in that the alkyl monocarboxylic acid includes a compound represented by the following chemical formula 1: 【Chemistry 1】 In the aforementioned chemical formula 1, R1 and R2 are each independently alkyl groups, and the total number of carbon atoms in R1 and R2 is 5 to 9.

12. The method for recovering a lithium compound according to claim 1, characterized in that the organic solvent in step (a) above includes one or more selected from the group consisting of kerosene, hexane, benzene, and toluene.

13. The method for recovering a lithium compound according to claim 1, characterized in that in step (a) above, the cation exchange extractant contains 0.9 to 2.5 moles per mole of lithium in the reduced roasted product of the positive electrode material of a lithium-ion battery.

14. The method for recovering a lithium compound according to claim 1, characterized in that, in step (a) above, the solid-liquid ratio of the reductive roasted product of the positive electrode material of the lithium-ion battery to the organic solvent containing the cation exchange extractant is 1 g / 8 mL to 1 g / 44 mL.

15. The method for recovering a lithium compound according to claim 1, characterized in that in step (b) above, vacuum filtration is used to separate the organic solvent from which lithium has been extracted from the extraction residue.

16. The method for recovering a lithium compound according to claim 1, characterized in that, in step (c) above, the volume ratio of the organic solvent from which lithium was extracted to the acidic solution is 0.5 to 10.

17. The method for recovering a lithium compound according to claim 1, characterized in that the acidic solution in step (c) is an aqueous sulfuric acid solution, an aqueous hydrochloric acid solution, or an aqueous nitric acid solution.

18. The method for recovering a lithium compound according to claim 1, characterized in that the carbonation in step (e) is carried out by introducing a carbonate or carbon dioxide.

19. The method for recovering a lithium compound according to claim 1, characterized in that the organic solvent separated in step (d) is reused for extraction in step (a).

20. The method for recovering lithium compounds from the positive electrode material of the lithium-ion battery, further comprising the step of leaching the extraction residue obtained in step (b) with an acid to obtain a leachate in which residual metal compounds are dissolved, as described in claim 1.

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