Method for removing aluminum from spent cathode material

Abstract

This invention relates to a method for removing aluminum from waste cathode material, the method comprising: step (a) pulverizing the waste cathode, wherein the waste cathode is coated with a cathode active material layer comprising a cathode material having an olivine structure on a current collector; step (b) obtaining the cathode active material layer as powder by sieving the pulverized waste cathode through a 140 to 400 mesh sieve; step (c) leaching the obtained cathode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L to form a leachate and a leachate residue; and step (d) separating the leachate and the leachate residue, wherein, in step (c), the solid-liquid ratio of the cathode active material layer powder to the alkaline aqueous solution is 1 g / 7 ml to 1 g / 35 ml. According to the method for removing aluminum from waste cathode materials of the present invention, by leaching cathode material powder with an olivine structure obtained from the cathode of a waste lithium-ion battery in a predetermined alkaline aqueous solution to form a leachate and a leachate residue, and separating the leachate and the leachate residue, lithium loss in the cathode material powder with an olivine structure can be minimized and aluminum removal rate can be improved, thereby significantly improving the purity of recovered lithium.

Description

Technical Field

[0001] [Cross-reference to related applications]

[0002] This application claims priority based on Korean Patent Application No. 10-2024-0111100 filed on August 20, 2024, and Korean Patent Application No. 10-2025-0114142 filed on August 18, 2025, the disclosures of which are incorporated herein by reference.

[0003] This invention relates to a method for removing aluminum from waste cathode materials, characterized in that the current collector component aluminum mixed in during the step of pulverizing the waste cathode to obtain a cathode active material layer in powder form is leached and removed in a predetermined alkaline aqueous solution, thereby enabling the recovery of high-purity lithium with excellent economic efficiency. Background Technology

[0004] Since the 1990s, the demand for lithium-ion batteries has grown steadily with the market for portable electronic devices, and has recently increased further globally due to the rapid expansion of the electric vehicle market. This trend may lead to instability in the supply and demand of lithium resources in the near future, and the continuous accumulation of waste batteries may cause significant environmental problems. To address these issues, the recycling of used lithium-ion batteries is a crucial technological challenge.

[0005] A lithium-ion battery mainly consists of a positive electrode formed by coating a layer of positive active material onto a metal foil such as aluminum, a negative electrode formed by coating a layer of negative active material onto a metal foil such as copper, a separator to prevent 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 over 60% of the cost of lithium-ion batteries. Lithium cobalt oxide (LiCoO2) is used as the cathode material due to its excellent reversibility, low self-discharge rate, high capacity, high energy density, and ease of synthesis. Alternatively, to reduce the use of expensive cobalt, lithium composite oxides containing Ni, Mn, etc., such as lithium nickel cobalt manganese oxide (LiNiMnCoO2), lithium manganese oxide (LiMnO2), and lithium iron phosphate (LiFePO4), are used. Since cathode materials contain approximately 5% to 7% lithium, methods for recovering lithium from cathode materials of spent lithium-ion batteries have received significant attention.

[0007] Valuable metals are recovered from lithium iron phosphate (LiFePO4), known for its highly stable olivine crystal structure, using a hydrometallurgical method. The process begins by pulverizing waste cathode material, consisting of a positive electrode active material layer (containing lithium iron phosphate, binder, and carbon) coated on an aluminum current collector. This step yields a powdered positive electrode active material layer. This powder is then treated with a high-concentration strong acid or strong alkali to recover lithium (Li), iron (Fe), and phosphorus (P) in their respective compound forms. However, a problem arises during this pulverization process: the aluminum current collector mixes with the positive electrode active material powder, which reduces the purity of the recovered lithium.

[0008] Therefore, it is necessary to develop a method to improve the purity of recovered lithium by removing aluminum from the current collector that is mixed into the cathode active material powder during the pulverization process of waste lithium-ion battery cathodes.

[0009] [Existing Technical Documents]

[0010] [Patent Literature]

[0011] KR 2007-0112278 A Summary of the Invention

[0012] [Technical Issues]

[0013] Therefore, the present invention was made in view of the above-mentioned problems, and one object of the present invention is to provide a method for removing aluminum from waste cathode materials. According to the method of the present invention, by sieving the cathode material powder with an olivine structure obtained from pulverized waste lithium-ion battery cathodes through a predetermined sieve to form a uniform particle size, and then leaching the powder in a predetermined alkaline aqueous solution, thereby forming and subsequently separating the leachate and leaching residue, the aluminum removal rate can be improved while minimizing lithium loss from the waste cathode material powder with an olivine structure, thus significantly improving the purity and yield of the recovered lithium.

[0014] The above and other objectives can be achieved by the invention described below.

[0015] [Technical Solution]

[0016] I) According to one aspect of the present invention, a method for removing aluminum from waste cathode material is provided, the method comprising the steps of: (a) pulverizing the waste cathode, the waste cathode being coated on a current collector with a cathode active material layer comprising a cathode material having an olivine structure; (b) obtaining the cathode active material layer as powder by sieving the pulverized waste cathode; (c) forming a leachate and a leach residue by leaching the obtained cathode active material layer powder in an alkaline aqueous solution; and (d) separating the leachate and the leach residue.

[0017] II) According to another aspect of the present invention, a method for removing aluminum from waste cathode material is provided, the method comprising the steps of: (a) pulverizing the waste cathode, the waste cathode being coated on a current collector with a cathode active material layer comprising a cathode material having an olivine structure; (b) obtaining the cathode active material layer as powder by sieving the pulverized waste cathode through a 140 to 400 mesh sieve; (c) forming a leachate and a leach residue by leaching the obtained cathode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L; and (d) separating the leachate and the leach residue, wherein, in step (c), the solid-liquid ratio of the cathode active material layer powder to the alkaline aqueous solution is from 1 g / 7 ml to 1 g / 35 ml.

[0018] III) According to I) or II), the cathode material having an olivine structure can be a compound represented by the following chemical formula 1.

[0019] [Chemical Formula 1] , In chemical formula 1, M contains 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 contains one or more elements 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.

[0020] IV) According to I) to III), the cathode material having an olivine structure may contain lithium iron phosphate.

[0021] V) According to I) to IV), the pulverization in step (a) can be carried out using a hand grinder, pin grinder, disc grinder, cutting grinder, hammer grinder, mixer or agitator.

[0022] VI) According to I) to V), the sieving in step (b) can be performed using a particle size separator equipped with a screen.

[0023] VII) According to I) to VI), the particle size of the positive electrode active material layer powder obtained in step (b) can be 35 to 107 µm.

[0024] VIII) According to I) to VII), the alkaline aqueous solution in step (c) may contain one or more of the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH) and calcium hydroxide (Ca(OH)2).

[0025] IX) According to I) to VIII), the pH of the alkaline aqueous solution may be above 12.

[0026] X) According to I) to IX), the leaching in step (c) can be carried out at a stirring speed of 100 to 500 rpm.

[0027] XI) According to I) to X), the leaching in step (c) can be carried out at a temperature of 15 to 40°C.

[0028] XII) According to I) to XI), the leaching in step (c) can be carried out for 30 minutes to 120 minutes.

[0029] XIII) According to I) to XII), the separation of leachate and leachate residue in step (d) can be carried out by vacuum filtration.

[0030] XIV) According to I) to XIII), in step (d), the aluminum leaching rate of the separated leachate can be more than 80% by weight and the lithium leaching rate can be less than 10% by weight.

[0031] According to (I) to (XIV), the method may include (e) recovering lithium from the leaching residue separated in step (d).

[0032] XVI) According to another aspect of the invention, lithium is provided to be recovered in the lithium recovery step according to XV).

[0033] [Beneficial Effects]

[0034] According to the present invention, by pulverizing a waste cathode having a cathode active material layer containing an olivine structure coated on an aluminum current collector to obtain a cathode active material layer in powder form, and then sieving the cathode active material layer powder to a predetermined uniform particle size, aluminum mixed in from the current collector is removed by leaching with a low-concentration alkaline aqueous solution. This method can improve the aluminum removal rate in the cathode active material layer powder while minimizing lithium loss, thereby improving the purity and yield of recovered lithium. Furthermore, reducing wastewater generation can significantly improve economic efficiency and environmental friendliness. Attached Figure Description

[0035] The accompanying drawings illustrate embodiments of the invention and, together with the detailed description provided below, serve to further understand the technical concept of the invention. Therefore, the invention should not be construed as being limited to the contents described in these drawings.

[0036] Figure 1 This is a flowchart illustrating a method for removing aluminum from waste cathode material according to an embodiment of the present invention. Detailed Implementation

[0037] The inventors have confirmed that, in a method for removing aluminum, a component of the current collector, during the process of obtaining a powdered positive electrode active material layer by pulverizing a waste positive electrode containing a positive electrode material with an olivine structure on an aluminum current collector, when the positive electrode active material layer powder is sieved through a predetermined sieve to obtain powder with a uniform particle size within a desired range, and then added to a low-concentration alkaline aqueous solution, aluminum is leached and easily removed, significantly improving the purity and yield of lithium, and reducing wastewater generation. Based on these results, the inventors conducted further research to complete this invention.

[0038] The method for removing aluminum from waste cathode materials according to the present invention will be described in detail below.

[0039] The terms and words used in this specification and the appended claims should not be construed as limited to their common or dictionary meanings, but rather as having meanings and concepts consistent with the technical spirit of the invention, thereby best illustrating the invention. Furthermore, since the embodiments shown in this specification and the accompanying drawings are merely implementations of the invention and do not represent the full technical spirit of the invention, it should be understood that many equivalents and variations exist that can replace the above-described embodiments, and the invention can be arranged, substituted, combined, separated, or designed in various other configurations.

[0040] Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] Methods for removing aluminum from waste cathode materials

[0042] The method for removing aluminum from waste cathode material according to the present invention includes: step (a) pulverizing the waste cathode, wherein the waste cathode is coated with a cathode active material layer comprising a cathode material having an olivine structure on a current collector; step (b) obtaining the cathode active material layer as powder by sieving the pulverized waste cathode; step (c) leaching the obtained cathode active material layer powder in an alkaline aqueous solution to form a leachate and a leaching residue; and step (d) separating the leachate and the leaching residue. In this case, by easily leaching and removing aluminum (current collector component mixed in during the waste cathode pulverization process), the purity of lithium can be improved and the economy can be improved.

[0043] The method for removing aluminum from waste cathode material according to the present invention includes: step (a) pulverizing the waste cathode, wherein the waste cathode is coated with a cathode active material layer comprising a cathode material having an olivine structure on a current collector; step (b) obtaining the cathode active material layer as powder by sieving the pulverized waste cathode through a 140 to 400 mesh sieve; step (c) leaching the obtained cathode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L to form a leachate and a leaching residue; and step (d) separating the leachate and the leaching residue. In step (c), the solid-liquid ratio of the cathode active material layer powder to the alkaline aqueous solution is 1 g / 7 ml to 1 g / 35 ml. In this case, by easily leaching and removing aluminum (current collector component mixed in during the waste cathode pulverization process), the purity of lithium can be improved and the economy can be improved.

[0044] The following section details each step of the method for removing aluminum from waste cathode materials.

[0045] (a) Waste current collector coated with a positive electrode active material layer containing a positive electrode material having an olivine structure Positive electrode pulverization

[0046] The method for removing aluminum from waste positive electrode material according to the present invention includes step (a) crushing the waste positive electrode, wherein the waste positive electrode has a positive electrode active material layer comprising a positive electrode material having an olivine structure coated on a current collector. In this case, the current collector can be easily separated from the waste positive electrode material.

[0047] In this disclosure, the olivine structure refers to a cathode material structure characterized by a three-dimensional cubic lattice arrangement in which phosphorus-oxygen (P–O) bonds are firmly bonded, allowing the structure to maintain its integrity even as all lithium ions are desorbed. This results in less performance degradation during charge-discharge cycles and provides excellent thermal stability. Furthermore, while the olivine structure offers an economic advantage by using inexpensive iron instead of expensive cobalt, its energy density, conductivity, and lithium-ion diffusion are lower compared to other cathode materials.

[0048] The olivine structure can be confirmed by X-ray diffraction (XRD) analysis.

[0049] The positive electrode material in this specification may include or may be a positive electrode active material.

[0050] For example, a cathode material with an olivine structure can be a compound represented by the following chemical formula 1. In this case, high-temperature stability, lifetime characteristics, and economic efficiency can be excellent.

[0051] [Chemical Formula 1]

[0052] (In chemical formula 1, M contains 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 contains one or more elements 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.)

[0053] For example, cathode materials with an olivine structure can contain lithium iron phosphate. In this case, high-temperature stability, lifetime characteristics, and economic efficiency can be excellent.

[0054] Lithium iron phosphate can preferably contain LiFePO4 with an olivine structure. In this case, high-temperature stability, lifetime characteristics, and economic efficiency can be excellent.

[0055] For example, the cathode material powder can be obtained by crushing the cathode of a waste lithium-ion battery and separating the cathode material powder from the current collector. In this case, economic benefits can be achieved because expensive lithium and FePO4, etc., can be recycled and reused.

[0056] For example, waste lithium-ion battery cathodes can be discarded lithium-ion battery cathodes, defective products generated during the cathode coating process, or waste cathode scraps after cutting electrode plates, preferably discarded lithium-ion battery cathodes. In this case, economic benefits can be achieved because expensive lithium and FePO4, etc., can be recycled and reused.

[0057] Before pulverizing the positive electrodes of waste lithium-ion batteries, a crushing step can be performed, which involves cutting or shredding the waste lithium-ion battery positive electrodes. In this case, pulverization can be facilitated.

[0058] For example, a hand grinder, pin grinder, disc grinder, cutting grinder, hammer grinder, mixer or agitator, preferably a mixer, can be used for pulverization. In this case, the current collector plate can be cut into small pieces, and the positive electrode material can be separated from the current collector plate.

[0059] (b) Obtaining positive electrode active material as powder by sieving the crushed waste positive electrode through a 140 to 400 mesh sieve. layer

[0060] The method for removing aluminum from waste cathode material according to the present invention includes step (b) obtaining a cathode active material layer as powder by sieving the pulverized waste cathode through a 140 to 400 mesh sieve. In this case, the powder is easy to handle and mixes well with the leaching solvent. Furthermore, the increased surface area of ​​aluminum in the powder promotes the leaching of aluminum even in low-concentration alkaline aqueous solutions in subsequent leaching steps, thereby reducing wastewater generation.

[0061] The screen mesh is preferably 160 to 330 mesh, more preferably 180 to 300 mesh, even more preferably 180 to 270 mesh, and even more preferably 180 to 230 mesh. Within this range, the particle size of the powder becomes more uniform and smaller, and as the surface area of ​​aluminum increases, the leaching of aluminum in the alkaline aqueous solution can be further promoted. Specifically, when the mesh number exceeds 400, the particle size of the powder decreases significantly, so the amount of positive electrode active material remaining on the screen is greater than the amount of positive electrode active material obtained from the powder, thereby reducing economic efficiency. In addition, in the subsequent leaching step, the powder is not easy to mix with the alkaline aqueous solution and floats, resulting in low aluminum leaching efficiency and significantly longer leaching time. On the other hand, when the mesh number is less than 140, the particle size of the powder increases, and the surface area of ​​aluminum within the particles decreases, which reduces the leaching efficiency of aluminum in low-concentration alkaline aqueous solutions, thus requiring a longer leaching time.

[0062] For example, the sieving in step (b) can be performed using a particle size separator equipped with a screen. In this case, the current collector can be separated from the pulverized waste cathode material, thereby obtaining a cathode active material layer in powder form.

[0063] For example, the particle size of the positive electrode active material layer powder obtained in step (b) can be 35 to 107 μm, preferably 43 to 96 μm, more preferably 46 to 84 μm, even more preferably 53 to 84 μm, and even more preferably 65 to 84 μm. Within this range, the surface area of ​​aluminum within the powder particles increases, thereby improving the aluminum leaching rate even in low-concentration alkaline solutions, minimizing the lithium leaching rate, shortening the leaching time, and reducing wastewater generation.

[0064] The particle size of the positive electrode active material layer powder can be measured using methods commonly used in this technical field, specifically by sieving with a sieve.

[0065] (c) By dissolving the obtained positive electrode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L... Leaching is carried out in the liquid to form leachate and leach residue.

[0066] The method for removing aluminum from waste cathode material according to the present invention includes step (c) leaching the obtained cathode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L to form a leachate and a leaching residue. The solid-liquid ratio of the cathode active material layer powder to the alkaline aqueous solution can be from 1 g / 7 ml to 1 g / 35 ml. In this case, since the current collector component aluminum mixed in during the crushing of the waste cathode is leached into the leachate and separated and removed in subsequent processes, the purity and yield of lithium can be improved.

[0067] For example, the alkaline aqueous solution in step (c) may contain one or more of the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), and calcium hydroxide (Ca(OH)2), preferably sodium hydroxide, ammonium hydroxide, or a mixture thereof. In this case, since the aluminum mixed into the positive electrode active material layer powder in the waste positive electrode crushing step will be selectively leached into the alkaline aqueous solution and removed, the purity of lithium can be improved in subsequent lithium recovery processes.

[0068] In this disclosure, leaching refers to the process of dissolving soluble substances to remove the solution and separate soluble and insoluble components.

[0069] For example, the molar concentration of the alkaline aqueous solution in step (c) can be from 0.06 to 0.22 mol / L, preferably from 0.09 to 0.20 mol / L, more preferably from 0.09 to 0.17 mol / L, even more preferably from 0.09 to 0.15 mol / L, and even more preferably from 0.09 to 0.13 mol / L. Within this range, lithium leaching can be minimized because aluminum mixed in with the cathode active material layer powder in the waste cathode pulverization step is selectively leached and easily removed in the low-concentration alkaline aqueous solution, thereby improving lithium purity and yield. Specifically, when the concentration is below 0.06 mol / L, the equivalence ratio of leached aluminum is insufficient, so aluminum cannot be sufficiently leached. On the other hand, at high concentrations exceeding 0.22 mol / L, the viscosity of the alkaline aqueous solution increases, making it difficult for the cathode active material layer powder to mix easily with the alkaline aqueous solution, and lithium is also leached in addition to aluminum. Therefore, the lithium yield may decrease, wastewater generation may increase, and process costs may also rise.

[0070] For example, the pH of the alkaline aqueous solution can be 12 or higher, preferably 12.5 or higher, more preferably 12.5 to 14, and even more preferably 12.5 to 13.5. In this case, since the aluminum mixed in with the positive electrode active material layer powder in the waste positive electrode crushing step will be selectively leached into the alkaline aqueous solution and removed, the purity of lithium can be improved.

[0071] In this disclosure, pH can be measured using measurement methods commonly used in the art to which this invention pertains. Unless otherwise specified, pH can be measured at room temperature using a general pH measuring device. Specifically, the Thermo Scientific Orion Star A series can be used.

[0072] In this disclosure, room temperature can be any point within the range of 20±5℃.

[0073] For example, the solid-liquid ratio of the positive electrode active material layer powder to the alkaline aqueous solution can be from 1 g / 7 ml to 1 g / 35 ml, preferably from 1 g / 9 ml to 1 g / 27 ml, more preferably from 1 g / 9 ml to 1 g / 20 ml, and even more preferably from 1 g / 9 ml to 1 g / 15 ml. Within this range, since the aluminum mixed in with the positive electrode active material layer powder during the waste positive electrode pulverization step will be selectively leached into the alkaline aqueous solution and removed, the purity of lithium can be improved, and wastewater generation can be reduced.

[0074] In this disclosure, the solid-liquid ratio refers to the ratio of solid to liquid, which is a value obtained by dividing the weight of the solid by the volume of the liquid, that is, by dividing the content (g) of the positive electrode material powder by the volume (mL) of the alkaline aqueous solution.

[0075] For example, the leaching in step (c) can be carried out under stirring. In this case, the leaching time can be shortened.

[0076] For example, the stirring speed can be 100 to 500 rpm, preferably 200 to 400 rpm, and more preferably 250 to 350 rpm. Within this range, aluminum mixed into the positive electrode active material layer powder during the waste positive electrode pulverization step can be fully leached into the alkaline aqueous solution, and the leaching time can be shortened.

[0077] For example, the leaching in step (c) can be carried out at a temperature of 15 to 40°C, preferably 20 to 35°C, and more preferably 20 to 30°C. Within this range, aluminum mixed into the positive electrode active material layer powder during the waste positive electrode pulverization step can be fully leached into the alkaline aqueous solution, and the leaching time can be shortened.

[0078] For example, the leaching in step (c) can be carried out for 30 to 120 minutes, preferably 30 to 100 minutes, and more preferably 50 to 80 minutes. Within this range, aluminum mixed into the positive electrode active material layer powder during the waste positive electrode crushing step can be fully leached into the alkaline aqueous solution, and the leaching time can be shortened.

[0079] (d) Separation of leachate and leachate residue

[0080] The method for removing aluminum from waste cathode material according to the present invention may include step (d) separating the leaching solution and the leaching residue. In this case, by obtaining a leaching residue in which aluminum is selectively removed, the purity of lithium can be improved in subsequent lithium recovery processes, thereby achieving excellent economic efficiency.

[0081] For example, the separation of the leachate and leaching residue in step (d) can be performed using vacuum filtration. In this case, the leachate and leaching residue can be easily separated using a simple process, thereby reducing process costs and providing eco-friendly advantages.

[0082] The reduced pressure filtration is preferably vacuum filtration, specifically vacuum filtration using a filter bottle. In this case, the leachate and leachate residue can be easily separated.

[0083] In this disclosure, the present invention may employ vacuum filtration commonly used in the technical field to which this invention pertains, without particular limitation. For example, vacuum filtration may include filtration under partial vacuum or low pressure.

[0084] For example, the leachate may contain aluminum. In this case, high-purity lithium can be recovered by leaching and removing the current collector component aluminum that was mixed into the cathode active material layer powder during the waste cathode crushing process.

[0085] For example, the leaching residue may contain a layer of positive electrode active material. In this case, high-purity lithium can be recovered from the leaching residue, which improves economic efficiency and has the advantage of resource recycling.

[0086] For example, the aluminum leaching rate of the separated leachate in step (d) can be 80% by weight or more, preferably 82% by weight or more, more preferably 84% by weight or more, and even more preferably 84% to 95% by weight. Within this range, since the current collector component aluminum mixed in during the waste cathode crushing process is removed, the purity of lithium can be improved in subsequent processes.

[0087] For example, the lithium leaching rate of the separated leachate in step (d) can be 10% by weight or less, preferably 8% by weight or less, and more preferably 6% by weight or less. Within this range, lithium loss in the positive electrode active material layer powder is minimized, which can improve the lithium recovery rate in subsequent processes.

[0088] In this disclosure, the aluminum removal rate in the leachate can be measured using any measurement method commonly used in the art to which this invention pertains, such as ICP analysis. Specifically, 0.2 g of leachate is collected and placed in a conical tube. The accurate weight of the leachate is then measured. Next, 0.1 ml of 70% nitric acid and 500 μl of a 1000 mg / kg internal standard (Sc) are added, and the volume of the mixture is adjusted to 50 ml with ultrapure water. Subsequently, the aluminum removal rate in the leachate is measured by ICP. If necessary, the sample concentration can be further diluted with ultrapure water to ensure it falls within the standard calibration curve. Furthermore, the aluminum content in the cathode material powder can be measured by ICP analysis in the manner described above, and the aluminum leaching rate can be calculated using the following mathematical formula 1.

[0089] [Mathematical Expression 1]

[0090] Aluminum leaching rate (wt%) = [Aluminum content in leachate (g) / Aluminum content in cathode material powder (g)] × 100

[0091] The method of removing aluminum from waste cathode material of the present invention may include step (e) recovering lithium from the separated leaching residue of step (d).

[0092] The separated leaching residue in step (e) may contain positive electrode active material. For example, the lithium recovery step may include dissolving the leaching residue in an alkaline or acidic solution.

[0093] Preferably, in step (e), lithium can be recovered from the leachate by dissolving the separated leaching residue in an acidic solution and then adding an oxidant.

[0094] For example, the acidic solution may be a solution comprising one or more of the group consisting of sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid and oxalic acid.

[0095] For example, the pH of the acidic solution can be from 0 to 2, preferably from 0 to 1. Within this range, lithium can be selectively dissolved and recovered.

[0096] For example, the oxidant may comprise one or more selected from the group consisting of hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, oxygen, and oxygen-containing air.

[0097] Figure 1 This is a flowchart of a method for removing aluminum and recovering waste lithium from waste cathode materials according to an embodiment of the present invention.

[0098] See Figure 1 First, prepare the positive electrode of the waste lithium-ion battery (step S10).

[0099] Waste lithium-ion battery positive electrodes can be discarded lithium-ion battery positive electrodes, defective products generated during the positive electrode coating process, or waste positive electrode scraps after cutting electrode plates, preferably discarded lithium-ion battery positive electrodes.

[0100] The positive electrode has a structure in which a layer of positive active material containing positive electrode material and conductive material is assembled on an aluminum foil by an adhesive.

[0101] Next, the prepared waste lithium-ion battery cathode is crushed to an appropriate size (step S20).

[0102] For example, in step S20, a mixer, hand grinder, pin mill, disc mill, cutting mill, or hammer mill can be used for pulverization. As a specific example, when a mixer is used for pulverization, the current collector sheet is shredded into small pieces, and the positive electrode material is separated from the current collector sheet.

[0103] Crushing can be performed before the crushing in step S20.

[0104] Here, crushing includes cutting or shredding the positive electrode into easily manageable dimensions. As a specific example, the size of the crushed positive electrode can be 1 cm × 1 cm. For example, various dry crushing equipment such as hand mills, pin mills, disc mills, cutting mills, and hammer mills can be used for crushing. Furthermore, to improve productivity, high-speed cutting machines can be used for crushing.

[0105] Preferably, the decision to crush, the size of the fragments, etc., can be determined by considering the equipment used to process the positive electrode and subsequent processes. For example, when using equipment capable of continuous processing, the positive electrode must be crushed into small fragments due to the requirement of high fluidity.

[0106] Next, the pulverized cathode material is sieved to obtain cathode material powder with an olivine structure (step S30).

[0107] By sieving, powders of uniform size can be obtained, and current collector sheets can be separated.

[0108] The cathode material is preferably a cathode material with an olivine structure, more preferably lithium iron phosphate, specifically LiFePO4 with an olivine structure. In this case, high-temperature stability, lifetime characteristics, and economic efficiency can be excellent.

[0109] For example, the sieving of waste positive electrodes can be performed using 140 to 400 mesh sieves, specifically 200 mesh sieves. In this case, easy processing can be achieved by separating the current collector fragments and obtaining a uniformly sized positive electrode active material layer powder. Furthermore, the increased surface area from the incorporated aluminum allows for the selective and easy leaching of aluminum from the positive electrode active material layer powder in a low-concentration alkaline aqueous solution.

[0110] As a specific example, in step S30, sieving can be performed using a particle size separator equipped with a screen. In this case, the current collector can be separated from the pulverized waste cathode material, thereby obtaining a cathode active material layer in powder form.

[0111] In step S30, the particle size of the positive electrode active material layer powder obtained after sieving can be 35 to 107 μm, specifically 65 to 84 μm. Within this range, the powder is easy to handle and mixes well with the leaching solvent. Furthermore, the increased surface area of ​​aluminum improves the removal rate of aluminum even in low-concentration alkaline solutions, thereby minimizing lithium loss and reducing leaching time and wastewater generation.

[0112] Next, the obtained positive electrode active material layer powder is leached in an alkaline aqueous solution to form a leachate and a leaching residue (step S40).

[0113] At this point, the molar concentration of the alkaline aqueous solution is preferably between 0.06 and 0.22 mol / L, with 0.1 mol / L as a specific example. Within this range, aluminum mixed into the positive electrode active material layer powder during the waste positive electrode pulverization step can be selectively leached into the leachate and easily removed, thereby improving the purity and yield of lithium.

[0114] For example, the alkaline aqueous solution may contain one or more of the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), and calcium hydroxide (Ca(OH)2), specifically an aqueous solution of sodium hydroxide. In this case, the purity of lithium can be improved because aluminum mixed in with the positive electrode active material layer powder is selectively leachable into the leachate and easily removed.

[0115] For example, the pH of the alkaline aqueous solution can be above 12, specifically between 12.5 and 13.5. In this case, since the aluminum mixed in the positive electrode active material layer powder is selectively leached into the leachate and easily removed, the purity of lithium can be improved in subsequent processes.

[0116] In step S40, the solid-liquid ratio of the positive electrode active material layer powder to the alkaline aqueous solution can be, for example, from 1 g / 7 ml to 1 g / 35 ml, specifically 1 g / 10 ml. Within this range, since the aluminum mixed in the positive electrode active material layer powder is selectively leached into the leachate and easily removed, the purity of lithium can be improved, and wastewater generation can be reduced.

[0117] For example, in step S40, leaching can be performed under stirring. Preferably, leaching can be performed at a stirring speed of 100 to 500 rpm, specifically 300 rpm. Within this range, aluminum mixed into the positive electrode active material layer powder can be fully leached in an alkaline aqueous solution, and the leaching time can be shortened.

[0118] In step S40, for example, leaching can be carried out at a temperature of 15 to 40°C, specifically 25°C. Within this range, aluminum mixed into the positive electrode active material layer powder can be fully leached and removed in an alkaline aqueous solution, thereby improving the purity of lithium.

[0119] For example, in step S40, the leaching can be performed for 30 to 120 minutes, specifically 60 minutes. Within this range, the aluminum mixed in with the positive electrode active material layer powder can be fully leached and removed in the alkaline aqueous solution, thereby improving the purity of lithium.

[0120] Next, the leachate and leachate residue are separated (step S50).

[0121] For example, the separation in step S50 can be performed using vacuum filtration. In this case, the leachate and leaching residue can be easily separated using a simple process, thereby reducing process costs and providing eco-friendly advantages.

[0122] The reduced pressure filtration is preferably vacuum filtration, specifically vacuum filtration using a filter bottle. In this case, the leachate and leachate residue can be easily separated.

[0123] This separation yields a leachate containing dissolved aluminum (step S60) and a positive electrode active material layer powder as leaching residue (step S70). In this case, high-purity lithium can be recovered from the leaching residue, thereby significantly improving economic efficiency.

[0124] For example, the aluminum leaching rate of the leachate separated in step S50 can be 80% by weight or 82% by weight or more. Within this range, since the current collector component aluminum mixed in during the waste cathode crushing process is removed, the purity of lithium can be improved in subsequent processes.

[0125] For example, the lithium leaching rate of the leachate separated in step S50 can be less than 10% by weight, preferably less than 8% by weight. Within this range, lithium loss in the positive electrode active material layer powder is minimized, which can improve the lithium recovery rate in subsequent processes.

[0126] Next, lithium is recovered from the leaching residue (step S70).

[0127] This may include the step of dissolving the leaching residue separated in step S50 in an alkaline or acidic solution.

[0128] The invention will now be described in more detail with reference to the following preferred embodiments. However, these embodiments are provided for illustrative purposes only and should not be construed as limiting the scope and spirit of the invention. Furthermore, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope and spirit of the invention, and such changes and modifications are also within the scope of the appended claims.

[0129] [Example]

[0130] Example 1

[0131] The positive electrode of the waste lithium-ion battery was crushed and then pulverized using a mixer to separate the current collector. The positive electrode material after the current collector was separated was sieved through a 200-mesh sieve to obtain a positive electrode material powder (LiFePO4) with an olivine structure. X-ray diffraction (XRD) analysis of the obtained positive electrode material powder confirmed that the powder has an olivine structure.

[0132] The obtained cathode material powder (LiFePO4) with olivine structure had an aluminum content of 2600 ppm as measured by ICP analysis, and a particle size of 75 µm as measured by sieve size.

[0133] 10 g of the obtained olivine-structured cathode material powder (LiFePO4) was leached for 60 minutes in 100 ml of a 0.1 mol / L sodium hydroxide aqueous solution at 25 °C with stirring, yielding a leachate and leaching residue from which aluminum was extracted. The pH of the sodium hydroxide aqueous solution was 13.01, and the solution was stirred at 300 rpm. At this point, the solid-liquid ratio of the cathode active material layer powder to the alkaline aqueous solution was 1 g / 10 ml.

[0134] The leaching solution and leaching residue from aluminum were separated by vacuum filtration. The aluminum and lithium content in the separated leaching solution was measured by ICP analysis, and the leaching rate was calculated.

[0135] Example 2

[0136] Except for changing the concentration of sodium hydroxide to a molar concentration of 0.07 mol / L, the same procedures as in Example 1 were performed.

[0137] Example 3

[0138] Except for changing the concentration of sodium hydroxide to 0.2 mol / L, the same procedures as in Example 1 were performed.

[0139] Example 4

[0140] Except that the 100 ml sodium hydroxide aqueous solution with a molar concentration of 0.1 mol / L was replaced with 250 ml, the same procedure as in Example 1 was performed.

[0141] Comparative Example 1

[0142] Except for changing the concentration of sodium hydroxide to a molar concentration of 0.03 mol / L, the same procedures as in Example 1 were performed.

[0143] Comparative Example 2

[0144] Except for changing the concentration of sodium hydroxide to 0.25 mol / L, the same procedures as in Example 1 were performed.

[0145] Comparative Example 3

[0146] Except that the 100 ml sodium hydroxide aqueous solution with a molar concentration of 0.1 mol / L was replaced with 30 ml, the same procedure as in Example 1 was performed.

[0147] Comparative Example 4

[0148] Except that the 100 ml sodium hydroxide aqueous solution with a molar concentration of 0.1 mol / L was replaced with 500 ml, the same procedure as in Example 1 was performed.

[0149] Comparative Example 5

[0150] Except for changing the sieve to 35 mesh, the same procedures as in Example 1 are performed.

[0151] Comparative Example 6

[0152] Except for changing the sieve to 100 mesh, the same procedures as in Example 1 are performed.

[0153] Comparative Example 7

[0154] The sieve in Example 1 was changed to 500 mesh to obtain cathode material powder with an olivine structure. A very small amount of cathode material powder was obtained, and a large amount of pulverized cathode material remained in the sieve; therefore, considering economic efficiency and productivity, subsequent steps were not performed.

[0155] [Experimental Example I: Leaching Rate of Aluminum and Lithium in Leachate]

[0156] The content of aluminum in the leaching solutions obtained in Examples 1 to 4 and Comparative Examples 1 to 6 was measured by ICP analysis, and the results are shown in Table 1 below.

[0157] Aluminum leaching rate (wt%) and lithium leaching rate (wt%): 0.2 g of the leachate was aliquoted into a conical tube and its accurate weight was measured. 0.1 ml of 70 wt% nitric acid was added, along with 500 μl of a 1000 mg / kg internal standard (Sc), and the mixture was then diluted to 50 ml with ultrapure water. The aluminum and lithium contents were measured using ICP analysis. Furthermore, the aluminum and lithium contents in the cathode material powder were measured by ICP analysis as described above, and the aluminum leaching rate was calculated using the following mathematical formula 1. The lithium leaching rate was calculated using the same method as described above.

[0158] [Mathematical Expression 1]

[0159] Aluminum leaching rate (wt%) = [Aluminum content in leachate (g) / Aluminum content in cathode material powder (g)] × 100

[0160] [Table 1]

[0161] - During the screening step, a large amount of pulverized positive electrode active material layer is discarded, which reduces economic efficiency and productivity, so subsequent steps are not carried out.

[0162] As shown in Table 1, for Examples 1 to 4 of the present invention, the aluminum leaching rate in the leachate was 80% by weight or more, while the lithium leaching rate was 10% by weight or less. That is, compared to Comparative Examples 1 to 6, Examples 1 to 4 exhibited a higher aluminum leaching rate and a lower lithium leaching rate. These results confirm that by leaching in an alkaline solution, aluminum mixed in with the positive electrode active material layer powder is cleanly removed, while lithium is not leached out; therefore, lithium can be recovered from the leaching residue in a high yield.

[0163] Specifically, in Comparative Examples 1 and 2, where the sodium hydroxide solution concentration was 0.03 mol or 0.25 mol, the aluminum leaching rate was low. In Comparative Example 4, with a solid-liquid ratio of 1 g / 3 ml, stirring was not performed well, resulting in a low aluminum leaching rate. In Comparative Example 4, with a solid-liquid ratio of 1 g / 50 ml, the aluminum leaching rate was high, but the lithium leaching rate also increased rapidly, therefore a decrease in lithium recovery was expected. Furthermore, in Comparative Examples 5 and 6, where sieves were used with 35 mesh and 100 mesh, the aluminum leaching rate decreased due to the reduced surface area of ​​aluminum. In particular, in Comparative Example 5, where sieves were used with 35 mesh, the aluminum leaching rate decreased further.

Claims

1. A method for removing aluminum from waste cathode materials, comprising the following steps: (a) The waste positive electrode is crushed, and the waste positive electrode is coated on the current collector with a positive electrode active material layer containing a positive electrode material having an olivine structure; (b) Obtaining a positive electrode active material layer as powder by sieving the crushed waste positive electrode through a 140 to 400 mesh sieve; (c) A leachate and a leachate residue are formed by leaching the obtained positive electrode active material layer powder in an alkaline aqueous solution with a molar concentration of 0.06 to 0.22 mol / L; and (d) Separate the leachate and the leachate residue. In step (c), the solid-liquid ratio of the positive electrode active material layer powder to the alkaline aqueous solution is from 1 g / 7 ml to 1 g / 35 ml.

2. The method of claim 1, wherein, The cathode material with an olivine structure is a compound represented by the following chemical formula 1: [Chemical Formula 1] ， Wherein, M includes 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 includes one or more elements 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.

3. The method of claim 2, wherein, The cathode material with an olivine structure comprises lithium iron phosphate.

4. The method of claim 1, wherein, The grinding in step (a) is carried out using a hand grinder, pin grinder, disc grinder, cutting grinder, hammer grinder, mixer or agitator.

5. The method of claim 1, wherein, The screening in step (b) is performed using a particle size separator equipped with a screen.

6. The method of claim 1, wherein, The particle size of the positive electrode active material layer powder obtained in step (b) is 35 to 107 µm.

7. The method of claim 1, wherein, The alkaline aqueous solution in step (c) contains one or more of the following: sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), and calcium hydroxide (Ca(OH)2).

8. The method of claim 1, wherein, The pH of the alkaline aqueous solution is above 12.

9. The method of claim 1, wherein, The leaching in step (c) is carried out at a stirring speed of 100 to 500 rpm.

10. The method of claim 1, wherein, The leaching in step (c) is carried out at a temperature of 15 to 40°C.

11. The method of claim 1, wherein, The leaching in step (c) is carried out for 30 to 120 minutes.

12. The method of claim 1, wherein, The separation of leachate and leachate residue in step (d) is carried out using vacuum filtration.

13. The method of claim 1, wherein, In step (d), the aluminum leaching rate of the separated leachate is more than 80% by weight and the lithium leaching rate is less than 10% by weight.

14. The method of claim 1, further comprising: (e) Recover lithium from the leaching residue separated in step (d).

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