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 cathode material powder including a cathode active material having an olivine structure in an acidic solution to prepare a solution; (b) adding the solution with an aqueous hydrogen peroxide (H2O2) solution to obtain a first leachate and a first leach residue, followed by separating same; (c) adding a calcium compound to the separated first leachate to obtain a second leachate and a second leachate residue, followed by separating same; (d) diluting the separated second leachate with water; (e) injecting carbon dioxide to the diluted second leachate to obtain a third leachate and a third leachate residue, followed by separating same; and (f) concentrating the separated third leachate. According to the present invention, there is an effect of providing a method for recovering lithium, in which cathode active material powder including a cathode active material having an olivine structure is dissolved in an acidic solution and an aqueous hydrogen peroxide solution is added thereto to obtain a leachate to which a calcium compound is then added to precipitate and remove impurities such as Fe, P, etc., followed by adding carbon dioxide to precipitate and remove residual calcium components, thereby increasing the purity and recovery rate 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. 10-2024-0087980, filed on July 4, 2024, and Korean Patent Application No. 10-2025-0088472, filed on July 2, 2025, which is hereby incorporated by reference in its entirety.

[0003] The present invention relates to a method for recovering lithium, and more specifically, to a method for recovering lithium, which increases the purity and recovery rate of recovered lithium by dissolving a cathode material powder containing a cathode active material having an olivine structure in an acidic solution, then adding a hydrogen peroxide aqueous solution to extract the extracted solution, adding a calcium compound to precipitate and remove impurities such as Fe and P components, and then adding carbon dioxide to precipitate and remove the remaining calcium components.

[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. For this cathode, lithium cobalt oxide (LiCoO2) is used because it has excellent reversibility, low self-discharge rate, high capacity, high energy density, and is easy to synthesize. Or, to reduce the amount of expensive cobalt, 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. Since the above cathode materials contain about 5 to 7% lithium, a method for recovering lithium from waste lithium-ion battery cathode materials is attracting great attention.

[0007] However, lithium iron phosphate (LiFePO4) has a very stable hexahedral crystal structure, and in order to break down this stable structure and recover valuable metals, a high concentration of strong acid or strong base is used to dissolve Li, Fe, and P and then extract Li. However, during this process, impurities such as Fe and P are mixed in, which reduces the purity of the recovered lithium compound.

[0008] Therefore, there is a need to develop a method for recovering lithium with high purity and high recovery rate from a cathode material having a very stable crystal structure obtained from the cathode of a spent lithium-ion battery.

[0009]

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] Korean Patent Publication No. 2012-0031832

[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, which comprises dissolving cathode material powder containing a cathode active material of an olivine structure in a low-concentration acidic solution, then adding a hydrogen peroxide aqueous solution to extract the solution, adding a calcium compound to the extract to precipitate and remove impurities such as Fe and P components, and then adding carbon dioxide to precipitate and remove the remaining calcium components, thereby increasing the purity and recovery rate of lithium.

[0014]

[0015] The above and other objects of the present invention can all be achieved by the present invention described below.

[0016] In order to achieve the above object, I) the present invention provides a method for recovering lithium, comprising the steps of: (a) dissolving a cathode material powder including an olivine-structured cathode active material in an acidic solution to prepare a solution; (b) adding a hydrogen peroxide (H2O2) aqueous solution to the solution to obtain a first leachate and a first leachate residue and separating them; (c) adding a calcium compound to the separated first leachate to obtain a second leachate and a second leachate residue and separating them; (d) adding water to the separated second leachate to dilute it; (e) injecting carbon dioxide into the diluted second leachate to obtain a third leachate and a third leachate residue and separating them; and (f) concentrating the separated third leachate.

[0017] II) In the above I), the positive electrode active material of the olivine structure may include lithium iron phosphate.

[0018] III) In the above I) or II), the positive electrode active material of the olivine structure may 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] IV) In the above I) to III), the positive electrode powder may be obtained by crushing the positive electrode of a spent lithium ion battery to separate the positive electrode powder and the current collector.

[0023] V) In the above I) to IV), in the step (a), the acid solution may contain 0.5 to 0.8 moles of acid per mole of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure.

[0024] VI) In the above I) to V), the acidic solution in step (a) may be a solution containing at least one selected from the group consisting of sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid.

[0025] VII) In the above I) to VI), in the step (b), the hydrogen peroxide aqueous solution may contain 1.8 to 2.3 moles of hydrogen peroxide per mole of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure.

[0026] VIII) In the above I) to VII), in step (b), the hydrogen peroxide aqueous solution can be injected continuously or in batches.

[0027] IX) In the above I) to VIII), in the step (c), the calcium compound may be present in an amount of 0.17 to 0.30 moles per mole of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure.

[0028] X) In the above I) to IX), the calcium compound in the step (c) may be at least one selected from the group consisting of Ca(OH)2, CaO, or a mixture thereof.

[0029] XI) In the above I) to X), the third leachate separated in the above step (e) may have an Fe component of 30 mg / L or less and a P component of 30 mg / L or less.

[0030] XII) In the above I) to XI), in the step (e), carbon dioxide can be injected in an amount of 0.4 to 1.7 L based on 10 g of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure.

[0031] XIII) In the above I) to XII), the third leachate separated in the step (e) may have a Ca component of 50 mg / L or less.

[0032] XIV) In the above I) to XIII), in the step (d), the water may be 0.8 to 2 times the volume of the second leaching liquid.

[0033] XV) In the above I) to XIV), the third leachate separated in the above step (e) may have a pH of 8 or higher.

[0034] XVI) In the above I) to XV), separation of the leachate and leach residue in step (b), step (c) or step (e) can utilize reduced pressure filtration.

[0035] XVII) In the above I) to XVI), in the step (e), the carbon dioxide may be 0.25 to 1.15 moles based on 1 mole of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure.

[0036] According to the present invention, a cathode material having an olivine structure, which is a very stable structure, is dissolved in an acidic solution, and then a hydrogen peroxide aqueous solution is added to the extracted solution, and a calcium compound is added to the extracted solution to precipitate and remove impurities such as Fe and P components, and then carbon dioxide is added to precipitate and remove the remaining Ca components, thereby significantly improving the purity and recovery rate of lithium recovered from a spent cathode.

[0037] 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.

[0038] Figure 1 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.

[0039] The present inventors, while studying a method for recovering lithium with high purity from a lithium-ion battery positive electrode material having a very stable olivine structure, confirmed that the recovery rate and purity of lithium were greatly improved when lithium was recovered as lithium carbonate from a waste positive electrode material by dissolving a positive electrode material having an olivine structure in a low-concentration acidic solution, adding an aqueous hydrogen peroxide solution to the solution, and then adding a calcium compound to the leachate from which Li, P, Fe, etc. were leached to precipitate and remove impurities such as P and Fe components, and then adding carbon dioxide to precipitate and remove the remaining Ca components. Based on this, they devoted themselves to further research and completed the present invention.

[0040]

[0041] The method for recovering lithium described herein is described in detail below.

[0042] 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.

[0043] 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.

[0044]

[0045] Lithium recovery method

[0046] The method for recovering lithium of the present invention comprises the steps of (a) dissolving a cathode material powder including an olivine-structured cathode active material in an acidic solution to prepare a solution; (b) adding a hydrogen peroxide (H2O2) aqueous solution to the solution to obtain a first leachate and a first leachate residue and separating them; (c) adding a calcium compound to the separated first leachate to obtain a second leachate and a second leachate residue and separating them; (d) adding water to the separated second leachate to dilute it; (e) injecting carbon dioxide into the diluted second leachate to obtain a third leachate and a third leachate residue and separating them; and (f) concentrating the separated third leachate. In this case, impurities such as iron and phosphorus are easily removed from the leachate of the waste cathode material, thereby increasing the purity and recovery rate of the recovered lithium.

[0047]

[0048] Below, the lithium recovery method is explained in detail step by step.

[0049]

[0050] (a) A step of preparing a solution by dissolving a cathode material powder containing a cathode active material having an olivine structure in an acidic solution.

[0051] The method for recovering lithium of the present invention includes (a) a step of preparing a solution by dissolving a cathode material powder including a cathode active material having an olivine structure in an acidic solution, and in this case, there is an advantage in that the elements in the cathode material are dissolved, thereby increasing the recovery rate and selectivity of lithium.

[0052]

[0053] The olivine structure in this paper is a type of cathode material structure, with a 3D hexahedral lattice structure. Since PO (phosphorus-oxygen) is strongly bonded, the structure can be maintained even when all lithium ions are lost, so it refers to a structure with little performance degradation due to charge and discharge and excellent thermal stability. In addition, it refers to a structure that is economical because it uses inexpensive iron instead of expensive cobalt metal, but its energy density is lower than that of other cathode materials, and its electrical conductivity and lithium ion diffusion are low.

[0054] The above olivine structure can be confirmed through X-ray diffraction analysis (XRD).

[0055]

[0056] The positive electrode active 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.

[0057] The positive electrode active 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.

[0058] [Chemical Formula 1]

[0059]

[0060] (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.)

[0061]

[0062] 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.

[0063]

[0064] The cathode material powder containing the cathode active material of the above olivine structure can 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, etc. together with expensive lithium.

[0065] 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.

[0066]

[0067] 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.

[0068]

[0069] 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.

[0070]

[0071] 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.

[0072]

[0073] The above acidic solution may contain, for example, 0.5 to 0.8 mol of acid, preferably 0.55 to 0.75 mol, more preferably 0.60 to 0.73 mol, and even more preferably 0.65 to 0.70 mol, per 1 mol of the positive electrode active material, and within this range, there is an advantage in that the recovery rate and selectivity of lithium are increased by dissolving elements in the positive electrode material through the low-concentration acid and the subsequent process (b).

[0074]

[0075] In this description, 1 mole of positive electrode active material is based on the positive electrode active material in the positive electrode powder.

[0076] In the present disclosure, the content (in moles) of the positive electrode active material in the positive electrode powder can be measured by a method commonly used in the technical field to which the present invention pertains to measure the content of the positive electrode active material. For example, the carbon content of the positive electrode powder can be measured through CS analysis, and the content obtained by excluding the carbon content from the positive electrode powder content can be used as the positive electrode active material content. The mole number can be calculated from the content of the positive electrode active material using the molecular weight. As a specific example, the CS analysis can be performed by measuring a blank for a calibration curve, measuring a carbon standard at least three times, adding a combustion agent to a crucible containing 10 mg of a sample, and then positioning it on the lower electrode of a CS analyzer, and then injecting the sample from the upper portion and burning it to measure the content of the carbon component.

[0077]

[0078] The above acidic solution may preferably be an aqueous acid solution, in which case there is an advantage in that the elements in the positive electrode material are dissolved, thereby increasing the recovery rate and selectivity of lithium.

[0079] The above acidic solution may be, for example, a solution containing acid at a molar concentration (mol / L) of 0.2 to 0.6, preferably at a molar concentration of 0.3 to 0.5, more preferably at a molar concentration of 0.35 to 0.45, and within this range, elements in the cathode material are dissolved, thereby increasing the recovery rate and selectivity of lithium.

[0080]

[0081] The above acidic solution may have, for example, a pH of 1 to 5, preferably 2 to 4, and more preferably 2 to 3, and within this range, there is an advantage in that the elements in the positive electrode powder are easily dissolved, thereby increasing the yield of recovered lithium.

[0082] 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.

[0083] In this description, room temperature may be a point within the range of 20 ± 5 ℃.

[0084]

[0085] The above acidic solution may be, for example, a solution containing at least one selected from the group consisting of sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid, and preferably a solution containing sulfuric acid. In this case, there is an advantage in that the elements in the positive electrode material are dissolved, thereby increasing the recovery rate and selectivity of lithium.

[0086]

[0087] The above step (a) can be performed at room temperature, for example, and in this case, there is an advantage in that the cathode material powder is easily dissolved.

[0088]

[0089] The above step (a) can be performed, for example, under stirring, in which case there is an advantage of shortening the dissolution time of the positive electrode powder.

[0090] The above stirring time can be carried out for, for example, 10 to 60 minutes, preferably 20 to 50 minutes, and more preferably 30 to 40 minutes, and within this range, there is an advantage in that the positive electrode powder is easily dissolved in the acidic solution and the stirring time is shortened.

[0091] 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 positive electrode material is easily dissolved in an acidic solution and the time is shortened.

[0092]

[0093] In the above solution, the cathode material powder containing the cathode active material of the olivine structure is dissolved in an acidic solution to form Li + , Fe 2+ , PO4 3- It can exist in the state of ions.

[0094]

[0095] (b) A step of adding a hydrogen peroxide (H2O2) aqueous solution to the above solution to obtain a first leaching solution and a first leaching residue and separating them.

[0096] The method for recovering lithium of the present invention may include (b) a step of adding a hydrogen peroxide (H2O2) aqueous solution to the above-described solution to obtain a first leachate and a first leachate residue and separating them. In this case, the hydrogen peroxide acts as an oxidizing agent to form Fe 2+ to Fe 3+ By precipitating in the form of FePO4 after oxidation, most of the iron and phosphorus components are removed as the first leaching residue, and Fe 2+ + and PO4 3- Some of the lithium compounds remain in the first leachate and become impurities in the recovered lithium compounds, which are removed in subsequent processes.

[0097]

[0098] In this description, leaching refers to dissolving soluble substances to remove the solution and separating the soluble and insoluble components.

[0099]

[0100] In the above step (b), the hydrogen peroxide aqueous solution may contain, for example, 1.8 to 2.3 mol of hydrogen peroxide, preferably 1.8 to 2.2 mol, and more preferably 1.9 to 2.1 mol, per 1 mol of the positive electrode active material, and within this range, most of the iron (Fe) component and phosphorus (P) component are precipitated in the form of FePO4 and are advantageously removed as the first leaching residue.

[0101]

[0102] In the above step (b), the hydrogen peroxide aqueous solution may be, for example, an aqueous solution containing 20 to 40 wt% of hydrogen peroxide, preferably 25 to 35 wt%, more preferably 27 to 32 wt%, and within this range, most of the iron (Fe) component and phosphorus (P) component are precipitated in the form of FePO4 and are advantageously removed as the first leaching residue.

[0103]

[0104] In the above step (b), the hydrogen peroxide aqueous solution may have, for example, a pH of 1 to 5, preferably a pH of 2 to 4, and more preferably a pH of 2 to 3, and within this range, most of the iron (Fe) component and phosphorus (P) component are precipitated in the form of FePO4 and are advantageously removed as the first leaching residue.

[0105]

[0106] The above step (b) can be performed, for example, under stirring, in which case there is an advantage of shortening the leaching time.

[0107] 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, most of the iron and phosphorus components in the solution are precipitated in the form of FePO4 and are advantageously removed as the first leaching residue.

[0108]

[0109] The above stirring time can be carried out for, for example, 20 to 60 minutes, preferably 30 to 50 minutes, and more preferably 30 to 40 minutes, and within this range, most of the iron and phosphorus components in the solution are removed as the first leaching residue, and further, when the first leaching residue is recovered, there is an advantage in that it can be reused as a raw material for lithium iron phosphate.

[0110]

[0111] 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 lithium is sufficiently leached from the solution. 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.

[0112] 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.

[0113]

[0114] The above step (b) can be carried out at room temperature, for example, and has the advantage that most of the iron (Fe) and phosphorus (P) components are precipitated in the form of FePO4 and removed as the first leaching residue within this range.

[0115]

[0116] The separation of the first leachate and the first leachate residue obtained in the above step (b) can be accomplished by, for example, using reduced pressure filtration. In this case, the leachate and leachate residue can be easily separated with a simple process, and the process cost is reduced, which has the advantage of being environmentally friendly.

[0117] 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.

[0118] 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.

[0119]

[0120] The above separated first leachate contains, for example, lithium, iron and phosphorus components.

[0121]

[0122] (c) A step of adding a calcium compound to the separated first leachate to obtain a second leachate and a second leach residue and separating them.

[0123] The method for recovering lithium of the present invention may include (c) a step of adding a calcium compound to the separated first leachate to obtain a second leachate and a second leach residue and separating them. In this case, there is an advantage in that the purity and recovery rate of the recovered lithium are increased by removing impurities such as iron components and phosphorus components of the first leachate.

[0124]

[0125] In the step (c), the calcium compound may be, for example, 0.17 to 0.30 mol, preferably 0.17 to 0.27 mol, more preferably 0.19 to 0.25 mol, and even more preferably 0.20 to 0.23 mol, per 1 mol of the positive electrode active material. Within this range, impurities such as iron and phosphorus components of the first leachate are removed and unreacted calcium components are reduced, thereby increasing the purity and recovery rate of the recovered lithium.

[0126]

[0127] In the above step (c), the calcium compound may be Ca(OH)2, CaO, or a mixture thereof, preferably Ca(OH)2, in which case the pH of the first leachate is increased and Ca 2+ There is an advantage in that the purity and recovery rate of lithium are increased by being easily removed as a second leach residue by combining with the iron and phosphorus components in the first leachate and precipitating them.

[0128]

[0129] For example, when Ca(OH)2 is added as a calcium compound to the first leachate, the iron component is combined with Ca(OH)2 and precipitated as Fe(OH)3, and the phosphorus component is combined with Ca(OH)2 and precipitated as Ca3(PO4)2, thereby being easily removed as the second leachate residue.

[0130]

[0131] For example, when CaO is added as a calcium compound to the first leachate, CaO combines with water to become Ca(OH)2, then combines with iron components to precipitate as Fe(OH)3, and similarly, phosphorus components are easily removed as second leachate residues by CaO combining with water to become Ca(OH)2, then combines with phosphorus components to precipitate as Ca3(PO4)2.

[0132]

[0133] The separation of the second leachate and the second leachate residue obtained in the above step (c) can be achieved by, for example, using reduced pressure filtration. In this case, the leachate and leachate residue can be easily separated with a simple process, and the process cost is reduced, which has the advantage of being environmentally friendly.

[0134] 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.

[0135]

[0136] The separated second leachate may have an iron content of 30 mg / L or less, preferably 20 mg / L or less, more preferably 10 mg / L or less, and even more preferably 5 mg / L or less, as measured by ICP analysis, for example, and has the advantage of increasing the recovery rate and purity of lithium within this range.

[0137] The separated second leachate may have a phosphorus content of 30 mg / L or less, preferably 20 mg / L or less, more preferably 10 mg / L or less, and even more preferably 5 mg / L or less, as measured by ICP analysis, for example, and has the advantage of increasing the recovery rate and purity of lithium within this range.

[0138]

[0139] (d) Step of diluting the separated second leachate by adding water

[0140] The method for recovering lithium of the present invention may include (d) a step of diluting the separated second leachate by adding water, in which case there is an advantage of preventing lithium from being carbonated in the subsequent step of injecting carbon dioxide.

[0141]

[0142] In the above step (d), the amount of water may be, for example, 0.8 to 2 times, preferably 0.8 to 1.7 times, and more preferably 1.0 to 1.5 times, the volume of the second leachate, and within this range, there is an advantage in that lithium is prevented from being carbonated and precipitated in the subsequent step of injecting carbon dioxide, and the energy and cost required for concentrating lithium are reduced.

[0143]

[0144] The above water may be, for example, distilled water or deionized water, preferably distilled water, in which case there is an advantage of reducing impurities in the leachate.

[0145]

[0146] (e) A step of injecting carbon dioxide into the diluted second leachate to obtain a third leachate and a third leach residue and separating them.

[0147] The method for recovering lithium of the present invention may include (e) a step of injecting carbon dioxide into a diluted second leachate to obtain a third leachate and a third leach residue and separating them. In this case, the lithium is not carbonated, and the residual calcium is carbonated and precipitated, so that it is easily removed as a third leach residue, thereby increasing the purity and recovery rate of lithium.

[0148]

[0149] In the step (e) above, carbon dioxide can be injected into the diluted second leachate in an amount of, for example, 0.4 to 1.7 L based on 10 g of the positive electrode active material in the positive electrode powder including the positive electrode active material having an olivine structure, preferably 0.4 to 1.5 L, more preferably 0.5 to 1.3 L, and even more preferably 0.5 to 1.1 L, and within this range, the residual calcium component in the diluted second leachate is carbonated and easily removed, thereby increasing the purity and recovery rate of lithium.

[0150]

[0151] In the step (e), the carbon dioxide may be, for example, 0.25 to 1.15 mol, preferably 0.25 to 1.0 mol, more preferably 0.3 to 0.8 mol, and even more preferably 0.3 to 0.6 mol, per 1 mol of the positive electrode active material, and within this range, the residual calcium component in the diluted second leachate is easily removed by carbonation, thereby increasing the purity and recovery rate of lithium.

[0152]

[0153] Injecting carbon dioxide into the second leachate has the advantage of increasing the purity and recovery rate of lithium by easily removing residual calcium through a reaction as shown in Chemical Formula 2 below. Here, lithium in the second leachate can also be removed by precipitation through a reaction as shown in Chemical Formula 3 below, so in the preceding step (d), water is added to dilute the solution, and the difference in solubility between CaCO3 and Li2CO3 is used to prevent lithium from being carbonated and precipitated. Specifically, the solubility of CaCO3 is approximately 0.0013 g / L at 25°C, and the solubility of Li2CO3 is approximately 1.33 g / L at 25°C. Therefore, when the second leachate is diluted with water, Li2CO3, which has a high solubility, becomes more easily dissolved, thereby suppressing lithium from being carbonated and precipitated by carbon dioxide.

[0154]

[0155] [Chemical Formula 2]

[0156] Ca(OH)2+ CO2--> CaCO3+ H2O

[0157] [Chemical Formula 3]

[0158] 2LiOH + CO2--> Li2CO3+ H2O

[0159]

[0160] In the step (e) above, if carbon dioxide is injected in excess of 1.7 L per 10 g of the positive electrode active material, the carbonation reaction progresses further as shown in the following chemical formula 4, and Ca(HCO3)2 is generated through a bicarbonation reaction. However, since the solubility of Ca(HCO3)2 is much greater than that of CaCO3, it exists in a dissolved state in the leachate, making it difficult to remove residual calcium.

[0161] [Chemical Formula 4]

[0162] CaCO3+ CO2+ H2O --> Ca(HCO3)2

[0163]

[0164] The carbon dioxide can be injected at, for example, a rate of 0.1 to 1.0 L / min, preferably 0.2 to 0.7 L / min, more preferably 0.3 to 0.6 L / min, and within this range, the reaction between calcium and carbon dioxide is smooth, so that it is easily removed as calcium carbonate, thereby increasing the purity and recovery rate of lithium.

[0165] The carbon dioxide can be injected for, for example, 30 seconds to 10 minutes, preferably 1 minute to 7 minutes, and more preferably 1 minute to 5 minutes, and within this range, the reaction between calcium and carbon dioxide is smooth, so that it is easily removed as calcium carbonate, thereby increasing the purity and recovery rate of lithium.

[0166]

[0167] The pH of the third leachate separated above may be, for example, 8 or more, preferably 9 or more, more preferably 10 or more, and within this range, calcium is removed by precipitating it as calcium carbonate, thereby increasing the purity and recovery rate of lithium.

[0168]

[0169] The separation of the third leachate and the third leachate residue obtained in the above step (e) can be achieved by, for example, using reduced pressure filtration. In this case, the leachate and leachate residue can be easily separated with a simple process, and the process cost is reduced, which has the advantage of being environmentally friendly.

[0170] 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.

[0171]

[0172] The third leachate separated in the above step (e) may have a Ca component measured by ICP analysis of, for example, 50 mg / L or less, preferably 30 mg / L or less, more preferably 20 mg / L or less, even more preferably 0.1 to 20 mg / L, and even more preferably 1 to 15 mg / L, and has the advantage of recovering high-purity lithium within this range.

[0173] The third leachate separated in the above step (e) may have an iron content of 30 mg / L or less, preferably 20 mg / L or less, more preferably 10 mg / L or less, even more preferably 5 mg / L or less, and even more preferably 1 mg / L or less, as measured by ICP analysis, and within this range, there is an advantage in that the recovery rate and purity of lithium are increased.

[0174] The third leachate separated in the above step (e) may have a phosphorus content of 30 mg / L or less, preferably 20 mg / L or less, more preferably 10 mg / L or less, even more preferably 5 mg / L or less, and even more preferably 1 mg / L or less, as measured by ICP analysis, and within this range, there is an advantage in that the recovery rate and purity of lithium are increased.

[0175]

[0176] (f) Step of concentrating the separated third leachate

[0177] The method for recovering lithium of the present invention may include a step of (f) concentrating the separated third leachate, in which case there is an effect of recovering lithium as lithium carbonate with high yield and high purity.

[0178]

[0179] The above concentration can be achieved by using, for example, 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.

[0180] 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.

[0181]

[0182] The third leachate is concentrated to recover lithium carbonate, and the recovery rate of lithium may be, for example, 97 wt% or more, preferably 98 wt% or more, and more preferably 99 wt% or more, and there is an advantage in that economic efficiency is maximized within this range.

[0183] In the present invention, the lithium recovery rate of the leachate can be measured by a measurement 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 and placed in a conical tube, the exact weight is measured, and then 0.1 ml of 70 wt% nitric acid is added thereto, followed by 500 ㎕ of 1000 mg / kg internal STD (Sc), and diluted to 50 ml with ultrapure water, and measured by ICP analysis. 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 using the following mathematical equation 1.

[0184] [Mathematical Formula 1]

[0185] Lithium recovery rate (wt%) = [Lithium content in the leachate (g) / Lithium content in the cathode powder (g)] * 100

[0186]

[0187] The following drawing 1 is a flow chart of a method for recovering lithium according to one embodiment of the present invention.

[0188]

[0189] Referring to Fig. 1, first, a waste lithium ion battery positive electrode is prepared (step S10).

[0190] 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.

[0191] 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.

[0192]

[0193] Next, the positive electrode of the prepared waste lithium ion battery is crushed and pulverized into an appropriate size (step S20).

[0194] 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.

[0195] 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.

[0196] Afterwards, the crushed positive electrode is crushed with a mixer, hand mill, pin mill, disk mill, cutting mill, or hammer mill, and as a specific example, 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.

[0197]

[0198] Next, the crushed cathode material is sieved to obtain cathode material powder containing a cathode active material of an olivine structure (step S30).

[0199] The above-mentioned constitution has the advantage of obtaining powder having a uniform size and separating the entire body pieces.

[0200] The cathode material including the cathode active material of 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.

[0201]

[0202] Next, the obtained cathode material powder is dissolved in an acidic solution to prepare a solution (step S40).

[0203] The above acidic solution may be, for example, a solution containing at least one selected from the group consisting of sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid, and as a specific example, may be a sulfuric acid aqueous solution, in which case there is an advantage of increasing the recovery rate of lithium.

[0204] The above acidic solution may contain, for example, 0.5 to 0.8 mol of acid, specifically 0.67 mol, per 1 mol of the positive electrode active material, and within this range, lithium in the positive electrode material is selectively dissolved by the low-concentration acid and the subsequent process, step S50, thereby increasing the recovery rate of lithium and precipitating iron and phosphorus components as FePO4.

[0205] The above acidic solution may have, for example, a pH of 1 to 5, and specifically, a pH of 2 to 3, and within this range, the positive electrode powder is easily dissolved, which has the advantage of increasing the recovery rate of lithium.

[0206] The above step S40 can be performed at room temperature, in which case there is an advantage that the cathode material powder is easily dissolved.

[0207] The above step S40 can be performed under stirring, for example, at a stirring speed of 300 to 700 rpm, specifically 500 rpm, and has the advantage that the cathode material powder is easily dissolved in an acidic solution and the time is shortened.

[0208] In the above step S40, stirring can be performed for, for example, 10 to 60 minutes, specifically 30 minutes, and has the advantage that the cathode material powder is easily dissolved in the acidic solution and the time is shortened.

[0209]

[0210] Next, a hydrogen peroxide (H2O2) aqueous solution is added to the solution to obtain a first leaching solution and a first leaching residue, and these are separated (step S50).

[0211] The above step S50 can be carried out, for example, at room temperature, and has the advantage that within this range, iron (Fe) components and phosphorus (P) components are removed as the first leachate residue, and the first leachate contains most of the lithium and part of the iron and phosphorus components.

[0212]

[0213] The above hydrogen peroxide solution acts as an oxidizing agent, for example, and easily leaches lithium from the solution, and Fe 2+ to Fe 3+ It induces precipitation of FePO4 by oxidation.

[0214]

[0215] The above-mentioned hydrogen peroxide (H2O2) aqueous solution may contain, for example, 1.8 to 2.3 moles of hydrogen peroxide per mole of the positive electrode active material, and as a specific example, may contain 2 moles. Within this range, iron (Fe) components and phosphorus (P) components are precipitated and removed as the first leaching residue, and the first leaching solution contains lithium and a portion of iron and phosphorus components.

[0216]

[0217] The above hydrogen peroxide (H2O2) aqueous solution can be injected continuously, for example, or can be injected drop-by-drop as a specific example. In this case, the pH of the solution does not change, so there is an advantage in that lithium is sufficiently and stably leached and iron and phosphorus components are precipitated.

[0218]

[0219] The above leaching can be carried out, for example, at a pH of 1 to 5, and specifically, at a pH of 2 to 3, and within this range, there is an advantage in that lithium is sufficiently leached from the solution and iron and phosphorus components are precipitated.

[0220]

[0221] The above leaching can be carried out under stirring, for example, and can be carried out under stirring at 500 rpm as a specific example, and within this range, there is an advantage in that lithium is easily leached from the solution and iron and phosphorus components are precipitated.

[0222] The above stirring time may be, for example, 20 to 60 minutes, and as a specific example, stirring may be performed for 30 minutes, and within this range, there is an advantage in that lithium is easily leached from the solution and iron and phosphorus components are precipitated.

[0223]

[0224] The first leachate and the first leachate residue obtained in the above step S50 can be separated using reduced pressure filtration. In this case, the leachate and the leachate residue are easily separated through a simple process, and the process cost is reduced, and there is an advantage of being environmentally friendly.

[0225]

[0226] Next, a calcium compound is added to the separated first leachate to obtain a second leachate and a second leach residue, and these are separated (step S60).

[0227]

[0228] The above calcium compound can be added in an amount of, for example, 0.17 to 0.30 moles per mole of the cathode active material in the cathode material powder including the cathode active material having an olivine structure, and as a specific example, 0.21 moles can be added. Within this range, impurities such as iron and phosphorus components of the first leachate are removed and residual calcium components are reduced, thereby increasing the purity and recovery rate of the recovered lithium.

[0229] The above calcium compound may be, for example, Ca(OH)2, CaO, or a mixture thereof, and as a specific example, may be Ca(OH)2, in which case the pH of the first leachate is increased and Ca 2+ There is an advantage in that the purity and recovery rate of lithium are increased by being easily removed by combining with iron and phosphorus components and precipitating them.

[0230] Specifically, when Ca(OH)2 is added as a calcium compound to the first leachate, the iron component is combined with Ca(OH)2 and precipitated as Fe(OH)3, and the phosphorus component is combined with Ca(OH)2 and precipitated as Ca3(PO4)2, which are easily removed through a separation process.

[0231] As another example, when CaO is added as a calcium compound to the first leachate, CaO combines with water to become Ca(OH)2, then combines with iron components to become Fe(OH)3 and precipitate, and the phosphorus component also precipitates as CaO combines with water to become Ca(OH)2, then combines with phosphorus components to become Ca3(PO4)2, thereby being easily removed as a second leachate residue.

[0232]

[0233] The separation of the second leachate and the second leachate residue obtained in the above step S60 can be achieved, for example, by using reduced pressure filtration. In this case, the leachate and leachate residue can be easily separated through a simple process, reducing process costs and providing the advantage of being environmentally friendly.

[0234]

[0235] Next, water is added to the separated second leachate to dilute it (step S70).

[0236] The above separated second leachate is diluted with water before the subsequent process to remove residual calcium components through carbonation, thereby preventing lithium from being carbonated and precipitated, thereby increasing the recovery rate and purity of lithium.

[0237] In the above step S70, water can be introduced in an amount of 0.8 to 2 times the volume of the second leachate, and as a specific example, can be introduced in an amount of 1 time. Within this range, there is an advantage in that lithium is prevented from being carbonated and precipitated in the subsequent process, and the energy and cost required for concentrating lithium are reduced.

[0238]

[0239] The above water may be, for example, distilled water or deionized water, and as a specific example, distilled water, in which case there is an advantage of reducing impurities in the leachate.

[0240]

[0241] Next, carbon dioxide is injected into the diluted second leachate to obtain a third leachate and a third leach residue, and these are separated (step S80).

[0242] The above step S80 is a carbonation step in which carbon dioxide is injected to remove the residue of the calcium compound that was introduced in the previous step S60 to precipitate and remove the iron and phosphorus components.

[0243] The carbon dioxide can be injected as a gas in an amount of, for example, 0.4 to 1.7 L, based on 10 g of the cathode active material in the cathode material powder containing the cathode active material having an olivine structure, and as a specific example, 0.5 to 1.1 L can be injected. Within this range, the residual calcium component in the second leachate is carbonated and precipitated, and a bicarbonation reaction is prevented, thereby increasing the purity and recovery rate of lithium.

[0244] Injecting carbon dioxide into the second leachate has the advantage of increasing the purity and recovery rate of lithium by removing calcium by precipitating it through a reaction as shown in the following chemical formula 2.

[0245] [Chemical Formula 2]

[0246] Ca(OH)2+ CO2--> CaCO3+ H2O

[0247]

[0248] Here, lithium in the second leachate can also be leached and removed by reacting as in the following chemical formula 3, so that lithium is prevented from being precipitated by using the difference in solubility between CaCO3 and Li2CO3 by diluting with water in step S70.

[0249] [Chemical Formula 3]

[0250] 2LiOH + CO2--> Li2CO3+ H2O

[0251]

[0252] In the above step S80, if carbon dioxide is injected in an amount exceeding 1.7 L based on 10 g of the positive electrode active material, the carbonation reaction progresses further as shown in the following chemical formula 4, and a bicarbonation reaction occurs to generate Ca(HCO3)2. However, since the solubility of Ca(HCO3)2 is much greater than that of CaCO3, it is difficult to remove residual calcium as it exists in a dissolved state in the second leachate.

[0253] [Chemical Formula 4]

[0254] CaCO3+ CO2+ H2O --> Ca(HCO3)2

[0255]

[0256] The carbon dioxide can be injected at a rate of, for example, 0.1 to 1.0 L / min, specifically, 0.3 to 0.6 L / min, and within this range, calcium and carbon dioxide easily react and precipitate into calcium carbonate, thereby removing impurities in the second leachate, thereby increasing the purity and recovery rate of lithium.

[0257] The carbon dioxide can be injected for, for example, 30 seconds to 10 minutes, specifically, 1 minute to 5 minutes, and within this range, calcium and carbon dioxide easily react and precipitate into calcium carbonate, thereby removing impurities in the second leachate, thereby increasing the purity and recovery rate of lithium.

[0258]

[0259] After carbon dioxide is injected into the above-described diluted second leachate, the pH can be, for example, 8 or higher, and within this range, calcium is easily converted into calcium carbonate and precipitated, thereby removing impurities in the second leachate, thereby increasing the purity and recovery rate of lithium.

[0260]

[0261] The separation of the third leachate and the third leachate residue obtained in the above step S80 can be accomplished by using reduced pressure filtration. In this case, the leachate and leachate residue are easily separated through a simple process, and the process cost is reduced, which has the advantage of being environmentally friendly.

[0262] The third leachate separated in the above step S80 has a Ca component of 50 mg / L or less, specifically 14 mg / L or less, as measured by ICP analysis, and has the effect of recovering high-purity lithium within this range.

[0263]

[0264] Next, the separated third leachate is concentrated (step S90).

[0265] The concentration of the above separated third leachate can be achieved, for example, by using 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.

[0266]

[0267] 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.

[0268] The above-mentioned leachate is concentrated to obtain lithium carbonate.

[0269]

[0270] As an optional step, the first leaching residue separated in step S50 is vacuum-dried to obtain a compound containing FePO4 (step S100).

[0271] As a specific example, the first leaching residue includes FePO4, the second leaching residue includes Fe(OH)3 and Ca3(PO4)2, and the third leaching residue includes CaCO3.

[0272] 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.

[0273]

[0274] 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.

[0275]

[0276] [Example]

[0277] Example 1

[0278] 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 as a result of X-ray diffraction (XRD) analysis. In addition, the carbon content of the obtained positive electrode powder was measured through CS analysis to calculate the positive electrode active material content in the positive electrode powder.

[0279] 10 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 100 ml of a 0.4 molar concentration (mol / L) sulfuric acid aqueous solution at room temperature under stirring to prepare a solution. At this time, sulfuric acid corresponds to 0.67 mol based on 1 mol of the positive electrode active material. Stirring was performed at 500 rpm.

[0280] The prepared solution was added drop-by-drop to 13 ml of a 30 wt% H2O2 aqueous solution at room temperature for 30 minutes under stirring, and then stirred for an additional hour to obtain a first leachate and a first leachate residue. The stirring was performed at 500 rpm. At this time, 2 moles of hydrogen peroxide were used based on 1 mole of the positive electrode active material.

[0281] The first leaching liquid and the first leaching residue obtained above were separated by vacuum filtration to obtain the first leaching liquid.

[0282] 100 ml of the first leaching solution was added with 21 g of Ca(OH) as a calcium compound to obtain a second leaching solution and a second leaching residue, which were separated by vacuum filtration. At this time, 0.21 mol of Ca(OH)2 was used based on 1 mol of the positive electrode active material.

[0283] The above separated second leachate was diluted with 100 ml of distilled water.

[0284] Carbon dioxide was injected into the above-described diluted second leachate at a rate of 0.5 L / min for 1 minute to obtain a third leachate and a third leachate residue, which were then separated by vacuum filtration. At this time, 0.5 L of carbon dioxide was used based on 10 g of the positive electrode active material. The third leachate separated here had a pH of 10.6.

[0285] The above pH measurements were performed using a Thermo Scientific Orion Star A Series at room temperature.

[0286] The contents of Li, Fe, P, and Ca components were measured by ICP analysis using the third leachate separated above.

[0287]

[0288] Example 2

[0289] The same procedure as Example 1 was followed, except that carbon dioxide was introduced at a rate of 0.5 L / min for 3 minutes. At this time, 1.5 L of carbon dioxide was used based on 10 g of positive electrode active material. The third leachate separated here had a pH of 8.2.

[0290]

[0291] Example 3

[0292] The same procedure as Example 1 was followed, except that the second leaching liquid separated in Example 1 was diluted with 60 ml of distilled water.

[0293]

[0294] Example 4

[0295] The same procedure as Example 1 was followed, except that the second leaching liquid separated in Example 1 was diluted with 220 ml of distilled water.

[0296]

[0297] Comparative Example 1

[0298] 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 as a result of X-ray diffraction (XRD) analysis. In addition, the carbon content of the obtained positive electrode powder was measured through CS analysis to calculate the positive electrode active material content in the positive electrode powder.

[0299] 10 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 100 ml of a 0.4 molar concentration (mol / L) sulfuric acid aqueous solution at room temperature under stirring to prepare a solution. At this time, sulfuric acid corresponds to 0.67 mol based on 1 mol of the positive electrode active material. Stirring was performed at 500 rpm.

[0300] The above-mentioned prepared solution was continuously added with stirring at room temperature for 30 minutes to 13 ml of a 30 wt% H2O2 aqueous solution, and then stirred for an additional 1 hour to obtain a first leachate and a first leachate residue, which were separated by vacuum filtration. The stirring was performed at 500 rpm. At this time, 2 moles of hydrogen peroxide were used based on 1 mole of the positive electrode active material.

[0301] The first leaching liquid separated above was subjected to ICP analysis to measure the contents of Li, Fe, P, and Ca components.

[0302]

[0303] Comparative Example 2

[0304] 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).

[0305] 10 g of the obtained positive electrode powder (LiFePO4) having the olivine structure was dissolved in 100 ml of a 0.4 molar concentration (mol / L) sulfuric acid aqueous solution at room temperature under stirring to prepare a solution. At this time, sulfuric acid corresponds to 0.67 mol based on 1 mol of the positive electrode active material. Stirring was performed at 500 rpm.

[0306] The prepared solution was continuously added with 13 ml of a 30 wt% H2O2 aqueous solution at room temperature for 30 minutes under stirring, and then stirred for an additional hour to obtain a first leachate and a first leachate residue. The stirring was performed at 500 rpm. At this time, 2 mol of hydrogen peroxide was used based on 1 mol of the positive electrode active material.

[0307] The first leaching liquid and the first leaching residue obtained above were separated by vacuum filtration.

[0308] To 100 ml of the first leachate separated above, 20.5 g of Ca(OH) as a calcium compound was added to obtain a second leachate and a second leachate residue, which were separated by vacuum filtration. At this time, 20.11 mol of Ca(OH) was used based on 1 mol of the positive electrode active material. The second leachate separated here had a pH of 8.

[0309] The contents of Li, Fe, P, and Ca components were measured by ICP analysis using the second leachate separated above.

[0310]

[0311] Comparative Example 3

[0312] In the above Comparative Example 2, the same procedure as in Comparative Example 2 was followed, except that 21 g of Ca(OH) as a calcium compound was added to 100 ml of the first leachate to obtain a second leachate and a second leachate residue. At this time, 0.21 mol of Ca(OH)2 was used based on 1 mol of the positive electrode active material. The second leachate separated here had a pH of 11.9.

[0313] The contents of Li, Fe, P, and Ca components were measured by ICP analysis using the second leachate separated above.

[0314]

[0315] Comparative Example 4

[0316] In the above Comparative Example 2, the same procedure as in Comparative Example 2 was followed, except that 22 g of Ca(OH) was added as a calcium compound to 100 ml of the first leachate to obtain a second leachate and a second leachate residue. At this time, 20.43 mol of Ca(OH) was used based on 1 mol of the positive electrode active material. The second leachate separated here had a pH of 12.5.

[0317] The contents of Li, Fe, P, and Ca components were measured by ICP analysis using the second leachate separated above.

[0318]

[0319] Comparative Example 5

[0320] In the above Comparative Example 2, 100 ml of the first leachate was added with 21 g of Ca(OH) as a calcium compound to obtain a second leachate and a second leachate residue, and these were separated by vacuum filtration. Carbon dioxide was injected into the obtained second leachate at a rate of 0.5 L / min for 10 minutes to obtain a third leachate and a third leachate residue, and these were separated by vacuum filtration, except that the same procedure as Comparative Example 2 was followed.

[0321] At this time, the calcium compound was used in an amount of 20.21 moles of Ca(OH) based on 1 mole of the positive electrode active material, and the second leachate separated here had a pH of 11.9, and 5 L of carbon dioxide was used based on 10 g of the positive electrode active material, and the third leachate separated here had a pH of 6.7.

[0322]

[0323] [Test Example I: Li, Fe, and P contents, Li recovery rate, and Li purity]

[0324] The contents of Li, P, Fe, and Ca in the extracts obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were measured through ICP analysis, and the results are shown in Table 1 below.

[0325] * ICP analysis: 0.2 g of the leachate 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, Fe, P, and Ca were measured through ICP analysis.

[0326] * Lithium recovery rate (weight%): The lithium content contained in the cathode material powder was measured by ICP analysis, and the recovery rate was calculated using the following mathematical formula 1.

[0327] [Mathematical Formula 1]

[0328] Lithium recovery rate (wt%) = [Lithium content (g) in 100 ml of leachate / Lithium content (g) in 10 g of cathode powder] * 100

[0329]

[0330] ClassificationLi content (mg / L)P content (mg / L)Fe content (mg / L)Ca content (mg / L)Li recovery rate (wt%)Example 120920014> 99Example 221140031> 99Example 32317001788Example 413260010> 99Comparative example 142124464090> 99Comparative example 24226024402> 99Comparative example 3422000405> 99Comparative example 4420800571> 99Comparative example 5421700408> 99

[0331] As shown in Table 1 above, Examples 1 to 4 did not have the P component and the Fe component and had a very small amount of Ca component compared to Comparative Examples 1 to 5, so that the purity of lithium was greatly increased, and Examples 1, 2, and 4 had a lithium recovery rate of over 99 wt%. Furthermore, it was expected that Examples 1 and 2 had the advantage of reducing energy consumption in the subsequent concentration process because the amount of water introduced was small. Specifically, Comparative Example 1, in which the cathode material powder was dissolved in an acidic solution and then leached with an aqueous hydrogen peroxide solution as in the prior art, had a large amount of P component and Fe component, and Comparative Example 2, in which 0.11 mol of a calcium compound was introduced based on 1 mol of the cathode active material and no carbon dioxide was introduced, the P component was not removed, and Comparative Example 3, in which 0.21 mol of a calcium compound was introduced based on 1 mol of the cathode active material and no carbon dioxide was introduced, had the P component and Fe components removed, but the Ca component was present in excess.

[0332] In addition, in Comparative Example 4, where 0.43 mol of calcium compound was injected based on 1 mol of positive electrode active material and carbon dioxide was not injected, the P component and Fe component were removed, but the residual amount of Ca component increased.

[0333] In addition, in Comparative Example 5, where the separated second leachate was not diluted with water but carbon dioxide was injected, the P component and the Fe component were removed, but a bicarbonation reaction occurred in the Ca component, so that the Ca in the leachate was dissolved and not precipitated as Ca(HCO3)2, making removal difficult.

Claims

1. (a) A step of preparing a solution by dissolving a cathode material powder containing a cathode active material having an olivine structure in an acidic solution; (b) a step of adding a hydrogen peroxide (H2O2) aqueous solution to the above-mentioned solution to obtain a first leaching solution and a first leaching residue and separating them; (c) a step of adding a calcium compound to the separated first leachate to obtain a second leachate and a second leach residue and separating them; (d) a step of diluting the separated second leachate by adding water; (e) a step of injecting carbon dioxide into the diluted second leachate to obtain a third leachate and a third leach residue and separating them; and (f) a step of concentrating the separated third leachate; characterized in that it comprises Method for recovering lithium.

2. In paragraph 1, The positive electrode active material of the above olivine structure is characterized in that it contains lithium iron phosphate. Method for recovering lithium.

3. In paragraph 1, The positive electrode active material of 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 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.) 4. In paragraph 1, The above cathode material powder is characterized in that it is obtained by crushing the cathode of a spent lithium ion battery and separating the cathode material powder and the current collector. Method for recovering lithium.

5. In paragraph 1, In the above step (a), the acid solution is characterized in that it contains 0.5 to 0.8 moles of acid per mole of the positive electrode active material in the positive electrode powder containing the positive electrode active material of the olivine structure. Method for recovering lithium.

6. In paragraph 1, In the above step (a), the acidic solution is characterized in that it is a solution containing at least one selected from the group consisting of sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid. Method for recovering lithium.

7. In paragraph 1, In the above step (b), the hydrogen peroxide aqueous solution is characterized in that it contains 1.8 to 2.3 moles of hydrogen peroxide per mole of the positive electrode active material in the positive electrode powder including the positive electrode active material of the olivine structure. Method for recovering lithium.

8. In paragraph 1, In the above step (b), the hydrogen peroxide aqueous solution is characterized by being injected continuously or in batches. Method for recovering lithium.

9. In paragraph 1, In the step (c), the calcium compound is characterized in that it is 0.17 to 0.30 moles per mole of the cathode active material in the cathode material powder including the cathode active material of the olivine structure. Method for recovering lithium.

10. In paragraph 1, In the above step (c), the calcium compound is characterized by being Ca(OH)2, CaO, or a mixture thereof. Method for recovering lithium.

11. In paragraph 1, The third leachate separated in the above step (e) is characterized in that the Fe component is 30 mg / L or less and the P component is 30 mg / L or less. Method for recovering lithium.

12. In paragraph 1, In the step (e), carbon dioxide is injected at 0.4 to 1.7 L based on 10 g of the cathode active material in the cathode powder containing the cathode active material of the olivine structure. Method for recovering lithium.

13. In paragraph 1, The third leachate separated in the above step (e) is characterized in that the Ca component is 50 mg / L or less. Method for recovering lithium.

14. In paragraph 1, In the above step (d), the water is characterized in that it is 0.8 to 2 times the volume of the second leachate. Method for recovering lithium.

15. In paragraph 1, The third leachate separated in the above step (e) is characterized by having a pH of 8 or higher. Method for recovering lithium.

16. In paragraph 1, The separation of the leachate and the leach residue in the above step (b), step (c) or step (e) is characterized by using reduced pressure filtration. Method for recovering lithium.

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