Method for recovering lithium

Abstract

The present invention relates to a method for recovering lithium and, more specifically, to a method for recovering lithium, the method comprising the steps of: (a) dissolving a positive electrode material powder, obtained from a positive electrode of a waste lithium ion battery, having an olivine structure in an acetic acid aqueous solution to prepare a solution; (b) adding the solution with an aqueous hydrogen peroxide (H2O2) solution to obtain a leachate containing dissolved lithium and a leaching residue; (c) separating the leachate from the leaching residue; and (d) concentrating the leachate, wherein step (b) is performed at 45 to 65°C, the acetic acid in step (a) is used in an amount of 0.8 to 1.2 mol per 1 mol of positive electrode active material in the positive active material powder, and the hydrogen peroxide in step (b) is used in an amount of 0.4 to 0.6 mol per 1 mol of positive electrode active material in the positive electrode material powder. According to the present invention, a positive electrode material having an olivine structure is selectively leached only with lithium in a predetermined temperature range by using an oxidizing agent in a weakly acidic acetic acid aqueous solution, thereby recovering lithium at a high yield. Furthermore, FePO4 is preserved as the leaching residue and is reused as a raw material for lithium iron phosphate, whereby the productivity and cost-efficiency are greatly improved and waste water treatment is not needed, thus providing an eco-friendly method for recovery of lithium.

Description

Lithium recovery method

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

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0114299, filed August 30, 2023, and Korean Patent Application No. 10-2024-0106755, filed August 9, 2024, which is hereby incorporated by reference in its entirety.

[0003] The present invention relates to a method for recovering lithium, and more specifically, to an environmentally friendly method for recovering lithium, which comprises dissolving a cathode material having an olivine structure in a weakly acidic acetic acid solution, then adding a hydrogen peroxide aqueous solution to selectively leach lithium within a predetermined temperature range, thereby recovering lithium with a high yield, and further preserving FePO4 as a leachate residue and reusing it as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic feasibility and requiring no wastewater treatment.

[0004] Demand for lithium-ion batteries has steadily increased since the 1990s alongside the growth of the portable electronic device market, and has recently surged further worldwide due to the rapid expansion of the electric vehicle market. This could lead to instability in the lithium resource supply and demand in the near future, and the continuous accumulation of waste batteries that have reached the end of their useful life 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, lithium composite oxides such as lithium nickel cobalt manganese oxide (LiNiMnCoO2), lithium manganese oxide (LiMnO2), or lithium iron phosphate (LiFePO4) that also contain nickel and manganese are used to reduce the amount of expensive cobalt used. Since the above cathode materials contain about 5-7% lithium, a method for recovering lithium from waste lithium-ion battery cathode materials is receiving a lot of attention.

[0007] However, lithium iron phosphate (LiFePO4) possesses a highly stable hexahedral crystal structure. To recover valuable metals by disrupting this stable structure, a wet process is used, using highly concentrated strong acids or bases to obtain Li, Fe, and P as their respective compounds. This process generates a large amount of toxic wastewater, which poses environmental problems and increases production costs due to the costs of treating it.

[0008] Therefore, there is a need to develop a method for recovering lithium with a high yield from a cathode material having a very stable crystal structure obtained from the cathode of a spent lithium-ion battery, while reducing production costs and being environmentally friendly.

[0009]

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 1) Korean Patent Publication No. 2007-0112278

[0013] In order to solve the problems of the prior art as described above, the present invention provides a method for recovering lithium from a cathode material of a spent lithium-ion battery, wherein a cathode material powder having an olivine structure obtained from a cathode of a spent lithium-ion battery is dissolved in an aqueous acetic acid solution to prepare a solution, and an aqueous hydrogen peroxide (H2O2) solution is added to the prepared solution at 45 to 65°C, thereby obtaining lithium with a high recovery rate, and the leachate residue is reused as a raw material for lithium iron phosphate oxide by preserving FePO4, thereby greatly improving economic efficiency, and is environmentally friendly because it does not use a strong acid or a strong base, and thus reduces process costs because neutralization and wastewater treatment are not required.

[0014] The above and other objects of the present invention can all be achieved by the present invention described below.

[0015] In order to achieve the above object, I) the present invention provides a method for recovering lithium, characterized by comprising the steps of: (a) dissolving a cathode material powder having an olivine structure obtained from a cathode of a spent lithium ion battery in an aqueous acetic acid solution to prepare a solution; (b) adding an aqueous hydrogen peroxide (H2O2) solution to the solution to obtain a leachate and a leachate residue in which lithium is dissolved; (c) separating the leachate and the leachate residue; and (d) concentrating the leachate.

[0016] In addition, II) the present invention provides a method for recovering lithium, comprising the steps of: (a) dissolving a cathode material powder having an olivine structure obtained from a cathode of a spent lithium-ion battery in an aqueous acetic acid solution to prepare a solution; (b) adding a hydrogen peroxide (H2O2) aqueous solution to the solution to obtain a leachate and a leachate residue in which lithium is dissolved; (c) separating the leachate and the leachate residue; and (d) concentrating the leachate; wherein step (b) is performed at 45 to 65°C, and in step (a), acetic acid is used in an amount of 0.8 to 1.2 moles per mole of the cathode active material in the cathode material powder, and in step (b), hydrogen peroxide is used in an amount of 0.4 to 0.6 moles per mole of the cathode active material in the cathode material powder.

[0017] III) In the above I) or II), the cathode material having the olivine structure may preferably include lithium iron phosphate.

[0018] IV) In the above I) to III), the cathode material having the olivine structure may preferably be a compound represented by the following chemical formula 1.

[0019] [Chemical Formula 1]

[0020]

[0021] (In the above chemical formula 1, M includes at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X includes at least one element selected from the group consisting of F, S, and N, and a, b, and c are -0.5≤a≤0.5, 0≤b≤0.5, and 0≤c≤0.1, respectively.)

[0022] V) In the above I) to IV), the cathode material powder may preferably be obtained by crushing the cathode of a spent lithium ion battery to separate the cathode material powder and the current collector.

[0023] VI) In the above I) to V), the weight ratio of the positive electrode powder and the acetic acid aqueous solution in step (a) may preferably be 1:6 to 1:10.

[0024] VII) In the above I) to VI), in the step (a), acetic acid can preferably be used in an amount of 0.8 to 1.2 mol per 1 mol of the positive electrode active material in the positive electrode powder.

[0025] VIII) In the above I) to VII), in the step (b), the hydrogen peroxide aqueous solution may preferably be used in an amount of 0.4 to 0.6 mol per 1 mol of the positive electrode active material in the positive electrode powder.

[0026] IX) In the above I) to VIII), the acetic acid aqueous solution in step (a) may have a concentration of 0.5 to 1 molar concentration (mol / L).

[0027] X) In the above I) to IX), the concentration of the hydrogen peroxide aqueous solution in step (b) may be 25 to 40 wt%.

[0028] XI) In the above I) to X), the lithium recovery method may have a lithium recovery rate of 90 wt% or more calculated by the following mathematical formula 1.

[0029] [Mathematical Formula 1]

[0030] Lithium recovery rate (wt%) = [Lithium content in the leachate (g) / Lithium content in the cathode powder (g)] * 100

[0031] XII) In the above I) to XI), the step (b) can preferably be performed at a pH of 3.5 to 5.5.

[0032] XIII) In the above I) to XII), the step (b) can preferably be carried out under stirring.

[0033] XIV) In the above I) to XIII), the separation of the leachate and the leach residue in the step (c) can preferably utilize reduced pressure filtration.

[0034] XV) In the above I) to XIV), the leaching residue may preferably include FePO4.

[0035] XVI) In the above I) to XV), the concentration of the extract in the step (d) can preferably utilize reduced pressure evaporation.

[0036] XVII) In the above I) to XVI), the method for recovering lithium may preferably include a step of vacuum drying the leaching residue obtained in the above step (c) to obtain a compound containing FePO4.

[0037] XVIII) In the above I) to XVII), the compound containing the obtained FePO4 can be manufactured into lithium iron phosphate, preferably including a step of adding lithium and calcining, and then adding carbon and calcining.

[0038] According to the present invention, by dissolving a cathode material having an olivine structure, which is a very stable structure, in a weakly acidic acetic acid aqueous solution, then adding a hydrogen peroxide aqueous solution and selectively leaching lithium at a predetermined temperature range, lithium is recovered at a high yield and FePO4 is preserved as a leaching residue and reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0039] In addition, since no strong acid or strong base is used for leaching, no wastewater is generated, reducing process costs and providing an environmentally friendly effect.

[0040] 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.

[0041] Figure 1 is an example according to the present invention, and is the result of measuring the leaching residue obtained in Example 1 using X-ray diffraction analysis (XRD).

[0042] Figure 2 shows the results of X-ray diffraction analysis (XRD) of the leaching residue obtained from Comparative Example 1.

[0043] Figure 3 shows the results of X-ray diffraction analysis (XRD) of the leaching residue obtained from Comparative Example 2.

[0044] Figure 4 is a process diagram for a method for recovering lithium from a waste lithium ion battery cathode material according to one embodiment of the present invention.

[0045] The present inventors, while studying a method for recovering lithium from a lithium-ion battery positive electrode material having a very stable olivine structure, confirmed that when a positive electrode material having an olivine structure is dissolved in a weakly acidic acetic acid solution, a hydrogen peroxide aqueous solution of a predetermined concentration is added to the solution, and leaching is performed at 45 to 65°C, the lithium recovery rate is high, and FePO4 is preserved in the leaching residue, so that it can be reused as a raw material for lithium iron phosphate, thereby greatly improving economic efficiency and recovering lithium in an environmentally friendly manner without using a strong acid or strong base. Based on this, they devoted themselves to further research and completed the present invention.

[0046]

[0047] The method for recovering lithium described herein is described in detail below.

[0048] 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.

[0049] 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.

[0050]

[0051] Lithium recovery method

[0052] The present invention provides a method for recovering lithium, comprising the steps of: (a) dissolving a cathode material powder having an olivine structure obtained from a cathode of a spent lithium-ion battery in an aqueous acetic acid solution to prepare a solution; (b) adding an aqueous hydrogen peroxide (H2O2) solution to the solution to obtain a leachate and a leachate residue in which lithium is dissolved; (c) separating the leachate and the leachate residue; and (d) concentrating the leachate. In this case, the recovery rate of lithium is high, the leachate residue preserves FePO4 and is reused as a raw material for lithium iron phosphate, which greatly improves economic efficiency, and is environmentally friendly because it does not use a strong acid or a strong base, and there is an advantage in that neutralization and wastewater treatment are not required, thereby reducing process costs.

[0053]

[0054] In addition, the method for recovering lithium of the present invention comprises the steps of (a) dissolving a cathode material powder having an olivine structure obtained from a cathode of a spent lithium-ion battery in an aqueous acetic acid solution to prepare a solution; (b) adding a hydrogen peroxide (H2O2) aqueous solution to the solution to obtain a leachate and a leachate residue in which lithium is dissolved; (c) separating the leachate and the leachate residue; and (d) concentrating the leachate; wherein the step (b) is performed at 45 to 65°C, and the acetic acid in the step (a) is used in an amount of 0.8 to 1.2 moles per mole of the cathode active material in the cathode material powder, and the hydrogen peroxide in the step (b) is used in an amount of 0.4 to 0.6 moles per mole of the cathode active material in the cathode material powder. In this case, the recovery rate of lithium is high, the leachate residue is reused as a raw material for lithium iron phosphate by preserving FePO4, which greatly improves economic efficiency, and it is environmentally friendly because it does not use strong acids or strong bases, and there is an advantage in that the process cost is reduced because neutralization and wastewater treatment are not required.

[0055]

[0056] Below, the lithium recovery method is explained in detail step by step.

[0057]

[0058] (a) A step of preparing a solution by dissolving the cathode material powder in an acetic acid aqueous solution.

[0059] The method for recovering lithium of the present invention comprises the step of (a) dissolving a cathode material powder having an olivine structure obtained from a cathode of a spent lithium ion battery in an aqueous acetic acid solution to prepare a solution, and in this case, lithium is recovered at a high yield without using a strong acid or strong base, and wastewater treatment is not required, so there is an environmentally friendly advantage.

[0060]

[0061] The olivine structure used in this paper is a type of cathode material structure, a hexahedral lattice structure with a 3D shape, where phosphorus and oxygen atoms are strongly bonded. Because this structure can be maintained even after all lithium ions have been lost, it exhibits minimal performance degradation due to charge and discharge and excellent thermal stability. Furthermore, it is economical because inexpensive iron can be used instead of expensive cobalt metal, but its energy density, electrical conductivity, and lithium ion diffusion are lower than those of other cathode materials.

[0062] The above olivine structure can be confirmed through X-ray diffraction analysis (XRD).

[0063]

[0064] The cathode material of this description means a cathode active material or a cathode active material.

[0065]

[0066] The cathode material having the above olivine structure may include, for example, lithium iron phosphate, in which case it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0067] The cathode material having the above olivine structure may be, for example, a compound represented by the following chemical formula 1, in which case it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0068]

[0069] [Chemical Formula 1]

[0070]

[0071] (In the above chemical formula 1, M includes at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X includes at least one element selected from the group consisting of F, S, and N, and a, b, and c are -0.5≤a≤0.5, 0≤b≤0.5, and 0≤c≤0.1, respectively.)

[0072]

[0073] The above lithium iron phosphate may preferably include LiFePO4 having an olivine structure, in which case it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0074]

[0075] The above cathode material powder may be obtained, for example, by crushing the cathode of a spent lithium-ion battery and separating the cathode material powder and the current collector. In this case, there is an economic advantage of recycling resources by recovering FePO4 and other materials together with expensive lithium.

[0076] The positive electrode of the above-mentioned waste lithium-ion battery may be, for example, a discarded lithium-ion battery positive electrode, a defective product generated during the positive electrode coating process, or a positive electrode scrap discarded after cutting the electrode plate, and preferably, may be a discarded lithium-ion battery positive electrode. In this case, there is an economic advantage of recycling resources by recovering FePO4, etc. together with expensive lithium.

[0077]

[0078] The above shredding may be, for example, cutting or shredding of a discarded lithium ion battery positive electrode, and may preferably be performed using dry shredding equipment, specifically, a hand mill, pin mill, disc mill, cutting mill, or hammer mill.

[0079]

[0080] The above-mentioned crushed positive electrode can be crushed, for example, with a mixer, a hand mill, a pin mill, a disk mill, a cutting mill, or a hammer mill, and preferably crushed with a mixer, in which case the current collector pieces are chopped into small pieces and the positive electrode material is advantageously separated from the current collector pieces.

[0081]

[0082] The above-mentioned crushed cathode material can be obtained as a powder, for example, through a sieve, and in this case, there is an effect that leaching is made easier.

[0083]

[0084] The above acetic acid aqueous solution may be, for example, an acetic acid aqueous solution having a molar concentration (mol / L) of 0.5 to 1, preferably an acetic acid aqueous solution having a molar concentration of 0.6 to 0.9, more preferably an acetic acid aqueous solution having a molar concentration of 0.7 to 0.9, and even more preferably an acetic acid aqueous solution having a molar concentration of 0.75 to 0.85, and within this range, lithium can be recovered at a high yield without using a strong acid or strong base, and wastewater treatment is not required, so there is an environmentally friendly advantage.

[0085]

[0086] In the above step (a), the weight ratio of the positive electrode powder and the acetic acid aqueous solution may be, for example, 1:6 to 1:10, preferably 1:6.5 to 1:9.5, more preferably 1:7 to 1:9, even more preferably 1:7.5 to 1:8.5, and even more preferably 1:7.5 to 1:8, and within this range, there is an advantage in that the positive electrode powder is easily dissolved in the acetic acid aqueous solution.

[0087]

[0088] The above acetic acid aqueous solution may have, for example, a pH of 2.0 to 3.5, preferably a pH of 2.5 to 3.5, and more preferably a pH of 2.5 to 3.0, and within this range, the positive electrode material is easily dissolved, which has the advantage of increasing the recovery rate of lithium.

[0089] In this description, pH measurement can be measured by a measurement method commonly used in the technical field to which the present invention belongs, and unless otherwise described, can be measured using a general pH measuring device at room temperature, and specifically, can be measured using a Thermo Scientific Orion Star A Series.

[0090] In this description, room temperature may be a point within the range of 20 ± 5 ℃.

[0091]

[0092] In the above step (a), acetic acid is used in an amount of, for example, 0.8 to 1.2 mol per 1 mol of the positive electrode active material in the positive electrode powder, preferably 0.85 to 1.15 mol, more preferably 0.9 to 1.1 mol, and even more preferably 0.95 to 1.05 mol, and within this range, there is an advantage in that the reaction between the positive electrode powder and acetic acid is smooth.

[0093] In this description, 1 mole of positive electrode active material is based on the positive electrode active material in the positive electrode powder containing the positive electrode active material having an olivine structure.

[0094]

[0095] The above step (a) can be carried out, for example, at room temperature to 70°C, preferably at 45 to 70°C, more preferably at 50 to 70°C, even more preferably at 52 to 65°C, even more preferably at 55 to 65°C, and particularly preferably at 57 to 62°C, and within this range, there is an advantage in that the cathode material is easily dissolved in an aqueous acetic acid solution.

[0096] The above step (a) can be performed, for example, under stirring, in which case there is an advantage of shortening the dissolution time.

[0097] The above stirring speed may be, for example, 300 to 700 rpm, preferably 350 to 650 rpm, more preferably 400 to 600 rpm, and even more preferably 450 to 550 rpm, and within this range, there is an advantage in that the cathode material is easily dissolved in an acetic acid aqueous solution and the time is shortened.

[0098]

[0099] (b) Step of obtaining the leachate and leach residue

[0100] The method for recovering lithium of the present invention may be a step (b) of adding a hydrogen peroxide (H2O2) aqueous solution to the above-described solution to obtain a leachate and a leachate residue in which lithium is dissolved. In this case, lithium is selectively leached into the leachate, so the recovery rate of lithium is high, and the leachate residue preserves FePO4 and is reused as a raw material for lithium iron phosphate, so that productivity and economic feasibility are greatly improved.

[0101]

[0102] In this description, leaching refers to dissolving soluble substances to remove the solution and separating the soluble and insoluble components.

[0103]

[0104] The above step (b) can be carried out, for example, at a temperature of 45 to 65°C, preferably at a temperature of 50 to 65°C, more preferably at a temperature of 52 to 65°C, more preferably at a temperature of 55 to 65°C, and even more preferably at a temperature of 57 to 62°C, and within this range, there is an advantage in that the recovery rate of lithium is greatly increased and the leaching of Fe and P components is greatly reduced.

[0105]

[0106] If step (a) is performed at a lower temperature than step (b), the temperature can be increased to that of step (b) and then the hydrogen peroxide aqueous solution can be added, which has the advantage of increasing the lithium recovery rate.

[0107]

[0108] In the above step (b), the hydrogen peroxide aqueous solution acts as an oxidizing agent and facilitates the leaching of lithium from the positive electrode material.

[0109] The above-mentioned hydrogen peroxide (H2O2) aqueous solution may have a hydrogen peroxide concentration of, for example, 25 to 40 wt%, preferably 27 to 35 wt%, and more preferably 27 to 32 wt%, and within this range, lithium is selectively leached, thereby increasing the lithium recovery rate and preserving FePO4 as a leaching residue to be reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0110]

[0111] In the step (b) above, the hydrogen peroxide aqueous solution may be used in an amount of, for example, 0.4 to 0.6 mol per mol of the positive electrode active material in the positive electrode powder, preferably 0.4 to 0.55 mol, more preferably 0.45 to 0.55 mol, and even more preferably 0.47 to 0.52 mol. Within this range, lithium is selectively leached, thereby increasing the lithium recovery rate, and FePO4 is preserved as a leaching residue, thereby being reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0112]

[0113] In the above step (b), the weight ratio of the positive electrode powder and the hydrogen peroxide aqueous solution may be, for example, 1:0.3 to 1:0.8, preferably 1:0.3 to 1:0.7, and more preferably 1:0.4 to 1:0.6, and within this range, there is an advantage in that lithium is selectively leached and the recovery rate is increased while the pH of the solution is maintained at 3.5 to 5.5.

[0114]

[0115] The above step (b) can be carried out, for example, at a pH of 3.5 to 5.5, preferably at a pH of 4.0 to 5.5, more preferably at a pH of 4.0 to 5.0, and within this range, there is no need for wastewater treatment by not using a strong acid or strong base, so there is an advantage of being environmentally friendly and reducing process costs.

[0116]

[0117] The above step (b) can be performed, for example, under stirring, in which case there is an advantage of shortening the leaching time.

[0118] The above stirring speed may be, for example, 300 to 700 rpm, preferably 350 to 650 rpm, more preferably 400 to 600 rpm, and even more preferably 450 to 550 rpm, and within this range, there is an advantage in that lithium is easily leached from the solution.

[0119]

[0120] 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, even more preferably 0.7 to 1.3 hours, and even more preferably 0.9 to 1.2 hours, and within this range, lithium is sufficiently leached from the solution, so that lithium is recovered at a high yield.

[0121]

[0122] In this description, the stirring method or stirring device is not particularly limited if it is a stirring method or stirring device generally used in the technical field to which the present invention belongs.

[0123]

[0124] In the above step (b), the hydrogen peroxide aqueous solution can be added continuously or in batches, for example, and preferably can be added continuously, and specifically can be added continuously while stirring, in which case there is an advantage that the pH of the solution does not change and lithium is selectively and sufficiently leached. The batch addition can be, for example, the hydrogen peroxide aqueous solution added in batches simultaneously with the start of stirring or immediately before stirring, in which case there is an advantage that lithium is selectively leached.

[0125]

[0126] In this description, 'continuous injection' means not 'batch injection', and refers to injection in a drop-by-drop, little-by-little, step-by-step or continuous flow manner for 10 minutes or more, preferably 30 minutes or more, within the leaching time range.

[0127]

[0128] The reaction mechanism occurring in the above dissolution step and leaching step is as follows, for example, in chemical formula 2.

[0129] [Chemical Formula 2]

[0130] LiFePO4+ CH3COOH + 0.5H2O2---> FePO4+ Li + + CH3COO - + H2O

[0131]

[0132] In the above chemical formula 2, the dissolved state of LiFePO4 varies depending on the pH of the solution in which it is dissolved. At pH 2 or lower, Li + , Fe 2+ PO4 3- It exists in the form of Li3PO4, Fe at pH 6 or higher. 3+ It exists in the form of Li at pH 2 to 6. + And exists in the form of FePO4. In the present invention, the pH of the acetic acid aqueous solution that dissolves the cathode material is controlled to 2.0 to 3.5, and an aqueous hydrogen peroxide solution is added thereto as an oxidizing agent to form Fe 2+ to Fe 3+ By oxidizing it, lithium ions can be more easily leached. Furthermore, a hydrogen peroxide aqueous solution is preferably continuously added so that the pH of the solution is within the range of 3.5 to 5.5, and leaching is performed at 45 to 65°C so that lithium leaching proceeds more stably and sufficiently, thereby obtaining lithium with a high recovery rate.

[0133]

[0134] (c) a step of separating the above-mentioned leachate and leach residue;

[0135] The method for recovering lithium of the present invention may include (c) a step of separating the leachate and the leach residue, in which case lithium is recovered from the leachate at a high yield and FePO4 is preserved from the leach residue and reused as a raw material for lithium iron phosphate, thereby having the advantages of excellent productivity and economic feasibility.

[0136]

[0137] In the above step (c), separation of the leachate and leach residue can be achieved by using, for example, reduced pressure filtration. In this case, the leachate and leach residue can be easily separated with a simple process, reducing process costs and providing the advantage of being environmentally friendly.

[0138] 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 which case there is an advantage that the leaching liquid and the leaching residue are easily separated.

[0139] 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.

[0140]

[0141] The above leaching residue may contain, for example, FePO4, in which case it can be reused as a raw material for lithium iron phosphate, thereby increasing economic benefits and providing the advantage of recycling resources.

[0142]

[0143] (d) a step of concentrating the above-mentioned extract;

[0144] The method for recovering lithium of the present invention may include (d) a step of concentrating the leachate, in which case there is an advantage of easily recovering lithium.

[0145]

[0146] In the above step (d), the concentration of the leachate can be achieved by, for example, using reduced pressure evaporation. As a specific example, the leachate can be directly evaporated under reduced pressure without a separate cooling process. In this case, there is an advantage of obtaining high-purity lithium with a high recovery rate.

[0147]

[0148] The above-mentioned reduced pressure evaporation can be carried out, for example, at 70 to 90°C and 5 to 20 mbar, and preferably at 75 to 85°C and 7 to 12 mbar, in which case there is an advantage of stably recovering lithium at a high yield within a short period of time.

[0149]

[0150] The above-mentioned leachate can be concentrated to recover lithium, and the lithium can be recovered as, for example, lithium acetate. At this time, the recovery rate of lithium can be, for example, 90 wt% or more, preferably 95 wt% or more, and there is an advantage in that economic efficiency is maximized within this range.

[0151]

[0152] The recovery rate of lithium in the above-mentioned leachate can be measured by a measuring method commonly used in the technical field to which the present invention pertains, and for example, it can be measured by ICP analysis of the leachate. Specifically, 0.2 g of the leachate is aliquoted, placed in a conical tube, and the exact weight is measured, and then 0.1 ml of 70% concentration nitric acid is added thereto, followed by adding 500 ㎕ of 1000 mg / kg internal STD (Sc), and diluted to 50 ml with ultrapure water, and measured by ICP. If necessary, further dilution with ultrapure water can be performed so that the sample concentration falls within the standard material calibration curve. In addition, the lithium content contained in the positive electrode powder can be measured by ICP analysis in the same manner as above, and the lithium recovery rate can be calculated by the following mathematical equation 1.

[0153] [Mathematical Formula 1]

[0154] Lithium recovery rate (wt%) = [Lithium content in the leachate (g) / Lithium content in the cathode powder (g)] * 100

[0155]

[0156] In addition, the method for recovering lithium of the present invention may include, for example, a step of vacuum drying the leaching residue obtained in step (c) to obtain a compound containing FePO4, and in this case, it is easily manufactured as a raw material for lithium iron phosphate, thereby recycling resources and providing excellent economic benefits.

[0157] The above vacuum drying can be performed, for example, at a temperature of 120 to 150°C, preferably 125 to 140°C, and more preferably 125 to 135°C, and has the advantage of obtaining a compound containing FePO4 within a short period of time within this range.

[0158] In this description, vacuum drying is not particularly limited as long as it is a vacuum drying method and / or condition commonly practiced in the technical field to which the present invention belongs.

[0159]

[0160] The FePO4 obtained above can be manufactured into lithium iron phosphate by including a step of adding lithium and calcining (hereinafter referred to as the 'first calcination step'), and then adding carbon and calcining (hereinafter referred to as the 'second calcination step'), for example, and is easily manufactured as a raw material for lithium iron phosphate, thereby recycling resources and providing excellent economic benefits.

[0161]

[0162] After adding the lithium, the calcination (first calcination step) can be performed, for example, at 600 to 800°C, preferably at 650 to 750°C, and within this range, there is an effect of sufficient introduction of lithium into FePO4.

[0163] After adding the lithium, the calcination (first calcination step) can be performed for, for example, 8 to 12 hours, preferably 9 to 11 hours, and more preferably 9.5 to 10.5 hours, and within this range, there is an effect of sufficient introduction of lithium into the FePO4.

[0164] After adding the lithium, the calcination (first calcination step) can be performed, for example, under an inert atmosphere, preferably under a nitrogen atmosphere, in which case there is an advantage of preventing oxidation.

[0165]

[0166] After adding the carbon, the calcination (second calcination step) can be performed at, for example, 500 to 700°C, preferably 550 to 650°C, and within this range, carbon is coated on the surface of LiFePO4, which has the advantage of improving electrical conductivity.

[0167] After adding the above carbon, the calcination (second calcination step) can be performed for, for example, 3 to 6 hours, preferably 4 to 5 hours, and more preferably 3.5 to 4.5 hours, and within this range, there is an advantage of improving the electrical conductivity of LiFePO4.

[0168] After adding the above carbon, the firing (second firing step) can be carried out, for example, under an inert atmosphere, preferably under a nitrogen atmosphere, in which case there is an advantage of preventing oxidation.

[0169]

[0170] The following Figure 4 is a flow chart of a method for recovering lithium from a lithium ion battery cathode material according to one embodiment of the present invention.

[0171] Referring to Fig. 4, first, a waste lithium ion battery positive electrode is prepared (step S10).

[0172] The above-mentioned waste lithium ion battery positive electrode may preferably be a discarded lithium ion battery positive electrode, a defective product generated during the positive electrode coating process, or a positive electrode scrap discarded after cutting the electrode plate, and preferably, a discarded lithium ion battery positive electrode can be prepared.

[0173] The above positive electrode has a structure in which a positive electrode material including a positive electrode active material layer and a conductive material are bonded by a binder on aluminum foil.

[0174]

[0175] Next, the positive electrode of the prepared waste lithium ion battery is crushed and pulverized into an appropriate size (step S20).

[0176] Here, shredding involves cutting or shredding the positive electrode into a manageable size. As a specific example, the shredded positive electrode may have a size of 1 cm x 1 cm. The shredding may be performed using various dry crushing equipment, such as a hand mill, pin mill, disc mill, cutting mill, or hammer mill, or a high-speed cutter to increase productivity.

[0177] The above crushing can be preferably performed or not, and the size of the pieces, etc. can be determined by considering the characteristics required by the equipment used in the handling of the positive electrode and the subsequent process. For example, if equipment capable of continuous processing is used, the positive electrode must be crushed into smaller pieces because the fluidity must be good.

[0178] Afterwards, the crushed positive electrode is crushed with a mixer, hand mill, pin mill, disc mill, cutting mill, or hammer mill. For example, when crushed with a mixer, the current collector pieces are crushed into small pieces and the positive electrode material is separated from the current collector pieces.

[0179]

[0180] Next, the crushed cathode material is sieved to obtain cathode material powder having an olivine structure (step S30).

[0181] The above-mentioned constitution has the advantage of obtaining powder having a uniform size and separating the entire body pieces.

[0182]

[0183] Next, the obtained cathode material powder is dissolved in an acetic acid aqueous solution to prepare a solution (step S40).

[0184] At this time, the concentration of the acetic acid aqueous solution may preferably be 0.5 to 1 molar concentration (mol / L), and as a specific example, it may be 0.8 molar concentration. Within this range, the cathode material powder is easily dissolved, and since a strong acid or strong base is not used, wastewater treatment is not required, and there is an advantage of being environmentally friendly and reducing process costs.

[0185] The cathode material having the above olivine structure may preferably be lithium iron phosphate having an olivine structure, and more preferably may be LiFePO4 having an olivine structure, in which case it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0186]

[0187] The weight ratio of the above cathode material powder and the acetic acid aqueous solution may be, for example, 1:6 to 1:10, and as a specific example, may be 1:7.8, and within this range, there is an advantage in that the cathode material powder is easily dissolved in the acetic acid aqueous solution.

[0188]

[0189] The above acetic acid aqueous solution may have a pH of, for example, 2.0 to 3.5, and as a specific example, a pH of 2.5 to 3.0. Within this range, wastewater treatment is not required, so it has the advantage of being environmentally friendly and reducing process costs.

[0190]

[0191] The above acetic acid is used in an amount of 0.8 to 1.2 moles per mole of the positive electrode active material in the positive electrode powder, and as a specific example, it can be used in an amount of 1 mole. Within this range, there is an advantage in that the reaction between the positive electrode powder and the acetic acid is smooth.

[0192]

[0193] The step (S40) of preparing the above-mentioned solution can be performed at, for example, room temperature to 70°C, and as a specific example, can be performed at 60°C, and has the advantage that the cathode material powder is easily dissolved within this range.

[0194]

[0195] Next, a hydrogen peroxide (H2O2) aqueous solution is added to the solution to obtain a lithium-dissolved leachate and leachate residue (step S50).

[0196] The above leaching step (S50) can be carried out, for example, at 45 to 65°C, and as a specific example, can be carried out at 60°C, and within this range, lithium is selectively leached at a high concentration, thereby increasing the lithium recovery rate and preserving FePO4 as a leaching residue to be reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economy.

[0197]

[0198] The above-mentioned hydrogen peroxide aqueous solution acts as an oxidizing agent, for example, and selectively leaches lithium from the solution.

[0199] The above-mentioned hydrogen peroxide (H2O2) aqueous solution may have a concentration of, for example, 25 to 40 wt%, and specifically, 30 wt%. Within this range, lithium is selectively and highly concentrated, thereby increasing the lithium recovery rate and preserving FePO4 as a leach residue, thereby reusing it as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0200]

[0201] The concentration of hydrogen peroxide in the above solution may be, for example, 1 to 3.5% by volume, and specifically, 1.8% by volume. Within this range, lithium is selectively and highly concentratedly leached, thereby increasing the lithium recovery rate and preserving FePO4 as a leaching residue to be reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0202]

[0203] The above-mentioned hydrogen peroxide aqueous solution may be used in an amount of, for example, 0.4 to 0.6 moles per mole of positive electrode active material in the positive electrode powder, and as a specific example, 0.5 moles may be used. Within this range, lithium is selectively leached, thereby increasing the lithium recovery rate and preserving FePO4 as a leaching residue to be reused as a raw material for lithium iron phosphate, thereby greatly improving productivity and economic efficiency.

[0204]

[0205] In the above leaching step (S50), the weight ratio of the cathode material powder and the hydrogen peroxide aqueous solution may be, for example, 1:0.3 to 1:0.8, and specifically, 1:0.6, and there is an advantage in that lithium is selectively and sufficiently leached within this range.

[0206]

[0207] The above leaching can be carried out, for example, at a pH of 3.5 to 5.5, and specifically, at a pH of 4 to 5. Within this range, lithium is selectively and sufficiently leached, impurities are reduced, and economic efficiency is greatly improved. In addition, since no strong acid or strong base is used, wastewater treatment is not required, so there is an advantage of being environmentally friendly and reducing process costs.

[0208]

[0209] The above leaching can be carried out under stirring, for example, and as a specific example, can be carried out under stirring at 500 rpm, and there is an advantage that lithium is easily leached from the solution within this range.

[0210] The above leaching can preferably be performed by continuously adding a hydrogen peroxide aqueous solution while stirring, and in this case, the pH of the solution does not change, so lithium is sufficiently and stably leached, which has the advantage of increasing the recovery rate.

[0211] The above stirring time may be, for example, 0.5 hours or more, and as a specific example, stirring may be performed for 1 hour, and within this range, lithium is sufficiently leached from the solution, which has the advantage of recovering lithium at a high yield.

[0212]

[0213] Next, the leachate and leach residue are separated (step S60).

[0214] The separation of the above-mentioned leachate and leach residue can preferably be accomplished by using reduced pressure filtration, in which case the leachate and leach residue can be easily separated with a simple process, reducing process costs and providing the advantage of being environmentally friendly.

[0215] Through the above separation, a lithium-dissolved leachate (step S70) and a leach residue (step S90) are obtained.

[0216] The recovery rate of lithium in the above-mentioned leachate can be calculated using the following mathematical formula 1, and can be, for example, 90 wt% or more, specifically 95 wt% or more, and within this range, there is an advantage in that economic feasibility is maximized with a high recovery rate.

[0217] [Mathematical Formula 1]

[0218] Lithium recovery rate (wt%) = [Lithium content in the leachate (g) / Lithium content in the cathode powder (g)] * 100

[0219]

[0220] Next, the lithium-dissolved leachate is concentrated (step S80).

[0221] The concentration of the above-mentioned leachate can be achieved by, for example, reduced pressure evaporation. As a specific example, the leachate containing dissolved Li can be concentrated directly by reduced pressure evaporation without a separate cooling process. In this case, there is an advantage in that high-purity lithium is obtained with a high recovery rate.

[0222]

[0223] The above-mentioned reduced pressure evaporation can be carried out, for example, at 70 to 90°C and 5 to 20 mbar, and as a specific example, can be carried out at 80°C and 10 mbar, in which case there is an advantage of stably recovering high-purity lithium at a high yield within a short period of time.

[0224] The above-mentioned leachate is concentrated to obtain lithium, and at this time, the lithium can be recovered as lithium acetate.

[0225]

[0226] As an optional step, the separated leaching residue is vacuum dried to obtain a compound containing FePO4 (step S100).

[0227] The above leaching residue may preferably contain FePO4, and in this case, there is an effect of increasing economic benefits by reusing it as a raw material for lithium iron phosphate.

[0228] The above vacuum drying can be performed at, for example, 120 to 150°C, specifically 130°C, and has the advantage of obtaining a compound containing FePO4 within this range in a short period of time.

[0229]

[0230] It can be manufactured into lithium iron phosphate by including the steps of first adding lithium to the above FePO4 and calcining it (first calcination step), and then adding carbon and calcining it (second calcination step). In this case, there is an effect of increasing economic benefits by recycling resources.

[0231] The above first calcination step can be performed by adding lithium to a compound including, for example, FePO4 and calcining at 600 to 800°C for 8 to 12 hours under an inert atmosphere, and within this range, lithium is sufficiently introduced into the FePO4 phase to have the effect of being converted into LiFePO4.

[0232] As a specific example, the first calcination step may be performed by adding lithium to a compound containing FePO4 and calcining at 700°C for 10 hours under a nitrogen atmosphere, and within this range, lithium is sufficiently introduced into the FePO4 phase to have the effect of being converted into LiFePO4.

[0233]

[0234] Thereafter, the secondary calcination step may be performed, for example, at 500 to 700°C for 3 to 6 hours under an inert atmosphere, and has the advantage of improving the electrical conductivity of LiFePO4 within this range.

[0235] As a specific example, the second calcination step may be performed by adding carbon to calcined LiFePO4 and calcining at 600°C for 4 hours under a nitrogen atmosphere, which has the advantage of improving the electrical conductivity of LiFePO4 within this range.

[0236]

[0237] Unless otherwise specified in this description, the atmosphere for reaction or firing, etc. may be air, the pressure may be atmospheric pressure, and the temperature may be room temperature, but there are no particular limitations.

[0238] In this description, room temperature may be a point within the range of 20 ± 5 ℃.

[0239]

[0240] 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.

[0241]

[0242] [Example]

[0243] Example 1

[0244] The positive electrode of a spent lithium-ion battery was crushed and then ground in a mixer to separate the current collector. The positive electrode material from which the current collector was separated was sieved to obtain positive electrode powder (LiFePO4) having an olivine structure. The obtained positive electrode powder was confirmed to be a powder having an olivine structure by X-ray diffraction analysis (XRD).

[0245] 12 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 94 ml of an acetic acid aqueous solution having a concentration of 0.8 molar (mol / L) at 60°C under stirring to prepare a solution. At this time, the pH of the acetic acid aqueous solution was 2.5 to 3.0, and 1 mol of acetic acid was used based on 1 mol of the positive electrode active material in the positive electrode powder. The stirring was performed at 500 rpm.

[0246] The above-mentioned solution was continuously added with 6 ml of a 30 wt% H2O2 aqueous solution at 60°C under stirring for 1 hour to obtain a leaching solution and a leaching residue containing dissolved Li. The stirring was performed at 500 rpm. At this time, 0.5 mol of hydrogen peroxide was used based on 1 mol of the positive electrode active material in the positive electrode powder.

[0247] The above Li-dissolved leachate and leach residue were separated by vacuum filtration, and then the Li-dissolved leachate was concentrated by vacuum evaporation without a separate cooling process to recover Li as lithium acetate. At this time, the recovery rate was measured using the Li-dissolved leachate.

[0248] The above leaching residue was evaporated under reduced pressure to obtain FePO4.

[0249]

[0250] Comparative Example 1

[0251] 16.75 g of powdered LiFePO4 having an olivine structure obtained from a spent lithium ion battery and 13.27 g of Na2S2O8 as an oxidizer were added to 100 ml of distilled water and leached at 25°C for 1 hour to obtain a leachate and a leachate residue. During leaching, stirring was performed at 500 rpm.

[0252] The above Li-dissolved leachate and leachate residue were separated by filtration under reduced pressure, and then the Li-dissolved leachate was evaporated under reduced pressure to obtain Li as lithium sulfate.

[0253]

[0254] Comparative Example 2

[0255] 10 g of powder-formed LiFePO4 having an olivine structure obtained from a spent lithium-ion battery was added to 100 ml of a 30 wt% H2O2 aqueous solution as an oxidizer and 400 ml of distilled water, and leached at 25°C for 1 hour to obtain a leached solution and a leached residue. During leaching, stirring was performed at 500 rpm. At this time, 15.5 mol of hydrogen peroxide was used based on 1 mol of positive electrode active material in the positive electrode powder.

[0256] The above Li-dissolved leachate and leachate residue were separated by vacuum filtration, and the Li-dissolved leachate did not undergo a concentration step because the lithium leaching was very low.

[0257]

[0258] Comparative Example 3

[0259] In the above Example 1, the dissolution and leaching were performed in the same manner as in the above Example 1, except that the dissolution and leaching were performed at 25°C.

[0260]

[0261] Comparative Example 4

[0262] In the above Example 1, the dissolution and leaching were performed in the same manner as in the above Example 1, except that the dissolution and leaching were performed at 80°C.

[0263]

[0264] Comparative Example 5

[0265] The same procedure as in Example 1 was followed, except that 12 g of powder-formed LiFePO4 having an olivine structure obtained from a spent lithium-ion battery was dissolved in a solution containing 94 ml of a 0.8 molar concentration acetic acid aqueous solution and 6 ml of a 30 wt% concentration H2O2 aqueous solution, and the mixture was leached for 1 hour while stirring at 500 rpm. At this time, the pH of the solution containing the mixed acetic acid aqueous solution and the hydrogen peroxide aqueous solution was 7.

[0266]

[0267] Comparative Example 6

[0268] In the above Example 1, the same procedure as in Example 1 was carried out, except that 1.5 ml of a 30 wt% H2O2 aqueous solution was continuously added to the prepared solution at 60°C under stirring for 1 hour to obtain a leaching solution and a leaching residue in which Li was dissolved. At this time, 0.2 mol of hydrogen peroxide was used based on 1 mol of the positive electrode active material in the positive electrode powder.

[0269]

[0270] Comparative Example 7

[0271] In the above Example 1, the same procedure as in the above Example 1 was carried out, except that 8 ml of a 30 wt% H2O2 aqueous solution was continuously added to the prepared solution at 60°C under stirring for 1 hour to obtain a leaching solution and a leaching residue in which Li was dissolved. At this time, 0.8 mol of hydrogen peroxide was used based on 1 mol of the positive electrode active material in the positive electrode powder.

[0272]

[0273] Comparative Example 8

[0274] In the above Example 1, except that 12 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 94 ml of an aqueous acetic acid solution having a concentration of 0.49 mol at 60°C under stirring to prepare a solution, the same procedure as in Example 1 was followed. In this case, acetic acid corresponds to 0.6 mol based on 1 mol of the positive electrode active material in the positive electrode powder.

[0275]

[0276] Comparative Example 9

[0277] In the above Example 1, except that 12 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 94 ml of an acetic acid aqueous solution having a concentration of 1.13 molar at 60°C under stirring to prepare a solution, the same procedure as in Example 1 was followed. In this case, acetic acid corresponds to 1.4 mol based on 1 mol of the positive electrode active material in the positive electrode powder.

[0278]

[0279] Comparative Example 10

[0280] In the above Example 1, the same procedure as in the above Example 1 was performed except that the prepared solution was leached at 70°C.

[0281]

[0282] [Test Example I: Li Recovery Rate According to the Amount of Acetic Acid and Hydrogen Peroxide Added]

[0283] In the above Example 1, Comparative Examples 1, 2 and 6 to 9, Li was dissolved in the leachate and measured through ICP analysis, and the results are shown in Table 1 below.

[0284]

[0285] * Li recovery rate (wt%): 0.2 g of the leachate was aliquoted and placed in a conical tube, and the exact weight was measured. 0.1 ml of 70% nitric acid was added, followed by 500 ㎕ of 1000 mg / kg internal STD (Sc) and diluted to 50 ml with ultrapure water. The lithium content was measured through ICP analysis, and the recovery rate was calculated using the following mathematical formula 1. In addition, the lithium content in the cathode material powder was measured through ICP analysis in the same manner as above, and the lithium recovery rate was calculated using the following mathematical formula 1.

[0286] [Mathematical Formula 1]

[0287] Lithium recovery rate (wt%) = [Lithium content in the leachate (g) / Lithium content in the cathode powder (g)] * 100

[0288]

[0289] ClassificationLi Recovery Rate (Wt%)Fe Recovery Rate (Wt%)P Recovery Rate (Wt%)Example 195.50.31.4Comparative Example 175.200Comparative Example 223.10.916.2Comparative Example 6310.10.8Comparative Example 774.60.31.4Comparative Example 844.90.21.0Comparative Example 975.50.31.3

[0290] As shown in Table 1 above, Example 1 according to the present invention had a very high Li recovery rate compared to Comparative Examples 1, 2, and 6 to 9, and the recovery rates of Fe and P were similar or equivalent. From this, it was confirmed that lithium was selectively leached in Example 1.

[0291]

[0292] [Experimental Example II: XRD Analysis]

[0293] The results of XRD analysis of the leaching residues separated in Example 1, Comparative Examples 1 and 2 are shown in Figures 1 to 3 below, respectively.

[0294] * XRD analysis: 2 g of the sample was placed in the XRD measurement holder, and measured at an accelerating voltage of 40 kV and 30 mA, 2-theta 10-80°, step size 0.02, and speed 2 ℃ / min.

[0295]

[0296] As shown in Figure 1 below, the XRD results of the leachate residue of Example 1 according to the present invention confirmed the FePO4 peak and the LiFePO4 peak was not observed. From this, it was confirmed that the leachate residue of Example 1 according to the present invention preserved FePO4. In addition, it was found that Example 1 had a more distinct FePO4 peak intensity than Comparative Examples 1 and 2.

[0297]

[0298] In addition, as shown in Figures 2 and 3 below, not only the FePO4 peak but also the LiFePO4 peak was observed in the XRD results of the leachate residues of Comparative Examples 1 and 2. From this, it was confirmed that the leachate residues of Comparative Examples 1 and 2 contained a large amount of Li.

[0299]

[0300] [Test Example III: Li, Fe, and P recovery rates according to leaching temperature]

[0301] The recovery rates of Li, Fe, and P from the leachates of Example 1, Comparative Examples 3, and 10 were measured through ICP analysis, and the results are shown in Table 2 below. Here, the recovery rates of Fe and P were measured through ICP analysis in the same manner as the recovery rate of Li.

[0302] Dissolution temperature (℃) Leaching temperature (℃) Li recovery rate (wt%) Fe recovery rate (wt%) P recovery rate (wt%) Example 1606095.50.31.4 Comparative example 3252574.40.21.2 Comparative example 4808075.90.21.2 Comparative example 10707080.20.31.3

[0303] As shown in Table 2 above, Example 1 according to the present invention had a much higher Li recovery rate than Comparative Examples 3, 4, and 10, and the recovery rates of Fe and P were similar or equivalent. From this, it was confirmed that only lithium was selectively leached from the leachate of Example 1.

[0304]

[0305] [Experimental Example IV: Recovery rates of Li, Fe, and P according to the order of addition of aqueous hydrogen peroxide solution]

[0306] The recovery rates of Li, Fe, and P from the leachates of Example 1 and Comparative Example 5 were measured through ICP analysis, and the results are shown in Table 3 below.

[0307] ClassificationLi Recovery Rate (Wt%)Fe Recovery Rate (Wt%)P Recovery Rate (Wt%)Example 195.50.31.4Comparative Example 590.80.815.3

[0308] As shown in Table 3 above, it was confirmed that Example 1 according to the present invention had a higher Li recovery rate than Comparative Example 5, and lower Fe and P recovery rates. From this, it was found that, compared to Comparative Example 5, in Example 1, only lithium was selectively leached, and Fe and P components were leached in trace amounts.

Claims

1. (a) A step of preparing a solution by dissolving a cathode material powder having an olivine structure obtained from the cathode of a spent lithium-ion battery in an aqueous acetic acid solution; (b) a step of adding an aqueous hydrogen peroxide (H2O2) solution to the above solution to obtain a leaching solution in which lithium is dissolved and a leaching residue; (c) a step of separating the above-mentioned leachate and leachate residue; and (d) a step of concentrating the above leachate; comprising, The above step (b) is carried out at 45 to 65 ℃, and In step (a) above, acetic acid is used in an amount of 0.8 to 1.2 moles per 1 mole of positive active material in the positive material powder, and The above step (b) is characterized by using 0.4 to 0.6 moles of hydrogen peroxide per 1 mole of positive active material in the positive material powder. Method for recovering lithium.

2. In Paragraph 1, The cathode material having the above-mentioned olivine structure is characterized by containing lithium iron phosphate. Method for recovering lithium.

3. In Paragraph 1, The cathode material having the above olivine structure is characterized by being a compound represented by the following chemical formula 1. Method for recovering lithium. [Chemical Formula 1] (In the above chemical formula 1, M comprises one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X comprises one or more elements selected from the group consisting of F, S, and N, and a, b, and c are each -0.5≤a≤0.5, 0≤b≤0.5, and 0≤c≤0.1.) 4. In Paragraph 1, The above-mentioned cathode material powder is characterized by being obtained by crushing the cathode of a waste lithium-ion battery and separating the cathode material powder from the current collector. Method for recovering lithium.

5. In Paragraph 1, The weight ratio of the cathode material powder and the aqueous acetic acid solution in step (a) above is characterized as being 1:6 to 1:

10. Method for recovering lithium.

6. In Paragraph 1, The aqueous acetic acid solution in step (a) above is characterized by having a concentration of 0.5 to 1 molar (mol / L). Method for recovering lithium.

7. In Paragraph 1, In step (b) above, the aqueous hydrogen peroxide solution is characterized by having a concentration of 25 to 40 weight%. Method for recovering lithium.

8. In Paragraph 1, The above method for recovering lithium is characterized by a lithium recovery rate of 90 weight% or more calculated using the following mathematical formula 1. Method for recovering lithium. [Mathematical Formula 1] Lithium recovery rate (weight%) = [Lithium content in leaching solution (g) / Lithium content in cathode powder (g)] * 100 9. In Paragraph 1, The above step (b) is characterized by being carried out at a pH of 3.5 to 5.

5. Method for recovering lithium.

10. In Paragraph 1, The above step (b) is characterized by being carried out under stirring. Method for recovering lithium.

11. In Paragraph 1, The separation of the leachate and leachate residue in step (c) above is characterized by using vacuum filtration. Method for recovering lithium.

12. In Paragraph 1, The above leaching residue is characterized by containing FePO4. Method for recovering lithium.

13. In Paragraph 1, The concentration of the leachate in step (d) above is characterized by using reduced pressure evaporation. Method for recovering lithium.

14. In Paragraph 1, The above lithium recovery method is characterized by including a step of vacuum drying the leaching residue obtained in step (c) to obtain FePO4. Method for recovering lithium.

15. In Paragraph 14, The above-mentioned obtained FePO4 is characterized by being prepared as lithium iron phosphate by including the step of adding lithium and calcining, and then adding carbon and calcining. Method for recovering lithium.

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