Method for recovering lithium compound from cathode material of lithium-ion battery

Abstract

The present invention relates to a method for recovering a lithium compound and, more specifically, to a method for recovering a lithium compound, comprising the steps of: (a) using an organic solvent containing a cation-exchange extractant, so as to extract a reduction roasted product of a cathode material of a lithium-ion battery, thereby obtaining an extraction residue and an organic solvent in which lithium is extracted; (b) separating the extraction residue and the organic solvent in which lithium is extracted; (c) stripping, with an acidic solution, the separated organic solvent in which lithium is extracted, so as to obtain a lithium-containing aqueous solution and the organic solvent; (d) separating the lithium-containing aqueous solution and the organic solvent; and (e) carbonating lithium in the separated lithium-containing aqueous solution so as to obtain lithium carbonate. The present invention relates to the method for recovering a lithium compound from a cathode material of a lithium-ion battery, comprising using an organic solvent containing a cation-exchange extractant, so as to directly extract lithium from a reduction roasted product of a cathode material of a lithium-ion battery, and then performing stripping with an acidic solution so as to have a high lithium recovery rate and reduce the energy, time and costs required for lithium recovery, and thus even economic feasibility and efficiency are improved.

Description

Method for recovering lithium compounds from lithium-ion battery cathode materials

[0001] 〔Cross-citation with the applicant(s)〕

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0088106, filed July 4, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for recovering a lithium compound from a lithium ion battery cathode material, and more particularly, to a method for recovering a lithium compound from a lithium ion battery cathode material, which directly extracts lithium from a reduced waste product of the lithium ion battery cathode material with an organic solvent containing a cation exchange extractant and then strips the lithium using an acidic solution, thereby increasing the lithium recovery rate and reducing the energy, time, and cost required for concentration to recover lithium, thereby improving both economy and efficiency.

[0004] Demand for lithium-ion batteries has steadily increased since the 1990s, alongside the growth of the portable electronic device market. The recent rapid expansion of the electric vehicle market has also led to a surge in global demand. This could lead to instability in the lithium resource supply and demand in the near future, and the continued accumulation of discarded batteries could also pose significant environmental problems. To address these issues, recycling used lithium-ion batteries is a critical technological challenge.

[0005] Lithium-ion batteries are largely composed of a cathode in which a positive active material layer is coated on a metal foil such as aluminum, a negative electrode in which a negative active material layer is coated on a metal foil such as copper, a separator that prevents the positive and negative electrodes from mixing, and an electrolyte that allows lithium ions to move between the positive and negative electrodes.

[0006] The cathode accounts for more than 60% of the cost of a lithium-ion battery. Lithium cobalt oxide (LiCoO2) is used as the cathode because it has excellent reversibility, low self-discharge rate, high capacity, high energy density, and is easy to synthesize. In addition, composite oxides such as lithium nickel cobalt manganese oxide (Li(Ni, Co, Mn)O2), lithium manganese oxide (LiMnO2), and lithium iron phosphate oxide (LiFePO4) that also contain nickel and manganese are used to reduce the amount of expensive cobalt used. Since the above cathode materials contain about 5 to 7 wt% of lithium, a method for recovering lithium compounds from waste lithium-ion battery cathode materials is attracting great attention.

[0007] Conventional methods for recovering lithium compounds from spent lithium-ion battery cathodes involve converting lithium to lithium carbonate through reduction heat treatment using carbon, followed by aqueous leaching. While this process allows for selective recovery of lithium, it suffers from low lithium recovery rates and significant energy, cost, and time consumption during processes such as evaporative concentration, vacuum concentration, or electrochemical concentration to concentrate the lithium carbonate.

[0008] Therefore, there is a need to develop a method for recovering lithium compounds from waste lithium-ion battery cathode materials, which can increase the recovery rate of lithium compounds recovered from waste lithium-ion battery cathode materials and reduce the energy, cost, and time required for lithium concentration.

[0009]

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] Korean Patent Publication No. 2015-0094412

[0013] In order to solve the problems of the prior art as described above, the present invention provides a method for recovering lithium compounds from a lithium ion battery cathode material, which has a high lithium recovery rate and reduces energy, time and cost required for lithium concentration by directly extracting lithium from a reduced waste product of a lithium ion battery cathode material with an organic solvent containing a cation exchange extractant and then removing the lithium using an acidic solution, thereby improving both economy and efficiency.

[0014] In addition, the present invention aims to provide a high-purity lithium compound.

[0015]

[0016] The above and other objects of the present invention can all be achieved by the present invention described below.

[0017] In order to achieve the above object, I) the present invention provides a method for recovering a lithium compound, comprising the steps of: (a) extracting a reduced waste 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 is extracted and an extraction residue; (b) separating the organic solvent from which lithium is extracted and the extraction residue; (c) stripping the separated organic solvent from which lithium is extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent; (d) separating the lithium-containing aqueous solution and the organic solvent; and (e) carbonating lithium in the separated lithium-containing aqueous solution to obtain lithium carbonate.

[0018] II) In the above I), the reduction product of the cathode material may preferably be obtained by mixing a lithium ion battery cathode material and a carbon-containing reducing agent, calcining the mixture at 550 to 750°C, and then pulverizing the mixture.

[0019] III) In the above I) or II), the carbon-containing reducing agent may preferably be used in an amount of 0 to 3 moles per mole of the positive electrode active material in the lithium ion battery positive electrode material.

[0020] IV) In the above I) to III), the carbon-containing reducing agent may preferably be an organic material containing carbon, an inorganic material containing carbon, a cathode material, or a mixture thereof.

[0021] V) In the above I) to IV), the oxidation can preferably be carried out under a reducing gas or an inert gas.

[0022] VI) In the above I) to V), the lithium ion battery positive electrode material may preferably be at least one 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 part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co).

[0023] VII) In the above I) to VI), the lithium ion battery cathode material may preferably be a discarded lithium ion battery cathode material.

[0024] VIII) In the above I) to VII), the grinding can preferably be performed using a milling machine.

[0025] IX) In the above I) to VIII), the cation exchange extractant in step (a) may preferably include an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof.

[0026] X) In the above I) to IX), the alkyl phosphate extractant may preferably include at least one selected from the group consisting of Di-(2-ethylhexyl) phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and Bis(2,4,4-trimethylpentyl)dithiophosphinic acid.

[0027] XI) In the above I) to X), the alkyl monocarboxylic acid may preferably include a compound represented by the following chemical formula 1.

[0028] [Chemical Formula 1]

[0029]

[0030] (In the above chemical formula 1, R1 and R2 are each independently an alkyl group, and the sum of the carbon atoms of R1 and R2 is 5 to 9.)

[0031] XII) In the above I) to XI), the organic solvent in the step (a) may preferably include at least one selected from the group consisting of kerosene, hexane, benzene, and toluene.

[0032] XIII) In the above I) to XII), the cation exchange extractant in the step (a) may preferably be included in an amount of 0.9 to 2.5 moles per mole of lithium in the reduced waste product of the lithium ion battery positive electrode material.

[0033] XIV) In the above I) to XIII), the solid-liquid ratio of the reduced product of the lithium ion battery positive electrode material and the organic solvent including the cation exchange extractant in the step (a) may preferably be 1 g / 8 mL to 1 g / 44 mL.

[0034] XV) In the above I) to XIV), the separation of the organic solvent from which lithium is extracted and the extraction residue in the step (b) can preferably be performed using reduced pressure filtration.

[0035] XVI) In the above I) to XV), the volume ratio (organic / aqueous volume ratio) of the organic solvent and acidic solution from which lithium is extracted in step (c) may preferably be 0.5 to 10.

[0036] XVII) In the above I) to XVI), the acidic solution in the step (c) may preferably be a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution or a nitric acid aqueous solution.

[0037] XVIII) In the above I) to XVII), carbonation in the step (e) can preferably be carried out by injecting carbonate or carbon dioxide gas.

[0038] XIX) In the above I) to XVIII), the organic solvent separated in the step (d) can preferably be reused in the extraction in the step (a).

[0039] XX) In the above I) to XIX), the method for recovering a lithium compound from the lithium ion battery positive electrode material may preferably further include a step of leaching the extraction residue obtained in the above step (b) with an acid to obtain a leaching solution in which the residual metal compound is dissolved.

[0040] According to the present invention, lithium is directly extracted from the reduced waste of a lithium ion battery cathode material using an organic solvent containing a cation exchange extractant and then removed using an acidic solution, thereby greatly improving the lithium recovery rate and reducing the loss of organic metals. In addition, the energy, time, and cost required in the concentration process for recovering lithium are greatly reduced, thereby improving both economic feasibility and efficiency.

[0041] In addition, the organic solvent containing the cation exchange extractant separated after stripping is reused for extraction, thereby reducing wastewater generation and reducing production costs.

[0042] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description given below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be construed as being limited to the matters described in these drawings.

[0043] Figure 1 shows kerosene containing a cation exchange extractant (di-2-ethylhexyl phosphate) before and after lithium extraction in Example 1 according to the present invention, with the left side being before extraction and the right side being after extraction.

[0044] Figure 2 is a process diagram for a method for recovering a lithium compound from a lithium ion battery cathode material according to one embodiment of the present invention.

[0045] Figure 3 is a graph showing the extraction rates of Li, Ni, Co, Mn, and Al in Examples 1 to 4 according to the present invention.

[0046] Figure 4 is a graph showing the extraction rates of Li, Ni, Co, Mn, and Al in Examples 2, 5, and 6 according to the present invention.

[0047] Figure 5 is a graph showing the extraction rates of Li, Ni, Co, Mn, and Al in Examples 7 to 9 according to the present invention.

[0048] Figure 6 shows lithium carbonate recovered from Example 8 according to the present invention.

[0049]

[0050] While studying a method for recovering lithium compounds from lithium-ion battery cathode materials, the inventors of the present invention discovered that when lithium is directly extracted from the reduced waste of lithium-ion battery cathode materials with an organic solvent containing a cation exchange extractant and then stripped with an acidic solution, the lithium recovery rate is high, and the energy, cost, and time required for the concentration process for recovering lithium are reduced while the concentration is easy, and based on this, they devoted themselves to further research and completed the present invention.

[0051]

[0052] Method for recovering lithium compounds from lithium-ion battery cathode materials

[0053] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention is characterized by including the steps of: (a) extracting a reduced waste 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 and 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 and 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 economic efficiency and efficiency.

[0054]

[0055] Below, a method for recovering lithium compounds from the lithium ion battery cathode material of the present invention is described in detail step by step.

[0056] However, the terms or words used in this specification and claims cannot be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own application in the best way. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only one embodiment of the present invention and do not represent all of the technical idea of ​​the present invention, and it should be understood that there may be various equivalents and modified examples that can replace them, and that they can be arranged, replaced, combined, separated, or designed in various other configurations.

[0057] All technical and scientific terms used in this document, unless otherwise defined, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains.

[0058]

[0059] (a) A step of extracting a reduced waste 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 is extracted and an extraction residue.

[0060] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include the step of (a) extracting a reduced waste 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 is extracted and an extraction residue. In this case, by directly extracting lithium from the reduced waste product of a lithium ion battery cathode material, the lithium recovery rate is greatly improved, and since the organic solvent contains a small amount of impurities such as Ni, Co, and Mn while the extraction residue contains a large amount of Ni, Co, and Mn, there is an economic advantage in that it can be easily manufactured as a precursor raw material.

[0061]

[0062] The cathode material of this description means a cathode active material or a cathode active material.

[0063]

[0064] In the step (a), the cation exchange extractant may include, for example, an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof, and in this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reduced waste of the lithium ion battery cathode material.

[0065] The above alkyl phosphate extractant may include at least one selected from the group consisting of, for example, Di-(2-ethylhexyl) phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and Bis(2,4,4-trimethylpentyl)phosphinic acid, and preferably Di-2-ethylhexyl phosphate. In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reduced waste of a lithium ion battery cathode material.

[0066] The above alkyl monocarboxylic acid may include, for example, a compound represented by the following chemical formula 1, and in this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reduced waste of a lithium ion battery cathode material.

[0067] [Chemical Formula 1]

[0068]

[0069] In the above chemical formula 1, R1 and R2 are each independently an alkyl group, and the sum of carbons of R1 and R2 is 5 to 9, preferably 6 to 8, and more preferably 7.

[0070]

[0071] The above cationic extractant may exist in the form of, for example, a monomer, a dimer, or a polymer, and in the case of a monomer, it reacts with lithium as in the following reaction scheme 1, and in the case of a dimer, it reacts with lithium as in the following reaction scheme 2.

[0072]

[0073] [Reaction Formula 1]

[0074] Li + (aq) + HA (org) = LiA (orq) + H + (aq)

[0075] [Reaction Formula 2]

[0076] Li + (aq) + (HA) 2(org) = Li(A·HA)n (orq) + H + (aq)

[0077] In the above reaction formulas 1 and 2, A is a cation exchange extractant.

[0078]

[0079] In the above step (a), the organic solvent is used to dilute the cation exchange extractant, and may include, for example, at least one selected from the group consisting of kerosene, hexane, benzene, and toluene, and preferably may be kerosene. In this case, there is an economic advantage in that the viscosity of the cation exchange extractant is lowered to facilitate binding to the reduced waste product of the lithium ion battery positive electrode material, and the amount of the cation exchange extractant used can be reduced.

[0080] The crude oil can be heated with the above kerosene, the gas vaporized at 180 to 250°C can be collected, and the resulting liquefied product can be used.

[0081] The crude oil can be heated with the above hexane, the gas vaporized at 65 to 70°C can be collected, and the resulting liquefied product can be used.

[0082] An aromatic compound manufactured by subjecting toluene to a hydrodealkylation process at 500 to 650°C using the above benzene can be used.

[0083] An aromatic compound obtained by separating and refining a byproduct generated when producing gasoline from crude oil using the above toluene can be used.

[0084]

[0085] In the above step (a), the organic solvent may include, for example, a cation exchange extractant at a molar concentration of 0.7 to 1.3 mol / L, preferably 0.8 to 1.2 mol / L, more preferably 0.9 to 1.1 mol / L, and within this range, there is an advantage in that lithium in the reduced waste of the lithium ion battery cathode material is easily leached.

[0086]

[0087] In the step (a), the cation exchange extractant may be included in an amount of, for example, 0.9 to 2.5 mol, preferably 1.0 to 2.4 mol, more preferably 1.2 to 2.3 mol, even more preferably 1.3 to 2.2 mol, and even more preferably 1.4 to 2.1 mol, per 1 mol of lithium in the reduced waste product of the lithium ion battery cathode material, and within this range, there is an advantage in that lithium in the reduced waste product of the lithium ion battery is sufficiently combined with the cation exchange extractant and easily extracted into an organic solvent.

[0088]

[0089] In the step (a), the solid-liquid ratio of the reduced waste of the lithium ion battery cathode material and the organic solvent containing the cation exchange extractant may be, for example, 1 g / 8 mL to 1 g / 44 mL, preferably 1 g / 15 mL to 1 g / 42 mL, more preferably 1 g / 18 mL to 1 g / 42 mL, even more preferably 1 g / 18 mL to 1 g / 35 mL, and even more preferably 1 g / 18 mL to 1 g / 25 mL. Within this range, lithium in the reduced waste of the lithium ion battery cathode material is smoothly combined with the cation exchange extractant, so that it is easily extracted into the organic solvent.

[0090] In this description, the volume of liquid relative to the weight of solid refers to the volume of liquid relative to the weight of solid, i.e., the volume (mL) of organic solvent including cation exchange extractant relative to the content (g) of reduced waste product of lithium ion battery positive electrode material.

[0091]

[0092] In the extraction of the above step (a), lithium in the reduced waste of the lithium ion battery cathode material is combined with a cation exchange extractant to form a complex and is extracted into an organic solvent.

[0093]

[0094] In the above step (a), the extraction can be performed, for example, by adding the reduced waste of a lithium ion battery cathode material to an organic solvent containing a cation exchange extractant and stirring the mixture using a stirrer at room temperature. In this case, there is an advantage in that lithium in the reduced waste of a lithium ion battery cathode material is easily extracted into the organic solvent and the extraction time is shortened.

[0095] In this description, room temperature may be a point within the range of 20 ± 5 ℃.

[0096]

[0097] The above stirring speed may be, for example, 100 to 500 rpm, preferably 200 to 400 rpm, and more preferably 250 to 350 rpm, and within this range, there is an advantage in that lithium in the reduced waste product of the lithium ion battery positive electrode material is easily extracted.

[0098] The above 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, and within this range, lithium in the reduced waste of the lithium ion battery positive electrode material is sufficiently extracted, so that there is an advantage in recovering the lithium compound at a high yield.

[0099]

[0100] In the step (a), the reduced product of the lithium ion battery cathode material may be, for example, obtained by calcining the lithium ion battery cathode material or a mixture of the lithium ion battery cathode material and a carbon-containing reducing agent at 550 to 750°C and then pulverizing the mixture. In this case, there is an advantage in that the lithium recovery rate is improved because lithium is easily extracted into an organic solvent containing a cation exchange extractant.

[0101]

[0102] The above-mentioned reduction process can obtain a reduced product of a lithium-ion battery cathode material by heat-treating, for example, a lithium-ion battery cathode material, or a lithium-ion battery cathode material and a carbon-containing reducing agent, at 550 to 750°C. In this case, the binder added during the manufacture of the cathode material is removed, and the metallic material combined with oxygen is reduced, thereby having the effect of recovering a high-purity lithium compound at a high yield.

[0103] As a specific example, a reduced lithium ion battery cathode material can be obtained by crushing a lithium ion battery cathode to separate a current collector, and then heat-treating the obtained powder-type lithium ion battery cathode material at 550 to 750°C. In this case, the conductive material and binder in the lithium ion battery cathode material act as a reducing agent, and the binder added during the manufacture of the cathode material is removed through roasting, and a metallic substance combined with oxygen is reduced, thereby providing an advantage of recovering a high-purity lithium compound at a high yield.

[0104]

[0105] As another specific example, a reduced lithium ion battery cathode material can be obtained by crushing a lithium ion battery cathode to separate the current collector, mixing a carbon-containing reducing agent with the obtained powdered lithium ion battery cathode material, and heat-treating the mixture at 550 to 750°C. In this case, there is an advantage in that a binder added during the manufacture of the cathode material is removed through roasting, and a metallic substance combined with oxygen is reduced, thereby recovering a high-purity lithium compound at a high yield.

[0106] The above lithium ion battery positive electrode material and carbon-containing reducing agent can preferably be dry mixed, and in this case, there is an advantage in that the reduction effect of carbon is maximized.

[0107] The carbon-containing reducing agent may be used in an amount of, for example, 0 to 3 mol, or more than 0 mol but less than or equal to 3 mol, preferably 0.3 to 3 mol, more preferably 0.3 to 2 mol, even more preferably 0.7 to 1.5 mol, and even more preferably 0.9 to 1.2 mol, per mol of the positive electrode active material in the lithium-ion battery positive electrode material. Within this range, the amount of the carbon-containing compound as the reducing agent can be reduced while increasing the heat treatment efficiency and shortening the reaction time. In addition, even if the carbon-containing reducing agent exceeds 3 mol per mol of the lithium-ion battery positive electrode material, the production cost increases without increasing the recovery rate of the lithium compound.

[0108] In the present invention, the content (in moles) of the positive electrode active material in the positive electrode material can be measured by a method commonly used in the technical field to measure the content of the positive electrode active material, and for example, can be calculated through the content of the metal component and its molecular weight measured through ICP analysis. As a specific example, the ICP analysis is performed by putting 0.01 g of the positive electrode material, 3 mL of HCl, and 20.5 mL of H2O into a conical tube, mixing them, heating them to dissolve them, and then, when the positive electrode material is dissolved, putting them into a 50 mL tube, diluting them, and measuring the content (in moles) of the metal component through ICP analysis.

[0109]

[0110] As another example, the weight ratio of the lithium ion battery positive electrode material and the carbon-containing reducing agent 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, and within this range, there is an effect of increasing heat treatment efficiency and shortening the reaction time.

[0111] The above carbon-containing reducing agent may be, for example, an organic material containing carbon, an inorganic material containing carbon, a negative electrode material, or a mixture thereof, and preferably, graphite. In this case, there is an advantage in that it readily reacts with lithium in a positive electrode material of a lithium-ion battery.

[0112] The above graphite preferably has a fixed carbon content of 90 wt% or more, more preferably 95 wt% or more, and even more preferably 98 wt% or more, and has the advantage of easily reacting with lithium in the positive electrode material within this range.

[0113] In this description, fixed carbon content (by weight) refers to the content of carbon excluding volatile matter, moisture and ash, which is the combustible residue remaining after volatile matter has volatilized from carbon.

[0114] The above graphite may preferably be graphite derived from a cathode material, in which case there is an advantage of reducing production costs and recycling resources.

[0115]

[0116] In this description, the term "sintering" may follow the definition used in the technical field to which the present invention belongs, and as a specific example, it may be defined as a process for causing a gas-solid reaction at a high temperature to impart advantageous chemical properties in a subsequent process.

[0117]

[0118] The above-mentioned step may not include a reducing agent other than a carbon-containing reducing agent, for example, in which case there is an advantage of reducing impurities and increasing the purity and recovery rate of the recovered lithium compound.

[0119]

[0120] The above-mentioned reduction can be carried out, for example, 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 which case the cathode material is easily reduced, and there is an advantage of recovering the lithium compound in a high yield.

[0121]

[0122] The above lithium ion battery cathode material may be at least one selected from the group consisting of, for example, 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). In this case, excellent reversible capacity and thermal stability are achieved.

[0123] As another specific example, the lithium ion battery cathode material has the following chemical formula 2

[0124] [Chemical Formula 2]

[0125] Li a Ni x Mn y Co z M w O 2+δ

[0126] (In the above chemical formula 2, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 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, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0127]

[0128] The above lithium ion battery cathode material may be, for example, a discarded lithium ion battery cathode material, in which case, there is an economic advantage of recycling resources since Ni, Co, Mn, etc. can be recovered together with expensive lithium.

[0129]

[0130] The flow rate of the reducing gas or inert gas may be, for example, 1 to 30 L / min, preferably 3 to 25 L / min, more preferably 5 to 20 L / min, and even more preferably 7 to 12 L / min, and within this range, there is an advantage of excellent reaction efficiency.

[0131]

[0132] The above-mentioned oxidation can be carried out, for example, at a temperature of 550 to 750°C, preferably at a temperature of 570 to 730°C, more preferably at a temperature of 600 to 720°C, and even more preferably at a temperature of 620 to 700°C. Within this range, lithium in the cathode material is converted to lithium carbonate at a high level, and there is an advantage of reducing the process cost.

[0133] After the above-mentioned firing, furnace cooling can be performed.

[0134] In this article, furnace cooling refers to a method of cooling heat-treated materials slowly at a high temperature in a furnace by cooling them in a furnace.

[0135]

[0136] The temperature rise rate until the above-mentioned firing temperature is reached may be, 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 firing equipment can be implemented without causing a strain, and there is an advantage of not causing thermal shock to the cathode material.

[0137] The above-mentioned oxidation 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, and within this range, there is an advantage that the binder in the positive electrode material is removed and lithium is converted to lithium carbonate by carbon at a high level.

[0138] In this description, the firing time refers to the time spent at the firing temperature and does not include the time taken to reach the firing temperature.

[0139] The above-mentioned process can be carried out, for example, at atmospheric pressure, in which case the process cost is reduced and the process is safe.

[0140] In this document, atmospheric pressure may be normal pressure, and refers to the pressure of air (atmosphere) as 1 atm.

[0141]

[0142] The above-mentioned sintering can be performed using, for example, various types of furnaces, preferably a box-type furnace, and more preferably a closed-type sintering furnace. In this case, continuous processing is possible, productivity is excellent, and the reduction reaction can be promoted, so there is an advantage of an excellent conversion rate into a lithium compound.

[0143]

[0144] The reaction mechanism occurring in the above-mentioned step is as follows, for example, in reaction formulas 3 to 5.

[0145] [Reaction Formula 3]

[0146] 4LiMeO2+ C --> 2Li2O + 4MeO + CO2

[0147] [Reaction Formula 4]

[0148] Li2O + CO2--> Li2CO3

[0149] [Reaction Formula 5]

[0150] 2MeO + C --> 2Me + CO2

[0151] In the above reaction formulas 3 to 5, Me is at least one of Ni, Co, and Mn.

[0152]

[0153] The reaction mechanism occurring in the above-mentioned step is specifically that phase decomposition occurs as in the above reaction formula 3 when 0.3 mol or more of carbon-containing reducing agent is added per 1 mol of cathode active material in the cathode material, and a phase change to Li2CO3 occurs simultaneously with the reaction formula 3 as in the above reaction formula 4. At this time, the reaction of the reaction formula 5 occurs due to the carbon-containing reducing agent added in an amount of 0.3 mol or more, and the excess Li2O generated in the above reaction formula 3 changes into Li2CO3 due to the CO2 generated at this time.

[0154] The above crushing refers to shredding, crushing or both.

[0155] The above-mentioned crushing step may be performed using, for example, a milling machine, preferably a roll press, a ball mill, or a pin mill, and more preferably a roll mill and a pin mill may be used sequentially. In this case, the specific surface area of ​​the reduced waste of the lithium-ion battery cathode material is increased, making it easy to extract lithium, and thus there is an advantage in that the recovery rate of lithium is increased.

[0156]

[0157] The reduced waste of the lithium ion battery cathode material obtained after the above-mentioned crushing step may have an average particle size (D50) of, for example, 0.5 to 50 ㎛, preferably 1 to 40 ㎛, more preferably 3 to 30 ㎛, and even more preferably 5 to 20 ㎛, and within this range, lithium extraction from the reduced waste of the lithium ion battery cathode material is easy, so there is an advantage of increasing the lithium recovery rate.

[0158] In the present invention, the average particle size (D50) of the reduced waste can be measured by a measuring method commonly used in the technical field to which the present invention pertains, and for example, can be measured using a laser diffraction method. Specifically, after the particles of the reduced waste are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac S3500, and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0159]

[0160] The above pulverization can be performed, for example, under dry conditions, in which case the reduced waste of the lithium ion battery cathode material is uniformly pulverized, which has the advantage of facilitating the extraction of lithium.

[0161] In this document, dry conditions are a concept opposite to wet conditions that use solvents or additives, and can mean a method that does not use solvents or additives.

[0162]

[0163] (b) A step of separating the organic solvent from which the lithium is extracted and the extraction residue.

[0164] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include (b) a step of separating the organic solvent from which the lithium is extracted and the extraction residue, in which case the organic solvent from which the separated lithium is extracted contains less impurities such as Ni, Co, and Mn, so that the lithium recovery rate is high, and the extraction residue contains a large amount of Ni, Co, and Mn, so that it is economically advantageous for easy manufacturing as a precursor raw material.

[0165]

[0166] In the above step (b), separation can be achieved, for example, by using reduced pressure filtration. In this case, the organic solvent from which lithium is extracted and the extraction residue can be easily separated through a simple process, and the process cost can be reduced.

[0167] The above-mentioned pressure-reducing filtration may preferably be vacuum pressure-reducing filtration, and specifically, may be vacuum pressure-reducing filtration using a filtration flask. In this case, there is an advantage in that the organic solvent from which lithium is extracted and the extraction residue are easily separated.

[0168] In the present invention, vacuum decompression filtration is not particularly limited as long as it is a conventional vacuum decompression filtration in the technical field to which the present invention belongs, and may include, for example, filtration in a partial vacuum state or a low pressure state.

[0169]

[0170] The organic solvent from which the lithium is extracted contains a cation exchange extractant.

[0171]

[0172] (c) A step of stripping the organic solvent from which separated lithium is extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent.

[0173] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include (c) a step of stripping the organic solvent from which separated lithium is extracted with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent. In this case, there is an advantage in that lithium extracted into the organic solvent by combining with a cation exchange extractant is reversely extracted into the acidic solution, thereby easily recovering lithium.

[0174]

[0175] In the above step (c), the volume ratio of the organic solvent and the acidic solution from which lithium is extracted (organic / aqueous volume ratio) may be, for example, 0.5 to 10, preferably 1 to 8, more preferably 1 to 7, still more preferably 1 to 6, still more preferably 1.5 to 6, particularly preferably 2.5 to 6, still more preferably 3.5 to 6.0, and most preferably 4 to 5.5. Within this range, lithium is easily back-extracted into the acidic solution, so that lithium is easily recovered in a subsequent process, and the energy, cost, and time required for concentrating lithium are reduced, thereby improving economic feasibility and efficiency.

[0176]

[0177] In the above step (c), the acidic solution may be, for example, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution, and preferably, a sulfuric acid aqueous solution. In this case, the lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate and providing the advantage of being able to easily concentrate and recover lithium.

[0178] The above acidic solution may contain, for example, an acid at a molar concentration (mol / L) of 0.5 to 1.5, preferably at a molar concentration of 0.7 to 1.3, more preferably at a molar concentration of 0.9 to 1.1, and within this range, lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate and enabling lithium to be easily concentrated and recovered.

[0179] The above acidic solution may have, for example, a pH of 1 or lower, preferably a pH of 0 to 1, and more preferably a pH of 0 to 0.5, and within this range, lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate and enabling easy concentration of lithium.

[0180]

[0181] In the above step (c), the removal can be performed, for example, by adding an acidic solution to the organic solvent from which the separated lithium has been extracted and stirring using a stirrer at room temperature.

[0182] The above stirring can be performed, for example, at 300 to 800 rpm, preferably 400 to 700 rpm, and more preferably 500 to 700 rpm, and within this range, there is an advantage in that reverse extraction of lithium from the organic solvent from which lithium is extracted is promoted into an acidic solution.

[0183] The above stirring can be performed for, for example, 20 minutes or more, preferably 20 to 60 minutes, more preferably 20 to 40 minutes, and within this range, there is an advantage in that lithium is sufficiently reversely extracted from the organic solvent into the acidic solution.

[0184]

[0185] (d) a step of separating the lithium-containing aqueous solution and the organic solvent;

[0186] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include (d) a step of separating the lithium-containing aqueous solution and the organic solvent, in which case there is an advantage that the subsequent carbonation process for carbonizing lithium is smoothly performed.

[0187] The organic solvent obtained after separation in the above step (d) can be reintroduced into the extraction in the above step (a), for example, thereby reducing the generation of wastewater, thereby reducing production costs and providing environmentally friendly benefits.

[0188]

[0189] (e) a step of carbonating lithium in a separated lithium-containing aqueous solution to obtain lithium carbonate;

[0190] The method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include a step of (e) carbonating lithium in a separated lithium-containing aqueous solution to obtain lithium carbonate, in which case there is an advantage in that the energy, cost, and time required for concentration to recover lithium are greatly reduced.

[0191]

[0192] In the above step (e), carbonation can be carried out, for example, by injecting carbonate or carbon dioxide gas, in which case there is an advantage in that lithium is recovered as lithium carbonate at a high yield and the energy, cost and time required for concentration to recover lithium are reduced.

[0193] The above carbonate may be, for example, at least one selected from the group consisting of sodium carbonate, ammonium carbonate, and potassium carbonate, and in this case, there is an advantage in that lithium is recovered as lithium carbonate at a high yield and the energy, cost, and time required for concentration to recover lithium are reduced.

[0194] The above carbon dioxide gas may be, for example, carbon dioxide, in which case there is an advantage in that lithium is recovered as lithium carbonate with a high yield and the energy, cost and time required for concentration to recover lithium are reduced.

[0195] The above carbonate may be added, for example, 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, and within this range, there is an advantage in that the energy, cost, and time required for concentration to recover lithium are reduced.

[0196]

[0197] Preferably, before the carbonation in step (e), a step of removing impurities from the separated lithium-containing aqueous solution may be further included, in which case impurities including Ni, Co, Mn, etc. contained in the lithium-containing aqueous solution are removed, thereby improving the purity of the lithium carbonate.

[0198] The above impurity removal step can be adjusted to pH 10 to 12, for example, by adding a basic compound. In this case, impurities including Ni, Co, Mn, etc. in the separated lithium-containing aqueous solution are removed, which has the advantage of improving the purity of lithium carbonate.

[0199] In this description, pH measurement can be performed using a measurement method commonly used in the technical field to which the present invention belongs, and unless otherwise described, can be performed using a general pH measurement device at room temperature, and specifically, can be performed using METTLER TOLEDO SevenDirect SD30.

[0200]

[0201] The above basic compound may be, for example, a metal hydroxide, a metal carbonate, or a mixture thereof, in which case there is an advantage in that impurities including Ni, Co, Mn, etc. in the separated lithium-containing aqueous solution are removed, thereby improving the purity of the lithium carbonate.

[0202] The metal hydroxide may preferably be sodium hydroxide, potassium hydroxide or a mixture thereof, in which case there is an advantage in that impurities including Ni, Co, Mn, etc. in the separated lithium-containing aqueous solution are removed, thereby improving the purity of the lithium carbonate.

[0203] The above metal carbonate may preferably be sodium carbonate, potassium carbonate, or a mixture thereof, in which case there is an advantage in that impurities including Ni, Co, Mn, etc. in the separated lithium-containing aqueous solution are removed, thereby improving the purity of the lithium carbonate.

[0204]

[0205] In the above step (e), the lithium carbonate obtained after carbonation can be washed using, for example, water and then dried to obtain the final lithium carbonate.

[0206]

[0207] In addition, the method for recovering a lithium compound from a lithium ion battery cathode material of the present invention may include a step of leaching the extraction residue separated in step (b) with, for example, an acid to obtain a leachate in which residual metal compounds are dissolved, and in this case, Ni, Co, Mn, etc. are recovered and easily manufactured into precursor raw materials, thereby recycling resources and having excellent economic benefits.

[0208] The acid may be, for example, sulfuric acid, nitric acid or hydrochloric acid, preferably sulfuric acid, in which case it has the effect of recovering residual metal compounds with high purity.

[0209]

[0210] The following Figure 2 is a flow chart of a method for recovering lithium carbonate from a lithium ion battery cathode material according to one embodiment of the present invention.

[0211]

[0212] Referring to Fig. 2, first, a lithium ion battery cathode material and a carbon-containing reducing agent are mixed and then calcined to produce a reduced calcined product of the lithium ion battery cathode material (step S10).

[0213] The above lithium ion battery cathode material may preferably be a discarded lithium ion battery cathode material, a defective product generated during the cathode coating process, or a cathode scrap discarded after cutting an electrode plate. It may preferably be a discarded lithium ion battery cathode material, and specifically, it may be a cathode material powder obtained by crushing a cathode.

[0214]

[0215] The above lithium ion battery cathode material may preferably be at least one 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 substituted with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co). In this case, excellent reversible capacity and thermal stability are achieved.

[0216]

[0217] The above carbon-containing reducing agent may preferably be an organic material containing carbon, an inorganic material containing carbon, a cathode material, or a mixture thereof, and specifically may be a cathode material, in which case lithium can be easily extracted in the extraction step.

[0218]

[0219] The carbon-containing reducing agent may be used, for example, in an amount of 0 to 3 moles or more than 0 moles to less than 3 moles per mole of the cathode active material in the lithium-ion battery cathode material, and as a specific example, may be used in an amount of 1 mole, and within this range, the conversion efficiency is high and the conversion time is shortened. In addition, even if the carbon-containing reducing agent is added in an amount exceeding 3 moles per mole of the cathode active material in the lithium-ion battery cathode material, the lithium recovery rate does not increase any further and the production cost increases.

[0220] As another example, the weight ratio of the lithium ion battery positive electrode material and the carbon-containing reducing agent may be 1:0.06 to 1:0.19, and as a specific example, may be 1:0.11 to 0.13, and within this range, there is an effect of increasing heat treatment efficiency and shortening the reaction time.

[0221]

[0222] The above lithium ion battery cathode material and carbon can preferably be dry mixed, and in this case, there is an advantage in that the reduction effect of the carbon-containing reducing agent is maximized.

[0223]

[0224] In general, the cathode material of lithium-ion batteries goes through a complex process such as a firing process, addition of carbon and other metal oxides, addition of a binder, and then thermal bonding to maintain or improve the battery characteristics during the manufacturing process. For this reason, the cathode material of discarded lithium-ion batteries contains various oxide forms of valuable metals and impurities, which can act as an obstacle to the recovery of lithium and valuable metals. Here, in order to eliminate these obstacles, the cathode material is mixed with a carbon-containing reducing agent and roasted at a high temperature to remove the binder added during the manufacture of the cathode material and reduce the metallic substances combined with oxygen. This process is the roasting step.

[0225] The above-mentioned reduction can be carried out, for example, in an atmosphere of a reducing gas or an inert gas, specifically nitrogen gas, in which case there is an advantage that the cathode material is easily reduced. At this time, the flow rate of the reducing gas or inert gas can be 1 to 20 L / min, specifically 10 L / min, and within this range, there is an advantage that the binder added during the manufacture of the cathode material is removed, and the reduction of the metallic material combined with oxygen is easily achieved.

[0226] The above-mentioned reduction can be carried out, for example, at a temperature of 550 to 750°C, and as a specific example, at 650°C, and within this range, the cathode material is sufficiently reduced.

[0227] The temperature rise rate until the above-mentioned firing temperature is reached may be, for example, 1 to 20 ℃ / min, specifically 3 ℃ / min. Within this range, the firing equipment can be implemented without causing a strain, and there is an advantage of not causing thermal shock to the cathode material.

[0228] The above reduction can be carried out for, for example, 0.5 to 7 hours, and as a specific example, for 5 hours, and within this range, the positive electrode material is sufficiently reduced.

[0229] The above-mentioned process can be carried out, for example, at atmospheric pressure, in which case the process is safe and production costs are reduced.

[0230] The above-mentioned combustion can preferably use a closed-type furnace, in which case continuous processing is possible, productivity is excellent, and the reduction reaction can be promoted, so there is an advantage of recovering high-purity lithium with a high yield.

[0231] After the above-mentioned firing, it can be cooled slowly or rapidly in the air.

[0232]

[0233] Next, the reduced waste of the lithium ion battery cathode material is pulverized to obtain a reduced waste of the lithium ion battery cathode material in powder form (step S20).

[0234] By crushing the reduced waste of the above lithium ion battery cathode material, the specific surface area increases, making lithium extraction easier, thereby increasing the lithium recovery rate.

[0235] The reduction product of the above-mentioned pulverized lithium ion battery cathode material may have an average particle size of, for example, 0.5 to 50 μm, and specifically, 10 to 15 μm, and has the advantage of maximizing the recovery rate of lithium within this range.

[0236] The above crushing can be performed using, for example, a milling machine, and specifically, a roll mill and a pin mill can be used sequentially, in which case there is an advantage of uniformly crushing or pulverizing the crushed material.

[0237] The above grinding may be dry grinding, in which case there is an advantage of uniformly crushing or pulverizing the grinding material and increasing the specific surface area of ​​the grinding material.

[0238]

[0239] Next, the reduced waste product of the crushed lithium ion battery cathode material is extracted with an organic solvent containing a cation exchange extractant, thereby obtaining an organic solvent from which lithium is extracted and an extraction residue (step S30).

[0240] The above cation exchange extractant may include, for example, an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof.

[0241] The above alkyl phosphate extractant may include at least one selected from the group consisting of, for example, Di-(2-ethylhexyl) phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and bis(2,4,4-trimethylpentyl)dithiophosphinic acid, and as a specific example, may include Di-(2-ethylhexyl) phosphate (D2EHPA). In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reduced waste of a lithium ion battery cathode material.

[0242] The above alkyl monocarboxylic acid may include, for example, a compound represented by the following chemical formula 1, and as a specific example, may include neodecanoic acid. In this case, there is an advantage in that the lithium recovery rate is greatly improved by directly extracting lithium from the reduced waste of a lithium ion battery cathode material.

[0243] [Chemical Formula 1]

[0244]

[0245] (In the above chemical formula 1, R1 and R2 are each independently an alkyl group, and the sum of carbons of R1 and R2 is 5 to 9, preferably 6 to 8, and more preferably 7.)

[0246]

[0247] The organic solvent may include, for example, at least one selected from the group consisting of kerosene, hexane, benzene, and toluene, and may be kerosene as a specific example. In this case, there is an economic advantage in that the viscosity of the cation exchange extractant is lowered to facilitate binding with the reduced waste product of the lithium ion battery positive electrode material, and the amount of the cation exchange extractant used can be reduced.

[0248] The above cation exchange extractant may be included in an amount of, for example, 0.9 to 2.5 moles per mole of lithium in the reduction waste of a lithium ion battery cathode material, and as a specific example, may be included in an amount of 1 to 2 moles, and within this range, there is an advantage in that lithium can be easily and directly extracted from the reduction waste of a lithium ion battery cathode material with an organic solvent containing the cation exchange extractant.

[0249] The high-liquid ratio of the reduced waste product of the lithium ion battery cathode material and the organic solvent containing a cation exchange extractant may be, for example, 1 g / 8 mL to 1 g / 44 mL, and as a specific example, may be 1 g / 10 mL to 1 g / 40 mL, and within this range, there is an advantage in that lithium is sufficiently directly extracted from the reduced waste product of the lithium ion battery cathode material with the organic solvent containing a cation exchange extractant.

[0250] In the above step S30, the extraction can be performed, for example, by adding an organic solvent containing a cation exchange extractant to the reduced waste of a lithium ion battery cathode material and stirring the mixture using a stirrer at room temperature. In this case, there is an advantage in that lithium in the reduced waste of a lithium ion battery cathode material is easily extracted and the extraction time is shortened.

[0251] The above stirring can be performed at, for example, 100 to 500 rpm, and as a specific example, at 300 rpm, and within this range, there is an advantage of promoting the extraction of lithium compounds from the crushed material.

[0252] The above stirring can be performed for, for example, 30 minutes or more, and specifically, for 60 minutes, and within this range, there is an advantage in that lithium compounds are sufficiently extracted from the reduced waste of the lithium ion battery positive electrode material, thereby obtaining lithium with a high recovery rate.

[0253]

[0254] The organic solvent from which lithium is extracted obtained after the above extraction step (step S30) has a low content of impurities such as Ni, Co, and Mn, so that high-purity lithium can be easily recovered, and the extraction residue contains Ni, Co, and Mn, so that it can be used as a precursor raw material, which has an economic advantage.

[0255]

[0256] Next, the organic solvent from which lithium is extracted and the extraction residue are separated (step S40).

[0257] The separation of the organic solvent from which lithium is extracted and the extraction residue can preferably be accomplished by using reduced pressure filtration. In this case, the organic solvent from which lithium is extracted and the extraction residue can be easily separated through a simple process, which has the advantage of reducing the process cost.

[0258] Through the above separation, an organic solvent containing a lithium compound dissolved therein and an extraction residue are obtained.

[0259]

[0260] Next, the organic solvent from which the separated lithium is extracted is stripped with an acidic solution to obtain a lithium-containing aqueous solution and an organic solvent (step S50).

[0261] In the above step S50, the stripping is performed by combining with a cation exchange extractant in an organic solvent to remove the extracted lithium and reversely extracting it with an acidic solution, thereby easily recovering the lithium in a subsequent process, and also has the advantage of reducing the energy, cost, and time required for the recovery.

[0262] The volume ratio (organic / aqueous volume ratio) of the organic solvent and acid solution from which the separated lithium is extracted may be, for example, 0.5 to 10, and specifically, may be 1 to 5. Within this range, lithium is easily removed, increasing the lithium recovery rate, and lithium is easily concentrated, reducing the energy, cost, and time required for this, thereby improving economic feasibility and efficiency.

[0263] The above acidic solution may be, for example, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution, and a specific example may be a sulfuric acid aqueous solution. In this case, lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate, and lithium is easily concentrated, thereby reducing the energy, cost, and time required for this, thereby improving economic feasibility and efficiency.

[0264] The above acidic solution may contain, for example, an acid at a molar concentration (mol / L) of 0.5 to 1.5, and as a specific example, may contain an acid at a concentration of 1 mol. Within this range, lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate and enabling lithium to be easily concentrated and recovered.

[0265] The above acidic solution may have, for example, a pH of 1 or lower, and as a specific example, a pH of 0. Within this range, lithium in the organic solvent is easily removed into the acidic solution, thereby increasing the lithium recovery rate and providing the advantage of easy lithium recovery.

[0266] The removal of the above step S50 can be performed by adding an acidic solution to the organic solvent from which the separated lithium has been extracted and stirring using a stirrer at room temperature.

[0267] The above stirring can be performed at, for example, 300 to 800 rpm, and as a specific example, can be performed at 600 rpm, and within this range, there is an advantage of promoting reverse extraction of lithium from an organic solvent into an acidic solution.

[0268] The above stirring can be performed for, for example, 20 minutes or more, and as a specific example, for 30 minutes, and within this range, there is an advantage in that lithium is sufficiently extracted back from the organic solvent into the acidic solution.

[0269]

[0270] Next, the lithium-containing aqueous solution and the organic solvent are separated (step S60).

[0271] In the above step S60, the separation is performed by separating the lithium-containing aqueous solution and 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.

[0272] In addition, the separated organic solvent can be transferred to the extraction step (step S30) and reused, in which case the generation of wastewater is reduced, which reduces production costs and has the advantage of being environmentally friendly.

[0273]

[0274] Next, lithium is carbonated in the separated lithium-containing aqueous solution to obtain lithium carbonate (step S70).

[0275] The above carbonation can be carried out by introducing a carbonate or carbon dioxide gas, and as a specific example, can be carried out by introducing sodium carbonate, in which case there is an advantage of quickly converting lithium into lithium carbonate.

[0276] The above carbonate can be added, for example, in an amount of 0.5 to 2.5 moles per mole of lithium in a lithium-containing aqueous solution, and as a specific example, 1.2 moles can be added, and in this case, there is an advantage of quickly converting lithium into lithium carbonate.

[0277]

[0278] The above separated lithium-containing aqueous solution can be adjusted to a pH of 10 to 12 by adding a basic compound before carbonation. For example, a step of removing impurities can be performed by adding sodium hydroxide to adjust the pH to 10 to 12. In this case, there is an advantage in that the purity and recovery rate of lithium carbonate are improved.

[0279]

[0280] The lithium carbonate obtained after carbonation in the above step S70 can be washed with water and then dried to obtain the final lithium carbonate.

[0281]

[0282] On the other hand, the extract residue obtained after separation in step S40 is leached with acid (step S80).

[0283] After the acid leaching, a leaching solution in which residual metal compounds are dissolved is obtained, and the acid may specifically be sulfuric acid.

[0284] The leachate (step S90) in which the above residual metal compound is dissolved contains residual metal compounds, specifically, contains Ni, Co, and Mn, and can be used as a precursor raw material, so it has an economic advantage.

[0285]

[0286] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0287]

[0288] [Example I: Extraction rates of Li, Ni, Co, Mn, and Al according to the high-liquid ratio in the extraction stage]

[0289] Example 1

[0290] 300 g of a positive electrode material in powder form obtained from a spent lithium-ion battery and 37.04 g of a negative electrode material (an amount corresponding to 1 mole per 1 mole of the positive electrode active material in the positive electrode material) were dry mixed, placed in a sealed kiln, heated to 650°C under a nitrogen atmosphere, maintained for 5 hours, heat-treated (roasted), and then cooled in the furnace for more than 10 hours to obtain a reduced roasted product of a lithium-ion battery positive electrode material. Here, the temperature increase rate until reaching the roasting temperature was 3°C / min, and nitrogen was supplied at 10 L / min.

[0291] The components of the positive electrode material in powder form obtained from the above-mentioned waste lithium-ion battery were analyzed by ICP analysis and are shown in Table 1 below. For the ICP analysis, 0.01 g of the positive electrode material, 3 mL of HCl, and 20.5 mL of H2O were placed in a conical tube, mixed, and heated to dissolve. Once the positive electrode material was dissolved, it was placed in a 50 mL tube, diluted, and measured by ICP analysis.

[0292]

[0293] The reduced waste of the above lithium ion battery cathode material was sequentially pulverized using a roll mill and a pin mill to obtain a reduced waste of the lithium ion battery cathode material in powder form with an average particle size (D50) of 11.5 ㎛.

[0294] The above average particle size (D50) was measured using the laser diffraction method. Specifically, the particles of the reduced waste were dispersed in a dispersion medium, and then introduced into a laser diffraction particle size measuring device of Microtrac S3500, and ultrasonic waves of approximately 28 kHz were irradiated at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device was calculated.

[0295] The components of the reduced waste product of the above lithium ion battery cathode material were analyzed by ICP analysis and are shown in Table 2 below.

[0296] Content of reduction waste of lithium-ion battery cathode material (weight%) 6.548.03.72.20.41

[0297] Kerosene containing 1 molar concentration (mol / L) of di-2-ethylhexyl phosphate (D2EHPA) as a cation exchange extractant (hereinafter referred to as “D2EHPA-containing kerosene”) was prepared. 20 mL of D2EHPA-containing kerosene was added to 1 g of the reduced waste product in powder form, and extraction was performed at room temperature for 1 hour to obtain an organic solvent from which lithium was extracted and an extraction residue. The mixture was stirred at 300 rpm during the extraction. The solid-liquid ratio was 1 g / 20 mL, and the amount of D2EHPA was 2 mol based on 1 mol of lithium in the reduced waste product of a lithium-ion battery cathode material.

[0298] The kerosene containing D2EHPA from which the lithium was extracted and the extraction residue were separated by vacuum filtration.

[0299] The above separated lithium-extracted D2EHPA-containing kerosene was stripped with a 1 molar concentration (mol / L) sulfuric acid aqueous solution so that lithium was back-extracted into the sulfuric acid aqueous solution, thereby obtaining a lithium-containing aqueous solution and D2EHPA-containing kerosene. At this time, the volume ratio (organic / aqueous volume ratio, O / A ratio) of the lithium-extracted D2EHPA-containing kerosene and the sulfuric acid aqueous solution was 1, and the stripping was performed for 30 minutes while stirring at 600 rpm at room temperature.

[0300] The above lithium-containing aqueous solution and D2EHPA-containing kerosene were separated using a separation funnel.

[0301] Since the separated lithium-containing aqueous solution contains impurities including Ni, Co, and Mn, a step of separating impurities was performed by adding sodium hydroxide at a concentration of 4 mol (mol / L) to raise the pH to 12 to obtain a precipitate containing Ni, Co, and Mn and a lithium-containing aqueous solution and separating them. The impurity separation step was performed while stirring at room temperature. The separation of the precipitate containing Ni, Co, and Mn and the lithium-containing aqueous solution was performed using reduced pressure filtration.

[0302] After separating the above impurities, sodium carbonate was added to the purified lithium-containing aqueous solution to carbonate it and recover lithium as lithium carbonate. Sodium carbonate was added in an amount of 1.2 moles per mole of lithium in the lithium-containing aqueous solution. At this time, sodium carbonate was added at 80°C while stirring.

[0303] After the carbonation was completed, lithium carbonate was separated from the aqueous solution in the form of a wet cake.

[0304] In order to remove sodium contained in large quantities in the synthesized lithium carbonate in the above wet cake state, the synthesized lithium carbonate was washed with water at 80°C. At this time, the mineral-liquid ratio (mineral-liquid ratio) of water and lithium carbonate powder was 1 g / 3 mL, and the washing process was performed while stirring.

[0305] The washed lithium carbonate was dried using a hot air dryer at 130°C to obtain the final lithium carbonate.

[0306]

[0307] Example 2

[0308] The same procedure as in Example 1 was followed, except that the ratio of the powder-type reduced waste and the high-liquid ratio of kerosene containing D2EHPA was changed to 1 g / 10 ml.

[0309]

[0310] Example 3

[0311] The same procedure as in Example 1 was followed, except that the ratio of the powder-type reduced waste and the high-liquid ratio of kerosene containing D2EHPA was changed to 1 g / 30 ml.

[0312]

[0313] Example 4

[0314] The same procedure as in Example 1 was followed, except that the ratio of the powder-type reduced waste and the high-liquid ratio of kerosene containing D2EHPA was changed to 1 g / 40 ml.

[0315]

[0316] [Test Example I: Extraction Amounts and Extraction Rates of Li, Ni, Co, Mn, and Al]

[0317] The contents of Li, Ni, Co, Mn and Al in the lithium-containing aqueous solution separated after stripping obtained in Examples 1 to 4 were measured through ICP analysis, and the results are shown in Table 3 and Figure 3 below.

[0318] * ICP analysis: 0.2 g of lithium-containing aqueous solution was aliquoted and placed in a conical tube, the exact weight was measured, 0.1 ml of 70 wt% nitric acid was added, 500 ㎕ of 1000 mg / kg internal STD (Sc) was added, and the total volume was diluted to 50 ml with ultrapure water. The contents of Li, Ni, Co, Mn, and Al were measured using ICP analysis.

[0319] * Extraction rate (weight %): The contents of Li, Ni, Co, Mn, and Al in the reduced waste of lithium-ion battery cathode material were measured by ICP analysis, and the extraction rate was calculated using the following mathematical formula 1.

[0320] [Mathematical Formula 1]

[0321] Extraction rate of M component (weight %) = [Content of M component in lithium-containing aqueous solution (g) / Content of M component in reduced waste of lithium-ion battery cathode material (g)] * 100

[0322] In the above mathematical formula 1, M is Li, Ni, Co, Mn, or Al.

[0323]

[0324] Classification High-Liquid Ratio (g / mL) Extraction Rate (Wt%) LiNiCoMnAl Example 11g / 20ml>990.170.315.7-Example 21g / 10ml61.70.440.070.81-Example 31g / 30ml>990.240.518.3-Example 41g / 40ml>993.040.728.6-

[0325] As shown in Table 3 and Figure 3 above, the Li extraction rate is high within the high-liquid ratio of 1 g / 10 ml to 1 g / 40 ml, while the extraction rates of Ni, Co, Mn, and Al are low. In particular, the Li extraction rate exceeds 99 wt% at the high-liquid ratio of 1 g / 20 ml or more, and the extraction rates of Co and Mn are lower at the high-liquid ratio of 1 g / 10 ml.

[0326]

[0327] [Example II: Extraction rate according to the molar ratio of lithium and D2EHPA in the reduction waste of lithium-ion battery cathode material in the extraction step]

[0328] Example 5

[0329] In the above Example 1, the same procedure as in Example 1 was performed except that D2EHPA was added in an amount of 1.41 mol based on 1 mol of lithium in the reduction product of a lithium ion battery cathode material.

[0330]

[0331] Example 6

[0332] In the above Example 1, the same procedure as in Example 1 was performed, except that D2EHPA was added in an amount of 1 mole based on 1 mole of lithium in the reduction product of a lithium ion battery cathode material.

[0333]

[0334] [Test Example II: Contents and extraction rates of Li, Ni, Co, Mn, and Al]

[0335] The contents of Li, Ni, Co, Mn, and Al were measured through ICP analysis using the same method as in Test Example I above, and are shown in Table 4 below. The extraction rate calculated from the measured contents is shown in Table 5 and Figure 4 below.

[0336]

[0337] Molar ratio of Li:D2EHPA Extraction amount (mg / L) LiNiCoMnAl Example 11: 2347541.15.763.8- Example 51: 1.41282618.33.240.0- Example 61: 121129.52.125.1-

[0338] As shown in Table 4 above, it was confirmed that the amount of Li extracted was high and the amounts of Ni, Co, Mn, and Al extracted were low at a molar ratio of 1 to 2 of D2EHPA per 1 mol of Li in the reduced powder form.

[0339]

[0340] ClassificationLi:D2EHPA molar ratioExtraction rate (wt%)LiNiCoMnAlExample 11:2>990.170.315.7-Example 51:1.4187.10.080.173.6-Example 61:165.10.040.112.3-

[0341] As shown in Table 5 above and Figure 4 below, it was confirmed that the extraction rate of Li was high and the extraction rates of Ni, Co, Mn, and Al were low when the molar ratio of D2EHPA was 1 to 2 for 1 mol of Li in the reduced powder.

[0342]

[0343] [Example III: Extraction amount according to O / A ratio in the stripping step]

[0344] Example 7

[0345] In the above Example 1, the same procedure as in Example 1 was performed except that the O / A ratio was changed to 3. At this time, the pH of the Li-containing aqueous solution was measured after stripping.

[0346]

[0347] Example 8

[0348] In the above Example 1, the same procedure as in Example 1 was performed except that the O / A ratio was changed to 5. At this time, the pH of the Li-containing aqueous solution was measured after stripping.

[0349]

[0350] [Test Example III: Extraction amounts of Li, Ni, Co, Mn, and Al and pH of Li-containing aqueous solution]

[0351] The contents of Li, Ni, Co, Mn, and Al were measured through ICP analysis using the same method as in Test Example I above, and are shown in Table 6 and Figure 5 below.

[0352] Additionally, pH measurements were performed at room temperature using a METTLER TOLEDO SevenDirect SD30.

[0353]

[0354] Classification O / A specific extractable amount (mg / L) pHLiNiCoMnAl Example 11347541.15.763.8-0 Example 739777127.916.4202.2-1 Example 8514781.5206.423.476.1-2

[0355] As shown in Table 6 above and Figure 5 below, it was confirmed that the amount of Li extracted was high and the amounts of Ni, Co, Mn, and Al extracted were low at O / A ratios of 1 to 5. Specifically, it was confirmed that the amount of Li extracted was the highest in Example 8 with an O / A ratio of 5.

[0356]

[0357] [Example IV: Recovery of lithium carbonate from a lithium-containing aqueous solution separated after stripping]

[0358] The contents of Li, Ni, Co, Mn and Al in the lithium-containing aqueous solution obtained in Example 8, the lithium-containing aqueous solution after pH adjustment and the remaining filtrate after carbonation were measured by ICP analysis and are shown in Table 7.

[0359]

[0360] Example 8 Content (mg / L) LiNiCoMnAl Lithium-containing aqueous solution obtained 14781.5206.423.476.1 - Lithium-containing aqueous solution after pH adjustment 14700----Filtered solution remaining after carbonation 2696----

[0361] As shown in Table 7 above, it was confirmed that the lithium-containing aqueous solution, from which impurities were removed by pH adjustment, was recovered as high-purity lithium carbonate, as there was no presence of Ni, Co, or Mn.

[0362] [Example V: Impurity content of recovered lithium carbonate]

[0363] The impurity content of lithium carbonate recovered by carbonation in Example 8 was measured through ICP analysis and is shown in Table 8 below.

[0364]

[0365]

[0366] * ND: Not Detected

[0367] As shown in Table 8 above, in addition to Na and Ca components, components such as Ni, Co, and Mn were not detected in the recovered lithium carbonate, confirming that it was recovered as high-purity lithium carbonate.

Claims

1. (a) A step of extracting a reduced waste 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 is extracted and an extraction residue; (b) a step of separating the organic solvent from which lithium is extracted and the extraction residue; (c) a step of stripping the organic solvent from which separated lithium is 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 and the organic solvent; and (e) a step of carbonating lithium in a separated lithium-containing aqueous solution to obtain lithium carbonate; characterized in that it comprises; Method for recovering lithium compounds.

2. In paragraph 1, In the above step (a), the reduction product of the lithium ion battery cathode material is characterized in that it is obtained by mixing the lithium ion battery cathode material and a carbon-containing reducing agent, calcining them at 550 to 750°C, and then pulverizing them. Method for recovering lithium compounds.

3. In paragraph 2, The carbon-containing reducing agent is characterized in that it is used in an amount of 0 to 3 moles per mole of the cathode active material in the lithium-ion battery cathode material. Method for recovering lithium compounds.

4. In paragraph 2, The carbon-containing reducing agent is characterized in that it is an organic material containing carbon, an inorganic material containing carbon, a cathode material, or a mixture thereof. Method for recovering lithium compounds.

5. In paragraph 2, The above-mentioned oxidation is characterized in that it is carried out under a reducing gas or an inert gas. Method for recovering lithium compounds.

6. In paragraph 2, The lithium ion battery cathode material is characterized in that it is at least one 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 part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co). Method for recovering lithium compounds.

7. In paragraph 2, The above lithium ion battery cathode material is characterized in that it is a discarded lithium ion battery cathode material. Method for recovering lithium compounds.

8. In paragraph 2, The above grinding is characterized by using a milling machine. Method for recovering lithium compounds.

9. In paragraph 1, In the above step (a), the cation exchange extractant is characterized in that it includes an alkyl phosphate extractant, an alkyl monocarboxylic acid, or a mixture thereof. Method for recovering lithium compounds.

10. In paragraph 9, The above alkyl phosphate extractant is characterized in that it includes at least one selected from the group consisting of Di-(2-ethylhexyl) phosphate, 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, and Bis(2,4,4-trimethylpentyl)dithiophosphinic acid. Method for recovering lithium compounds.

11. In paragraph 9, The above alkyl monocarboxylic acid is characterized in that it includes a compound represented by the following chemical formula 1. Method for recovering lithium compounds. [Chemical Formula 1] (In the above chemical formula 1, R1 and R2 are each independently an alkyl group, and the sum of the carbon atoms of R1 and R2 is 5 to 9.) 12. In paragraph 1, In the above step (a), the organic solvent is characterized in that it includes at least one selected from the group consisting of kerosene, hexane, benzene, and toluene. Method for recovering lithium compounds.

13. In paragraph 1, In the step (a), the cation exchange extractant is characterized in that it contains 0.9 to 2.5 moles per mole of lithium in the reduced waste of the lithium ion battery cathode material. Method for recovering lithium compounds.

14. In paragraph 1, In the above step (a), the solid-liquid ratio of the reduced product of the lithium ion battery cathode material and the organic solvent containing the cation exchange extractant is 1 g / 8 mL to 1 g / 44 mL. Method for recovering lithium compounds.

15. In paragraph 1, In the above step (b), the separation of the organic solvent from which lithium is extracted and the extraction residue is characterized by using reduced pressure filtration. Method for recovering lithium compounds.

16. In paragraph 1, In the above step (c), the volume ratio of the organic solvent and the acidic solution from which lithium is extracted (organic / aqueous volume ratio) is 0.5 to 10. Method for recovering lithium compounds.

17. In paragraph 1, In the above step (c), the acid solution is characterized in that it is a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution. Method for recovering lithium compounds.

18. In paragraph 1, In the above step (e), carbonation is characterized in that it is carried out by injecting carbonate or carbon dioxide gas. Method for recovering lithium compounds.

19. In paragraph 1, The organic solvent separated in the above step (d) is characterized in that it is reused in the extraction in the above step (a). Method for recovering lithium compounds.

20. In paragraph 1, The method for recovering a lithium compound from the above lithium ion battery cathode material is characterized in that it further includes a step of leaching the extraction residue obtained in the above step (b) with acid to obtain a leaching solution in which the residual metal compound is dissolved. Method for recovering lithium compounds.

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